Sometimes in class I get into
the weeds talking about Anatomy and physiology. Sometimes I forget that while I
took this in university and even worked in a field that required me to know
basic physiology and a LOT about anatomy….most of the people in the Dojo don’t now
this stuff. This is a SUPER Simplified
version of some of the stuff I talk about.
1) The Human Body. Organization of the Human
Body.
a) The human body is organized based on the
jobs that the different systems do. You have the:
i)
Circulatory system/Cardiovascular system:
(1)
Circulates
blood around the body via the heart, arteries and veins, delivering oxygen and
nutrients to organs and cells and carrying their waste products away, as well
as keeping the body's temperature in a safe range.
ii)
Digestive system:
(1)
System to
absorb nutrients and remove waste via the gastrointestinal tract, including the
mouth, oesophagus, stomach and intestines.
iii)
Endocrine system:
(1)
Influences the
function of the body using hormones.
iv)
Integumentary/exocrine system:
(1)
System that
comprises skin, hair, nails, and sweat and other exocrine glands.
v)
Immune system/Lymphatic system:
(1)
Defends the body against pathogens that may
harm the body. The system contains a network of lymphatic vessels that carry a
clear fluid called lymph.
vi)
Muscular system:
(1)
Enables the body to move using muscles.
vii) Nervous system:
(1)
Collects and processes information from the
senses via nerves and the brain and tells the muscles to contract to cause
physical actions.
viii)
Renal system/urinary system:
(1)
The system where the kidneys filter blood to
produce urine, and get rid of waste.
ix)
Reproductive system:
(1)
The reproductive organs required for the
production of offspring.
x)
Respiratory system:
(1)
Brings air
into the and out of the lungs to absorb O2 and remove Co2
xi)
Skeletal system:
(1)
Bones maintain
structure for movement and to protect the body
2)
Cytology and histology: Cells and tissue
a)
Cell types and cell membrane:
i)
Nucleus: The “brain” of the cell,
directs most action and also houses the most DNA in the cells. Nucleus dictates
the action of the cell.
ii)
Plasma Membrane: the protector and
gatekeeper of the cell. Also the reception point or communication point for the
cell. Also fastens cells together.
iii)
Cytoplasm: a jelly like fluid called
Cytosol that helps protect the inner organelles of the cell.
iv)
Cytoskeleton: The inner “Scaffolding”
that gives each cell its correct shape.
v)
Endoplasmic Reticulum: Helps with Cell
movement and transports proteins in and across the cell itself.
vi)
Golgi Apparatus: the “Post office for
the cells” this puts markers on the products of different cells to allow cells
that need this product to identify it easier.
vii)Mitochondria:
The “power house” of the cells. Takes ATP and makes energy for the body to
work. Also stores Calcium and
catabolizes parts of the body to create ATP.
viii)
Ribosomes: Transcribe parts or segments
of DNA into RNA to create new amino acids. The Ribosomes “Read” the RNA and
create the Amino acids based on the blue prints that the RNA create.
b)
Tissue types
i)
Connective tissue:
(1)
Connective tissues bind structures together, form a framework
and support for organs and the body as a whole, store fat, transport
substances, protect against disease, and help repair tissue damage. They occur
throughout the body. Connective tissues are characterized by an abundance of
intercellular matrix with relatively
few cells. Connective tissue cells are able to
reproduce but not as rapidly as epithelial cells. Most connective tissues have
a good blood supply but some do
not.
ii)
Epithelial tissue:
(1)
Epithelial tissues are widespread
throughout the body. They form the covering of all body surfaces, line body
cavities and hollow organs, and are the major tissue in glands. They perform a
variety of functions that include protection, secretion, absorption, excretion,
filtration, diffusion, and sensory reception. The cells in epithelial tissue
are tightly packed together with very little intercellular matrix. Because the
tissues form coverings and linings, the cells have one free surface that is not
in contact with other cells. Opposite the free surface, the cells are attached
to underlying connective tissue by a non-cellular basement membrane. This
membrane is a mixture of carbohydrates and proteins secreted by the epithelial
and connective tissue cells. Epithelial cells may be squamous, cuboidal, or
columnar in shape and may be arranged in single or multiple layers.
iii)
Muscle cells:
(1)
Muscle tissue is composed of cells that
have the special ability to shorten or contract in order to produce movement of
the body parts. The tissue is highly cellular and is well supplied with blood
vessels. The cells are long and slender so they are sometimes called muscle
fibers, and these are usually arranged in bundles or layers that are surrounded
by connective tissue. Actin and myosin are contractile proteins in muscle
tissue. Muscle tissue can be categorized into skeletal muscle tissue, smooth
muscle tissue, and cardiac muscle tissue. Skeletal
muscle fibers are cylindrical, multinucleated, striated, and under voluntary
control. Smooth muscle cells are spindle shaped, have a single, centrally
located nucleus, and lack striations. They are called involuntary muscles.
Cardiac muscle has branching fibers, one nucleus per cell, striations, and
intercalated disks. Its contraction is not under voluntary control.
iv)
Nerve Cells:
(1)
Nervous tissue is found in the brain,
spinal cord, and nerves. It is responsible for coordinating and controlling
many body activities. It stimulates muscle contraction, creates an awareness of
the environment, and plays a major role in emotions, memory, and reasoning. To
do all these things, cells in nervous tissue need to be able to communicate
with each other by way of electrical nerve impulses. The cells in nervous
tissue that generate and conduct impulses are called neurons or nerve cells.
These cells have three principal parts: the dendrites, the cell body, and one
axon. The main part of the cell, the part that carries on the general
functions, is the cell body. Dendrites are extensions, or processes, of the
cytoplasm that carry impulses to the cell body. An extension or process called
an axon carries impulses away from the cell body. Nervous tissue also includes
cells that do not transmit impulses, but instead support the activities of the
neurons. These are the glial cells (neuroglial cells), together termed the
neuroglia. Supporting, or glia, cells bind neurons together and insulate the
neurons. Some are phagocytic and protect against bacterial invasion, while
others provide nutrients by binding blood vessels to the neurons.
3)
The Skeleton/Bone
a)
Bone tissue and development
i)
Intramembranous ossification involves
the replacement of sheet-like connective tissue membranes with bony tissue.
Bones formed in this manner are called intramembranous bones. They include
certain flat bones of the skull and some of the irregular bones. The future
bones are first formed as connective tissue membranes. Osteoblasts migrate to
the membranes and deposit bony matrix around themselves. When the osteoblasts
are surrounded by matrix they are called osteocytes. Bones grow in
length at the epiphyseal plate by a process that is similar to endochondral
ossification. The cartilage in the region of the epiphyseal plate next to the
epiphysis continues to grow by mitosis. The chondrocytes, in the region next to
the diaphysis, age and degenerate. Osteoblasts move in and ossify the matrix to
form bone. This process continues throughout childhood and the adolescent years
until the cartilage growth slows and finally stops. When cartilage growth
ceases, usually in the early twenties, the epiphyseal plate completely ossifies
so that only a thin epiphyseal line remains and the bones can no longer grow in
length. Bone growth is under the influence of growth hormone from the anterior
pituitary gland and sex hormones from the ovaries and testes. Even
though bones stop growing in length in early adulthood, they can continue to
increase in thickness or diameter throughout life in response to stress from
increased muscle activity or to weight. The increase in diameter is called
appositional growth. Osteoblasts in the periosteum form compact bone around the
external bone surface. At the same time, osteoclasts in the endosteum break
down bone on the internal bone surface, around the medullary cavity. These two
processes together increase the diameter of the bone and, at the same time,
keep the bone from becoming excessively heavy and bulky.
b)
Axial and Appendicular Skeleton
i)
You often here the terms Axial vs
Appendicular or Axial and peripheral, this simply means the core part of the
body and the limbs. The limbs mostly play a role in mobility and work while the
axillary protects the organs and is less mobile, however it is also involved in
movement and work as well.
c)
Classification of bones
i)
Long bones:
(1)
The bones of the body come in a variety
of sizes and shapes. The four principal types of bones are long, short, flat
and irregular. Bones that are longer than they are wide are called long bones.
They consist of a long shaft with two bulky ends or extremities. They are
primarily compact bone but may have a large amount of spongy bone at the ends
or extremities. Long bones include bones of the thigh, leg, arm, and forearm.
ii)
Short bones:
(1)
Short bones are roughly cube shaped with
vertical and horizontal dimensions approximately equal. They consist primarily
of spongy bone, which is covered by a thin layer of compact bone. Short bones
include the bones of the wrist and ankle.
iii)
Flat bones:
(1)
Flat bones are thin, flattened, and
usually curved. Most of the bones of the cranium are flat bones.
iv)
Irregular bones:
(1)
Bones that are not in any of the above
three categories are classified as irregular bones. They are primarily spongy
bone that is covered with a thin layer of compact bone. The vertebrae and some
of the bones in the skull are irregular bones.
d)
Movement
i)
Put simply the skeleton acts as a
scaffolding and structure for the muscles to pull against to create movement
and to do work.
4)
Integumentary system
a)
The skin:
i)
The integumentary system
is the largest organ of the body that forms a physical barrier between the
external environment and the internal environment that it serves to protect and
maintain. The integumentary system includes the epidermis, dermis, hypodermis,
associated glands, hair, and nails. In addition to its barrier function, this
system performs many intricate functions such as body temperature regulation,
cell fluid maintenance, synthesis of Vitamin D, and detection of stimuli. The
various components of this system work in conjunction to carry out these
functions—for example, body temperature regulation occurs through
thermoreceptors that lead to the adjustment of peripheral blood flow, degree of
perspiration, and body hair.
5)
Muscles of the body
a)
Muscle types:
b)
Skeletal Muscle:Skeletal muscle,
attached to bones, is responsible for skeletal movements. The peripheral
portion of the central nervous system (CNS) controls the skeletal muscles.
Thus, these muscles are under conscious, or voluntary, control. The basic unit
is the muscle fiber with many nuclei. These muscle fibers are striated (having
transverse streaks) and each acts independently of neighboring muscle fibers.
c)
Smooth Muscle:Smooth muscle, found in
the walls of the hollow internal organs such as blood vessels, the
gastrointestinal tract, bladder, and uterus, is under control of the autonomic
nervous system. Smooth muscle cannot be controlled consciously and thus acts
involuntarily. The non-striated (smooth) muscle cell is spindle-shaped and has
one central nucleus. Smooth muscle contracts slowly and rhythmically.
d)
Cardiac Muscle:Cardiac muscle, found in
the walls of the heart, is also under control of the autonomic nervous system.
The cardiac muscle cell has one central nucleus, like smooth muscle, but it
also is striated, like skeletal muscle. The cardiac muscle cell is rectangular
in shape. The contraction of cardiac muscle is involuntary, strong, and
rhythmical.
e)
Structure of muscles
i)
A whole skeletal muscle is considered an
organ of the muscular system. Each organ or muscle consists of skeletal muscle
tissue, connective tissue, nerve tissue, and blood or vascular tissue. Skeletal
muscles vary considerably in size, shape, and arrangement of fibers. They range
from extremely tiny strands such as the stapedium muscle of the middle ear to
large masses such as the muscles of the thigh. Some skeletal muscles are broad
in shape and some narrow. In some muscles the fibers are parallel to the long
axis of the muscle; in some they converge to a narrow attachment; and in some
they are oblique. Each skeletal muscle fiber is a single
cylindrical muscle cell. An individual skeletal muscle may be made up of
hundreds, or even thousands, of muscle fibers bundled together and wrapped in a
connective tissue covering. Each muscle is surrounded by a connective tissue
sheath called the epimysium. Fascia, connective tissue outside the epimysium,
surrounds and separates the muscles. Portions of the epimysium project inward
to divide the muscle into compartments. Each compartment contains a bundle of
muscle fibers. Each bundle of muscle fiber is called a fasciculus and is
surrounded by a layer of connective tissue called the perimysium. Within the
fasciculus, each individual muscle cell, called a muscle fiber, is surrounded
by connective tissue called the endomysium. Skeletal muscle cells (fibers),
like other body cells, are soft and fragile. The connective tissue covering
furnish support and protection for the delicate cells and allow them to
withstand the forces of contraction. The coverings also provide pathways for
the passage of blood vessels and nerves. Commonly, the epimysium, perimysium,
and endomysium extend beyond the fleshy part of the muscle, the belly or
gaster, to form a thick ropelike tendon or a broad, flat sheet-like
aponeurosis. The tendon and aponeurosis form indirect attachments from muscles
to the periosteum of bones or to the connective tissue of other muscles.
Typically a muscle spans a joint and is attached to bones by tendons at both
ends. One of the bones remains relatively fixed or stable while the other end
moves as a result of muscle contraction. Skeletal muscles have an abundant
supply of blood vessels and nerves. This is directly related to the primary
function of skeletal muscle, contraction. Before a skeletal muscle fiber can
contract, it has to receive an impulse from a nerve cell. Generally, an artery
and at least one vein accompany each nerve that penetrates the epimysium of a
skeletal muscle. Branches of the nerve and blood vessels follow the connective
tissue components of the muscle of a nerve cell and with one or more minute
blood vessels called capillaries.
f)
Muscle terminology for beginers….how we
named them:
i)
There are more than 600 muscles in the
body, which together account for about 40 percent of a person's weight. Most
skeletal muscles have names that describe some feature of the muscle. Often
several criteria are combined into one name. Associating the muscle's
characteristics with its name will help you learn and remember them. The
following are some terms relating to muscle features that are used in naming
muscles.
(1)
Size: vastus (huge); maximus (large);
longus (long); minimus (small); brevis (short).
(2)
Shape: deltoid (triangular); rhomboid
(like a rhombus with equal and parallel sides); latissimus (wide); teres
(round); trapezius (like a trapezoid, a four-sided figure with two sides
parallel).
(3)
Direction of fibers: rectus (straight);
transverse (across); oblique (diagonally); orbicularis (circular).
(4)
Location: pectoralis (chest); gluteus
(buttock or rump); brachii (arm); supra- (above); infra- (below); sub- (under
or beneath); lateralis (lateral).
(5)
Number of origins: biceps (two heads);
triceps (three heads); quadriceps (four heads).
(6)
Origin and insertion: sternocleidomastoid
(origin on the sternum and clavicle, insertion on the mastoid process);
brachioradialis (origin on the brachium or arm, insertion on the radius).
(7)
Action: abductor (to abduct a
structure); adductor (to adduct a structure); flexor (to flex a structure);
extensor (to extend a structure); levator (to lift or elevate a structure);
masseter (a chewer).
g)
Relaxation and contraction
i)
Muscles can actually only do two things
(Skeletal muscles specifically)…contract or expand/Relax. A Muscle Contraction Is Triggered When an
Action Potential Travels Along the Nerves to the Muscles. Muscle contraction
begins when the nervous system generates a signal. The signal, an impulse
called an action potential, travels through a type of nerve cell called a motor
neuron.
ii)
Beyond Nerve action there is a chemo
electric signal that will cause both contraction and relaxation of the muscle,
you much have both to create the contract extend action of the muscle. Some
nutrient deficiencies and illnesses or injuries to the brain and body can
interfere with this signal and create systems issues like tetanus and other
health issues less life threatening.
h)
Muscle action: movement and heat
i)
Part of the biproduct of the chemo
electric contraction of a muscle is movement. The contraction pulls on the
skeletal system and causes movement, or contraction based attempted movement.
The other biproduct of the contraction of muscle is the creation of a
thermogenic response, or heat.
i)
Effects of tight muscles, what are
triggers and why I cant relax.
i)
Tight muscles or muscle stiffness can be
the result of many different things. Muscle stiffness most commonly arises
after the overuse of skeletal muscles, which tends to happen after a long
period of minimal motion (e.g., after extended bed rest) or after engaging in
new exercises. These actions can cause temporary damage to the muscle cells,
leading to stiffness. Muscle stiffness from overuse of the muscles occurs most
frequently among people who do not exercise often or those that are trying a
new type of exercise that they are not adapted too, or at a level of intensity
they are not used to. Electrolyte imbalances may also cause muscle stiffness,
especially after exercise. Electrolytes (e.g., sodium, potassium, etc.) are
important minerals in the body that play a role in conducting nerve impulses
and contracting muscles, among other functions. When a person exercises,
electrolytes are lost with water (e.g., sweat), making it more difficult for
the nervous system to facilitate muscle movement. Muscle stiffness can also
develop due to an underlying myopathy, or a disease of the muscles, which can
result from metabolic, inflammatory, endocrine, infectious, or
medication-related causes. Metabolic disorders, such as mitochondrial disease
and McArdle’s disease, disrupt the balance of nutrients and energy in the body.
Inflammatory conditions, such as polymyalgia rheumatica, are characterized by
increased inflammation in the body due to an overreaction by the body’s immune
system. Endocrine disorders, like hypothyroidism and acromegaly, are caused by
hormone imbalances in the body. Disruptions in metabolic processes, the immune
system, and hormone levels can all produce muscle stiffness. Infections, such
as the flu, COVID-19, and meningitis, are also often associated with muscle
stiffness. Finally, muscle stiffness can occur as a side effect of certain
medications, such as statins, which are prescribed to treat high cholesterol,
or anesthetics, which are commonly given during surgery. Since muscle movement
depends on communication between the nervous system and the muscles, muscle
stiffness can also arise from issues with the nerves and muscles (i.e.,
neuromuscular disorders) or problems affecting only the nerves (i.e.,
neurologic disorders). Stiff-person syndrome, a rare cause of muscle stiffness,
is a type of neuromuscular disorder in which motor neurons can cause
involuntary muscle spasms. Other disorders, such as Parkinson’s disease,
Myasthenia gravis, and Lambert Eaton syndrome, are characterized by progressively
worsening muscle stiffness, or rigidity. Individuals with a history of stroke
may also experience muscle stiffness.
ii)
Trigger points: Trigger Point (TrP) is a
hyperirritable spot, a palpable nodule in the taut bands of the skeletal
muscles' fascia. Direct compression or muscle contraction can elicit jump sign,
local tenderness, local twitch response and referred pain which usually
responds with a pain pattern distant from the spot. Jump sign is the
characteristic behavioural response to pressure on a TrP. Individuals are
frequently startled by the intense pain. They wince or cry out with a response
seemingly out of proportion to the amount of pressure exerted by the examining
fingers. They move involuntarily, jerking the shoulder, head, or some other
part of the body not being palpated. A jump sign thus reflects the extreme
tenderness of a TrP. This sign has been considered pathognomonic for the
presence of TrPs. Local twitch response - defined as a transient visible or
palpable contraction of the muscle and skin as the tense muscle fibers contract
when pressure is applied through needle penetration or by transverse snapping
palpation. A local twitch response on stimulating active TrPs is a widely
accepted diagnostic sign. Referred pain, also called reflective pain, is pain
perceived at a location other than the site of the painful stimulus. Pain is
reproducible and does not follow dermatomes, myotomes, or nerve roots. There is
no specific joint swelling or neurological deficits. Pain from a myofascial TrP
is a distinct, discrete and constant pattern or map of pain with no gender or
racial differences able to reproduce symptoms - referred pain map. Trigger
points develop in the myofascia, mainly in the center of a muscle belly where
the motor endplate enters (primary or central TrPs)[6]. Those are palpable
nodules within the tight muscle at the size of 2-10 mm and can demonstrate at
different places in any skeletal muscles of the body. We all have TrPs in the
body. Can be present even in babies and children, but their presence does not
necessarily result in the formation of pain syndrome. When it happens, TrPs are
directly associated with myofascial pain syndrome*, somatic dysfunction,
psychological disturbance and restricted daily functioning. *Myofascial Pain
Syndrome refers to regional pain of soft tissue origin and is associated with
muscle tenderness that arises from TrPs, focal points of tenderness, a few
millimeters in diameter, found at multiple sites in a muscle and the fascia of
muscle tissue.
iii)
Causes - Usually, TrPs happen due to:
(1)
Ageing,
(2)
Injury sustained by a fall, by stress or
birth trauma.
(3)
Lack of exercise - commonly in sedentary
persons between 27,5-55 years, of which 45% are men[10],
(4)
Bad posture - upper and lower crossed
pattern, swayback posture, telephone posture, cross-legged sitting,
(5)
Muscle overuse and respective
micro-trauma - weightlifting,
(6)
Chronic stress condition - anxiety,
depression, psychological stress trauma,
(7)
Vitamin deficiencies - vitamin C, D, B;
folic acid; iron;
(8)
Sleep disturbance,
(9)
Joint problems and hypermobility.
6)
The Heart and circulatory system
a)
The heart is a pump, usually beating
about 60 to 100 times per minute. With each heartbeat, the heart sends blood
throughout our bodies, carrying oxygen to every cell. After delivering the
oxygen, the blood returns to the heart. The heart then sends the blood to the
lungs to pick up more oxygen. This cycle repeats over and over again. The
circulatory system is made up of blood vessels that carry blood away from and
towards the heart. Arteries carry blood away from the heart and veins carry
blood back to the heart. The circulatory system carries oxygen, nutrients, and
hormones to cells, and removes waste products, like carbon dioxide. These
roadways travel in one direction only, to keep things going where they should.
b)
What Are the Parts of the Heart?
i)
The heart has four chambers — two on top
and two on bottom: The two bottom chambers are the right ventricle and the left
ventricle. These pump blood out of the heart. A wall called the interventricular
septum is between the two ventricles. The two top chambers are the right atrium
and the left atrium. They receive the blood entering the heart. A wall called
the interatrial septum is between the atria. The atria are separated from the ventricles
by the atrioventricular valves: The tricuspid valve separates the right atrium
from the right ventricle. The mitral valve separates the left atrium from the
left ventricle. Two valves also separate the ventricles from the large blood
vessels that carry blood leaving the heart: The pulmonic valve is between the
right ventricle and the pulmonary artery, which carries blood to the lungs. The
aortic valve is between the left ventricle and the aorta, which carries blood
to the body.
c)
What Are the Parts of the Circulatory
System?
i)
Two pathways come from the heart: The
pulmonary circulation is a short loop from the heart to the lungs and back
again. The systemic circulation carries blood from the heart to all the other
parts of the body and back again. In pulmonary circulation: The pulmonary
artery is a big artery that comes from the heart. It splits into two main
branches, and brings blood from the heart to the lungs. At the lungs, the blood
picks up oxygen and drops off carbon dioxide. The blood then returns to the
heart through the pulmonary veins. In systemic circulation: Next, blood that
returns to the heart has picked up lots of oxygen from the lungs. So it can now
go out to the body. The aorta is a big artery that leaves the heart carrying
this oxygenated blood. Branches off of the aorta send blood to the muscles of
the heart itself, as well as all other parts of the body. Like a tree, the
branches gets smaller and smaller as they get farther from the aorta. At each
body part, a network of tiny blood vessels called capillaries connects the very
small artery branches to very small veins. The capillaries have very thin
walls, and through them, nutrients and oxygen are delivered to the cells. Waste
products are brought into the capillaries. Capillaries then lead into small
veins. Small veins lead to larger and larger veins as the blood approaches the
heart. Valves in the veins keep blood flowing in the correct direction. Two
large veins that lead into the heart are the superior vena cava and inferior
vena cava. (The terms superior and inferior don't mean that one vein is better
than the other, but that they're located above and below the heart.) Once the
blood is back in the heart, it needs to re-enter the pulmonary circulation and
go back to the lungs to drop off the carbon dioxide and pick up more oxygen.
d)
How Does the Heart Beat? The heart gets
messages from the body that tell it when to pump more or less blood depending
on a person's needs. For example, when we're sleeping, it pumps just enough to
provide for the lower amounts of oxygen needed by our bodies at rest. But when
we're exercising, the heart pumps faster so that our muscles get more oxygen
and can work harder. How the heart beats is controlled by a system of
electrical signals in the heart. The sinus (or sinoatrial) node is a small area
of tissue in the wall of the right atrium. It sends out an electrical signal to
start the contracting (pumping) of the heart muscle. This node is called the
pacemaker of the heart because it sets the rate of the heartbeat and causes the
rest of the heart to contract in its rhythm. These electrical impulses make the
atria contract first. Then the impulses travel down to the atrioventricular (or
AV) node, which acts as a kind of relay station. From here, the electrical
signal travels through the right and left ventricles, making them contract. One
complete heartbeat is made up of two phases: The first phase is called systole
(SISS-tuh-lee). This is when the ventricles contract and pump blood into the
aorta and pulmonary artery. During systole, the atrioventricular valves close,
creating the first sound (the lub) of a heartbeat. When the atrioventricular
valves close, it keeps the blood from going back up into the atria. During this
time, the aortic and pulmonary valves are open to allow blood into the aorta
and pulmonary artery. When the ventricles finish contracting, the aortic and
pulmonary valves close to prevent blood from flowing back into the ventricles.
These valves closing is what creates the second sound (the dub) of a heartbeat.
e)
The second phase is called diastole
(die-AS-tuh-lee). This is when the atrioventricular valves open and the
ventricles relax. This allows the ventricles to fill with blood from the atria,
and get ready for the next heartbeat.
7)
The
Brain:
i)
Three layers of protective
covering called meninges surround the brain
and the spinal cord.
ii)
The outermost layer,
the dura mater, is thick and tough. It includes two layers:
The periosteal layer of the dura mater lines the inner dome of the skull
(cranium) and the meningeal layer is below that. Spaces between the layers
allow for the passage of veins and arteries that supply blood flow to the
brain.
iii)
The arachnoid mater is a thin,
weblike layer of connective tissue that does not contain nerves or blood
vessels. Below the arachnoid mater is the cerebrospinal fluid, or CSF. This
fluid cushions the entire central nervous system (brain and spinal cord) and
continually circulates around these structures to remove impurities.
iv)
The pia mater is a thin membrane
that hugs the surface of the brain and follows its contours. The pia mater is
rich with veins and arteries.
b)
Gray vs white matter
i)
Gray and white matter are two different regions
of the central nervous system. In the brain, gray matter refers to the darker,
outer portion, while white matter describes the lighter, inner section
underneath. In the spinal cord, this order is reversed: The white matter is on
the outside, and the gray matter sits within. Gray matter is primarily composed
of neuron somas (the round central cell bodies), and white matter is mostly
made of axons (the long stems that connects neurons together) wrapped in myelin
(a protective coating). The different composition of neuron parts is why the
two appear as separate shades on certain scans. Each region serves a different
role. Gray matter is primarily responsible for processing and interpreting
information, while white matter transmits that information to other parts of
the nervous system.
c)
Three main parts of the brain
Cerebellum, Cerebrum, Brain stem.
d)
Cerebrum “latin for Bark” describes the
outer gray matter covering the surface.
i)
Cortex
is Latin for “bark,” and describes the outer gray matter covering of the
cerebrum. The cortex has a large surface area due to its folds, and comprises
about half of the brain’s weight. The cerebral cortex is divided into two
halves, or hemispheres. It is covered with ridges (gyri) and folds (sulci). The
two halves join at a large, deep sulcus (the interhemispheric fissure, AKA the
medial longitudinal fissure) that runs from the front of the head to the back.
The right hemisphere controls the left side of the body, and the left half
controls the right side of the body. The two halves communicate with one
another through a large, C-shaped structure of white matter and nerve pathways
called the corpus callosum. The corpus callosum is in the center of the
cerebrum.
e)
Brain
Stem
i)
The brainstem (middle of
brain) connects the cerebrum with the spinal cord. The brainstem includes the
midbrain, the pons and the medulla.
- Midbrain. The
midbrain (or mesencephalon) is a very complex structure with a range of
different neuron clusters (nuclei and colliculi), neural pathways and
other structures. These features facilitate various functions, from
hearing and movement to calculating responses and environmental changes.
The midbrain also contains the substantia nigra, an area affected by
Parkinson’s disease that is rich in dopamine neurons and part of the basal
ganglia, which enables movement and coordination.
- Pons. The
pons is the origin for four of the 12 cranial nerves, which enable a range
of activities such as tear production, chewing, blinking, focusing vision,
balance, hearing and facial expression. Named for the Latin word for
“bridge,” the pons is the connection between the midbrain and the medulla.
- Medulla. At
the bottom of the brainstem, the medulla is where the brain meets the
spinal cord. The medulla is essential to survival. Functions of the
medulla regulate many bodily activities, including heart rhythm,
breathing, blood flow, and oxygen and carbon dioxide levels. The medulla
produces reflexive activities such as sneezing, vomiting, coughing and
swallowing.
The spinal cord extends from the bottom of the medulla
and through a large opening in the bottom of the skull. Supported by the
vertebrae, the spinal cord carries messages to and from the brain and the rest
of the body.
f)
Cerebellum
i)
The cerebellum (“little
brain”) is a fist-sized portion of the brain located at the back of the head,
below the temporal and occipital lobes and above the brainstem. Like the
cerebral cortex, it has two hemispheres. The outer portion contains neurons, and
the inner area communicates with the cerebral cortex. Its function is to
coordinate voluntary muscle movements and to maintain posture, balance and
equilibrium. New studies are exploring the cerebellum’s roles in thought,
emotions and social behavior, as well as its possible involvement in addiction,
autism and schizophrenia.
8)
Respiratory anatomy
a)
When the respiratory system is
mentioned, people generally think of breathing, but breathing is only one of
the activities of the respiratory system. The body cells need a continuous
supply of oxygen for the metabolic processes that are necessary to maintain
life. The respiratory system works with the circulatory system to provide this
oxygen and to remove the waste products of metabolism. It also helps to
regulate pH of the blood. Respiration is the sequence of events that results in
the exchange of oxygen and carbon dioxide between the atmosphere and the body
cells. Every 3 to 5 seconds, nerve impulses stimulate the breathing process, or
ventilation, which moves air through a series of passages into and out of the
lungs. After this, there is an exchange of gases between the lungs and the
blood. This is called external respiration. The blood transports the gases to
and from the tissue cells. The exchange of gases between the blood and tissue
cells is internal respiration. Finally, the cells utilize the oxygen for their
specific activities: this is called cellular metabolism, or cellular
respiration. Together, these activities constitute respiration.
9)
Digestive Anatomy
a)
The digestive system includes the
digestive tract and its accessory organs, which process food into molecules
that can be absorbed and utilized by the cells of the body. Food is broken
down, bit by bit, until the molecules are small enough to be absorbed and the
waste products are eliminated. The digestive tract, also called the alimentary
canal or gastrointestinal (GI) tract, consists of a long continuous tube that
extends from the mouth to the anus. It includes the mouth, pharynx, esophagus,
stomach, small intestine, and large intestine. The tongue and teeth are
accessory structures located in the mouth. The salivary glands, liver,
gallbladder, and pancreas are major accessory organs that have a role in
digestion. These organs secrete fluids into the digestive tract. Food undergoes
three types of processes in the body:
i)
Digestion
ii)
Absorption
iii)
Elimination
b)
Digestion and absorption occur in the
digestive tract. After the nutrients are absorbed, they are available to all
cells in the body and are utilized by the body cells in metabolism. The
digestive system prepares nutrients for utilization by body cells through six
activities, or functions.
c)
Ingestion: The first
activity of the digestive system is to take in food through the mouth. This
process, called ingestion, has to take place before anything else can happen.
d)
Mechanical Digestion: The
large pieces of food that are ingested have to be broken into smaller particles
that can be acted upon by various enzymes. This is mechanical digestion, which
begins in the mouth with chewing or mastication and continues with churning and
mixing actions in the stomach.
e)
Chemical Digestion: The
complex molecules of carbohydrates, proteins, and fats are transformed by
chemical digestion into smaller molecules that can be absorbed and utilized by
the cells. Chemical digestion, through a process called hydrolysis, uses water
and digestive enzymes to break down the complex molecules. Digestive enzymes
speed up the hydrolysis process, which is otherwise very slow.
f)
Movements: After ingestion
and mastication, the food particles move from the mouth into the pharynx, then
into the esophagus. This movement is deglutition, or swallowing. Mixing
movements occur in the stomach as a result of smooth muscle contraction. These
repetitive contractions usually occur in small segments of the digestive tract
and mix the food particles with enzymes and other fluids. The movements that
propel the food particles through the digestive tract are called peristalsis.
These are rhythmic waves of contractions that move the food particles through
the various regions in which mechanical and chemical digestion takes place.
g)
Absorption: The simple
molecules that result from chemical digestion pass through cell membranes of
the lining in the small intestine into the blood or lymph capillaries. This
process is called absorption.
h)
Elimination: The food
molecules that cannot be digested or absorbed need to be eliminated from the
body. The removal of indigestible wastes through the anus, in the form of
feces, is defecation or elimination.
10) Endocrine
system and the immune system/lymphatics
a)
The endocrine system, along with the
nervous system, functions in the regulation of body activities. The nervous
system acts through electrical impulses and neurotransmitters to cause muscle
contraction and glandular secretion. The effect is of short duration, measured
in seconds, and localized. The endocrine system acts through chemical
messengers called hormones that influence growth, development, and metabolic
activities. The action of the endocrine system is measured in minutes, hours,
or weeks and is more generalized than the action of the nervous system.
b)
There are two major categories of glands
in the body - exocrine and endocrine.
i)
Exocrine Glands:
Exocrine glands have ducts that carry their secretory product to a surface.
These glands include the sweat, sebaceous, and mammary glands and, the glands
that secrete digestive enzymes.
c)
Endocrine Glands: The
endocrine glands do not have ducts to carry their product to a surface. They
are called ductless glands. The word endocrine is derived from the Greek terms
"endo," meaning within, and "krine," meaning to separate or
secrete. The secretory products of endocrine glands are called hormones and are
secreted directly into the blood and then carried throughout the body where
they influence only those cells that have receptor sites for that hormone. The
endocrine system is made up of the endocrine glands that secrete hormones.
Although there are eight major endocrine glands scattered throughout the body,
they are still considered to be one system because they have similar functions,
similar mechanisms of influence, and many important interrelationships.
d)
Some glands also have non-endocrine
regions that have functions other than hormone secretion. For example, the
pancreas has a major exocrine portion that secretes digestive enzymes and an
endocrine portion that secretes hormones. The ovaries and testes secrete
hormones and also produce the ova and sperm. Some organs, such as the stomach,
intestines, and heart, produce hormones, but their primary function is not
hormone secretion.
e)
Chemical Nature of Hormones: Chemically,
hormones may be classified as either proteins or steroids. All of the hormones
in the human body, except the sex hormones and those from the adrenal cortex,
are proteins or protein derivatives.
f)
Mechanism of Hormone: Action
Hormones are carried by the blood throughout the entire body, yet they affect
only certain cells. The specific cells that respond to a given hormone have
receptor sites for that hormone. This is sort of a lock-and-key mechanism. If
the key fits the lock, then the door will open. If a hormone fits the receptor
site, then there will be an effect. If a hormone and a receptor site do not
match, then there is no reaction. All the cells that have receptor sites for a
given hormone make up the target tissue for that hormone. In some cases, the
target tissue is localized in a single gland or organ. In other cases, the
target tissue is diffuse and scattered throughout the body so that many areas
are affected. Hormones bring about their characteristic effects on target cells
by modifying cellular activity. Protein hormones react with receptors on the
surface of the cell, and the sequence of events that results in hormone action
is relatively rapid. Steroid hormones typically react with receptor sites
inside a cell. Because this method of action actually involves synthesis of
proteins, it is relatively slow.
g)
Control of Hormone Action:
Hormones are very potent substances, which means that very small amounts of a
hormone may have profound effects on metabolic processes. Because of their
potency, hormone secretion must be regulated within very narrow limits in order
to maintain homeostasis in the body. Many hormones are controlled by some form
of a negative feedback mechanism. In this type of system, a gland is sensitive
to the concentration of a substance that it regulates. A negative feedback
system causes a reversal of increases and decreases in body conditions in order
to maintain a state of stability or homeostasis. Some endocrine glands secrete
hormones in response to other hormones. The hormones that cause secretion of
other hormones are called tropic hormones. A hormone from gland A causes gland
B to secrete its hormone. A third method of regulating hormone secretion is by
direct nervous stimulation. A nerve stimulus causes gland A to secrete its
hormone.
11) The
nervous system
a)
Cell types:
i)
Although the nervous system is very
complex, there are only two main types of cells in nerve tissue. The actual
nerve cell is the neuron. It is the "conducting" cell that transmits
impulses and the structural unit of the nervous system. The other type of cell
is neuroglia, or glial, cell. The word "neuroglia" means "nerve
glue." These cells are nonconductive and provide a support system for the
neurons. They are a special type of "connective tissue" for the
nervous system.
ii)
Neurons: Neurons, or
nerve cells, carry out the functions of the nervous system by conducting nerve
impulses. They are highly specialized and amitotic. This means that if a neuron
is destroyed, it cannot be replaced because neurons do not go through mitosis.
The image below illustrates the structure of a typical neuron. Each
neuron has three basic parts: cell body (soma), one or more dendrites, and a
single axon.
iii)
Dendrites: Dendrites and
axons are cytoplasmic extensions, or processes, that project from the cell
body. They are sometimes referred to as fibers. Dendrites are usually, but not
always, short and branching, which increases their surface area to receive
signals from other neurons. The number of dendrites on a neuron varies. They
are called afferent processes because they transmit impulses to the neuron cell
body. There is only one axon that projects from each cell body. It is usually
elongated and because it carries impulses away from the cell body, it is called
an efferent process.
iv)
Axon: An axon may
have infrequent branches called axon collaterals. Axons and axon collaterals
terminate in many short branches or telodendria. The distal ends of the
telodendria are slightly enlarged to form synaptic bulbs. Many axons are
surrounded by a segmented, white, fatty substance called myelin or the myelin
sheath. Myelinated fibers make up the white matter in the CNS, while cell
bodies and unmyelinated fibers make the gray matter. The unmyelinated regions
between the myelin segments are called the nodes of Ranvier. In the peripheral
nervous system, the myelin is produced by Schwann cells. The cytoplasm,
nucleus, and outer cell membrane of the Schwann cell form a tight covering
around the myelin and around the axon itself at the nodes of Ranvier. This
covering is the neurilemma, which plays an important role in the regeneration
of nerve fibers. In the CNS, oligodendrocytes produce myelin, but there is no
neurilemma, which is why fibers within the CNS do not regenerate. Functionally,
neurons are classified as afferent, efferent, or interneurons (association
neurons) according to the direction in which they transmit impulses relative to
the central nervous system. Afferent, or sensory, neurons carry impulses from
peripheral sense receptors to the CNS. They usually have long dendrites and
relatively short axons. Efferent, or motor, neurons transmit impulses from the
CNS to effector organs such as muscles and glands. Efferent neurons usually
have short dendrites and long axons. Interneurons, or association neurons, are
located entirely within the CNS in which they form the connecting link between
the afferent and efferent neurons. They have short dendrites and may have
either a short or long axon.
v)
Neuroglia: Neuroglia
cells do not conduct nerve impulses, but instead, they support, nourish, and
protect the neurons. They are far more numerous than neurons and, unlike
neurons, are capable of mitosis.
b)
Peripheral nervous system
i)
The organs of the peripheral nervous
system are the nerves and ganglia. Nerves are bundles of nerve fibers, much
like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves
extend from the CNS to peripheral organs such as muscles and glands. Ganglia
are collections, or small knots, of nerve cell bodies outside the CNS. The
peripheral nervous system is further subdivided into an afferent (sensory)
division and an efferent (motor) division. The afferent or sensory division
transmits impulses from peripheral organs to the CNS. The efferent or motor
division transmits impulses from the CNS out to the peripheral organs to cause
an effect or action. Finally, the efferent or motor division is again
subdivided into the somatic nervous system and the autonomic nervous system.
The somatic nervous system, also called the somatomotor or somatic efferent
nervous system, supplies motor impulses to the skeletal muscles. Because these
nerves permit conscious control of the skeletal muscles, it is sometimes called
the voluntary nervous system. The autonomic nervous system, also called the
visceral efferent nervous system, supplies motor impulses to cardiac muscle, to
smooth muscle, and to glandular epithelium. It is further subdivided into
sympathetic and parasympathetic divisions. Because the autonomic nervous system
regulates involuntary or automatic functions, it is called the involuntary
nervous system.
c)
Central nervous system:
i)
The brain and spinal cord are the organs
of the central nervous system. Because they are so vitally important, the brain
and spinal cord, located in the dorsal body cavity, are encased in bone for
protection. The brain is in the cranial vault, and the spinal cord is in the
vertebral canal of the vertebral column. Although considered to be two separate
organs, the brain and spinal cord are continuous at the foramen magnum.
d)
Sympathetic and parasympathetic nervous
system:
i)
Sympathetic Autonomic Nervous System: It
is the part of the autonomic nervous system located near the thoracic and
lumbar regions in the spinal cord. Its primary function is to stimulate the
body’s fight-or-flight response. It does this by regulating the heart rate,
rate of respiration, pupillary response and more. Parasympathetic Autonomic Nervous System: It
is located in between the spinal cord and the medulla. It primarily stimulates
the body’s “rest and digest” and “feed and breed” responses. The
sympathetic nervous system prepares the body for the “fight or flight” response
during any potential danger. On the other hand, the parasympathetic nervous
system inhibits the body from overworking and restores the body to a calm and
composed state. The sympathetic and parasympathetic nervous systems are
differentiated based on how the body responds to environmental stimuli.
(1)
Sympathetic: Involved in the fight or
flight response, The sympathetic system prepares the body for any potential
danger, Has a shorter neuron pathway hence a faster response time, Increases
heartbeat, muscles tense up, the pupil dilates to let in more light, salivation
is inhibited, In “fight and flight” situations, Adrenaline is released by the
adrenal glands; more glycogen is converted to glucose.
(2)
Parasympathetic: Involved in maintaining
homeostasis and also permits the rest and digest response, Aims to bring the
body to a state of calm, Compatibly longer neuron pathways, hence a slower
response time, Reduced heartbeat, muscles relaxes, the pupils contract, saliva
secretion increases and digestion increases. No such functions exist in fight
or flight situations.
e)
Autonomic vs Somatic nervous system
i)
The somatic nervous system is a
component of the peripheral nervous system associated with the voluntary
control of the body movements via the use of skeletal muscles. It is
responsible for all the functions we are aware of and can consciously
influence, including the movement of our arms legs and other parts of our body.
A substantial portion of the peripheral nervous system is the 43 different
segments of nerves- 12 pairs of cranial and 31 pairs of spinal nerves, which
help us perform daily functions. The somatic nervous system consists of both
afferent (sensory) and efferent (motor) nerves. It is also responsible for the
reflex arc, which involves the use of interneurons to perform reflexive
actions. Besides these, there are thousands of other association nerves in the
body. Cranial nerves are responsible for carrying information in and out of the
brain. Ten of the cranial nerves originate from the brain stem and mainly
control the voluntary movement and structures of the head with some exceptions.
The nucleus of the olfactory and optic nerve are located in the forebrain and
thalamus, respectively, and are not considered true cranial nerves. The others
originating from the brainstem include oculomotor, trochlear, trigeminal,
abducens, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory,
and hypoglossal. Of note, the accessory nerve innervates the
sternocleidomastoid and trapezius muscles, neither of which control muscles
used exclusively in the head. Spinal nerves carry somatosensory information
into and motor instructions out of the spinal cord. They arise from the spinal
cord as nerve roots and merge to form a web (plexus) of interconnected nerve
roots and once again branch to form nerve fibers. The formation of nerve
plexuses rather than a direct continuation of the nerve roots to peripheral
nerves serves as an essential safety measure so that injury at one site or body
region may not affect the vital functions of our body. The spinal nerves help
to control the function and movement for the rest of the body. The 31 pairs of
spinal nerves include 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1
coccygeal. Their names match the adjacent spinal vertebra from which they exit.
In the cervical region, the nerve root exits above the corresponding vertebrae
(the nerve root between the skull and C1 vertebrae is the C1 spinal nerve). In
the thoracic to the coccygeal region, the spinal nerve root originates below
the corresponding vertebrae. The reason for this difference is due to the
naming and location of the spinal root between C7 and T1 vertebrae (C8 spinal
nerve root). In the lumbar region, the spinal cord ends at L1 from the region
named conus medullaris, but the spinal nerve roots travel within the dural sac
below the L2 level, this region is known as the cauda equina. Information in
the form of electrical impulses is relayed to and from the CNS (brain and
spinal cord) to the neuromuscular junction (NMJ), which converts electrical
signals into chemical signals allowing for muscle contraction. Information from
the periphery is detected by sensory receptors and coveted as electrical
signals back to the central nervous system.
ii)
Structure and Function
iii)
The somatic nervous system contains both
afferent nerves traveling from the periphery towards the CNS and efferent
nerves that are responsible for sending signals from the CNS to the periphery.
The brain and spinal cord are responsible for processing and integrating the
various sources of information to allow us to develop a response. Therefore the
main function of the somatic nervous system is to connect the CNS with organs
and striated muscle to perform our daily functions. The basic motor pathway involves
the upper motor neurons located in the precentral gyrus (primary motor cortex),
which sends signals through the corticospinal tract via axons in the spinal
cord to the lower motor neurons. These signals travel through the ventral horn
of the spinal cord and synapse with the lower motor neurons and send their
signals through peripheral axons to the NMJ of skeletal muscle. UMN release
neurotransmitters acetylcholine, which binds to nicotinic acetylcholine
receptors of the alpha-motor neurons creating a stimulus that propagates
towards the NMJ, which innervates muscles. The peripheral(outside of the CNS)
processes of the somatic nervous system form the somatic peripheral nerves,
which are structurally and functionally different from the autonomic nervous system.
The somatic peripheral nervous system is a single neuron system with the motor
neurons lying inside the brainstem or spinal cord and the sensory neurons lying
in the dorsal root ganglia. The autonomic peripheral nervous system is a two
neuron system with a neuron lying outside of the CNS in the autonomic ganglia.
The nerve fibers have different sizes with different conduction velocities. The
size depends on the actual size of the axons and, more importantly, the degree
of myelination, which provides electrical insulation and fast conduction seed
through the so-called "saltatory conduction." The fastest conducting
fibers are, therefore, the most heavily myelinated. They are the motor fibers
from the motor neurons and sensory fibers serving discriminative touch, joint
position, and vibratory sensations. The small fibers are mainly sensory fibers
serving pain and temperature sensations.
iv)
Somatic Reflex Arc: These are neural
pathways that are responsible for the automatic response between a sensory and
motor neuron. The sensory input generates a specific motor output. The simplest
spinal reflex is mediated by a single synaptic process called the monosynaptic
reflex. It contains only one synapse between the two neurons involved in the
arc (sensory and motor). An example to illustrate this is the patellar reflex-
Striking the patellar ligament just below the patella with a reflex hammer leads
to automatic contraction of the quadriceps, this results in knee extension. The
next order of a simple reflex involves two or more synapses termed the
polysynaptic reflex (one or more interneurons). For example, the sensory neuron
becomes stimulated, which activates the interneuron, which then directly
stimulates the motor neuron, causing a movement.
If you made it this far....Im going to have to put you through more in the coming post, I hope you enjoyed it.
