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Human Physiology
By: Susie Zhou
Period 5
Areas of Human Physiology
Nervous System
Respiratory System
Circulatory System
Excretory System
Skeletal System
Endocrine System
Muscular System
Digestive System
Integumentary System
Immune Response
Reproductive System
Nervous System
Structures  Brain, spinal cord, peripheral nerves
Basic Function  Coordinates the body’s response to changes in its internal and
external environments
State Standards
● Students know how the nervous system mediates communication
between different parts of the body and the body's interactions with the
environment
● Students know the functions of the nervous system and the role of
neurons in transmitting electrochemical impulses
● Students know the roles of sensory neurons, interneurons, and motor
neurons in sensation, thought, and response.
The messages carried by the nervous
system are electrical signals called
impulses, which are transmitted by cells
called neurons. There are three kinds.
Sensory neurons carry impulses from the
sense organs to the spinal cord and brain.
Motor neurons carry them from the brain
and spinal cord to muscles and glands.
Interneurons connect sensory and motor
neurons and carry impulses between them.
The biggest part of an average neuron is its
cell body, which has the nucleus and most
of the cytoplasm. It’s where most metabolic
activity of the cell takes place.
Motor Neuron
A nerve impulse beings when a neuron is
stimulates by another neuron or by its
environment. The minimum level of a
stimulus that is required to activate a
neuron is called the threshold.
The central nervous system (brain and
spinal cord) relays messages, processes
information, and analyzes information.
Interneuron
The brain consists of about 100 billion neurons, which are mainly interneurons.
The largest part of the human brain is the cerebrum (site of learning and
judgment) which controls the activities of the body. The brain stem connects the
brain and spinal cord, and controls blood pressure, heart rate, breathing, and
swallowing. The thalamus and hypothalamus are located between the cerebrum
and the brain stem. The thalamus “receives information from the sense organs” and
the hypothalamus is the “control center for analysis of hunger, thirst, fatigue, anger,
and body temperature”. The spinal cord is the main communications link
between the brain and the rest of the body where certain kinds of information are
processed, such as reflexes (quick, automatic responses to a stimulus).
The peripheral nervous system lies outside of the central nervous system consisted of the
brain and spinal cord. “The sensory division of the peripheral nervous system transmits impulses
from sense organs to the central nervous system. The motor division transmits impulses from the
central nervous system to the muscles of glands”. The body contains millions of sensory receptors,
neurons that react to stimuli from the environment. They react to light, sound, motions, etc and
there are five kinds of sensory receptors: pain receptors, thermoreceptors,
mechanoreceptors, chemoreceptors, and photoreceptors.
We use eyes to sense light, which enters through the cornea. Lens focuses your eyes. Optic nerves
carry impulses to the brain and the brain interprets them as images and provides information
about of the outside environment. The human ear is used to hear and maintain balance in the
nervous system. Sense of smell is an ability to detect chemical, as well as taste. Taste buds are
the sense organs that detect taste.
Circulatory System
Structures  The heart, blood vessels, blood
Function  Brings oxygen, nutrients, and hormones to cells; fights
infection; regulates blood temperature
The heart, located near the center of your
chest, delivers oxygen and its beating
produces the force to move oxygen-rich
blood through the circulatory system. The
septum serves as a wall between the right
part of the heart and the left. It prevents
oxygen-poor blood from mixing with
oxygen-rich blood. The atrium is the
upper chamber of the heart, and the lower
chamber is the ventricle, which pumps
blood out from the heart. There is a total of
two atriums and two ventricles.
Blood enters the heart through the arias and
blood flows into the ventricles and out when
the heart contracts. The one-way flow of the
blood makes the pumping of the heart more
efficient. Valves are extremely important
because it keeps the blood flow flowing one
way.
“The heart serves as two separate pumps”.
On the right side of the heart, the
pulmonary circulation pumps blood
from the heart to the lungs. Carbon dioxide
leaves the blood in the lungs and oxygen is
absorbed. The pathway called systemic
circulation is responsible for the oxygenrich blood that flows into the left side of the
heart that is then pumped to the rest of the
body. “Blood that returns to the right side
of the heart is oxygen-poor because cells
have absorbed much of the oxygen and
loaded the blood with carbon dioxide.”
When blood leaves the left ventricle,
it passes into the aorta, a large blood
vessel. It’s the first of a series of blood
vessels that carry the blood
throughout the body and back to the
heart. The blood moves through
arteries, capillaries, and veins while
traveling through the body. Arteries
are the large vessels that all carry
oxygen-rich blood. Capillaries are
the smallest of the blood vessels.
Their walls are only one cell thick and
most blood cells have to pass through
them in a single file. Capillaries
brings nutrients and oxygen to the
body’s tissues and absorbs carbon
dioxide and other waste products.
Veins are in charge of bring the blood
make to the heart once it has passed
through the capillaries. The blood
flow that takes place in veins usually
defies gravity.
Many circulatory system disorders come
from atherosclerosis, in which plaque builds
up on artery walls. High blood pressure may
also cause medical problems. A heart attack
occurs when the arteries bringing nutrients
to the heart becomes blocked, causing the
heart to die from lack of oxygen. Blood clots
that break free and become lodged in blood
vessels leading to the brain are known as a
stroke. Such disorders are easily prevented
with exercise, weight control, and a good
healthy diet.
The heart produces pressure
when pumping blood, caused by
the force of blood against the
arteries’ walls. Blood pressure
decreases when the heart relaxes,
although the system still remains
under pressure. Without blood
pressure, blood would stop
flowing throughout the body. The
average blood pressure of an
adult is 120/80. Whenever blood
pressure is too high,
neurotransmitters are released to
relax the muscles around blood
vessels. When blood pressure is
too low, the muscles are
contracted. Kidneys also help
regulate blood pressure by
removing more from the blood
when blood pressure is too high.
Skeletal System
Structures  Bones,
cartilage, ligaments,
tendons
Function  Supports
the body and protects
internal organs. Allows
movements and provides
a site for blood cell
formation.
The bones in the skeletal system supports
the human body like a frame supporting a
house. The skull serves as a protective
shell around the brain and the ribs is a
cage that protects the heart and lungs.
Together with muscles, bones allow the
body to move. Bones are also where blood
cells form. The skeletal system is divided
into two sections, the axial skeleton and
the appendicular skeleton. The axial
skeleton consists of the skull, vertebral
column, and the rib cage. The
appendicular system consists of the bones
of the arms and legs, the bones of the
pelvis and shoulder area.
Bones are living tissue, with a
network of living cells and fibers that
are surrounded with calcium salts.
The bone is surrounded with the
periosteum, a layer of connective
tissue. Haversian canals run through
compact bone that contain blood
vessels and nerves. After the compact
bone is the spongy bone. There are
also cavities that contain soft tissues
called bone marrow, which can be
either yellow (fat cells) or red (blood
cells).
Bones begin as cartilage, a type of
connective tissue. Cartilage does not
contain blood vessels like bones, so
they much rely on the blood vessels in
its surrounding tissues. Even though
cartilage is extremely flexible, it can
still support weight with its density.
During ossification, bone forms and
replaces cartilage. It beings seven
months after birth. Long bones grow
plates at either end and lengthen when
cartilage grow at the plates. Eventually,
that cartilage is replaced with bone
tissue, which makes the bone stronger.
Ossification finished around late teens
or early adulthood, and bone growth
stops completely. When a bone is
broken, bone formation will occur also.
Once bone growth stops, cartilage is
only found where flexibility is needed,
like the nose and ears.
Immovable joints as the name suggests
are not movable. The joints are locked or
fused together, like in the places where
bones in the skull meet.
Some joints are slightly movable; the
bones are separated from each other.
Freely movable joints (ball-and-socket,
pivot, saddle) allow movement in many
directions.
Bones that are movable
are covered with cartilage
at the end that protects
the bone as it moves
against other bones.
Those joint capsules
consists of two layers, one
with strips of though
tissue called ligaments.
They hold the bones
together and the bursa
reduces the friction
between the bones of a
joint and even serves as a
shock absorber. When a
tissue is damaged,
symptoms such as
swelling and redness will
occur.
Muscular System
Structures  skeletal muscle, smooth muscle, cardiac muscle
Function  Helps produce movement and circulate blood while moving food
around the digestive system
State Standards
● Students know the cellular and molecular basis of muscle contraction,
including the roles of actin, myosin, Ca+2, and ATP
Skeletal muscles are usually attached to bones and are responsible are voluntary
actions. The muscle, when viewed under a microscope, has light and dark bands called
striations. Most of the skeletal muscles are control by the nervous system. The muscles
consist of muscle fibers, connective tissues, blood vessels, and nerves.
Smooth muscles are found in the stomach, blood vessels, and the large and small
intestines. They help move food through the digestive system, controls blood flow, and
changes the size of your pupil in light. Most smooth muscles can function without
nervous stimulation since they are connected, which allows electric impulses to travel
from one cell to another.
Cardiac muscle is found
only in the heart. Cardiac
muscle is similar to skeletal
muscle, except cardiac
muscles have smaller cells.
It is also similar to smooth
muscle because they are
connected and do not need
the nervous system to
function.
Acetylcholine is a neurotransmitter that is
released by vesicles. They produce an impulse
in the cell membrane of the muscle fiber,
which causes the release of calcium ions in the
fiber. A muscle cell stays contracted until the
release of acetylcholine stops and any
remaining is destroyed by an enzyme.
Tendons join skeletal muscles to bones and
cause them to work like levers. A few muscle
cells are being stimulated while others are
not. That causes some muscles to tighten,
which is called resting muscle tone. It’s
responsible for keeping the back and legs
straights and the head upright.
Muscle fibers are made of smaller
structures called filaments. Thick
filaments contain a protein called
myosin. Thin filaments are made up
mainly of another protein called
actin. They are arranged in units,
called sarcomeres. When a muscle
relaxes, there are no thin filaments
in a sarcomere. “A muscle contracts
when the thin filaments in the
muscle fiber slide over the thick
filaments”. ATP supplies the energy
needed for muscle contraction. ATP
can be produced by either cellular
respiration or fermentation.
Integumentary System
Structures  Skin, hair, nails, sweat and oil glands
Function  Acts as a barriers against infection and injury, helps regulate
body temperature, provides protection against radiation from
sun
State Standards
● Students know the role of the skin in providing
nonspecific defenses against infection.
The skin’s main purpose is for protection. It’s made up of two layers: the epidermis
and the dermis. The epidermis itself has two layers. The outer layer is made of dead
cells, while the inner layer is made of living cells. Older cells that move up being
making keratin, a tough protein. The outer layer of skin is shed or washed away once
every four to five weeks. Melanocytes in the epidermis produce melanin, a dark
brown pigment.
The dermis lies beneath the epidermis and consists of fibers, blood vessels, never
endings, glands, sense organs, muscles, and hair follicles. The blood vessels narrow
or widen, depending on the outside temperature that limit of increase heat loss. The
dermis also contains sweat glands and oil glands. Release of perspiration is
stimulated by nerve impulses.
Hair and nails are made up of mostly keratin. Hair on the
head protects the scalp from light from the sun and provides
insulation from the cold. Hairs in ear canals, nostrils, and
around the eyes are there to prevent dirt and small particles
from entering the body. Hair follicles are structures where
hair is produced. They are pockets of epidermal cells that
extend down into the dermis. Nails serve to protect the tips
of the fingers and toes. They grow from the nail root, where
cells are constantly dividing. The cells of the nail root fill
with keratin and produces a tough nail on the tips of fingers
and toes. Fingernails grow about three millimeters per
month, about four times as fast as toenails.
Respiratory System
Structures  Nose, pharynx, larynx, trachea, bronchi, bronchioles, lungs
Function  Provides oxygen for cellular respiration and removes carbon dioxide
from the body
State Standards
● Students know how the complementary activity of major body
systems provides cells with oxygen and nutrients and removes
toxic waste products such as carbon dioxide.
Respiration is defined as the release of
energy from the breakdown of
molecules in food in the presence of
oxygen. Air moves through the nose to a
tube called the pharynx, a passageway
for both air and food. Then the air
moves from the pharynx into the
trachea (windpipe). The larynx, which
contains two elastic folds of tissue called
vocal cards, enable us to produce
sounds. The air then passes from the
larynx, through the trachea, and into
two passageways in the chest called
bronchi, which leads to the lungs. The
real work of the respiratory system
takes place in alveoli (tiny air sacs) that
are surrounded with thin capillaries.
The lungs are sealed in two sacs, and at
the bottom of the chest cavity is a flat
muscle called the diaphragm. The brain
controls breathing in a center in the
medulla oblongata.
“There are about 350 million alveoli in
a healthy lung, providing an enormous
surface area for gas exchange”. Carbon
dioxide in the bloodstream diffuses in
the opposite direction as oxygen. The
lungs remove about one third of the
oxygen in the air and increases the
carbon dioxide content of that air by a
factor of 100. Hemoglobin, the
oxygen-carrying protein in the blood,
is needed for efficiency. It increases
the oxygen-carrying capacity of the
blood.
When you breath, the diaphragm
contracts and expands. It creates a
partial vacuum inside the chest cavity.
Breathing only works because the
chest cavity is tightly sealed. Chest
wounds are particularly serious
because if the chest is punctured, air
can leak into the chest cavity and
make breathing impossible.
Breathing can not be completely
controlled because the nervous system
does not let you since it’s such an
important function. The brain controls
the breathing in a center in the medulla
oblongata. Cells in the breathing center
keep track of the amount of carbon
dioxide in the blood.
When the level of carbon
dioxide rises, nerve impulses
from the breathing center
makes the diaphragm contract,
which brings air into the lungs.
The strength of the impulse
depends on the level of carbon
dioxide.
While oxygen decreases as
altitude increases, passengers
in a plane do not need oxygen
masks because the cabin is
pressurized. Even though their
bodies are starving for oxygen,
they have no more carbon
dioxide in their blood than
usual.
Smoking reduces life expectancy. It can
cause respiratory diseases such as chronic
bronchitis, emphysema, and lung cancer.
The lungs in the respiratory system can
be damaged by dust and foreign
particles, especially tobacco. Nicotine,
carbon monoxide, and tar are three of
the most dangerous substances to the
body. Nicotine increases heart rate and
blood pressure. Carbon monoxide is a
poisonous gas that blocks the transport
of oxygen in the blood and deprives the
heart of the oxygen they need in order
to function. Tar also causes cancer.
Smoking causes coughing and reduces
air flow to the alveoli.
Excretory System
Structures  Skin, lungs, kidneys
Function  Removes and eliminates metabolic wastes such as
excess salts, carbon dioxide, and urea
State Standards
● Students know the homeostatic role of the kidneys in the
removal of nitrogenous wastes and the role of the liver in
blood detoxification and glucose balance.
● Students know how hormones (including digestive,
reproductive, osmoregulatory) provide internal feedback
mechanisms for homeostasis at the cellular level and in whole
organisms.
Homeostasis not only involves the
outside environment, but it also
requires the body to deal with
internal processes and might
disturb the cellular environment.
Each cell in the body produces
waste, including salts, carbon
dioxide, and urea (a toxic
compound produce when amino
acids are used for energy). The
skin is the organ that excretes
water and salts, and small amounts
of urea as sweat. The lungs excrete
carbon dioxide as well. The
kidneys are another part of the
excretory system. The kidneys are
located on either side of the spinal
cord, with a tube called the ureter
carrying urine to the urinary
bladder. The kidneys collect waste
as urine and the clean filtered
blood is returned to circulation.
The inner part of the kidney is called the
renal medulla, and the outer part is
called the renal cortex. Nephrons are
small, processing units of the kidney. It
filters and purifies blood. There are
three stages of purification: filtration,
reabsorption, and secretion.
Most filtration occurs in the glomerulus.
Fluids flows from the blood into
Bowman’s capsule. The kidneys filter
the blood every forty-five minutes.
During reasborption, material removed
from the blood goes back into the blood.
99% of the water that goes into
Bowman’s capsule is reabsorbed into
the blood.
The material that remains after
reabsorption is urine. It is then
minimized in the loop of Henle.
Kidneys regulate the water content
of the blood, maintain blood pH, and
remove waste products from the
blood. The activity of the blood is
controlled mainly by the
composition of the blood.
Humans can survive with only one
kidney. However, if both are
damaged, they can get a kidney
transplant or a kidney dialysis
machine.
Endocrine System
Structures 
Hypothalamus,
pituitary, thyroid,
parathyroids, adrenals,
pancreas, ovaries
Function  Controls
growth, development,
metabolism, and
reproduction
The endocrine system is made up of
glands that release substances out into
the bloodstream, which broadcast
messages throughout the body.
Hormones are chemicals that travel
through the bloodstream and affect
other cells’ activities. Target cells are
cells that have receptors for a certain
hormone.
Hypothalamus: makes hormones that
control the pituitary gland
Pituitary gland: produces hormones
that control many of the other
endocrine glands
Thymus: releases thymosin, which
stimulates T-cell development
Adrenal glands: deals with stress
Pineal gland: involved with rhythmic
activities
Thyroid: regulates metabolism
Pancreas: produces insulin and
glucagon, which regulate the level of
glucose in the blood
Ovary: produces estrogen and
progesterone and prepares the uterus
for a fertilized egg
The pituitary gland is a small bean shaped
structure located at the base of the skull. It
releases hormones that control many body
functions and controls other endocrine
glands.
Hypothalamus controls secretions of the
pituitary gland. It’s influenced by the levels
of hormones in blood.
The thyroid gland has the most important
role in regulating the body’s metabolism.
Thyroid cells produce thyroxine, which
affects almost all of the cells in the body by
regulating their metabolic rates.
Adrenal glances helps the body prepare for
and deal with stress, and consists of an outer
part called the adrenal cortex and an inner
part called the adrenal medulla. A hormone
called cortisol helps control the rate of
metabolism of carbs, fats, and proteins.
The nervous system regulates the release
of hormones from the adrenal medulla.
The adrenal medulla releases two
hormones: epinephrine and
norepinephrine. It also produces the
“fight-or-flight” response to stress, which
occurs whenever one is excited or scared.
The pancreas releases insulin and
glucagon to keep the glucose in the blood
stable. It causes sugar to be removed
from the blood and stores it as glycogen
or fat. It also makes the liver break down
or release glucose back into the blood.
Digestive System
Structures  Mouth, pharynx, esophagus, stomach, small and large
intestines
Function  Coverts food into smaller molecules, absorbs food
State Standards
● Students know the individual functions and sites of
secretion of digestive enzymes (amylases, proteases,
nucleases, lipases), stomach acid, and bile salts.
The mouth beings the work of the digestive
system. The teeth is used to tear and crush
food, which begins mechanical digestion
(breaking down large pieces of food into
smaller pieces). Saliva helps moisten the
food and make it easier to chew and swallow.
It eases food through the digestive system. It
contains amylase, an enzyme that breaks
chemical bonds between sugar monomers in
starches. After food is swallowed, enzymes
begin to break down food molecules into
smaller molecules. The process is called
chemical digestion.
Once chewed, the clump of food
also called a bolus is pushed down
the throat, passes through the
esophagus, and goes into the
stomach. Food does not travel down
the esophagus because of gravity, it
is pushed down by contractions of
smooth muscle. The cardiac
sphincter, a thick ring of muscle,
prevents food from moving back up
the esophagus.
The combination of pepsin and
hydrochloric acid starts the process
of protein digestion.
Stomach muscles contract to churn
and mix stomach fluids and food,
which produces a mixture called
chyme. After an hour or two, the
chyme is released and flows into the
small intestine.
After the chyme is pushed out, it enters
the duodenum, the first of three parts of
the small intestine. It’s where most of
the chemical digestion takes place.
When it enters the duodenum, it mixes
with enzymes and digestive fluids from
the pancreas, the liver, and the lining of
the duodenum.
Below the stomach is the pancreas,
which produces hormones and enzymes
and sodium bicarbonate, a base that
neutralizes stomach acid so they can be
effective. The liver helps the pancreas
with its job by making bile, a fluid filled
with lipids and salts. It dissolves and
disperses droplets of fat found in fatty
foods. That makes it possible for
enzymes to reach and break down fat
molecules.
The rest of the small intestine consists
of the jejunum and the ileum, which
are about three meters long. When it
enters these two parts of the small
intestine, chemical digestion would
have been almost completed. The
surfaces of the intestine is covered
with villi which makes it easier for
nutrient molecules to be absorbed.
Molecules of fat and fatty acids are
absorbed by lymph vessels called
lacteals.
When food finally leaves the small
intestine, it’s mostly nutrient-free.
Only water, cellulose, and other
indigestible substances are left
behind. The large intestine
removes water from the material
that is left. Water is quickly
moved across the wall of the large
intestine. Bacteria growing on the
material help digestive process.
Some bacteria produces
compound that can be used by the
body, like vitamin K. The waste
material that is left after the water
is removed by passed out and
eliminated from the body. When
water is not removed from the
waste, it creates a condition
known as diarrhea, which results
from bacterial infections and
drinking contaminated water.
Immune Response
Structures  Skin, inflammatory response, interferons
Function  Defends the body against pathogens and guards the body
against infections
State Standards
Students know the role of the skin in providing nonspecific defenses
against infection.
Students know the role of antibodies in the body's response to infection.
Students know how vaccination protects an individual from infectious
diseases.
Students know there are important differences between bacteria and
viruses with respect to their requirements for growth and replication,
the body's primary defenses against bacterial and viral infections, and
effective treatments of these infections.
Students know why an individual with a compromised immune system
(for example, a person with AIDS) may be unable to fight off and survive
infections by microorganisms that are usually benign.
The body’s most important barrier against pathogens is the skin.
However, it can easily be infected with a minor scrape or cut.
Pathogens can enter through the skin and afterwards can multiply,
which causes an infection with redness, swelling, and pain. However,
if bacteria enters the body through the nose or mouth, there are
several ways the body eliminates them. Mucus in the throat and nose
can trap viruses and keep them from entering. The cilia in the lungs
pushes the bacteria away. If they make their way to the stomach,
stomach acid and digestive enzymes will destroy them. Bodily
secretions (mucus, saliva, sweat, and tears) also gets rid of
pathogens.
When pathogens enter the body, they can multiply and release toxins. Once that
occurs, the inflammatory response is activated. The tissue area may become
swollen and painful as white blood cells released from the expanded blood
vessels are engulfing the bacteria. When many pathogens are detected, a fever
may also occur. A fever means that body temperature is elevated, and the heat
can fight off pathogens, as well as increase white blood cell production.
Interferons are also produced by virus infected cells to help slow down infection
and give the immune system time to respond.
If a pathogen still gets past those defenses, an antigen will trigger the immune
response. B cells produce antibodies, which are proteins that destroy pathogens.
Cell-mediated immunity, another
immune response, causes the
pathogen cell to rapidly loss
material and die. It is important
in regards to diseases especially
caused by eukaryotic pathogens.
Killer T cells make it difficult to
transplant organs. The second
person’s organ is recognized as
foreign and attacks it. The
immune system ends up
damaging and destroying the
new organ.
Some people are have a
permanent immunity. If they
survive a disease, it would not
develop a second time. “Once the
body has been exposed to a
pathogen, millions of memory B
and T cells remain capable of
producing specific antibodies to
that pathogen”.
A vaccination can be injected to weaken a
pathogen and produce immunity. The body of
the person getting vaccinated can mount an
immediate immune response against the
pathogen after getting a vaccine.
Reproductive System
Structures  Testes, epididymis, vas deferens, urethra, penis (male),
vagina (female)
Function  Produces reproductive cells, nurtures embryo for females
The primary reproductive organs are
the ovaries in the female and the testes
for male.
The female reproductive system
usually does through the menstrual
cycle, in which an egg is released so
that it can be fertilized. The lining of
the uterus is eliminated. The phase
lasts about four to five days.
In order for a woman to become
pregnant, the sperm must swim
through the cervix and meet with the
released egg. One sperm must enter
the egg for their nuclei to fuse, which
is called fertilization. The egg then
beings to divide and develop further to
produce progesterone.
Works Cited
1.) Google Image Search
2.) ClipArt.com
3.) Biology Textbook
4.) http://mcb.berkeley.edu/courses/mcb135k/outline/repro.html
5.)
http://training.seer.cancer.gov/module_anatomy/unit12_1_repdt_intro.
html
6.) http://www.biotopics.co.uk/human2/reprsy.html
7.)
http://www.cerebromente.org.br/n07/fundamentos/neuron/parts_i.htm
Quoted Work From: Biology Textbook