The Systems of the Body
Neuron
• Cell body – source of life of the cell
• Dendrites – branches on the cell bodies that act
as receivers of messages from adjacent neurons.
• Axon – projection through which messages travel.
• Synaptic knobs: Tips of branches at end of axon.
Sends messages to adjacent neurons.
• Synapse: Fluid filled gap between neurons.
The Nervous System
Nervous
System
Central nervoussystem
Peripheral nervoussystem
(carriesvoluntarynerveimpulsesto
musclesandskin; carriesinvoluntary
impulsestomusclesandglands)
Brain
Spinal cord
Somaticnervoussystem
Autonomicnervoussystem
(controlsvoluntary
movement)
(controlsorgansthat
operateinvoluntarily)
Sympatheticnervoussystem Parasympatheticnervous
(mobilizesthebody
foraction)
system
(maintainsand
restoresequilibrium)
Three sections of the brain
Hindbrain
•Medulla
•Pons
•cerebellum
Midbrain
•Pathway connecting
hindbrain and
Forebrain.
Forebrain
•Diencephalon
•Telecephalon
Diencephalon
Telecephalon
•Thalamus
•Cerebrum
•Hypothalamus •Limbic system
Four lobes of the cerebral cortex
Frontal
•Motor activity
•Higher level
intelligence
•Planning
•Problem solving
•Emotions
•Self-awareness
Parietal
•Bodily sensations,
e.g., pain, heat
•Body movement
Temporal
•Hearing
•Vision
•Smell
•Memory
Occipital
•Primary visual
area of the brain
Diencephalon
Hypothalamus
Thalamus
•Command for the
•Chief relay centre for
control of autonomic
directing sensory messages functions such as heart
Helps regulate awareness
rate, blood pressure,
•Relays commands going
hunger, thirst.
to the skeletal muscles
•Role in emotions and
from the motor cortex.
motivation (e.g., thoughts
about fear get translated into
arousal through hypothalamus.)
Three sections of the brain
Hindbrain
•Medulla
•Pons
•cerebellum
Midbrain
•Pathway connecting
hindbrain and
Forebrain.
Forebrain
•Diencephalon
•Telecephalon
Diencephalon
Telecephalon
•Thalamus
•Cerebrum
•Hypothalamus •Limbic system
Cerebellum
• Maintains body balance and coordination of
movement
– Damage to the cerebellum results motor disorders
such as ataxia.
– Ataxia is a condition where our movements
become jerky and uncoordinated.
Hindbrain continued
• Consists of:
– Pons – involved in eye movement, facial
expressions and eye movement
– Medulla – controls breathing, heart rate, blood
pressure
Midbrain
• Midbrain – top of brain stem, receives visual
and auditory information, also important in
muscle movement.
• Reticular formation – controls states of sleep,
arousal, and attention.
Spinal cord
• Transmits messages from the brain to the
other areas of the body.
– Efferent – away from the brain out to the body
• Produces muscle action
– Afferent – from the periphery to the brain
• Relays information from the sensory organs
Peripheral Nervous System
• Autonomic nervous system
• Somatic nervous system
Somatic nervous system
• Involved in both sensory and motor functions,
serving mainly the skin and skeletal muscles.
• Efferent impulses: carry messages from
the brain to the skeletal muscles
• Afferent impulses: carry messages from
the sensory organs to the brain
Autonomic nervous system
• Controls what is generally involuntary,
automatic activity
• Consists of the sympathetic and
parasympathetic nervous systems.
Sympathetic nervous system
• Fight of flight response
– Sends out messages (neurotransmitters) to the
body preparing the body for fight or flight.
• Also prepares the body for strenuous activity
Fight or Flight Response
•
•
•
•
•
Increase in
Epinephrine &
norepinephrine
Cortisol
Heart rate & blood pressure
Levels & mobilization of
free fatty acids, cholesterol
& triglycerides
Platelet adhesiveness &
aggregation
Decrease in
• Blood flow to the kidneys,
skin and gut
Parasympathetic nervous system
• Restores equilibrium in the body
• Decreases arousal, slows breathing and heart
rate, lowers heart rate and blood pressure,
etc.
Neurotransmitters
• Electrochemical messengers:
– Catecholamines, consisting of epinephrine and
norepinephrine
– Dopamine
– Acetycholine
– Serotonin
The Endocrine System
• Set of glands
• Works in close association with the autonomic
nervous system
• Communicates via chemical substances like
hormones
• Examples are adrenaline, cortisol,
somatotropic hormone, gonadotropic
hormone, etc.
Endocrine and autonomic systems
work together
• Connection between the hypothalamus in the
brain and the pituitary gland (“master gland”)
• The pituitary gland sends out hormones that
communicates with other glands to send out
hormones
Adrenal gland
• Located on top of each kidney
• Comprised of the adrenal medulla and the
adrenal cortex.
– Adrenal medulla secretes adrenaline
(epinephrine) and noradrenaline (norepinephrine)
– Adrenal cortex secretes steroids (including
mineralocorticoids and glucocorticoids,
androgens, and estrogens)
Thyroid gland
• Located in the neck
• Produces hormone (thyroxin) that regulates activity
level and growth.
• Hypothyroidism: Insufficient thyroid hormones (leads
to low activity levels and weight gain)
• Hyperthyroidism: Over-secretion of thyroid
hormones (leads to hyperactivity and weight loss,
insomnia, tremors, etc.)
Pancreas
• Located below the stomach
• Regulates level of blood sugar by producing
insulin which absorbs blood sugar.
• Important gland in diabetes mellitus
Digestive system
• Enzymes: break-downs food substances
• Commands from the brain stem activates the
production of saliva. Saliva contains enzymes
that breakdown starches.
• Esophagus pushes food to the stomach using
peristalsis.
Digestive system - continued
• Stomach uses gastric juices and churning to further
breakdown food.
• Peristalsis moves food from the stomach to the
duodenum (small intestine)
• Acid food mixture becomes chemically alkaline from
secretions of the pancreas, gallbladder, and small
intestine wall.
Digestive system - continued
• Additional enzymes and bile continue the food
breakdown.
• Absorption occurs.
• Large intestine (mainly colon) continues
absorption of water and passes the remaining
waste to the rectum for excretion.
Disorders of the Digestive System
• Peptic ulcers – open sores in the stomach or
duodenum. Causes by excessive gastric juices and
bacterial infection.
• Hepatitis – liver becomes inflamed.
• Cirrhosis – liver cells die and are replaced by scar
tissue. Caused by hepatitis and heavy alcohol
consumption.
Disorders of these Systems
Diabetes
• Type I – insulin-dependent diabetes where person
has to take exogenous insulin to make up for the lack
of insulin produced by the pancreas.
• Type II – non-insulin dependent diabetes where body
is not sufficiently responsive to insulin
• Leading cause of blindness in adults and 50% of
dialysis patients (kidney failure) have diabetes.
Respiratory System
• Air enters the body through the nose and
mouth.
• It travels past the larynx and down the trachea
and bronchial tubes into the lung.
• Bronchial tubes divide into small branches
called bronchioles, and then tiny sacs call
alveoli.
Disorders of the Respiratory System
• Asphyxia – too little oxygen and too much carbon
dioxide (can occur in small breathing space).
• Anoxia – shortage of oxygen (occurs at very high
altitudes). Person looses judgment, pass into
comma.
• Hyperventilation – deep rapid breaths that reduce
the amount of carbon dioxide.
Disorders of the Respiratory System continued
• Hay fever – seasonal allergic reactions. Body
produces histamines in response to the
irritants entering the lungs.
• Asthma – more severe allergic reaction.
Muscles surrounding the air tubes constrict.
• Viral infections (e.g., flu)
• Bacterial infections (e.g., strep throat)
Cardiovascular System
• Transport system of the body.
• Consists of the heart, blood, and blood vessels
• Blood vessels consist of:
– Arteries that carry oxygenated (red) blood from
the heart to the periphery and brain.
– Veins carries de-oxygenated (blue) blood back to
the heart and lung
Heart
• Fist-sized muscle that circulates blood to and
from the lungs to the body.
• Four chambers – atrium (right & left) and
ventricles (right & left)
• Left side pumps oxygenated blood from lungs
out to periphery and brain.
• Right side takes deoxygenated blood in to the
lungs.
Blood pressure (BP)
• Pressure of blood in the arteries.
• As the heart contracts and pushed blood into
the arteries (systolic cardiac cycle) the BP
rises.
• As the heart rests between beats and no
blood is pumped (diastolic cardiac cycle) BP is
at its lowest.
Dynamics of Blood Pressure (BP)
• Cardiac output – force of contraction of the
heart muscle
• Heart rate – speed of contraction
• Blood volume – amount of blood in the
system
• Peripheral resistance – ease with which blood
can pass through the arteries (as resistance
increases, BP increases)
Dynamics of Blood Pressure (BP)
• Elasticity – is the give and take in the arterial
walls. As elasticity decreases BP increases.
• Viscosity – thickness of the blood. BP
increases when the thickness of the blood
increases.
Blood pressure (BP) is Dynamic
• When arteries dilate (e.g., in heat) diastolic BP
decreases.
• BP increases when heart rate or cardiac
output increases in response to activity,
change in posture, while talking, when under
stress, temperature, etc.
• BP follows a circadian (daily) rhythm such that
it is lowest when in deep sleep.
Hypertension
• Permanently high blood pressure
– Systolic blood pressure >= 140 mmHg
– Diastolic blood pressure >= 90 mmHg
• Essential (primary) – no known physical cause
(90-95% of cases are of this type)
• Secondary hypertension – due to specific
cause, e.g., adrenal tumor.
Risk Factors for Essential Hypertension
•
•
•
•
Lack of exercise
Body weight
Salt consumption
Stress
• Age
• Gender
• Ethnicity (blacks at
higher risk)
• Genetics
Blood
• Two components
– Formed elements
– Plasma
• Formed elements consist of three elements:
– Red blood cells
– Leukocytes (white blood cells)
– Platelets
Formed Blood –
Red Blood Cells
• Most abundant cells
• Formed in bone marrow
• Contains hemoglobin – a protein that attaches
to oxygen and transports it to the cells and
tissue
• Anemia is when level of red blood cells are
below normal
Leukocytes (white blood cells)
• Serve a protective function (e.g., destroys
bacteria).
• Produced in bone marrow and various organs
of the body.
• Leukemia is when there is an excessive
production of white blood cells that crowd out
plasma and red blood cells.
Platelets
• Granular fragments that can clump together
to prevent blood loss at site of cuts.
• Produced by bone marrow
• Hemophilia is when platelets don’t function
properly to produce clotting and so if the
person receives a cut could bleed excessively.
Plasma
• 55% of the blood is plasma
• Composed of 90% water and 10% plasma
protein and other organic and inorganic
substances.
• Other substances include hormones, enzymes,
waste products, vitamins, sugars, fatty
material etc.
Plasma - continued
• An important fatty substance is lipids.
• Consist of:
– Cholesterol
– Low and high-density lipoprotein
– Triglycerides
• High lipid content in the plasma can lead to plaque
build-up on arteries and lipid deposits in arterial wall,
causing hardening of the arteries.
Disorders of the Cardiovascular System –
Hardening of Arteries
• Atherosclerosis – deposits of cholesterol and
other substances on the arterial wall, forming
plaques that can block the artery.
• Ateriosclerosis – calcium and other substances
get deposited on the arterial wall leading to
hardening of the plaques.
Risk Factors for Atherosclerosis
•
•
•
•
•
•
•
•
Hypertension
High fat intake leading to hyperlipidemia
Smoking
Stress
Diabetes,
Lack of exercise
Genetics
Gender
Consequences of Atherosclerosis
• Angina pectoris – insufficient oxygen supply to
the heart for its need and removal of waste
products resulting in chest pain.
• Myocardial infarction (heart attack) – when there
is a blockage of blood supply to an area of the
heart cutting off oxygen supply to the tissue in
the area and resulting in tissue death
Immune System
The Immune System
• Antigens are any substance (e.g., bacterial, viral,
fungi) that can trigger an immune response.
• Bacterial – microorganisms in the environment.
Grow rapidly and compete with our cells for
nutrients.
• Fungi – organisms like mould and yeast. Also,
absorbs nutrients.
• Viruses – proteins and nucleic acid. They take over
the cell and generate their own genetic instructions.
Immune System
• Immune system recognizes itself and foreign
material
• Transplant success can by increased by:
– Using close genetic tissue match.
– Using medications that inhibit the immune
system’s attack on the foreign material.
Immune System
• Allergies are immune response to (normally)
harmless substances.
• Allergins are substances that trigger an allergic
response (e.g., pollen, cat dander)
Organs of the Immune System
• Lymphatic and lymphoid organs
– Deploys lymphocytes
• Lymphocytes
– White blood cell that provides main defense
against foreign material
– Produced by bone marrow
Organs of the Immune System
• Lymphocytes
– Form of white blood cells that provide main
defense against foreign matter
• Lymphocytes originate from bone marrow
Organs of the Immune System
• Lymph Nodes
– Bean-shaped spongy tissue
– Largest are in the neck, arm-pit, abdomen, and groan
– Filters to capture antigens (foreign material) and has
compartments for lymphocytes.
• Lymph vessels
– Connects to lymph nodes and carries fluid called lymph
into the blood stream
Organs of the Immune System
• Spleen
– Upper left side of the abdomen
– Filters antigens that the lymph vessels put into
the bloodstream
– Home base for white blood cells
– Removes worn out red blood cells
Soldiers of the Immune System
• Phagocytes
– Engulf and ingest antigens
• Two types:
– Macrophages – attach to tissue and stay there
– Monocytes – circulate in the blood
• Nonspecific immune processes
Immune System
• Antibodies – proteins produced in the body in
response to antigens. They combine
chemically with antigens to overcome their
toxic effects.
• B lymphocytes – secrete antibodies that
protect body against bacterial infection and
viral infections.
Why Can’t We Fight Cancer
• Some cancer cells release substances that
suppress the immune response.
• Some antigens may be difficult for the
immune system to recognize.
Less Than Optimal Defenses
• Immune function changes during the lifespan,
increasing in childhood and decreasing in old age.
• Unhealthy lifestyles impair immune functioning
– Insufficient vitamin A or E decrease production of
lymphocytes and antibodies
– Vitamin C in important in effectiveness of phagocytes
– High fat and cholesterol intake impair immune
functioning
– Poor sleep impairs immune functioning
Diseases of the Immune System
• Autoimmunity Disorders
– Immune response attacks its own tissue
•
•
•
•
Arthritis
Rheumatic fever
Multiple sclerosis
AIDS
Stress and the Immune System
• Stress appears to suppress the immune response.
• Killer T-cells are lower during periods of high
stress.
• Adrenaline and cortisol that are released during
stress appear to increase suppressor T-cells,
decrease helper T-cells, and decrease functioning
of phagocytes and lymphocytes.
• Chemicals released by our nerves suppress
immune functioning in nearby cells.