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

Bra in S pina l cord

C entra l ne rvous sys tem(c a rries vo lu n ta ry n e rve im p u ls es to

m u s c les an d s k in ; c a rries in vo lu n ta ryim p u ls es to m u sc les an d g lan d s )

S om atic ne rvous sys tem(c on tro ls vo lu n ta ry

m ovem en t)

S ym pathe tic ne rvous sys tem(m ob ilizes th e b od y

fo r ac tion )

Parasym pathe tic ne rvouss ys tem

(m a in ta in s an dres to res eq u ilib riu m )

A utonom ic nervous sys tem(c on tro ls o rg an s th a top era te in vo lu n ta rily)

Periphera l ne rvous sys tem

NervousS ys tem

Three sections of the brain

Hindbrain•Medulla•Pons•cerebellum

Midbrain•Pathway connectinghindbrain andForebrain.

Forebrain•Diencephalon•Telecephalon

Diencephalon•Thalamus•Hypothalamus

Telecephalon•Cerebrum•Limbic system

Telencephalon

Upper and largest portion of the brain Involved in higher order intelligence,

memory, and personality Composed of two hemispheres

Left hemisphere – language processes, etc.

Right hemisphere – visual imagery, emotions, etc.

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

Reticular Activating System and Limbic System Reticular activating system runs

from the medulla through the midbrain into the hypothalamus. Responsibility for activation of all

areas of the brain and if damaged – coma ensues

Limbic system controls emotion It has three sub-circuits

Limbic System - emotions

Amygdala and hippocampus – essential for self-preservation, includes aggression.

Cingulate gyrus, the septum, and areas of the hypothalamus – pleasure and sexual excitement.

Areas of the thalamus and hypothalamus – important to socially relevant behaviour

Diencephalon

Thalamus•Chief relay centre for directing sensory messagesHelps regulate awareness•Relays commands going to the skeletal muscles from the motor cortex.

Hypothalamus•Command for the control of autonomic functions such as heart rate, blood pressure, hunger, thirst.•Role in emotions and motivation (e.g., thoughts about fear get translated into arousal through hypothalamus.)

Three sections of the brain

Hindbrain•Medulla•Pons•cerebellum

Midbrain•Pathway connectinghindbrain andForebrain.

Forebrain•Diencephalon•Telecephalon

Diencephalon•Thalamus•Hypothalamus

Telecephalon•Cerebrum•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 ResponseIncrease 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 SystemsDiabetes 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

Stress and AtherosclerosisCoronary Artery Plaque in Monkeys

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Stress and AtherosclerosisCoronary Artery Plaque in Monkeys

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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

Specific Immune Processes Cell-mediated immunity Killer t-cells (CD8) – destroy foreign

tissue, cancerous cells, cells invaded by antigens

Memory t-cells – remember previous antigen in order to defend against subsequent invasions.

Specific Immune Processes

Delayed hypersensitivity t-cells – involved in delayed immune reactions. Produce lymphokines that stimulate other t-cells to grow, reproduce and attack.

Helper t-cells (CD4 cells) – get information of invasions and report to spleen and lymph nodes to stimulate lymphocytes for attack.

Suppressor t-cells – slow down or stop 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.

Immune Response

Foreignmaterial

CoughSneeze

Phagocytesengulf it

Th

cells

KillerTc cellsB cells

Gamma-interferon

Interlukin-1

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.

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