circulation and immunity science 30 the heart virtual heart

Circulation and Immunity

Science 30

the heart

virtual heart

1.1) Circulatory System

• 4 main roles of the circulatory system:– Transportation (gases, nutrients, wastes).– Regulation (by hormones).– Protection/Defense (immunity and injury).– Distributes body heat.

• Divided into 2 parts:– 1. Cardiovascular system (heart, blood

vessels).– 2. Lymphatic system ( lymph vessels and

nodes).

Ideas about the heart

• Historical ideas:– Galen: Greek physician (2nd century)

• Believed that heart sucked blood from veins, blood flowed like the tides.

– Leonardo da Vinci: 15th century• Complete and realistic sketches of the heart.

– William Harvey: 17th century• Discovered valves in heart and veins, 1 way

movement of blood.• Calculated cardiac output.• Aided by Malpighi’s discovery of capillaries.

A. Cardiac Output

• The amount of blood that flows from each side of the heart per minute.

• Two factors affect this output:1. Stroke volume: quantity of blood pumped

with each beat of the heart (~ 70mL).

2. Heart rate: # of times heart beats/minute.

Cardiac output = stroke volume x HR.

Applications of Cardiac Output

Provides comparison for fitness levels:

- Low heart rate = high stroke volume.

- High heart rate = low stroke volume.

B) The heart• There are 4 chambers in the heart:

– Left and Right atria (receive blood from lungs and body).

– Left and Right ventricles (pump blood to lungs and body).

• Double sided pump: Left and Right sides of the heart are separated by a muscular wall called the septum.

• The sac that encloses the heart = pericardium. Fluid inside is called the pericardial fluid.

Did you know that your heart is the size of your fist?

septum

(a.k.a tricuspid) (a.k.a bicuspid or mitral valve)

chordae tendinae

(a.k.a pulmonary valve) (a.k.a. aortic valve)

Descending aorta

apex

1) The Heart Pumps

• There are 2 pumps that work simultaneously; these are synchronized.

• Left pump = oxygenated blood received.

• Right pump = deoxygenated blood received.

heart

2) Blood Flow- Low oxygen

• Blood low in oxygen (from the body) enters the right atrium and is pumped to the right ventricle.

• The right ventricle pumps deoxygenated blood to the pulmonary arteries and then to the lungs. This blood is then oxygenated.

Blood flow- high oxygen

• Blood high in oxygen (from the lungs) enters pulmonary veins to the left atrium.

• The left atrium pumps blood to the left ventricle, pumped to the aorta, to the arteries and then to the body.

• Arteries divide into arterioles and then into capillaries. All gas, nutrient and waste exchange happens using the capillaries.

Blood flow

• Capillaries branch into venules, becoming veins, then the vena cava and blood enters the right atrium.

• Why is the left ventricle (8-10mm) thicker than the right( 2-3 mm) ?

blood flow

Vena Cava

The largest vein in the body. There are 2 branches of the vena cava:1. Superior Vena Cava (receives blood from the

diaphragm up).

2. Inferior Vena Cava (receives blood from below the diaphragm).

3) Heart Valves

• Valves open and close to let the blood flow through the heart.

• 2 types:– Atrioventricular (AV) valves: between atria

and ventricles.• Open when atria contract, close when ventricles

contract.

– Semilunar: between ventricles and arteries.• Open when ventricles contract, close when atria

contract.

HeartValves

virtual heart

4) Heartbeat• “lub-dub” sound caused by closing of

heart valves.• “lub”= AV valves close (ventricles contract)• “dub”= Semi lunar valves close (atria

contract).• “gurgle” = heart murmur (valves do not

close properly).• Diastole = ventricular relaxation (“dub”).• Systole = Ventricular contraction (“lub”).

heart murmur

Ventricles relaxed

Ventricles Contract

Heart Beat

5) Factors affecting heart rate

• Many factors affect heart rate including:– Fear/Adrenaline.– Temperature change (↑ temp = ↑ HR).– Cardiovascular exercise (running, swimming,

cycling) can decrease heart rate.

• A stronger heart is NOT a larger heart but a more elastic/efficient one!

6) Target Heart rate• Once your body reaches 85% of its max. HR,

lactic acid is made and pain increases.• To calculate target HR, use:

220 - age = target HR

Target Heart Rates

Health goal % of maximum HR

Maintain fitness level 50 -60%

Increase fat burning 60-70%

Increase cardio 70-80%

1.2) Blood Vessels

• 3 types of blood vessels in the body:1. Artery: take blood away from the heart.

1. Thick elastic walls that can stretch.

2. Vein: takes blood to the heart.1. Thin walled with valves for 1 way flow.

3. Capillaries: connect arteries and veins.1. 1 cell thick to allow diffusion into cells.

Arteries and Veins

1)Blood pathway in vessels

• Heart --- arteries ---- arterioles ---- capillaries ---- venules ---- veins ---- vena cava --- heart.

• Arterioles and venules are just smaller versions of arteries and veins.

• Arteries always carry oxygen rich blood (except for pulmonary artery).

• Veins always carry oxygen poor blood (except for pulmonary vein).

• Pressure drops as you get to the capillaries; builds going back to the heart.

bruises

2) Varicose veins• Raised veins due to damaged valves and

stretched walls.

• Blood pools and bunches veins.

• Prolonged standing can cause this.

3) Blood Pressure (BP)

• The force of blood against the artery walls during ventricular contraction (systole) and during atrial contraction ( diastole).

Heart rate = Systole/Diastole= 120/80 (average)

• Diastole is most important because it determines the pressure on arteries when ventricles are relaxed.

• Measured using a sphygmomanometer.

a) Factors that affect BP1. Heart rate (HR): High HR = high BP.

2. Blood vessel size: narrower = high BP.

3. Blood volume: High volume = high BP.

4. Stroke volume: High volume = high BP.

b) Regulation of Blood Pressure (BP)

• Low BP = difficulty transporting blood to tissues (especially head).

• High BP = weaken artery, ruptures blood vessels.

• Baroreceptors (in aorta and carotid arteries) detect changes in BP. Brain receives message and either speeds up (sympathetic) or slows down (parasympathetic) impulses.

c) Hypertension: The Silent Killer

High blood pressure

Caused by increased resistance to blood flow

Blood vessels weaken and may rupture

Body compensates by increasing support

provided by connective tissues

Arteries become hard

During systole, blood pressure increases even more

Further stress and weakening

Causes of Hypertension1. Hereditary

2. Diet

Excess salt

High fat

Silent killer

Symptoms not noticeable until a heart attack or

stroke results

d) Pressure and Blood flow

• As the area that blood flows through increases, the pressure drops (because velocity does too).

• Blood travels the slowest through the capillaries; allows for all nutrients to be picked up!

• Velocity of blood decreases from arteries --- capillaries --- veins.

1.3) Blood

• Average 70kg person has 5L of blood.• 55% of blood is fluid,45% is blood cells.• Plasma = fluid; 90% water and 10%

proteins, vitamins, glucose...• There are 3 groups of proteins in plasma:

1. Albumins: draws water back into capillaries2. Globulins: produces antibodies 3. Fibrinogens: used to clot blood.

A. Red Blood cells (erythrocytes)

• Make up 99% of blood cells.

• Main function = transport oxygen (each rbc can have 4 oxygen molecules).

• Respiratory pigment hemoglobin allows rbc’s to carry oxygen ( 70x more than without hemoglobin)- gives red color!

• Without hemoglobin, life can be maintained for 4.5s; with = 5 minutes.

•biconcave shape to maximize SA for gas exchange.

•Enucleated = no nucleus when mature, allows for more oxygen to be carried. Bone marrow produces rbc’s, can not reproduce without a nucleus.

Bone marrow

• Erythropoiesis = rbc production ( occurs in bone marrow).

• Rbc’s begin as stem cells, divide and shrink- losing nucleus.

• Age of rbc’s is monitored by wbc’s; when rbc is 120 days, it releases hemoglobin and is transported from the cell.

• Iron (globin) is recycled and used in new rbc’s; heme is converted into bile pigments (bilirubin).

B. White blood cells (Leukocytes)• Around 1% of blood.• Responsible for:

housekeeping/ defence.• Have a nucleus.• Made in bone marrow; last

13- 20 days.• Destroy invaders by:

– Phagocytosis: move towards microbe. Enzymes released digest leukocyte and microbe; fragments = pus.

C. Platelets (thrombocytes)• Have no nucleus.

• Produced in bone marrow; last 5-9 days.

• Irregularly shaped, very fragile and responsible for blood-clotting reactions.

blood

D. Blood Clotting• Maintains homeostasis.

• Platelets break when striking a sharp object .

• Fibrinogen breaks up into fibrin threads. These seal the cut: prevent bacteria from entering and create a framework for wbc’s to patch up cut.

• A thrombus is a blood clot that seals the vessel = blocks vessel and prevents gas exchange.

• 2 types:– Cerebral: clot in brain, causes a stroke.– Coronary: clot in artery, causes heart attack.

• Embolus = dislodged blood clot, travels to other organs; life threatening

Blood Clotting Process

Hemophilia

The ability to produce fibrinogen to form a clot is hindered.

Czar Nicholas II son had hemophilia.

1.4) Cardiovascular diseases and disorders

• There are many diseases that affect the heart and blood vessels:– Atherosclerosis ( hardening of arteries due to

plaque).– Coronary Heart disease ( restricted blood flow

to artery(s) of the heart).– Heart Attack ( no blood flow to coronary artery).– Stroke (no blood flow to brain).– Aneurysm ( bulging of artery or vein).– Septal Defect ( septum is not completely

closed- “hole in the heart”).

a) Plaque and cholesterol

• Cholesterol that is deposited on the artery is called plaque.

• LDL fats are “bad” because they build up in the artery (found in saturated fats).

• HDL’s are “good” because they take LDL’s away to the liver (found in fish, etc).

b) Atherosclerosis

c) Problems with the heart

• Angina = chest pains that occur when too little oxygen from the coronary arteries reach the heart.

• Treatment:– Drugs to reduce plaque in arteries.– Coronary bypass surgery (used in severe

cases, grafts a new vein to the heart around the blockage). Heart must be stopped to do this!

Coronary Artery

coronary heart bypass surgery

What are these?

Tapeworms, influenza and HIV.

Syphilis and Elephantitis

1.5) Immune system

• Pathogens (an agent that causes disease) enter the body in many ways:– Protozoans (parasites): example – malaria.– Fungi ( mold, etc): example – athlete’s foot.– Bacteria (rapidly reproduce; stopped by

antibodies): example – tetanus.– Viruses (infect host cell and reproduce DNA):

example- HIV, cold virus.

Viruses

1) Immune response• 2 lines of defence:

– 1st line = primarily physical (skin, mucous).– 2nd line = within the body (antibodies

produced).

• 1st line: Non-specific Immunity– Barriers: skin mucous, cilia.– Phagocytosis: wbc’s engulf the foreign

invader (packman)- releases pus.– Fever: raises body temperature to 40° destroy

bacteria (at 43° all cells die).

Immunity game

a. 1st line : PhysicalMainly physical

Skin – protective

Acidic secretions (pH of 3 – 5)

Respiratory tract (windpipe) – mucus and cilia sweep

foreign material away from lung

Stomach – acids and protein digesting enzymes

destroy microbes

Tears, saliva, mucous secretions – lysozyme

(enzyme) destroys bacterial cell walls

immune system

b) 2nd line: specific Immunity

• Lymphocytes: produced in bone marrow and seed in lymph nodes.

• When a foreign antigen (protein) is present, immune system responds. Foreign cell has different antigen markers than body cells; this initiates a response.

• Complement proteins (in plasma) activated by foreign microbes, attach to invader and help phagocytes.

• 2 Types: T and B cells.

a. B cells• Formed and mature in the bone marrow.• Each b cell produces a single type of

antibody.• Plasma cells can produce up to 2000

antibody molecules/second.• Recognize the foreign antigen and start

dividing into 2 groups:1. Memory cells: provide life-time immunity.2. Plasma cells: produce antibodies that stick

to antigen and disable the invader.

b. T cells• Formed in bone marrow, mature in

thymus gland.• Recognize foreign protein on cell

membrane and divides into 4 types:1. Memory cells: Provide lifetime immunity.2. Helper T cells: secrete cytokines that

activate B cells and Killer T-cells.3. Killer T cells: cytotoxic cells = destroy any

infected body cells; destroy mutated cells. Responsible for rejection of organs (transplantation).

4. Suppressor T cells: shuts down immune response.

B cells

T cellsImmune response

c. Antibodies

• Y shaped proteins that target foreign invaders.

• Specific to the antigen on the invader.

• Each antibody has a complementary shape to it’s antigen; each antibody will only attach to a specific site.

• Larger molecule is then engulfed by macrophage (phagocytotic wbc’s).

• Invaders can’t access the cells and can’t pass through cell membrane- await death.

• Body contains 100 000 different antibodiescell wars

Immune response

• Bacteria enters----macrophage attacks ----helper T cells release lymphokine ---- B cells activated--- antibodies released --- released into circulatory system.

• B cells also activate killer T cells ---- puncture cell membrane or attack cell membrane of infected cell (by virus)--- kill cells.

• Once foreign cells destroyed suppressor T-cell stops immune response---- body maintains antibodies to kill antigen--- phagocytes clean debris and tissues repair.

2) Vaccinations

• Memory T cells can provide immunity to viruses; you never get sick from the same 1 twice.

• Vaccinations are a dead/weakened strain of the virus injected, antibodies are produced and immunity is created.

Immunization

Polio virus

Smallpox virusRabies Virus

3) Autoimmune Disorders

Immune system mistakenly attacks body cells

Renegade lymphocytes treat body’s cells as foreign and

attack cells (Usually held in check)

Mutated T and B cells

Theory: suppressors secrete a substance that tells

macrophage to engulf renegade cells

Examples: Lupus, MS, Type 1 diabetes, AIDS.

AIDS

CausesWeakening of suppressor T cells:

Drugs or serious infections

Decline with age

Some people are born with defective

suppressor T cells

Treatment

Immune suppressing drugs

Reduce intensity of renegade cells

allergic reaction