Vertebrate Physiology - Ch 9

Fick’s Law

Rate at which molecule moves through material proportional to concentration gradient and inversely proportional to thickness of membrane

Components of the circulatory system:

1) Fluid to carry molecules and cells

2) Pump to move fluids

3) Vessels to carry fluid

Open circulatory system

Hemolymph suffuses entire body; could be directly open to environment

Closed circulatory system

Blood contained within vessels

What is the primary structure that distinguishes closed circulatory systems from open circulatory systems?

Capillaries

What are circulatory fluids divided into?

Plasma and formed elements (RBC, WBC, Platelets)

Hematocrit

Percentage of red blood cells in blood

What do erythrocytes do?

Transport oxygen from lungs or gills to tissues

Describe the shape of a red blood cell and the benefits of this shape

Biconcave disc without organelles; flexibility of shape allows it to squeeze through tight spaces

What does the spleen do?

Removes old rbcs and stores healthy rbcs, platelets, and lymphocytes

What are hemopoeitic tissues and what do they do?

Red bone marrow; generate new erythrocytes (erythropoiesis)

What regulates erythropoiesis?

Erythropoietin (hormone) secreted by kidneys

How is erythropoiesis controlled?

Negative feedback loop

Describe the negative feedback loop of erythropoeisis

1) Kidneys detect low oxygen carrying capacity in blood

2) Lack of oxygen in kidneys activates erythropoeitin secretion

3) Erythropoietin stimulates erythropoeiss

4) New rbcs increase oxygen carrying capacity in blood

5) Increased oxygen relieves initial stimulus

What do thrombocytes do?

Responsible for blood clotting

Where do thrombocytes come from?

Shed from megakaryocytes (bone marrow cells) in bone marrow

When types of cells can an undifferentiated pluripotent stem cell become?

Myeloid stem cell or lymphoid stem cell

What do lympoid stem cells eventually become?

Lymphocytes → type of white blood cell

What types of cells can myeloid stem cells become?

1) Platelets

2) Granulocytes → immune cells

3) Erythrocytes

4) Monocytes → type of white blood cell

What type of tissue is blood considered to be?

Connective tissue

What is the role of blood?

1) Transport oxygen

2) Clotting/injury response

3) Protect bodily functions

How many heart chambers do fish have?

2 → atrium and ventricle

What do the atrium and ventricle do in fish?

Atrium collects returning blood

Ventricle pumps blood to body

What are the three auxiliary chambers in fish?

1) Sinous venosus

2) Conus arteriosus

3) Bulbous arteriosus

What does the sinus venosus do?

Collects blood from veins before entering atrium

What do the conus arteriosus and bulbus arteriosus do?

Suppress pulsatile pressure output of ventricle

How does blood move through the heart of a cartilaginous fish?

1) Atrium receives blood from circulation

2) Blood enters ventricle

3) Ventricle and heart contract → propel blood out

How would you distinguish between the ventricle and atrium?

Ventricle has thick walls to pump blood while atriumhas thin walls to push blood between chambers

How many chambers do mammalian and avian hearts have?

Four → 2 ventricles and 2 atria

What does the right half of the mammalian heart do?

Pumps oxygen-depleted blood into pulmonary circulation

What does the left half of the mammalian heart do?

Pumps oxygen rich blood into systemic circulation

Pulmonary circulation

Circuit through lungs where blood is oxygenated

Systemic circulation

Circuit throughout body to provide oxygen

How much blood does each side of the heart pump respectively?

Both sides of hear pump the same amount of blood

What do heart valves do?

Ensure unidirectional flow of blood

What do the atrioventricular valves do?

Allow blood to flow from atrium into ventricle; prevent backflow during ventricular contraction

What do the semilunar (aortic and pulmonary) valves do?

Allow blood to flow from ventricles to arteries; prevent backflow during ventricular relaxation

What do vertebrate heart walls consist of?

Muscular myocardium between endocardium and epicardium

What does myocardium consist of?

Interlacing bundles of cardiac muscle fibers arrange spirally

What do cardiac muscle fibers consist of?

Cardiac muscle cells (branching) joined by intercalated discs

How do intercalated discs connect cardiac muscle fibers mechanically? Electrically?

Mechanically → desmosomes

Electrically → gap junctions

Functional syncytium

Group of cells that function as single unit

What depolarizes the membrane potential of pacemaker cells?

Increased inward Na+ and Ca2+ current

Decreased outward K+ current

Describe the conductive pathway

1) Sinoatrial node → atrial excitation

2) Atrioventricular node/bundle of His/Purkinje fibers → ventricular excitation

Does the SA node or the AV node have a faster rate of autorhythmic depolarization?

SA node

Describe the changing action potential in pacemaker cells

1) Rising → Na+ channels open (slight depolarization)

2) Plateau phase → Ca2+ channels open (rapid depolarization)

3) Falling → K+ channels open, Ca2+ channels shut (rapid repolarization)

Can cardiac muscle cells experience the summation of action potentials?

No; have a long refractory period

Systole

Period of contraction and emptying

Diastole

Period of relaxation and filling

Which side of the heart experiences greater pressure?

Left side has more pressure

What happens during early ventricular diastole?

AV valves open, semilunar valves closed

Blood: veins → atria → ventricle

What happens during late ventricular diastole?

SA node fires, atria depolarize (P), atria contract

What happens at the end of ventricular diastole?

Ventricles are full

What happends during onset of ventricular systole?

Impulse travels through AV node and bundle of His, ventricles depolarize (QRS), ventricles contract, AV valves close

What happens during isovolumetric ventricular contraction?

Ventricular pressure rises

What happens during ventricular ejection?

Semilunar valves open when ventricular pressure exceeds arterial pressure, blood forced into arteries

What happens during the end of ventricular systole?

Ventricles empty

What happens during onset of ventricular diastole?

Ventricles repolarize (T), semilunar valves close

What happens during isovolumetric ventricular relaxation?

Ventricular pressure falls

What happens during ventricular filling?

AV valves open when ventricular pressure falls below arterial pressure, ventricles begin to fill with blood

Cardiac output

Volume of blood pumped per minute by heart to body

What increases cardiac output?

Warmer body temp, age during development, increased activity

What is heart rate influenced by?

Antagonistic regulation by autonomic nervous system

How is heart rate slowed by the parasympathetic nervous system?

ACh sent from vagus nerve to SA and AV node

Binds to muscanaric receptors

How is heart rate increased by the sympathetic nervous system?

NE and EP from adrenal medulla bind to beta 1-adrenergic receptors

Intrinsic control of stroke volume

Direct correlation between EDV and SV

Frank-Starling Law of Heart

Stroke volume directly correlated to end diastolic volume

Extrinsic control of heart

Sympathetic stimulation

What is the main driving force of blood flow through vessels?

Pressure

What is pressure in the circulatory system generated by?

Contraction of heart and gravity

What is the average driving pressure of humans?

100 mmHg

What is the average driving pressure of fish?

40 mmHg

Describe the circulatory system of fish

Two-chambered heart, gills, parallel system

Describe the circulatory system of amphibians

Double-circuit, three chambered (two atria, one ventricle)

*oxygenated and deoxygenated blood mix in ventricle

Describe the circulatory system of reptiles

Three-chambered heart, ventricle divided into subchambers

What are the two subchambers of a reptiles ventricle?

Cavum arteriosum and cavum pulmonale

Describe the circulatory system of crocodiles

Four-chambered heart, two aorta connected by Foramen of Panizza

Foramen of Pinazza

Coglike valves between right ventricle and pulmonary arteries that controls diversion of blood flow

Describe the circulatory system of birds and mammals

Four-chambered, complete separation of pulmonar and systemic flow

What to arteries do?

Provide rapid passage of blood from heart to tissues and serve as pressure reservoir

What drives continued blood flow during diastole?

Elastic recoil

What do arterioles do?

Provide resistance to blood flow

What do arterioles consist of?

Thick layers of smooth muscle innervated by sympathetic nerve fibers

What does vasoconstriction lead to?

Decreased radius → increased resistance

What does vasodilation lead to?

Increased radius → decreased resistance

What intrinsic controls affect blood flow?

Local metabolic changes, histamine, temperature → vasodilation

What extrinsic controls affect blood flow?

Neurons and hormones

What causes vasoconstriction in most arterioles?

Activation of alpha-1-adrenergic receptros by NE or epinephrine

What causes vasodilation in arterioles of skeletal and heart muscles?

Activation of beta-2-adrenergic receptors by epinephrine

What do capillaries do?

Maximize diffusion rates for exchange of materials

How do capillaries maximize diffusion rates?

Thin walls, narrow, branching, high permeability

What do veins do?

Serve as blood reservoir annd return blood to heart

How much of the total blood volume do mammalian veins contain?

More than 60%

What are the goals of cardiovascular regulatioN?

Proper gas/heat transport, maintain arterial blood pressure

How high must arterial blood pressure be?

High enough to overcome resistance factors and for ultrafiltration in kidneys

What monitors blood pressure?

Baroreceptors in heart → increased signals to brain → sympathetic or parasympathetic responses to increase/decrease pressure