chapter 21 physiology, muscle blood flow and cardiac output during exercise; coronary circulation and ischemic heart disease Flashcards Preview

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Flashcards in chapter 21 physiology, muscle blood flow and cardiac output during exercise; coronary circulation and ischemic heart disease Deck (45):

how fast does blood flow through skeletal muscle during rest?

3-4 ml/min/100g of muscle


besides adenosine acting as a vasodilator during exersize, what else causes vasodilation?

potassium ions, adenosine triphosphate, lactic acid, carbon dioxide


what 3 main affects occur during excersize that are essential for circulatory system to supply alot of blood to the muscles?

1.. mass discharge of sympathetic nervous sustem throughout the body
2. increase in arterial pressure
3. increase in cardiac output


what 3 things cause increase in arterial pressure during excersize?

1. vasoconstriction of arterioles and small arteries in most tissue (except active muscles)
2. increased pumping by heart
3. increase in mean systemic filling pressure caused by venous contraction


what happens with the vessels inside the muscles as they contract?

they vasodilate, everywhere else vasoconstricion occurs


why is the arterial pressure increase during exercise so important?

it allows up to 20 times more blood flow to the muscles


what do almost all elderly people have some sort of?...

coronary artery disease


what vessel supplies the heart with nutrients?

coronary arteries


left coronary artery suppies what part of the heart?

anterior and leftlateral portions of the left ventricle


right coronary artery supplies what?

most of the right ventricle, as well as the posterior part of the left ventricle in 80-90 percent of people


where is the Coronary sinus

where the coronary arteries empty into the right atrium


thebesian veins do what?

a small amount of venous blood also flows back into the heart throuogh these veins


the resting coronary blood flow is what percent of the total cardiac output?

4-5 %


describe the capillary blood flow through the left ventricle during systole

the blood flow falls during systole while the blood flow in the capillaries through out the body rises


how is the coronary system regulated?

by the nutritional need of the cardiac muscle. So when the heart needs to pump harder, the coronary vessels dialte


describe adenosine's role in vasodilation in regards to ATP

muscles use ATP which turns into Adenosine monophosphate which is degraded into adenosine which causes vasodilation


name some other vasodilators

adenosine phoshpate compounds, potassium ions, hydrogen ions, carbon dioxide, prostaglandins, nitric oxide


what does sympathetic stimulation release?

noreepinephrine and epinephrine


what does the parasympathetic stimulation release?



what does epinephrine and noreepinephrine do in the coronary vessels?

they actually have dilator and constrictor receptors. The constrictor receptors are called alpha receptors and the dilator receptors are called beta receptors


what happens if the alpha receptors are over stimulated?

Angina can occur and ischemia can occur


while at rest, from which molecule does the heart get its nutrients?

fatty acids


what causes anginic pain in anaerobic conditions?

with lack of O2 the heart tissue performs anaerobic respiration which produces lactic acid. This is whats though to cause angina during ischemia.


what is the most frequent cause of diminished coronary flood flow and where does it most oftenly occur?

atherosclerosis, most frequently in the first few cm of major coronary arteries


name one way to have acute coronary occlusion

thrombus development. ( a flowing thrombus is called an embolus)


name another way to have acute coronary occlusion

mucsular spasm of coronary artery which can develope a secondary thrombus


describe the collateral development of vessels and the coronary artery

Collateral vessels develop if the coronary constriction is slow over a period of years. They grow to compensate for atherosclerosis. Even the collateral vessels can develope atherosclerosis and the heart becomes weak and has a low output. ( this is one of the most common causes of cardiac failure)


what is myocardial infarction?

heart muscle has zero flow


requirements for cardiac muscle to stay alive

1.3 ml of oxygen per 100 g


describe what subendocardial muslce is and why its important in regards to infarction.

subendocardial muslce has difficulty obtaining adequate blood flow because the blood vessels in the subendocardium are intensely compressed by systolic contraction of the heart. Subendocardium is usually the first heart tissue to become damaged during an infaction


common causes of death after acute coronary occlusion

decreaed cardiac output, dammin of blood in pulmonary blood vessels and then death resulting from pulmonary edema, fibrillation of the heart, rupture of heart


what is systolic stretch

when normal portions of ventricular muscle contract, the ischemic portion of the muscle is forced outward which dissipates much of the pumping force


whats happening to the heart during coronary shock/cardiac shock

heat becomes incapable of contracting with sufficient force to pump enough blood into the peripheral arterial tree


what is low cardiac output failure

more than 40% of left ventricle is infacted


name 1 factor that leads the heart to fibrillate in regards to blood supply

loss of blood supply to the cardiac muscle causes rapid depletion of potassium from ischemic musculature. This increases the potassium level of the extracellular fluid which causes fibrillation


name 1 factor that leads the heart to fibrillate in regards to polarization

ischemic musculature often cannot completely replarize its membranes after a heartbeat


name 1 factor that leads the heart to fibrillate in regards to sympathetic stimulation

powerful sympathetic reflexes often develop after massive infarction


name 1 factor that leads the heart to fibrillate in regards to the conduction pathway

cardiac muscled that is infected dilates and causes the condution pathway to increase which predisposes the deveopment of circus movements and fibrillation


cardiac tamponade

compression of the heart from the outside of by blood collecting in the pericardial cavity


replacement of dead muscle by scar tissue

fibrous tissue develops among the dead fibers because ischemia stimulates fibroblasts. Then the normal areas of the heart gradually hypertrophy to try and compensate for the tissue loss


coronary steal syndrome

with an excessively active heart the vessels dilate which allows most of the blood in the coronary vessels to flow through the normal muscle tissue. This leaves little blood in the coronary vessels to flow through the small anastomotic channels into the ischemic area so the ischemic condition worsens


angina pectoris

pain associated with contriction of coronary arteries. Usually below upper sternum over the heart, left arm and left shoulder, neck, side of face


what else is associated with angina?

cold temperatures, full stomach, increase of workload of heart


common drugs for vasodilation

nitroglycerin, nitrate


what do beta blockers do?

block sympathetic beta-adregenic receptors which prevent sympathetic enhancement of heart rate and cardiac metabolism during exercise or emotional episodes