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

Question 1

how fast does blood flow through skeletal muscle during rest?

Answer 1

3-4 ml/min/100g of muscle

Question 2

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

Answer 2

potassium ions, adenosine triphosphate, lactic acid, carbon dioxide

Question 3

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

Answer 3

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

Question 4

what 3 things cause increase in arterial pressure during excersize?

Answer 4

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

Question 5

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

Answer 5

they vasodilate, everywhere else vasoconstricion occurs

Question 6

why is the arterial pressure increase during exercise so important?

Answer 6

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

Question 7

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

Answer 7

coronary artery disease

Question 8

what vessel supplies the heart with nutrients?

Answer 8

coronary arteries

Question 9

left coronary artery suppies what part of the heart?

Answer 9

anterior and leftlateral portions of the left ventricle

Question 10

right coronary artery supplies what?

Answer 10

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

Question 11

where is the Coronary sinus

Answer 11

where the coronary arteries empty into the right atrium

Question 12

thebesian veins do what?

Answer 12

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

Question 13

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

Answer 13

4-5 %

Question 14

describe the capillary blood flow through the left ventricle during systole

Answer 14

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

Question 15

how is the coronary system regulated?

Answer 15

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

Question 16

describe adenosine’s role in vasodilation in regards to ATP

Answer 16

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

Question 17

name some other vasodilators

Answer 17

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

Question 18

what does sympathetic stimulation release?

Answer 18

noreepinephrine and epinephrine

Question 19

what does the parasympathetic stimulation release?

Answer 19

acetylcholine

Question 20

what does epinephrine and noreepinephrine do in the coronary vessels?

Answer 20

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

Question 21

what happens if the alpha receptors are over stimulated?

Answer 21

Angina can occur and ischemia can occur

Question 22

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

Answer 22

fatty acids

Question 23

what causes anginic pain in anaerobic conditions?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

name one way to have acute coronary occlusion

Answer 25

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

Question 26

name another way to have acute coronary occlusion

Answer 26

mucsular spasm of coronary artery which can develope a secondary thrombus

Question 27

describe the collateral development of vessels and the coronary artery

Answer 27

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)

Question 28

what is myocardial infarction?

Answer 28

heart muscle has zero flow

Question 29

requirements for cardiac muscle to stay alive

Answer 29

1.3 ml of oxygen per 100 g

Question 30

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

Answer 30

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

Question 31

common causes of death after acute coronary occlusion

Answer 31

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

Question 32

what is systolic stretch

Answer 32

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

Question 33

whats happening to the heart during coronary shock/cardiac shock

Answer 33

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

Question 34

what is low cardiac output failure

Answer 34

more than 40% of left ventricle is infacted

Question 35

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

Answer 35

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

Question 36

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

Answer 36

ischemic musculature often cannot completely replarize its membranes after a heartbeat

Question 37

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

Answer 37

powerful sympathetic reflexes often develop after massive infarction

Question 38

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

Answer 38

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

Question 39

cardiac tamponade

Answer 39

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

Question 40

replacement of dead muscle by scar tissue

Answer 40

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

Question 41

coronary steal syndrome

Answer 41

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

Question 42

angina pectoris

Answer 42

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

Question 43

what else is associated with angina?

Answer 43

cold temperatures, full stomach, increase of workload of heart

Question 44

common drugs for vasodilation

Answer 44

nitroglycerin, nitrate

Question 45

what do beta blockers do?

Answer 45

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