CH 21

Question 1

What are five factors that increase blood flow to muscles during exercise?

Answer 1

-Low oxygen concentration in tissues
-Potassium ions
-ATP
-Lactic acid
-Carbon dioxide

Question 2

Describe the effect(s) of Epi and NorEpi on blood vessels in muscles

Answer 2

Norepi is secreted by SNS fibers and causes vasoconstriction via alpha vasoconstrictor vessels. Epi secreted from the adrenal medulla also binds to beta adrenergic receptors, causing both vasoconstriction and vasodilation

Question 3

What are the 3 main effects during exercise that supply muscles with needed blood flow?

Answer 3

1. mass discharge of the SNS
2. increased arterial pressure
3. increased cardiac output

Question 4

How does increased SNS stimulation during exercise increase arterial pressure?

Answer 4

1. vasoconstriction of arterioles/sm arteries in the nonactive tissues
2. increased cardiac pumping activity
3. increased mean systemic filling pressure via venous contraction

Question 5

Which areas of the heart are supplied with blood by the left and right coronary arteries, respectively?

Answer 5

LCA: supples anterior and left lateral portions of the L ventricle
RCA: supplies most of the r ventricles and posterior left ventricle

Question 6

Where does the majority of the energy for cardiac muscle come from?

Answer 6

fatty acids

Question 7

Briefly describe the changes that occur to cardiac muscle after an infarction, if no blood supply resumes

Answer 7

1. All hemoglobin is used, so muscle goes bluish-brown
2. Vessels are engorged due to collateral flow and venous dilation and stagnation
3. Tissue becomes edematous and muscle swells because vessels become permeable and leak

Question 8

When cardiac perfusion is compromised, which region is compromised first, and why?

Answer 8

Subendocardial muscle because subendocardial blood vessels are additionally compressed during systole

Question 9

What is meant by “systolic stretch” in the context of cardiac muscle malfunction?

Answer 9

When normal portions of the ventricular muscle contract, the ischemic portion is forced outward, dissipating the force of contraction and weakening the pumping action overall

Question 10

Which main four factors explain the heart’s increased susceptibility to fibrillate after myocardial infarction?

Answer 10

1. Acute blood loss = K+ depletion from deprived muscle
2. Injury current because ischemic musculature cannot completely repolarize
3. Powerful SNS stimulation irritates musculature
4. Myocardial weakness leads to dilation and abnormal conduction pathways

Question 11

What is the mechanism of action of propanolol?

Answer 11

-blocks beta adrenergic receptors to prevent SNS enhancement of HR and cardiac metabolism to decrease the heart’s need for extra metabolic oxygen