Cardiac muscle

Question 1

what are two similarities between cardiac and smooth muscle?

Answer 1

both are striated and use the t-tubule mechanism (acting on sarcoplasmic reticulum)

Question 2

what are the major differences between cardiac and smooth muscle?

Answer 2

the t-tubules store larger amounts of Ca++, cardiac muscle plateaus (longer contraction time), the strength of contraction depends on extracellular Ca++

Question 3

the ability of cardiac muscle to depolarize and contract is ____________

Answer 3

intrinsic

Question 4

what are some features of the S-A node?

Answer 4

almost no contractile muscle fibers, cell membrane is naturally leaky to Na+ and Ca++ ions – less (-) resting potential than other cardiac mm

Question 5

what is end diastolic volume?

Answer 5

amount of blood left in heart at the end of diastole

Question 6

what is end systolic volume?

Answer 6

volume of blood left after systole

Question 7

what is ejection fraction?

Answer 7

the fraction of blood left in the heart after systole

Question 8

where does the majority of the returning venous blood flow too?

Answer 8

directly from atria to ventricles

Question 9

what is preload?

Answer 9

the amount of pressure on the ventricles when they are full

Question 10

what is afterload?

Answer 10

peripheral pressure the ventricles have to pump against

Question 11

the heart relies almost exclusively on __________ for energy metabolism. the energy primarily comes from _________

Answer 11

oxygen, oxidative metabolism of fatty acids

Question 12

what is the extrinsic regulation of heart rate?

Answer 12

SNS by way of releasing norepinephrine to increase cardiac output

Question 13

what type of message does the S-A node receive at rest?

Answer 13

inhibitory or “vagal tone”