Chapter 14 (Part 4) (Study Questions)

Question 1

what is the role of NO in vasodilation? (2)

Answer 1

• vascular endothelial cells make NO in response to hypoxia
• NO triggers vasodilation to increase blood flow

Question 2

what is the role of nitroglycerin tablets in heart disease?

Answer 2

substrate for endothelial cells to make NO

nitroglycerin serves as a substrte for blood vessel endothelial cells to make NO

Question 3

1. NO activates _________ to make _____ …. (4 more)

Answer 3

2. cGmp activates PKG
3. activated PKG leads to CLOSING of Ca+2 channels; OPENING K+ channels
4. and ACTIVATION of myosin light chain phosphatase
5. to INACTIVATE myosin light chain in smooth muscle around blood vessel endothelial cells to cause vasodilation

Question 4

what are the components of the cardiac AP conduction system? (5)

Answer 4

• sinoatrial node
• atrioventricular node
• right bundle branch
• bundle of HIs
• left bundle branch

Question 5

what is the SA node?

Answer 5

sinoatrial node. pacemaker of the heart; AP initiated here

Question 6

what is the SA node? (2)

Answer 6

sinoatrial node. pacemaker of the heart; AP initiated here

Question 7

what is the bundle of His?

Answer 7

splits into R and L branches that extend to the heart apex

Question 8

what is the AV node?

Answer 8

sends AP to the bundle of His

Question 9

what is the significance of the delay in conducting the AP from the SA node to the AV node?

Answer 9

ensures the atria complete their contraction before the ventricles contract to ensure ventricles fill properly

Question 10

how does an autorhythmic cell initiate its own AP? (4)

Answer 10

• spontaneously fires APs
• no delays between APs
• funny channels
• voltage-gated K+ channels

Question 11

how are autorhythmic APs different from neuron APs? (2)

Answer 11

• no voltage-gated Na+ channels
• depolarization is spontaneously triggered by 2 channels: ion funny channels and voltage-gated K+ channels

Question 12

describe ion funny channels

Answer 12

channels that are activated by hyperpolarization, and allow both sodium and potassium to flow through them

Question 13

describe voltage-gated K+ channels

Answer 13

close at peak (-)Vm (hyperpolarization) to trap K+ inside the cell

Question 14

yellow chart

Answer 14

got it

Question 15

how is an AP triggered in a cardiac contractile cell? (2)

Answer 15

• Ca+2 release delays repolarization
• creates a refractory period

Question 16

what is the significance of the plateau in a cardiac contractile cell contraction contractify?

Answer 16

• creates a refractory period that delays another AP, prevents summation or tetanus

Question 17

what would be the effects of summation?

Answer 17

another immediate contraction aka too rapidly that causes rapid and shallow heart beats

Question 18

what would be the effect of tetanus

Answer 18

sustained contraction without relaxation, holding a contraction can cause heart to miss the next Ap, cardiomyocytes get out of sync and heart can stop beating

Question 19

what is required to stop a contractile cell contraction?

Answer 19

clearing Ca+2 from the sarcomeres

Question 20

what would clearing Ca+2 from the sarcomeres require ?

Answer 20

3 ways to do this
1. Ca+2 ATPases pump Ca+2 back into SR
2. Ca+2 ATPase pump on the sarcolemma pumps Ca+2 out of the cardiac muscle cell
3. Na+/Ca+2 exchangers on sarcolemma move Na+ in and Ca+2 out

Question 21

why would i possibly want to remove Ca+2 from sarcomeres?

Answer 21

stopping a contractile cell contraction