Chapter 14 (Part 4) (Study Questions) Flashcards
what is the role of NO in vasodilation? (2)
- vascular endothelial cells make NO in response to hypoxia
- NO triggers vasodilation to increase blood flow
what is the role of nitroglycerin tablets in heart disease?
substrate for endothelial cells to make NO
nitroglycerin serves as a substrte for blood vessel endothelial cells to make NO
- NO activates _________ to make _____ …. (4 more)
- cGmp activates PKG
- activated PKG leads to CLOSING of Ca+2 channels; OPENING K+ channels
- and ACTIVATION of myosin light chain phosphatase
- to INACTIVATE myosin light chain in smooth muscle around blood vessel endothelial cells to cause vasodilation
what are the components of the cardiac AP conduction system? (5)
- sinoatrial node
- atrioventricular node
- right bundle branch
- bundle of HIs
- left bundle branch
what is the SA node?
sinoatrial node. pacemaker of the heart; AP initiated here
what is the SA node? (2)
sinoatrial node. pacemaker of the heart; AP initiated here
what is the bundle of His?
splits into R and L branches that extend to the heart apex
what is the AV node?
sends AP to the bundle of His
what is the significance of the delay in conducting the AP from the SA node to the AV node?
ensures the atria complete their contraction before the ventricles contract to ensure ventricles fill properly
how does an autorhythmic cell initiate its own AP? (4)
- spontaneously fires APs
- no delays between APs
- funny channels
- voltage-gated K+ channels
how are autorhythmic APs different from neuron APs? (2)
- no voltage-gated Na+ channels
- depolarization is spontaneously triggered by 2 channels: ion funny channels and voltage-gated K+ channels
describe ion funny channels
channels that are activated by hyperpolarization, and allow both sodium and potassium to flow through them
describe voltage-gated K+ channels
close at peak (-)Vm (hyperpolarization) to trap K+ inside the cell
yellow chart
got it
how is an AP triggered in a cardiac contractile cell? (2)
- Ca+2 release delays repolarization
- creates a refractory period
what is the significance of the plateau in a cardiac contractile cell contraction contractify?
- creates a refractory period that delays another AP, prevents summation or tetanus
what would be the effects of summation?
another immediate contraction aka too rapidly that causes rapid and shallow heart beats
what would be the effect of tetanus
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
what is required to stop a contractile cell contraction?
clearing Ca+2 from the sarcomeres
what would clearing Ca+2 from the sarcomeres require ?
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
why would i possibly want to remove Ca+2 from sarcomeres?
stopping a contractile cell contraction
