Cardiac Muscle

Question 1

Potassium permeability is highest in what phase of ventricular muscle action potential?

Answer 1

falling phase (3)

Question 2

spastic contraction of the heart is most likely caused by…

Answer 2

excess extracellular Ca++ ions

Question 3

the plateau phase of cardiac muscle action potential is due to…

Answer 3

replacement of voltage-gated Na+ channels with slow Ca++ channels

Question 4

name the 4 phases of cardiac muscle AP

Answer 4

0. rising phase
1. plateau phase
2. falling phase
3. RMP

Question 5

flaccid contraction is caused by…

Answer 5

excess K+ or low Ca++

Question 6

what happens when an AP is initiated?

Answer 6

Rising phase:
Fast Na+ and slow Ca++ channels open from DHP receptor (voltage gated)

Question 7

the DHP receptor is a ____ channel in the ____

Answer 7

Ca++
T-tubule membrane

Question 8

what happens during the plateau phase?

Answer 8

• K+ channels are open
• Ca++ binds to ryanodine receptor, activates Ca++ release from SR

Question 9

what happens during the falling phase?

Answer 9

K+ open more

Question 10

what is responsible for restoring RMP?

Answer 10

Na/K ATPase pump

Question 11

after cardiac muscle contraction, what happens to Ca?

Answer 11

pumped back into SR and back into T-tubule

Question 12

Ca concentration is restored by what 2 pumps?

Answer 12

Ca/Na antiporter (Ca out/Na in)
Ca++ ATPase pump

Question 13

what type of transport is the Ca/Na antiporter?

Answer 13

secondary active transport

Question 14

the Ca ATPase pump requires ____

Answer 14

ATP

Question 15

the period when the heart chamber remains contracted to keep blood out is termed ____

Answer 15

absolute refractory period

Question 16

cardiac muscle action potential occurs in what part of the heart?

Answer 16

ventricle

Question 17

what is the RMP of cardiac muscle?

Answer 17

-90mV