lecture 2-electrophys

Question 1

Is cardiac or skeletal action potential longer

Answer 1

Cardiac takes longer due to calcium channels?100-130ms

Question 2

Funny current

Answer 2

“Funny” current; Hyperpolarization-activated Cyclic Nucleotide-gated channel (esp. cAMP)- (nodal) “pacemaker channels” allow positive charge to enter cell during repolarization/hyperpolarization, closed during depolarization
“Funny” current; Hyperpolarization-activated Cyclic Nucleotide-gated channel (esp. cAMP)- (nodal) “pacemaker channels” allow positive charge to enter cell during repolarization/hyperpolarization, closed during depolarization

Question 3

AP: Phase 0

Answer 3

depolarization

- FAST due to opening of sodium channels

Question 4

AP: Phase 1

Answer 4

Phase 1: early repolarization
Early repolarization
sodium channels close, but some potassium channels open
repolarization is incomplete since calcium channels are also open but slower than potassium channels

Question 5

AP: Phase 2

Answer 5

Phase 2: plateau
membrane potential approx. zero (this will be important for ECG!!)
due to slow calcium channels
requires concurrent movement opposite to calcium
allows blood to be ejected from heart

Question 6

Resting membrane potential?

Answer 6

-85 to -90

Question 7

AP: Phase 3

Answer 7

Phase 3: rapid repolarization

- more calcium channels are closing, opening of (more) potassium channels

Question 8

Phase 4

Answer 8

Phase 4: resting membrane potential
only potassium channels are open
resting potential maintained until next stimulus

Question 9

Cardiac action potential receptors

Answer 9

NA, Ca+, K+, funny current, 4 phases