Lecture 8: Diversity in AP shape

Question 1

Factors influencing AP shape

Answer 1

• variation in structure and function of VG Na+ and VG K+ channels
• variation in ion channel density
• influence of other channels (Ca2+, Cl-)

Question 2

How does AP shape affect neuron function?

Answer 2

• differences in Na+ VG and K+ VG channels affect the duration, and the absolute and relative refractory periods
• consequently affect the excitability of the neuron and the maximum frequency of AP

Question 3

Isoforms

Answer 3

variants of the same proein encoded by different genes or as a result of alternative splicing
-variations can lead to differences in function

Question 4

Na+ channel Isoforms

Answer 4

• 11 isoforms in mammals
• affects activation threshold voltage, speed of activation and inactivation, time remains open or inactive,
• therefore also affects the length and shape of the AP

Question 5

K+ channel isoforms

Answer 5

• highly diverse: 50 isoforms in mammals
• affect the activation threshold voltage, speed of activation, and time channel remains open
• therefore also affect length and shape of the AP

Question 6

How does diversity in Na+ channel density affect excitability?

Answer 6

-higher the density, the lower the threshold required for an action potential, aka increased excitability

Question 7

Influence of VG Ca2+ channels

Answer 7

-VG Ca2+ channels affect AP shape
-when opened, Ca2+ enters, depolarizaing the membrane
-sometimes used with Na+channels, or instead of them
Ca2+ influx is often slower and more prolonged than Na+
-lower frequency of AP due to longer resulting refractory period

Question 8

Influence of Cl- channels

Answer 8

• some neurotransmitters open ligand-gated Cl- channels, hyperpolarizing the membrane
• function of these channels is not well understood