Transmitters and excitability

Question 1

How and why does the resting membrane potential fall during development?

Answer 1

The r.m.p becomes more negative

1. There are new channels and pumps in the membranes
2. No. of glial cells increase, decreasing [K+]o

Question 2

What happens to the input resistance and membrane time constant?

Answer 2

Input resistance falls- more channels

Membrane time constant falls- cells get larger and can store more charge

Question 3

How do A.Ps change from earlier to later in development?

Answer 3

Earlier on: slower, Ca2+ dependent

Later on: short, Na+ dependent

Question 4

What do outward K+ delayed rectifiers do

Answer 4

Allow K+ to leave neurons after an action potential has occurred
These neurons shorten the A.P

Question 5

What are the 3 calcium currents, what are they known for

Answer 5

1.T-current
Low voltage activated
Open during membrane depolarisation
2.N-current
High voltage activated
Critically involved in the release of n.mitter
3.L-current
High voltage activated
Involved in excitation-coupling in muscles- also
Release of Ca2+ from S.R

Question 6

What do waves of calcium influence?

Answer 6

1. Process growth

2. Differentiation

Question 7

What channels are responsible for making GABA switch from being excitatory to inhibitory?

Answer 7

Increased expression of KCC2- CL- out of cell

Decreased expression of NKCC1-CL- into cell

Question 8

Difference between immature and mature neurons in regards to GABA and Ca2=

Answer 8

Immature neurons-
high [CL-]i
GABAa activated- depolarisation
Mature neurons-
low [CL-]i
GABAa activated- hyperpolarisation