Resting membrane potential and some neurophysio questions?

[sameeralord]

Hello everyone,

These are true,false questions. I'm on holiday so can't get help yet and this is not homework.

1.Increased permeability of the cell membraneto K+ than Na+ is important for maintaining resting membrane potential of cell?

Ok I know this is true but I don't understand this. In a normal cell I know this is how it is, but if there was a cell that was more permeable for Na+ why won't it be able to maintain a resting membrane potential of a different value.

2. Orthodontic conduction of a nerve impulse dies out at first synapse?
I know orthodonic conduction is going from stroma to axon, but I don't understand the question.
Myelinated nerves only carry out othrodromic conduction?
I don't understand why?

3. Latent period obeserved in a simple muscle twitch obtained from a nerve muscle preparation.

*Is mostly due to delay at the neuromuscular junction
I know latent period is the time taken for stimulation to migrate to the recording electrode. So false I think.
*Becomes shorter when the strength of stimulus is increased
Due to all or none principle, which has no emphasis on strength of stimulus. I think this has no effect. So false I think.
*Is shorter if adrenalin is added to the solution
I don't know this. Does neurotransmitter decrease latent period
*Can be varied by altering the point of stimulation along the length of the nerve.
This is true I think. This decreases the distance between stimulating and recording electrodes.
*Increased with repeated and prolonged stimulation of nerve.
This is false due to habituation I think.

4. Nerve condcution velocity
* Is reduced when nerve is compressed
* Is reduced in fibres supplying fatigued muscles.

I don't know the answers for these. First one obviously looks true, but what is the reasoning. Second one I think is false.

Thanks a lot in advance

 

[Lievo]

1- what is the equilibrum potential of K and Na, respectively? What happens to the membrane potential when the permeability for a ion increase?

2- I don't understand the question

3-
*ok
*ok
*more adrenalins means more excitability of the neuromuscular jonction. Does this change the latent period?
*ok
*that false, but not because of habituation. What is the cellular locus of most plasticity? Does a repeated stimulation affect the all or none principle?

4-ok. Can mechanical deformations affect the electrical properties of a membrane?