Changes to the membrane potential

Question 1

Two types of channels

Answer 1

Leakage (always open)

Gated (open when triggered)

Question 2

In what ways are gated channels gated / triggered

Answer 2

Chemically, mechanically, voltage - gated

Question 3

What is a graded potential and how far does it travel

Answer 3

An incoming signal (eg. from release of neurotransmitters) over short distances in the dendrites usually

Question 4

What is an action potential

Answer 4

Signal travelling along an axon

Question 5

What is a graded potential

Answer 5

A short lived, localised change in membrane potential triggered by the opening of a chemically gated channel (most likely by the release of neurotransmitter by a pre synaptic neuron)

Question 6

What is a depolarisation and how does it affect the chance of producing an action potential

Answer 6

A decrease in membrane potential by making the inside of the cell less negative. increase the chances of PAAP
on signal

*ASK LECTURER HOW DOES THIS ACTUALLY INCREASE CHANCES OF RAAP

Question 7

Hyperpolarisation and its effect on action potential production

Answer 7

Increase in action potential making the inside of the cell more negative. decreases the chances of producing an action potential
off signal inhibits ability to do work

Q for lecturer : why are the chances decreased when the separation of charge increases, aka positive ions are more attracted to the increased negative ICF

Question 8

How does an graded potential work

Answer 8

An active site where the stimulus eg chemical release happens triggers a chemically gated Chanel to open eg. sodium channel, letting sodium into the cell which will be attracted to the negative cell membrane and spread out from the active site. This spread is a current and it’s short-lived and localised

Question 9

What is an action potential triggered by

Answer 9

Stimulated by a change in voltage across the membrane - sodium or potassium channels (voltage-gated)

Question 10

Three steps of action potential

Answer 10

Depolarisation (all the way to being positive), repolarisation (back to down to RMP), hyper polarisation (more negative than RMP, like an oops it’s gotten too much momentum and gone too far)

Question 11

Sodium vs Potassium channel openings

Answer 11

Sodium - closed, open or inactivated (can’t be open again for a period of time)
Potassium - closed or opened

Question 12

Initial step of action potential

Answer 12

At rest no na or k channels open other than leakage channels due to not enough voltage present to open them

Question 13

First step of action potential

Answer 13

Depolarisation - graded potential has been received if depolarising, causes membrane potential to become less negative. causes Na channels to open letting Na ions into cell. this influx makes ICF more positive triggers more Na channels to open

Question 14

What is he threshold point

Answer 14

Point where all sodium channels are open causing huge influx into the cell

Question 15

What happens if threshold is not reached

Answer 15

An action potential is not created - all or none

Question 16

Second step of AP

Answer 16

Na channels start to close no more inflow of positive ions at same time K chenille opens and positive K ions outflow. This reestbishes the negative ICF

Question 17

Third step of AP

Answer 17

Hyperpolarisation - K chennels stay open for too long causing too much K ions to leave the cell making it too negative for a period of time

Question 18

How does an action potential travel along the axon

Answer 18

Only in one direction, an Na flux causes a current to trigger he threshold of other Na channels Na flows in attracts to negative of membrane travels along etc. etc.

Question 19

What stops active potential to spread backwards

Answer 19

Inactivation of sodium channels + hyper polarisation (third step)

Question 20

What is a refractory period and what are the two types

Answer 20

A time during which an action potential can’t be triggered in a neuron
Absolute - goes from time Na channels open to when the inactivation stage of them is complete (enforces one way transmission)
relative - sodium channels are starting to go back to resting state, but due to hyper polarisation it takes a stronger stimulus to reach threshold and trigger an action potential. AP can still be created though, just wth a stronger stimulus