Lecture 3 - Neural

Question 1

What is membrane potential?

Answer 1

The difference in electrical charge between inside and outside of neuron.

Question 2

Passive or leakage channels

Answer 2

Are always open.

Question 3

Chemically gated channels

Answer 3

Open with binding of specific neurotransmitter/chemical.

Question 4

Voltage-gated channels

Answer 4

Open and close in response to membrane potential.

Question 5

Resting membrane potential

Answer 5

The steady transmembrane potential of a cell that is not producing an electrical signal.

Generated by different concentrations of Na+, K+, Cl- and protein anions.

Question 6

What is the potential difference across the membrane of a resting neuron?

Answer 6

-70 mV

Question 7

What factors affect the establishment of the resting membrane potential?

Answer 7

1. Concentration differences of two particular ions (Na+, K+) inside and outside the cell.
2. Permeability differences between these two ions (K+ is 50 to 75 times more permeable than Na+)
3. Intracellular negativity due to largely negatively charged anions (mostly proteins) trapped inside the cell, and are impermeable.
4. Na+, K+ ATPase (pump) maintains concentrations differences across the membrane (3 Na+ out; 2K+ in).

Question 8

Changes in membrane potential are caused by what three events?

Answer 8

1. De-polarization
2. Re-polarization
3. Hyper-polarization

Question 9

Depolarization

Answer 9

Inside of the membrane becomes LESS NEGATIVE.

Question 10

Repolarization

Answer 10

Membrane returns to its resting membrane potential.

Question 11

Hyperpolarization

Answer 11

The inside of the membrane becomes MORE NEGATIVE than the resting potential.

Question 12

Graded potentials

Answer 12

Short-lived, local changes in the membrane potential.

They decrease in intensity with distance.

Their magnitude varies directly with the strength of the stimulus.

Sufficiently strong graded potentials can initiate action potentials.

Voltage changes in graded potentials are decremental. Can only travel over short distances.

Can be excitatory and inhibitory. Can also be “summed” both temporally and spatially.

Question 13

Action potential

Answer 13

A rapid depolarization of the membrane potential.

Only generated by muscle cells and neurons.
They are the principal means of neural communication.

Question 14

What voltage in mV is the threshold?

Answer 14

-55 to -50 mV

-40mV also counts