nerve physiology

Question 1

what does the phrase, “resting membrane potential” mean

Answer 1

1. this is a property of all living cells
2. also the measure of potential energy between the inside or outside of a cell membrane (negative & positive charges)

Question 2

Why does it matter where K or Na concentration are during resting membrane potential?

Answer 2

K+ should be inside the cell
Na+ should be outside the cell. These locations are important because they are important for action potentials.

Question 3

Where are the highest concentrations of Na+, K+, A-, and Cl-

Answer 3

Inside cell: K+, A-
Outside cell: Na+, Cl-

Question 4

what ion has increased permeability and can move freely through leaky gated channels?

Answer 4

K+

Question 5

How does the Na+/K+ pump affect membrane potential?

Answer 5

The net movement of these ions is 3 Na+ OUT and 2 K+ IN .This is active transport that requires ATP and helps maintain concentration gradients and a steady state of a polarized cell membrane. Without this pump, K and Na would eventually reach equilibrium inside and outside the cell.

Question 6

Does the Na/K pump make the membrane potential more or less (-) on the inside with respect to the outside.

Answer 6

This makes the inside more negative because there are more positive ions being transported to the outside.

Question 7

What are the two properties of excitable cells (neurons and muscles cells) that make them unique?

Answer 7

1. excitability: ability to form action potential
2. conductivity: ability of neurons to transmit signals from one neuron -> another OR one neuron -> muscles/gland.

Question 8

what are ion channels?

Answer 8

1. leakage channels: alloq selective ions to always pass through
2. gated channels: voltage (open and close due to membrane potential) and chemical (open when appropraite neurotransmitter binds to receptor associted with channel)

Question 9

where do the excess K+ charges go once they have diffused out of the cell

Answer 9

They stay within the vicinity of the membrane because the anions inside the cell attract K+ back

Question 10

what are the two distinct characteristics of excitable cells?

Answer 10

1. excitability: ability to form action potentials
2. conductivity: ability to propagate an action potential

Question 11

how are changes in membrane potential created

Answer 11

1. changes in ion permeability across membrane
2. changes in concentration of ions on either side of the membrane

Question 12

what is a graded potential

Answer 12

changes in membrane potential either above or below resting membrane potential that are directly proportional to amplitude of stimulus who initiates it

Question 13

when a gated channel is open with the appropriate stimulus, how long do they stay open?

Answer 13

As long as appropriate conditions exist

Question 14

what is the all or non law of action potentials in a neuron

Answer 14

if stimulus is adequate to reach threshold, a maximal response is evoked

Question 15

what factors influence conduction velocitiy?

Answer 15

1. diameter of conducting fiber (larger fiber = faster AP)
2. temperature of cell : warmer = faster
3. presence of myelin sheath
4. pharmacologic agents: stop Na from entry into cell

Question 16

what is a synpase?

Answer 16

specialized junction where impulses pass from one neuron to another.

Question 17

what makes nerve transmission unidirectional?

Answer 17

the synapse

Question 18

what is property that all living cells have?

Answer 18

resting membrane potential

Question 19

what is the definition of a resting membrane potential

Answer 19

potential energy difference between he inside and the outside of a cell membrane

Question 20

is a resting membrane potential is -70mV - what does that mean?

Answer 20

the number tells the charge inside the cell

Question 21

the electrical gradient (driving force) of K

Answer 21

The (+) outside environment repulses K+ from moving outside the cell because 2 positive’s do not attract

Question 22

what are the two forces trying to move ions across the cell membrane that equate to the NET

Answer 22

1. concentration gradient
2. electrical gradient

Question 23

what direction does the concentration gradient try to drive K+ (inside or outside cell)

Answer 23

There are more K+ inside so the concentration gradient wants to move them out of the cell

Question 24

what is the process of localized separation of charges

Answer 24

some molecules have low permeability through the cell membrane ( A-) so they line up along the cell wall with their (+) charges on the other side (Na+)

Question 25

what is the role of the electrical gradient?

Answer 25

slows the diffusion of K+ because the outside of cell is already more (+) and like charges DO NOT attract