neurophysiology

Question 1

what are the 2 fundamental discoveries that allowed the elucidation of basic neural function?

Answer 1

1. microelectrode

2. squid giant axon

Question 2

what does a giant axon do?

Answer 2

.the bigger the axon the faster electricity is conducted

Question 3

what is a nervous signal?

Answer 3

.nervous signal is a change in resting potential

Question 4

what is neuron resting potential?

Answer 4

.neuron has a negative resting potential (-60mV)

. inside neuron is negative charge

Question 5

what happens when two electrodes rest on surface of axon?

Answer 5

. no potential difference

Question 6

what are the two ways resting membrane potential can change?

Answer 6

. hyperpolarisation- more negative neuron

.depolarisation - less negative neuron

Question 7

what is the ionic composition of a resting neuron?

Answer 7

. inside neuron we have k+ and A-

. outside neuron we have Na+ and Cl-

Question 8

what are the two types of force that can act on an ion?

Answer 8

1. chemical force - ion will move from area of high concentration to low concentration
2. electrostatic force - an ion will be attracted to the opposite polarity

Question 9

what happens to Na+ in a neuron?

Answer 9

.sodium is positive and inside the neuron is negative
.Na+ has strong tendency to move inside the negative neuron
.both electrostatic and chemical forces tend to push sodium into the cell

Question 10

what happens to K+ in a neuron?

Answer 10

.K+ has lower tendency to get out of neuron

Question 11

what forces act on K+?

Answer 11

. 2 opposing forces act on K+ in a resting neuron.
. electrostatic force holds K+ within the cell
. chemical force pushes K+ outside cell
. chemical force is stronger than electrostatic
. there is a weak net resultant force pushing K+ out cell

Question 12

what are the 2 factors that will determine the movement of an ion across a membrane?

Answer 12

. size of the electrochemical gradient

. permeability of the membrane

Question 13

why is the resting potential of a neuron negative?

Answer 13

. membrane is only permeable to K+
. k+ will leave the neuron
. this will lead to a build up of positive charge outside the neuron which will begin to oppose exit of K+
.eventually an eq is set up when chemical force pushing K+ out cell is equalled by electrostatic force holding it in

Question 14

when is an eq reached?

Answer 14

. this occurs when the inside of neuron is -75mv which is resting potential of most neurons

Question 15

how is the leakage of Na+ stopped in resting neuron?

Answer 15

sodium/potassium pump

Question 16

what is a sodium/potassium pump?

Answer 16

an enzyme that spans the membrane

Question 17

what is the function of sodium/potassium pump?

Answer 17

for every 3 sodium ions removed from the cell , 2 potassium ions are pumped in

Question 18

What happens when equilibrium is established?

Answer 18

when the chemical force is exactly balanced by the electrical force.