1. intro to Nervous System and review membrane physiology

Question 1

List 5 general functions of the nervous system

Answer 1

-Sensation
-Motor Capability
-Cognition
-Homeostasis
-Emotions

Question 2

Define electrochemical equilibrium potential for an ion species

Answer 2

This is when the membrane potential would produce an electrical force that would equal the opposite direction driving chemical force produced by the concentration gradient of the ion.

Question 3

For E-Na+ and E-K+ describe the direction of chemical and electrical forces

Answer 3

-For K+ the chemical forces drive K+ out and causing the cell to become more negative as it leaves, then the electrical force driving in starts small but progressively gets bigger as more K leaves.

-For NA+, the chemical forces drive Na+ into the cell and it makes the inside more positive as each enters. Then the electrical forces driving outward starts small and gets bigger as positivity grows inside.

Question 4

Quantitively describe the membrane potential at E-Na+ and E-K+.

Answer 4

-K+ has a negative membrane potential, cells inside is negative
-Na+ has a positive membrane potential, cells positive inside

Question 5

How would E-K+ change if you add extracellular K+?

Answer 5

It would depolarize

Question 6

Define resting membrane potential

Answer 6

its the electrical potential of the inside of the cell relative to the outside of the cell

Question 7

Describe the importance of K+ ions in producing the resting membrane potential of a neuron

Answer 7

The K+ ion is the main determinant of the resting membrane potential.

Question 8

Why is the resting membrane potential not the same as E-K+?

Answer 8

• Because at rest the cell IS NOT completely permeable to K+ ions, only 70% so it cant get to E-K+

Question 9

Describe the resulting effect on resting membrane potentials to E-K+, or by changing the permeability of the membrane for K+ and Na+ ions

Answer 9

If you change the permeability of the membrane to ions, the potential will go down/hyperpolarize
and if you change the E-K+ the RMP will also change accordingly

Question 10

Explain how differences in opening and closing times of voltage dependent Na+ and voltage dependent K+ channels underlie an action potential

Answer 10

An action potential is genrated and once it hits the threshold a rapid opening of the Na+ channels occur and both forces are driving inward causing the cell to depolarize but before reaching E-Na+ the channels deactivate and opens up K+ channels which begins to hyperpolarize the cell

Question 11

Explain how an potential is conducted by myelinated and unmyelinated axons

Answer 11

The myelinated axons can conduct a action potential quicker than the unmyelinated ones as when they go through the axon, they encounter several nodes of ranvier and that is where the Na+ and K+ channels are concentrated so the potential jumps from node to node but unmyelinated cant do this so its much slower

Question 12

Define depolarization

Answer 12

loss of the difference in charge between the inside and outside of the plasma membrane

Question 13

Define Hyperpolarization

Answer 13

when the membrane potential becomes more negative at a particular spot on the neuron’s membrane

Question 14

Define threshold

Answer 14

its the level you have to reach to activate something

Question 15

Define repolarization

Answer 15

restoration of the difference in charge between the inside and outside of the cell membrane following depolarization

Question 16

Define afterhyperpolarization

Answer 16

where the cell’s membrane potential falls below the normal resting potential

Question 17

Define equilibrium potential

Answer 17

its when neither ion is flowing in or out, its balanced

Question 18

Define absolute refractory period

Answer 18

the period of time during which a second action potential ABSOLUTELY cannot be initiated, no matter how large the applied stimulus

Question 19

Define relative refractory period

Answer 19

the interval immediately following the Absolute Refractory Period during which initiation of a second action potential is INHIBITED, but not impossible