Lecture 3: Nervous System 3 Cont

Question 1

More ____ is going to be going outside the cell than _____ going into the cell

Answer 1

K

Na

Question 2

Equilibrium potential for K is

Answer 2

-90mV

Question 3

Equilibrium potential for Na is

Answer 3

+60mV

Question 4

At resting potential is Na or K at equilibrium?

If not, what direction do they leak?

Answer 4

Nope
K into the cell
Na out of the cell

Question 5

What counterbalances the leakage of Na and K across the membrane?

Answer 5

The Na/K pump

Question 6

What is responsible for the electrical property of the membrane?

Answer 6

The unequal distribution of a few key ions between the ICF and the ECF and their selective movement across the plasma membrane

Question 7

Permeability of the axon membrane to Na and K is regulated by ____, which open in response to _______

Answer 7

gates

stimulation

Question 8

Two stages of net diffusion of Na and K

Answer 8

1. Na moves into the axon

2. K moves out

Question 9

Ion channels are made of

Answer 9

integral membrane proteins

Question 10

Ion channels are selective, meaning

Answer 10

they only permit the passage of certain ions

Question 11

Ion channels are controlled by

Answer 11

gates which open or close the channels

Question 12

Three types of gates

Answer 12

Voltage-gated
Ligand-gated
Modality-gated

Question 13

Ligand-gated

Answer 13

A chemical binds to the gate, opening the channel

Question 14

Voltage-gated

Answer 14

Controlled by changes in the membrane potential

Activation gate opened by the depolarization of nerve cell membrane

Question 15

Example of a voltage-gated ion channel

Answer 15

Na+

Question 16

Modality-gated ion channel

Answer 16

Specialized structures that transform the energy of a specific, local stimulus into action potentials

Question 17

4 examples of modality-gated ion channels

Answer 17

1. Mechanoreceptors
2. Thermoreceptors
3. Chemoreceptors
4. Nociceptors

Question 18

Mechanoreceptors

Answer 18

sensing touch, stretch, and pressure

Question 19

Chemoreceptors

Answer 19

Sensing taste, smell, and specific chemicals such as O2 and H+

Question 20

Changes in the membrane potential can take two basic forms:

Answer 20

Graded potentials

Action potential

Question 21

Graded potentials

Answer 21

Local changes in resting membrane potential that travel in a decremental fashion and does not reach the initiation segment

Question 22

Why are local potentials called graded potentials?

Answer 22

Because they vary from large to small depending on the stimulus strength or frequency

Question 23

Temporal summation

Answer 23

Increased frequency of stimulation can cause two or more local potentials to combine

Question 24

Local potentials occur most often where?

Answer 24

• In dendrites and cell bodies of neurons

- Near the sites where the neurons innervate muscle cells

Question 25

What is the basic mechanism for transmission of information in the nervous system and in all types of muscle

Answer 25

Action potential

Question 26

Threshold potential

Answer 26

When a local potential depolarizes to this point, it will cause an action potential

Question 27

Polarization

Answer 27

The membrane has potential

There is a separation of opposite charges

Question 28

Depolarization

Answer 28

Process of making the membrane potential less negative

Also referred to as a decrease in potential

Question 29

Repolarization

Answer 29

Return of the membrane to resting potential after having been depolarized.
Also referred to as an increase in potential

Question 30

Hyperpolarization

Answer 30

The process of making the membrane potential more negative than the resting potential

Question 31

Refractory period

Answer 31

• Period during which another action potential cannot be elicited from an excitable cell. Can be absolute or relative.
• Ensures the unidirectional propagation of the action potential down the axon, away from the initial site of activation

Question 32

What kind of response does an action potential have?

Answer 32

All or nothing

Question 33

An action potential is inevitable once

Answer 33

the membrane is depolarized to threshold

Question 34

Action potential propagation - does the original action potential travel along the membrane?

Answer 34

Nope, instead it triggers an identical new action potential in the adjacent area of the membrane.
It is non-decremental

Question 35

Two types of action potential propagation

Answer 35

1. Local current flow

2. Saltatory conduction

Question 36

Saltatory conduction

Answer 36

Action potential “jumps” between the nodes of Ranvier

Question 37

Nodes of Ranvier

Answer 37

Places in the fibers that are not covered in the myelin sheath. Sodium channels are concentrated here.