Action potentials I & II

Question 1

Most common type of Neuron?

Answer 1

Multipolar neuron

Question 2

Structure of Neuron:
Large central area?

Answer 2

Cell body or soma, contains nucleus and most organelles

Question 3

Structure of Neuron:
Numerous short projections from cell body?

Answer 3

Dendrites

Question 4

Structure of Neuron:
One long projection?

Answer 4

Axon

Question 5

Structure of Neuron:
Location on cell body where axon connects is

Answer 5

Axon Hillock

Question 6

Structure of Neuron:
Portion of axon that connects to axon hillock is

Answer 6

Initial Segment or spike initiation zone

Question 7

Structure of Neuron:
Axons branch out at the ends, these ends are called

Answer 7

terminal branches

Question 8

Structure of Neuron:
Terminal branches end in small swelling bulbs called

Answer 8

Axon terminal or presynaptic terminal.

Question 9

Structure of Neuron:
Myelin sheath are made of _______ cells

Answer 9

Glial cells

Question 10

Structure of Neuron:
Myelin sheath is interupted at intervals by gaps called

Answer 10

Nodes of Ranvier

Question 11

What are graded potentials?
Where are they produced?
What is their function in neurons?

Answer 11

-Graded potentials are small changes in membrane potential AKA postsynaptic potentials.
-Produced on the dendrites, can also be from cell body.
-They regulate action potential production at the initial segment

Question 12

Where are action potentials produced?
What is their function?

Answer 12

-Produced at initial segment
-They stimulate the release of neurotransmitters by propagating along the axon to each axon terminal.

Question 13

Other names for:
-Cell body
-Graded potential
-Presynaptic terminal
-Spike initiation zone

Answer 13

-Soma
-Postsynaptic potential
-Axon terminal
-Initial segment

Question 14

3 Characteristics of Action Potentials (AP):

Answer 14

-Every AP produced is IDENTICAL
-AP have an ALL-OR-NONE RESPONSE to a stimulus
-AP are TRANSMITTED WITHOUT DECREMENT

Question 15

Depolarization:

Answer 15

Change in membrane potential to a less negative value than resting potential.

Question 16

Hyperpolarization:

Answer 16

Change in membrane potential from a depolarized state.

Question 17

What is needed to reach the threshold?

Answer 17

A depolarization.

Question 18

Repolarization:

Answer 18

Return to resting potential from a depolarized state.

Question 19

Typical resting potential for a neuron

Answer 19

-70 mV (milliVolts)

Question 20

Threshold potential.

Answer 20

-55mv.

Question 21

Depolarization:

Answer 21

Stimulates action potential
Results in an increase in sodium ion permeability.

Question 22

Hyperpolarization:

Answer 22

Inhibits action potential

Question 23

Types of Depolarization stimuli?

Answer 23

Threshold Stimulus
Sub-threshold Stimulus
Suprathreshold Stimulus

Question 24

Threshold potential:

Answer 24

The membrane potential at which occurrence of the action potential is inevitable.

Question 25

Threshold Stimulus:

Answer 25

The minimum depolarization needed to induce an action potential, when the membrane is at resting potential.

Question 26

Sub-threshold Stimulus:

Answer 26

Cannot induce an action potential because it is less than the threshold. Less than +15mv.

Question 27

Suprathreshold Stimulus:

Answer 27

A depolarization above the threshold. Geater than 15mv.

Question 28

What amount of depolarization is typically needed to reach threshold?

Answer 28

+15 mV depolarization If resting potential is -70 mV (typical) then threshold potential is -55 mV (-70 mV + 15 mV = -55 mV)

Question 29

Name 3 phases of action potential:

Answer 29

-Depolarization phase -Repolarization phase -Undershoot phase

Question 30

How much mv is needed to go from resting potential to threshold potential?

Answer 30

+15mv.

Question 31

Alternate names for depolarization phase

Answer 31

-Rapid depolarization phase -Rising phase

Question 32

Alternate name for repolarization phase

Answer 32

-Falling phase

Question 33

Alternate names for undershoot phase

Answer 33

-Hyperpolarizing after potential -After hyperpolarization phase

Question 34

What can induce an action potential when the cell is at resting potential?

Answer 34

A threshold and superthreshold stimuli.

Question 35

Membrane potential during depolarization phase (phase 1)

Answer 35

Depolarizes from threshold (-55 mV) to +30 mV

Question 36

Membrane potential during repolarization phase (phase 2)

Answer 36

Changes from +30 mV to -70 mV

Question 37

Membrane potential during undershoot phase (phase 3)

Answer 37

Is slightly hyperpolarized (less than -70 mV)

Question 38

Na+ Channels can open ______

Answer 38

In response to a depolarization to any change in membrane potential. The higher the strength of depolarization the higher the chance of opening.

Question 39

When does Na+ permeability exceed K+ permeability?

Answer 39

At threshold. This is due to leak channels.

Question 40

Conductance:

Answer 40

Local changes in membrane permeability to Na+ & K+ that induce and maintain action potential.

Question 41

What starts the Hodgkin cycle?

Answer 41

When Na+ permeability exceeds that of k+. It is a positive feedback loop.

Question 42

The Hodgkin cycle is terminated by

Answer 42

The closing of the inactivation gate.

Question 43

What causes conductance to occur?

Answer 43

Opening and closing of voltage-gated ion channels within membrane.

Question 44

Another name for depolarization?

Answer 44

Rising Phase.

Question 45

Ion channels:

Answer 45

small pores in the membrane that are created by specialized membrane proteins.

Question 46

Inactivations state:

Answer 46

Activation gate opens, Inactivation gate is closed.

Question 47

Another name for repolarization:

Answer 47

Falling Phase

Question 48

Specificity in ion channels mean:

Answer 48

only certain ions can move through particular ion channels.

Question 49

Ungated ion channels:

Answer 49

always open AKA leak channels

Question 50

Undershoot:

Answer 50

A slight Hyperpolarization. K+ channels close slowly.

Question 51

Potassium ion leak channels:

Answer 51

Responsible for increased permeability of K+ at resting potential.

Question 52

Gated ion channels:

Answer 52

Can be opened and closed in response to stimulis.

Question 53

Changes in permeability are called?

Answer 53

Conductance.

Question 54

Voltage-gated ion channels:

Answer 54

open and close in response to changes in membrane potential

Question 55

Refractory period:

Answer 55

The initial segment is less important than another stimulus during an action potential. Reduced responsiveness to stimuli during the action potential.

Question 56

Phases of the refractory periods:

Answer 56

Absolute refractory Relative refractory

Question 57

Absolute refractory period:

Answer 57

Begins @ threshold, and ends at the repolarization phase. The membrane cannot respond to another stimulus.

Question 58

Relative refractory period:

Answer 58

Begins at the end repolarization phase and ends in undershoot.

Question 59

What is required for an action potential in a relative refractory period?

Answer 59

A superthreshold.

Question 60

What type of cells are in myeline sheets?

Answer 60

Shawn cells.