Lecture 8 Neurons and AP

Question 1

What are Neurons

Answer 1

specialized nerve cells that transmit messages

Question 2

what is the structure of neurons

Answer 2

1. cell body (soma)

2. processes

Question 3

what does the cell body contain

Answer 3

Nucleus

Question 4

What is the cell body the site of

Answer 4

site of metabolism

Question 5

what are processes

Answer 5

fibers taht extend from the soma

Question 6

what are the types of processes

Answer 6

dendrites: receive info
axons: sends info

Question 7

Functional properties of Neurons

Answer 7

Irritability

conductiity

Question 8

What is irritability

Answer 8

ability to respond to a stimulus

Question 9

what is conductivity

Answer 9

ability to transmit an impulse

Question 10

what is a Resting Neuron

Answer 10

Plasma Membrane is polariezd
High concentration of Na+ outside the cell
High concentration of K+ inside the cell
fewer + ions vs. outside –> Resting membrane potential (RMP= _ 70mV)

Question 11

How is the RMP maintained

Answer 11

1. Na+/K+ pump

2. Leak channels

Question 12

Na+/ K+ pump does what?

Answer 12

generate concentration gradient
3 Na+ out
2 K+ in
cost 1 ATP

Question 13

What are Leak Channels

Answer 13

Small Na+ leak at rest
why:
High force (large gradient) low permwability (Less Channels)
small K+ leak at rest
Why:
Low force (less gradient) high permeability (more channels)

Question 14

Types of Channels on Neurons

Answer 14

1. Leak Channels
2. ligand- gated channel
3. voltage gated channels

Question 15

what are Leak Channels

Answer 15

always open

location throughout th neuron

Question 16

what are Ligand gated channels

Answer 16

open or close when ligand binds to receptors on the membrane
location: usually dendrites and soma

Question 17

what are voltage gated channels

Answer 17

opens or closes when membrane potential changes

Question 18

what is Action potential

Answer 18

Rapid large depolarization for communication

Question 19

What are the stages of Action Potential

Answer 19

1. Depolarization
2. Repolarization
3. hyperpolarization

Question 20

What is depolarization

Answer 20

Na+ gates causes Na+ to rush in
RMP: increase from -70mV –> +30 mV
upward movement = depolarization

Question 21

What is Repolarization?

Answer 21

K+ gate to open –> K+ to rush out
Na+ gate is clsoed
RMP= drops -30mV–> -70mV

Question 22

What is hyperpolarization?

Answer 22

K+ clsoing after RMP

RMP: drops below –> -70mV

Question 23

What is Action potential time?

Answer 23

Time: 1-2 ms

Question 24

What is Action Potential properties?

Answer 24

1. All or nothing

2. undirectional propagation

Question 25

What is the all or nothing princple?

Answer 25

Threshold: get to or above threshold , minimum depolarization necessary to open Na+ channels--> AP - if stimulus is at or above the threshold --> Ap of same magnitude (100mV)

Question 26

All or nothing Terminology

Answer 26

subthreshold depolarization--> no AP Threshold depolarization --> AP Suprathreshold depolarization --> AP

Question 27

what is unidirectional propagation

Answer 27

- Ap moves down axon toward the terminal | - deoolarization in one patch --> depolarization n adjacent patch

Question 28

what are Voltage gated Na+ channels

Answer 28

2 gates 1. Activation gate 2. Inactivation gate

Question 29

What is activation gate

Answer 29

- Voltage dependent | - opened threshold and depolarization

Question 30

what is inactivation gate

Answer 30

- voltage and time dependent - opened in 1st part of depolarization - closed: second part of depolarization

Question 31

3 stages of voltage gated channels (Inactivation/activation gate)

Answer 31

1. Activation: cosed and inactivation gate closed - during resting state - activation gate capable of opening with stimulus 2. Activation opened - Inactivation closed - during depolarization - allows sodium to rush into the cell 3. Activation opened --> Inactivation closed - During 1 ms follwoing depolarization - will not open untill returned to resting state

Question 32

what are the 2 types of Refactory period

Answer 32

1. absolute | 2. relative

Question 33

what is absolute refractory period ?

Answer 33

second AP can not be generated Na+ gates are inactivated Time: a;; of depolarization and part of repolarization

Question 34

what is relative refractory period ?

Answer 34

second AP can be generated but with a stronger stimulus Na+ gates closed some inactive Time: end of polarization and hyperpolarization

Question 35

What are the consequences of Refractory period ?

Answer 35

1. All or nothing 2. unidirectional propagation 3. frequency coding

Question 36

what is Frequency Coding

Answer 36

Intensity of the stimulus is coded in AP frequency Higher intensity = Higher frequncy lower Intensity = lower frequency