Lec 26 - Introduction to Neurons

Question 1

What do we mean by ‘neuroscience’ or ‘brain research’?

Answer 1

A scientific discipline concerned with the structure and function of the nervous system

Question 2

Nervous system =

Answer 2

CNS + PNS

Question 3

What are the two major types of cells in the nervous system?

Answer 3

Neurons and Glia

Question 4

What is the main goal for neuroscientists?

Answer 4

To treat or prevent psychiatric or neurological disorders

Question 5

What releases chemical signals in the neurons?

Answer 5

Synapses on the axon terminals

Question 6

What parts of the neuron carry electrical signals?

Answer 6

dendrites, axon, cell body

Question 7

How did hodgkin and huxley calculate RMP (resting membrane potential)?

Answer 7

By getting a giant squid axon and putting one electrode in and one outside to measure the difference

Question 8

What is the voltage on the inside of a cell?

Answer 8

-50mV to -70mV

Question 9

How many cells in your body have a negative resting membrane potential?

Answer 9

Almost all cells

Question 10

What is RMP important for in the body?

Answer 10

Circadian rhythm, wound healing

Question 11

What are the only cells where the RMP can suddenly change?

Answer 11

Muscle fibres and neurons

Question 12

Why are muscle fibres and neurons referred to as ‘excitable tissues’?

Answer 12

because they can suddenly respond with a transient change of potential (action potential) in response to a stimulus

Question 13

What membrane protein causes an action potential in neurons and muscle fibres?

Answer 13

Voltage gated ion channels. Since these VGIT can respond to the voltage.

Question 14

What are the two ways to measure intracellular potentials?

Answer 14

Patch clamp technique
micro electrode recording technique

Question 15

How does the micro electrode recording technique work?

Answer 15

Similar to hodgkins and huxleys- one part is poked inside the cell and the other part is outside to measure the difference

Question 16

Name the reasons why the RMP is a negative value

Answer 16

1. Uneven concentrations of Na+ and K+ inside and outside the cell, resulting in electrochemical gradients
2. unequal permeability (ie more permeable to K+ and less permeable to Na+)

Question 17

What are the values of unequal concentrations of both K+ and Na+ inside and outside the cell?

Answer 17

K+ outside = 5mM
K+ inside = 100mM
Na+ outside = 150mM
Na+ inside = 15mM

Question 18

Does the NaKATPase require ATP?

Answer 18

Yes

Question 19

How does K+ and Na+ leak down their concentration gradients?

Answer 19

Through non-gated ‘leak’ channels

Question 20

What are non-gated ‘leak’ channels?

Answer 20

They are open at rest- so it allows diffusion of ions down their electrochemical gradients

Question 21

In the membrane of neurons, are there more K+ leak channels or Na+ leak channels?

Answer 21

More K+ leak channels

Question 22

What is the ratio for the permeability at rest?

Answer 22

PK+ / PNa+ = 40/1

Question 23

What is the concept of equilibrium potential?

Answer 23

For one ion type, an intracellualr potential at which the net flow of ions is zero according to its electrochemical gradient (where the forces of charge and concentration difference are equal and opposite)

Question 24

What is the nernst equation?

Answer 24

E(ion) = 61.5mV x log[ion]/[ion]i
extracellular ion concentration / intracellular

Question 25

What is the equilibrium potential for K+ in a cell?

Answer 25

~ -80 mV

Question 26

What is the equilibrium potential for Na+ in a cell?

Answer 26

~ +60 mV

Question 27

Can a neuron have only ion channel?

Answer 27

No, they will always have two or more leak channels. So it is difficult to use nernst equation

Question 28

What leak channels do glia have?

Answer 28

Only the K+ leak channel. So RMP = EK+

Question 29

If a membrane is more permeable to K+, which of these is the most likely equilibrium potential?
E = +20 mV
E = -70 mV

Answer 29

• 70 mV because it is closer to the E of K+

Question 30

Is the RMP more negative for neurons or glial cells and why?

Answer 30

More negative for glial cells, because they are only permeable to K+, and neurons are permeable to both

Question 31

what is the goldman equation?

Answer 31

Question 32

What does the goldman equation take into account?

Answer 32

The permeability of the membrane and concentration gradients

Question 33

What factors does the Nernst equation take into account when calculating equilibrium potential?

Answer 33

[ion] inside cell
[ion] outside cell
R - gas constant
T - temperature
F - Faradays
Z - Valence of the ion