Lecture 3 + 4 - Basics of Neurophysiology

Question 1

What is an electrolyte?

Answer 1

A fluid with a high concentration of ions

Question 2

Where is potassium highly concentrated?

Answer 2

Inside the cell

Question 3

Where is sodium highly concentrated?

Answer 3

outside the cell

Question 4

Where is chloride highly concentrated?

Answer 4

outside the cell

Question 5

Where is calcium highly concentrated?

Answer 5

outside the cell

Question 6

What is electric current?

Answer 6

the rate of flow of electric charge past a point or region. it exists when there is a net flow of electric charge

Question 7

How is electric current carried (in the body)?

Answer 7

Carried by ions in an electrolyte

Question 8

In terms of neurons, when do we see a current?

Answer 8

When ions flow through specialized pore in the cellular membrane

Question 9

What is voltage?

Answer 9

a electrical potential difference between 2 points

Question 10

How do neurons create a electrical potential difference (voltage)?

Answer 10

by controlling ion concentrations on either side of the membrane (intra vs extracellular)

Question 11

What are the different states of the Na voltage gated ion channel?

Answer 11

Open, Closed, inactivated

Question 12

What are the different states of the potassium voltage gated ion channels?

Answer 12

Open, closed

Question 13

What does “gate” mean in terms of trans-membrane protein channels?

Answer 13

refers to what causes the ion channel to change states

Question 14

How do ligand-gated ion channels work?

Answer 14

they open when they come in contact with a ligand or “a key” which can be another ion or a compound

Question 15

Where are thermally and mechanically gated ion channels found?

Answer 15

primarily in sensory neurons

Question 16

What are the 2 forces need for electrochemical equilibrium?

Answer 16

1. Electrostatic force
2. Molecular diffusion force

Question 17

What are the 2 key concepts of electrostatic force (coulombs law)?

Answer 17

• Opposites attract, like repels
• greater the distance, weaker the the attractive force (closer the distance, stronger the attractive force)

Question 18

What occurs at electrochemical equilibrium?

Answer 18

electro-static force is equal and opposite to the force of chemical diffusion

Question 19

Which ligand allows Na to rush in?

Answer 19

Glutamate, acetylcholin

Question 20

What ligand allows Cl to rush in?

Answer 20

GABA

Question 21

What is the difference between Na+ and K+ voltage gated ion channels?

Answer 21

Na+ has 3 states, K+ has 2 states

Question 22

True/false: leak channels are always open?

Answer 22

true

Question 23

What are leak channels critical for?

Answer 23

establishing baseline resting voltage of the neuron

Question 24

Which ion has the most leak channels?

Answer 24

K+

Question 25

What does the Nerst equation calculate?

Answer 25

Voltage at equilibrium

Question 26

What is the equilibrium potential for potassium?

Answer 26

-84mV

Question 27

What is the equilibrium potential for sodium?

Answer 27

67mV

Question 28

What is the equilibrium potential for chloride?

Answer 28

-67mV

Question 29

What is the equilibrium potential for Calcium?

Answer 29

116mV

Question 30

What is the resting potential of a neuron?

Answer 30

-65mV

Question 31

What 2 factors determine the resting potential of a neuron?

Answer 31

1. Permeability (neuron primarily permeable to K+ via leak channels)
2. Intra vs extracellular concentration (K+ more concentrated inside)

Question 32

Rank the following ions MOST to LEAST permeable at rest: Na, Cl, K

Answer 32

1. K (1) - most
2. Cl (0.45)
3. Na (0.04) - least

Question 33

Explain the process of a action potential:

Answer 33

1. All voltage gated channels closed (K+ leak channels open)
2. Na+ enters the neuron, making the the membrane potential more +, causing more voltage gated Na+ channels to open
3. Na+ channels inactivate while the K+ channels slowly open
4. K+ is still entering the cell making the voltage more - than at rest