BIOL 273 - Unit 2.2

Question 1

How do neurons transmit electrical impulses

Answer 1

via energy stored as an electrochemical gradient

Question 2

Describe the charge differences between the inside and outside of the cell , creating an electrical gradient

Answer 2

Intracellular fluid - has a net negative charge
Extracellular fluid - has a net positive charge

A relative difference in the # of cations and # of anions

Question 3

What is the difference of electrical potential between the inside and outside of the cell called

Answer 3

membrane potential

Question 4

What two factors determines the membrane electrical properties

Answer 4

1. an unequal distribution of key ions between the ICF and the ECF
2. Selective movement of these ions across the membrane

Question 5

Describe the unequal distribution of key ions between the ICF and the ECF (3)

Answer 5

1. Na+ and Ca+2 and Cl- are higher in ECF
2. K+ is higher in ICF
3. Anions are higher in the ICF

Question 6

How are concentration differences of Na+ and K+ maintained

Answer 6

by an Na+ and K+ pump
- uses ATP for energy to drive ions against the gradient

Question 7

What is the Equilibrium potential

Answer 7

the membrane potential that exactly opposes the concentration gradient of an ion
- the electrical and chemical forces acting on the ion are equal and opposite

Question 8

Describe the Nernst equation

Answer 8

calculates the electrical potential of a single ion needed to generate an equilibrium state
- the equilibrium potential

• looks at what membrane potential would be if the membrane was permeable to only one ion (ex Na+ only or K+ only)

Question 9

What is the equilibrium potential for K+ in a typical neuron

Answer 9

-90 mV

Question 10

What is the equilibrium potential for Na+ in a typical neuron

Answer 10

60mV

Question 11

What does the resting membrane potential refer to, what is the magnitude of the resting membrane potential of a neuron

Answer 11

Refers to the charge difference between the inside and outside of a cell at rest

• 70MV

Question 12

What does membrane potential refer to

Answer 12

the electrical and chemical gradients caused by the distribution of ions across the cell membrane is a source of stored (potential) energy

Question 13

What happens when a neuron sends a signal

Answer 13

it is no longer at rest, it moves away from the resting membrane potential

Question 14

What sets the resting membrane potential

Answer 14

The concentrations of each of the ions and their relative permeability

Question 15

What is the ion contribution to the resting membrane potential proportional to

Answer 15

permeability - the more easily it can cross the membrane, the more important it will be for the resting membrane potential

Question 16

Describe Depolarization

Answer 16

A decrease in the membrane potential difference
- cell membrane potential become less negative

Question 17

Describe Hyperpolarization

Answer 17

An increase in the membrane potential difference
- cell membrane potential becomes more negative

Question 18

What are the three gated ion channels used to regulate the movement of ions

Answer 18

1. Mechanically gated
2. Ligand gated
3. Voltage gated

Question 19

where are Mechanically gated ion channels found and how do they open

Answer 19

They are found in sensory neurons , open in response to physical forces

Question 20

What does Ligand gated ion channels respond to

Answer 20

respond to ligands such as neurotransmitters

Question 21

What does voltage gated ion channels respond to , why are they important

Answer 21

respond to changes in voltage
- important in initiation and conduction of electrical signals along the axon

Question 22

What are the 4 major types of selective ion channels in the neuron

Answer 22

1. Na+ channels
2. K+ channels
3. Ca+2 channels
4. Cl- channels