Lecture 7

Question 1

VG Na+ Channel does what

Answer 1

• opens quickly
• inactivates quickly
• drives rapid reversal of membrane potential

Question 2

VG K+ Channel what does it do:

Answer 2

• opens slowly
• Stays open longer
• drives repolarization and after - hyperpolarization

Question 3

The Characteristic Phases of the AP

Answer 3

Opening/closing of voltage gated ion channels

Question 4

Depolarization involves

Answer 4

A 30x increase in Na+ conductance

Question 5

Repolarization involves

Answer 5

A decrease in gNa and a delayed increases in gk

Question 6

What is Conductance

Answer 6

Movement of charge per unit space

Question 7

The VG Na+ Channel has two gates:

Answer 7

1. A voltage dependent activation gate
2. A voltage-dependent time-delayed inactivation gate

Question 8

AP move down the axon

Answer 8

Without decrement

Question 9

Local Na+ currents spread longitudinally via:

Answer 9

Electronic conduction and depolarize adjacent particles

Question 10

The innactivation gate

Answer 10

Prevents AP from traveling backwards

Question 11

After an AP is triggered

Answer 11

Neurons enter a refractory period

Question 12

During the absolute refractory Periods

Answer 12

No AP can be triggered because the voltage-gated Na+ channels are in an inactivated state

Question 13

It is generally harder to generate a new AP during the relative refractory period because:

Answer 13

The membrane is hyperpolarized

Question 14

Signal Conduction can Occur by:

Answer 14

• Passive spread (electronic)
• action Potentials (AP)
• Saltatory conduction
• chemical and electronically synapses

Question 15

Axonal Conditions

Answer 15

• combination of electronic current flow and APs
• electronic current flow is much faster than APs
• electronic current flow is graded and can only travel short distances

Question 16

Factors Affecting Conduction Speed: 1. The Length Constant (lambda)

Answer 16

• the decay of Vm with distance in described by the length constant: lambda

Question 17

Factors Affecting Conduction Speed: 2. The Time Constant (T)

Answer 17

Membrane voltage changes are reduced by high membrane capacitance and resistance

Question 18

Factors Affecting Speed of Propagation: 1. Axon myelination

Answer 18

• the axon of some neurons are wrapped with myelin
• Myelination increases speed of propagation
• Segmented myelination leads to fast saltatory conduction of APs

Question 19

Myelination prevents ions from leaking out through:

Answer 19

a membrane as the charge spreads

Question 20

Charge spreads until it reaches the:

Answer 20

Node of Ranvier, which is packed with Na+ and K+ channels

Question 21

Factors Affecting Speed of Propagation: 2. Axon Diameter

Answer 21

Increased axonal diameter reduces longitudinal resistance (RI), thereby increasing the length constant and conduction velocity