Electrical Synapse - McCool - Exam 1

Question 1

•The resting membrane potential (Vm) of the cell is equal to the summed contribution by individual permeant __ ___.

Answer 1

•The resting membrane potential (Vm) of the cell is equal to the summed contribution by individual permeant ion potentials

Question 2

• The equilibrium potential of ___ ___ determine the membrane potential
• Ionic permeability depends on: ____, “____” or leak

There are also active transport mechanisms

•__ ___ (charge distribution)

Answer 2

• The equilibrium potential of individual ions determine the membrane potential
• Ionic permeability depends on: Diffusion, “Channels” or leak

There are also active transport mechanisms

•Electrical potential (charge distribution)

Question 3

What are the four characteristics of an AP?

Answer 3

1. Threshold

•A critical level of depolarization is required to generate an AP.

2. All or None

•Once initiated, it will run its course regardless of the stimulus.

An inherent property of the membrane.

3. Five Phases – constant

•Depolarization (1), overshoot (Vm>0mV) (2), repolarization (3), after-hyperpolarization(4), recovery (5)

4. Refactory Period

Question 4

Refractory Periods:

• __ ___ period – impossible to initiate another AP
• __ __ period – possible to initiate, but has higher threshold and smaller amplitude

Answer 4

•Absolute refactory period – impossible to initiate another AP

•Relative refactory period – possible to initiate, but has higher threshold and smaller amplitude

Question 5

What mechanisms control the characteristics of the Action Potential?

Answer 5

• Sodium-dependence of the overshoot (not repolarization or after-hyperpolariztion)
• Ion-selective “channels” control the action potential

Question 6

Voltage-gated K+ channels

• Selective for K+
• 10,000X more effective than ___+
• Na+ – 0.95Å; K+ – 1.33Å

•Pharmacology

•____ (bee venom)

•Subunit structure

____ subunits

• MANY ____
• Distinct from ‘____’ K channels and ____-activated K channels

Answer 6

Voltage-gated K+ channels:

• Selective for K+
• 10,000X more effective than Na+
• Na+ – 0.95Å; K+ – 1.33Å

•Pharmacology

•Apamin (bee venom)

• Subunit structure
• Four subunits
• MANY isoforms
• Distinct from ‘leak’ K channels and hyperpolarization-activated K channels

Question 7

Voltage-Gated Sodium Channels

• Subunit structure (K-channel X 4)
• Nine distinct genes
• NaV 1.1-1.9
• Highly similar
• Tissue distribution
• Pharmacology
• Local anesthetics
• Novacaine, Lidocaine
• Anti-epileptics
• Anti-arrhythmics (lidocaine)

Many naturally occuring toxins (tetrodotoxin, saxitoxin, scorpion toxins

Answer 7

Voltage-Gated Sodium Channels

• Subunit structure (K-channel X 4)
• Nine distinct genes
• NaV 1.1-1.9
• Highly similar
• Tissue distribution
• Pharmacology
• Local anesthetics
• Novacaine, Lidocaine
• Anti-epileptics
• Anti-arrhythmics (lidocaine)

Many naturally occuring toxins (tetrodotoxin, saxitoxin, scorpion toxins

Question 8

Voltage gated Ca++ channels:

• Subunit structure – similar to sodium channels
• Accessory subunits
• a2/d, b, g – expression/function
• Pharmacology
• La3+, Co2+, Cd2+
• Conotoxins, agatoxins
• Natural toxins/paralytics

•Antihypertensives

• Dihyropyridines (nitrendipine, nifedipine)
• Diltiazem, Verapamil

•Anti-arrhythmics

•Verapamil

•Positive Modulators

•Beta adrenergic receptors

Answer 8

Voltage gated Ca++ channels:

• Subunit structure – similar to sodium channels
• Accessory subunits
• a2/d, b, g – expression/function
• Pharmacology
• La3+, Co2+, Cd2+
• Conotoxins, agatoxins
• Natural toxins/paralytics

•Antihypertensives

• Dihyropyridines (nitrendipine, nifedipine)
• Diltiazem, Verapamil

•Anti-arrhythmics

•Verapamil

•Positive Modulators

•Beta adrenergic receptors