SM36

Question 1

A highly positive equilibrium potential (for ex. sodium) means what?

Answer 1

Sodium is high outside cells but low inside

Question 2

The ________ _________ for a particular ion is the membrane potential at which there will be no movement of that ion across the membrane

Answer 2

Equilibrium Potential

Question 3

The Na/K-ATPase pump pushes ___ out of the cell and ___ into the cell. How many ions for each cycle?

Answer 3

3 Na+ ions moved out of cell and 2 K+ ions moved into cell

Question 4

Nernst Equation

Answer 4

Used to calculate equilibrium potential

Question 5

In these tissues, Cl conductance is important for stabilizing the resting membrane potential

Answer 5

Skeletal Muscle

Question 6

Goldman-Hodgkin-Katz Equation

Answer 6

Question 7

Ionophores

Answer 7

Chemical pores formed in membranes that promote K+ leakage and lead to cell death

Question 8

graded potentials

Answer 8

Transient changes in membrane potential. Amplitude and direction of graded potential is dependent on stimulus

Question 9

Acetylcholine receptors at the neuromuscular junction; glutamate receptors at neuronal synapses

Answer 9

examples of receptors permeable to Na2+ or Ca2+ whose activation causes EPSP

Question 10

Glycine receptors and GABA receptors

Answer 10

examples of receptors permeable to Cl- whose activation causes IPSP

Question 11

Disorder that results from loss of “safety factor” for motor neurons at neuromuscular junction. What is the mechanism of loss of the safety factor? How can it be treated?

Answer 11

Myasthenia Gravis – loss of acetylcholine receptors. Can be treated by inhibiting degradation of acetylcholine (inhibiting acetylcholinesterase)

The term ‘safety factor’ refers to the ability of neuromuscular transmission to remain effective under various physiological conditions and stresses. This is a result of the amount of transmitter released per nerve impulse being greater than that required to trigger an action potential in the muscle fibre. The safety factor is a measure of this excess of released transmitter.

Question 12

______ cells exhibit longer action potentials (hundreds of milliseconds) than _____ cells ( a few milliseconds)

Answer 12

heart muscle cell has longer AP than nerve and skeletal muscle cells

Question 13

-80 mV

Answer 13

approximate resting membrane potentials of neuronal membranes

Question 14

What is the electrochemical potential that is favorable towards repolarization

Answer 14

High intracellular K+ concentration (chemical) and depolarized membrane / positive cell interior (electrical)

Question 15

______ channel inactivation is a major reason for nerve cells having a refractory period (absolute and relative)

Answer 15

Sodium

Question 16

Phase 0 depolarization of cardiac muscle

Answer 16

Influx of Na via voltage gated sodium channels causes transiet depolarization

Question 17

Phase 1 of cardiac muscle action potential

Answer 17

Transient repolarization due to fast gating voltage-gated potassium channels accompanied with rapid inactivation of sodium channels. Voltage gated (L-type) calcium channels begin to activate.

Question 18

Phase 2 of cardiac muscle action potential

Answer 18

plateau phase - delicate balance between inward current (L-type calcium channels + residual Na channels) and outward current (two types of potassium channels - not the same type as in phase 1)

Question 19

Phase 3 of cardiac muscle action potential

Answer 19

Inward rectiyfing potassium current finish repolarization (Ik1). Occurs following inactivation of calcium channel, tipping the balance in favor of outward current.

Question 20

Long QT syndrome: causes and pathology

Answer 20

Causes: drugs that impair potassium currents, genetic mutations in genes encoding proteins responsible for ion currents

Pathology: prolonged cardiac porential due to diminished repolarizing potassium current or enhanced depolarizing Ca/Na currents. Predisposition to chaotic electrical impulses (aka ventricular fibrillation)

Question 24

Inward Current

Answer 24

The influx of positive charge (via influx of positive ions or efflux of negative ions)

Question 25

Outward Current

Answer 25

Efflux of positive charge (when positive ions exit cell or negative ions enter cell)