L7 Action Potentials

Question 1

Which is greater: Na+’s inward driving force or K+’s outward driving force?

Answer 1

Na+’s inward driving force is greater due to it’s electrical pull (+65 to -70 they want to be together)

Question 2

Is the permeability for Na+ High or Low at resting membrane potential?

Answer 2

LOW

Question 3

During the absolute refractory period, are the sodium inactivation gates open or closed?

Answer 3

They are CLOSED

When will they reopen? Once the potential gets back down to -55

Question 4

During the relative refractory period, are the sodium inactivation gates opened or closed?

Answer 4

They are starting to reopen.

Reopening starts once the cell gets back down to -55 mV

Question 5

What effect does hyperkalemia have on muscle contraction?

Answer 5

Causes episodes of painful muscle contractions followed by paralysis.

Paralysis due to membrane potential getting above -55 and the sodium inactivation gates closing, not allowing another action potential to fire

Question 6

Does a neuron fiber with a larger diameter conduct currents faster or slower than a more narrow diameter?

Answer 6

Faster!

Larger neurons are usually motor neurons, where as smaller ones are for internal organs like glands and guts

Question 7

What is contiguous conduction/

Answer 7

Conduction in unmyelinated fibers

Slow

Question 8

What is saltatory conduction?

Answer 8

Nerve impulse jumps between nodes of ranvier (myelinated nerve fiber)

50x faster than saltatory conduction

Question 9

How can you code for the strength of a stimulus if all action potentials are identical?

Answer 9

Frequency of action potentials

More frequent AP’s= more neurotransmitters released, =stronger signal

Question 10

What effect would degeneration of myelin have on AP frequency and therefore, muscle strength?

Answer 10

Frequency would slow down, and the person would have trouble getting maximal stimulus to their muscles….muscle weakness, trouble maintaining posture, etc

Question 11

What effect would overgrowth of myelin have on muscles contraction?

Answer 11

If myelin grew over the nodes of ranvier, the action potential could not continue, and it would fizzle out before it got to the end of axon

Question 12

What tupe of channel determines resting membrane potential?

Answer 12

Leaky channels

Question 13

What types of channels affect graded potentials?

Answer 13

Chemically gated channels

Question 14

What types of channels cause action potentials?

Answer 14

Voltage gated channels