Physiology Unit 2: Module 8 - Membrane Potentials
Which of the following is the mechanism of the absolute refractory period?
K+ is high inside of the cell and low outside of the cell
Na+ channels are inactivated
Period of time after an action potential where it is impossible to trigger a new action potential
Na+ is high outside of the cell and low inside of the cell
Two neighboring neurons are at rest. Neuron A has a resting membrane potential of -80mV, Neuron B has a resting membrane potential of -70mV. Which is likely to be TRUE?
Neuron B has more Na+ channels open than Neuron A
Neuron A has more Na+ channels open than Neuron B
Neuron B has more K9 channels open than Neuron A
Neuron A has more K+ channels open than Neuron B
Novocain (used to stop pain) is a drug that blocks Na+ voltage-gated-channels. When present, what would happen in a neuron?
Graded potentials are possible and the neuron will have the depolarizing phase of the action potential, but will be unstable to repolarize
Neither graded potentials nor action potentials will occur
Graded potentials are possible, but the neuron will not have the depolarizing phase of the action potential
No phase of the action potentials will be affected
Which is TRUE about the resting membrane potential?
Only nerve and muscle cells have a resting a membrane potential
It requires disequilibrium of certain ions
It is not altered by changing concentration gradients of permeating ions
The inside of the cell is always positive
All of the above are correct
You are a neuroscientist. Using a micropipette, you inject an axon with enough Na+ ions to move the membrane potential -35mV (from resting -70mV). What happens next?
Na+ voltage-gated-channels will be triggered to open
The membrane potential will become less positive
The neuron membrane will be hyperpolarized
Na+ channels will be inactivated
A neurotransmitter binds to its receptor (a ligand-gated channel). The ligand- gated channels opens and ions travel down their concentration gradient into the cell, causing the voltage to go from -70mV to -90mV. This event describes:
Hyperpolarization in an axon
Hyperpolarization in a dendrite
Depolarization in a cell body
Repolarization in a cell body
What would occur first in a typical nerve cell that suddenly lost the ability to make ATP?
The concentration gradient for Na+ would remain the same
Resting membrane potential would become less negative
There would be no change in the resting membrane potential
Resting membrane potential would become more negative
The resting membrane potential would eventually become positive inside with respect to outside
When multiple, possibly even conflicting signals reach a neuron, the neuron evaluates the signals and may respond or not. This type of signaling is called:
Resting potential
Action potential
Graded potential
Refractory period
A person has a heart condition where they have lost their ability to repolarize, causing their heart to beat irregularly. This condition could be caused by an issue with which channel(s)? Choose the most correct answer.
Na+
Cl-
K+
Na+ & K+ (either or both)
Although a concentration gradient is still present, what causes K+ to stop diffusing out of the cell?
Lack of concentration gradient for K+
Increased concentration gradient
Electrochemical gradient
Equilibrium of K+ concentration
What information is presented in this graph?
The amount of voltage needed to feel a sensation in the finger
The amount of sensation felt in the finger
The amount of voltage & its frequency needed to feel a sensation in the finger
The stimulus frequency needed to feel a sensation in the finger
As voltage increases, the sensation decreases
Interpret the data in this graph.
As frequency ↓ = voltage ↓
� frequency of stimulus causes summation, resulting in a change of voltage needed to stimulate a sensation
As frequency ↑ = voltage ↓
� frequency of stimulus causes summation, resulting in a change of voltage needed to stimulate a sensation
What statement(s) are true regarding the relationship between voltage and signal frequency on the threshold required to stimulate a sensation?
� signal frequency → ↑ voltage needed
� signal frequency → ↓ voltage needed
� signal frequency → ↓ voltage needed
� signal frequency → ↑ voltage needed
Explain the data below.
As frequency ↓ = voltage ↓
As frequency ↑ = voltage ↓
� stimulus frequency causes summation, resulting in a ↓ voltage needed to meet threshold
� stimulus frequency causes summation, resulting in a ↓ voltage needed to meet threshold
Interpret the data below between finger & wrist:
Finger requires ↓ voltage than wrist
Finger 1 stimulus ≈ 24 volts
Finger requires ↑ voltage than wrist
Finger 1 stimulus ≈ 24 volts & wrist stimulus ≈ 27 volts
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