Physiology Mastering Ch. 8
Which membrane potential opens a sufficient number of the voltage-gated Na+ channels to cause a significant change in the membrane potential (making it much less negative).
-60mv
What is the resting membrane potential of the neuron used in the experiment?
-80 mv
Which two properties determine the conduction velocity in a mammalian neuron?
Axon diameter and the leak resistance of the membrane
Which of the following describes a similarity between graded potentials and action potentials?
Both can involve voltage-gated sodium channels.
The part of the neuron that receives most of the incoming signals is the __________.
Dendrite
The multiple thin, branched structures on a neuron whose main function is to receive incoming signals are the
Dendrites
Anterograde and retrograde axonal transport are forms of ________ transport.
Fast
An axon that is more negative than the resting membrane potential is said to be _______.
Hyperpolarized
Where do most action potentials originate?
Initial segment
During an action potential, activation of voltage-gated sodium and potassium channels occurs at different rates. What is the effect of this difference on ion flow across an axon membrane?
Initially, Na+ flows into the cell followed by K+ flowing out of the cell.
If an increase in extracellular potassium hyperpolarizes a neuron, which of the following would be correct?
It would change the membrane potential to a more negative value.
What would happen to the membrane potential if a resting cell suddenly becomes more permeable to Na+?
It would depolarize
The channels that provide for the movement of potassium in the resting neuron are _______.
Leakage
Which type of receptor would bind acetylcholine and be found in skeletal muscle?
Nicotinic cholinergic
Which glial cells form myelin in the central nervous system?
Oligodendrocytes
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
What effect did decreasing the extracellular sodium have on the resting membrane potential?
Only a small change occurred, because the resting neuron is not very permeable to sodium.
Interneurons are found
Only in the CNS
The afferent and efferent axons together form the
Peripheral nervous system
Most neurons have at least two processes extending from the soma, or cell body. Which type of neuron only has one process extending from the cell body?
Pseudounipolar neuron
Myelin is formed by
Schwann cells and oligodendrocytes.
Which of the following neurons or groups of neurons are NOT considered to be a part of the efferent pathway?
Sensory
Establishing the resting membrane potential requires energy through the use of the _______.
Sodium-potassium pump
In this experiment, which stimulus causes the membrane potential to reach the threshold value?
Stimulus 3
The sympathetic and parasympathetic nervous systems are divisions of which system?
The autonomic nervous system
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What effect did increasing the extracellular potassium have on the resting membrane potential?
The resting membrane potential became less negative
Why are Na+, K+, and Cl- the only ions considered in the GK equation when calculating resting membrane potential (Vm)?
These are the ions to which cell membranes are permeable at rest.
The minimum voltage that is required to generate an action potential is called the _______.
Threshold voltage
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, and their activation gates open.
A weak, subthreshold stimulus will result in _______.
a small depolarization at the receiving end of the neuron
Information coming into the central nervous system is transmitted along ________ neurons.
afferent and sensory
A depolarizing synaptic potential is also known as _______.
an excitatory postsynaptic potential
An excitatory postsynaptic potential occurs _______.
at the receiving end of the interneuron
Neurotransmitter is stored and released from
axon terminals and axon varicosities.
A suprathreshold stimulus results in _______.
more action potentials
Increasing the voltage resulted in which of the following?
no change to the action potential
A single action potential is described as _______.
not graded
Which of the following would NOT cause the membrane potential to change from -70 mV to +30 mV?
potassium ions leaving the cell
The stimulus for graded potentials includes _______.
sensory stimuli and neurotransmitter
Autonomic motor neurons are subdivided into the
sympathetic and parasympathetic divisions.
Increasing the strength of the stimulus applied to the sensory receptor increased _______.
the frequency of action potentials in the sensory neuron, the amount of neurotransmitter released at the axon terminal of the sensory neuron and the frequency of action potentials in the interneuron
Which stimulus was at or above threshold?
the moderate and strong stimuli
Whether or not a neuron produces an action potential at a given moment depends on ________.
the total potential change reaching threshold voltage at the trigger zone
