Chapter 12 Mastering A&P Questions
Which ion triggers synaptic vescicles to dicharge neurotransmitters into the synaptic cleft?
calcium
The release of acetylcholine into the synaptic cleft by exocytosis is triggered by __________.
calcium ions flooding into the synaptic terminal
The main inhibitory neurotransmitter of the CNS is __________.
gamma-aminobutyric acid (GABA)
If EPSPs summate to a sustained value above threshold, then the initial segment will __________.
generate a string of action potentials
Which of the following is the most excitatory neurotransmitter in the brain and functions in learning and memory?
glutamate
In contrast to the internodes of a myelinated axon, the nodes __________.
have lower membrane resistance to ion movement
Josh and a bunch of friends decided to see how many people they could squeeze into a small car for a charity event. Once inside, Josh felt it get hot, smelly, and like the air was getting squished out of his lungs. He also noticed aches and pains in his joints. Which of the following statements best describes the type of sensory neurons involved?
his interoreceptors, exteroreceptors, and proprietoreceptors were all monitoring his condition
What is phase 3 of action potential?
hyperpolarzation - enough K+ leaves that membrane potential goes all the way down to -90 for a second
Compared to the electrical gradient for sodium at rest, the electrical gradient for potassium at rest is __________.
in the same direction and of the same magnitude
In a typical neuron, what is the equilibrium potential for sodium?
+66
The concentrations of which two ions are highest outside the cell?
Na+ and Cl- are highest in ECF
Neurotransmitters and neuromodulators may belong to all of the following molecular classes EXCEPT __________. a. carbohydrates b. amino acids c. purines d. lipids
a. carbohydrates
Where in the neuron is an action potential initially generated?
axon hillock
Where do most action potentials originate?
axon hillock of cell body and initial segment of axon
The simplest level of information processing takes place at the ______.
axon hilock
Resynthesis of ACh occurs in the _____.
axon terminal
At a chemical synapse, the intensity of the stimulus is coded by _______.
the amount of neurotransmitter released and the amount of calcium that enters the axon terminal
When magnesium was added to the extracellular solution, _______.
the amt of neurotransmitter released decreased
Proprioception is _______.
the awareness of one's position and movement of skeletal muscles and joints
What forces are involved in creating the electrochemical gradient for potassium?
the chemical gradient moves potassium out of the cell, while the electrical gradietn keeps potassium in the cell
Why does regeneration of the action potential occur in one direction rather than in two directions?
the inactivation gates of voltgae gated Na+ channels close in the node, or segment, that has just fired an action potential
Which of the following is true of axons?
the larger the diameter of the axon, the faster the rate of transmission
What changes shape of voltgae gated channels?
threshold stimulus; causes activation gates to open marking beginning of phase 1 of action potential called depolarization
The term for the minimum membrane potential needed to trigger an action potential to occur is __________.
threshold
Saltatory propagation conducts impulses along an axon __________.
five to seven times faster than does continuous conduction
Around what transmembrane potential does threshold commonly occur?
-60mV
The sodium-potassium exchange pump stabilizes resting potential of the neuron membrane at about __________.
-70mV
What is the value for the resting membrane potential for most neurons?
-70mV
In a typical neuron, what is the equilibrium potential for potassium?
-90mV
Approximately how fast do action potentials propagate in unmyelinated axons in humans?
1 meter per second
What is the magnitude (amplitude) of an action potential?
100mV
Identify the number that represents the portion of the action potential when voltage-gated sodium channels open.
2
What is the typical duration of a nerve action potential?
2ms
How does acetylcholine (ACh) stimulate the postsynaptic membrane?
ACh causes Na+ inflow, which depolarizes the postsynaptic membrane
What happens to acetylcholine (ACh) after it is released from the presynaptic membrane?
ACh is broken down and the choline is reabsorbed.
The neurotransmitter glutamate opens channels that are permeable to sodium ions. What effect does glutamate produce on the postsynaptic neuron?
EPSP's
Emma is very excited because after taking up running several months ago, she has begun to experience the phenomenon called "runner's high." This is caused by the production of endorphins. What is the effect of endorphins on Emma when she runs?
Endorphins block the transmission of substance P, a neurotransmitter that sends information about pain to the CNS.
What ion causes repolarization of the neuron during an action potential?
K+
In which direction is each ion pumped in the sodium-potassium channels?
Na+ is pumped out; K+ is pumped in
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.
One possible condition resulting from damage to or destruction of neurons that produce dopamine in a part of the brain controlling movement is __________.
Parkinson's disease
Tyson decides to travel overseas, but he does not get all the needed vaccines before he goes on the trip. While on his trip, he contracts diphtheria. Which type of glial cells are particularly at risk from this disease?
Schwann cells
Which neuroglia cells form the myelin sheath of motor nerves?
Schwann cells
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential.
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.
In terms of neurotransmitter function, what is meant by the term "direct effect" on the target cell?
The neurotransmitter has its effect on receptors on the target cell membrane.
If 100 excitatory neurons released their neurotransmitter from synapses on the same neuron, and at the same time 40 inhibitory neurons released their neurotransmitter on the same neuron at the same time, what would the net effect be on the postsynaptic neuron's membrane potential?
The postsynaptic cell's membrane would be depolarized and excited.
Female gymnasts can contort their bodies in many different ways and land on a 4" beam with accuracy. Which fiber type is responsible for this ability
Type A fibers
What occurs during repolarization?
Voltage-gated potassium channels open and some voltage-gated sodium channels inactivate. Potassium flows out of the cell
The electrochemical gradient for potassium ions when the transmembrane potential is at the resting potential (-70mV) is caused by what?
a chemical gradient going out of the cell and an electrical gradient going into the cell
Motor neurons are an example of what type or class of neuron?
a multipolar neuron that has two or more dendrites and a single axon
Which of the following describes multipolar neurons?
a neuron with two or more dendrites; characteristic of all motor neurons
The membrane potential that occurs when neurotransmitters bind to their receptors is called _____.
a postsynaptic potential
Rabies illustrates a negative consequence to otherwise healthy retrograde flow within axons. Which of the following components will NOT be involved in retrograde flow? a. kinesin b. neuronal cell body c. axon hillock d. axoplasm
a. kinesin
Which of the following is NOT a characteristic of a graded potential? a. propagates along the entire membrane without a decrease in strength b. can be depolarizing or hyperpolarizing c. passively spreads outward in all directions from the site of stimulation with a decrease in intensity d. amount of stimulation depends on the intensity of the stmiulus
a. propagates along the entire membrane without a decrease in strength (this is NOT a characteristic of a graded potential)
Which of these substances is NOT considered a neuromodulator? a. substance P b. opioids c. endorphins d. enkephalins
a. substance P
Both poliomyelitis and Guillain-Barré syndrome can involve paralysis where control over skeletal muscle function is lost. What is the neurotransmitter that a motor neuron uses to communicate with a skeletal muscle?
acetylcholine
Which division of the PNS would contain sensory nerve fibers from special sensory receptors?
afferent
Interneurons are responsible for __________.
analysis of sensory inputs and coordination of motor outputs
What most directly causes the exocytosis of ACh in the synaptic vescicles?
arrival of calcium ions at the axon terminal
When a person has a stroke, blood leaks into the brain tissue. Which type of neuroglia cells would make structural repairs to the damage?
astrocytes
Where are action potentials regenerated as they propagate along an unmyelinated axon?
at every segment of the axon
The release of neurotransmitter occurs _____.
at the axon terminal
Where are action potentials regenerated as they propagate along a myelinated axon?
at the nodes
When a neuron communicates with another at a synapse with a dendrite, this is called a ______ synapse.
axodendritic
Which of the following occurs first? a. extracellular calcium enters the axon terminal b. an action potential arrives at the axon terminal c. voltage-gated calcim channels are opened d. synaptic vescicles exit by exocytosis
b. an action potential arrives at the axon terminal
Which of these types of neuroglia are abundant in peripheral ganglia? a. microglia b. satellite cells c. astrocytes d. oligodendrocytes
b. satellite cells
At rest, why is the transmembrane potential of a neuron (70mV) much closer to the potassium equilibrium potential (-90mV) than it is to the sodium equilibrium potential?
because the membrane is much more permeable to potassium than it is to sodium
During depolarization, which gradient moves NA+ into the cell?
both the electrical and chemical gradients
The afferent division of the PNS __________.
carries sensory information
Typical CNS neurons are amitotic due to the absence of what structure?
centrioles
Leak channels allow the movement of potassium and sodium ions by what type of membrane transport?
channel-mediated diffusion
The electrochemical gradient for sodium ions in a neuron when the transmembrane potential is at the resting potential is caused by what?
chemical and electrical gradients both going into the cell
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.
chemically gated; postsynaptic
In order to communicate with multiple cells at the same time, an axon may branch along its length, producing side branches called __________.
collaterals
What type of conduction takes place in unmyelinated axons?
continuous conduction (propagation)
Compared to type A axons, type C axons are ____. a. smaller diameter b. slower propagating c. unmyelinated d. all of the above
d. all of the above
During propagation of the action potential, _________. a. after threshold is reached, voltage-gated sodium channels open b. the axon hilock depolarized the inital segment c. local currents depolarize a spot adjacent to the active zone d. all of the above.
d. all of the above
In which cell does a graded potential occur? a. adipocytes b. epithelial cells c. neurons d. all of the above
d. all of the above
A synaptic cleft, or synaptic gap, can be found between a neuron and a _____. a. muscle cell b. another neuron c. a gland d. all of these
d. all of these
Which of these neurotransmitters is released at CNS adrenergic synapses? a. adrenaline b. serotonin c. GABA d. norepinephrine
d. norepinephrine
Which of the following occurs first in the generation of an action potential? a. voltage-gated sodium channels open b. voltage-gated potassium channels open c. the membrane repolarizes d. the membrane depolarizes
d. the membrane depolarizes
Demyelination disorders such as multiple sclerosis are particularly dangerous because they __________.
decrease the speed of action potential transmission
An action potential is self-regenerating because _____.
depolarizing current established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Calcium and magnesium are both _______.
divalent cations
During the action potential, when does sodium permeability initially decrease?
during the peak of depolarization
Which of the following has/have effects similar to those of morphine and function(s) to relieve pain? a. dopamine b. GABA c. endorphins d. serotonin
enndorphins
What type of membrane transport causes the depolarization phase of the action potential in neurons?
facilitated diffusion
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
inactivation gates of Na+ channels close; activation gates of K+ channels open
Increase in stimulus intensity _______.
increases the frequency of action potentials
How do neurotransmitters like norepinephrine and dopamine exert their effect on their target cells?
indirect effect using G proteins in target cell membrane
Phase 1 of action potential is marked by what?
influx of sodium ions and increase in membrane potential (going from negative to positive)
In what part of the neuron does the action potential typically initiate?
initial segment of the axon
In an electrical synapse, what allows the action potential to pass from one cell to the next?
integral membrane proteins called connexons allow the action potential to be transmitted
After a large meal, Michelle's stomach feels very full. The sensory neurons responsible for sending this sense of fullness are __________.
interoreceptors
The time interval between action potentials is called the _______.
interspike interval
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron...
ion channels in the plasma membrane of the receiving neuron open
What is the function of the myelin sheath?
it increases the speed of action potential conduction from the initial segment to the axom terminals
If a nereve cell receives many IPSP's in different locations at the same time, _______.
it will show spatial summation
In what type of axons will action potential propagate fastest?
largest diameter, myelinated
Which type of ion channel is always open?
leak
What happens as potassium ions diffuse out?
membrane potential goes down
Most CNS neurons fall into which structural category?
multipolar
A molecule that carrries information across a synaptic cleft is a ____.
neurotransmitter
Which of these neurotransmitters does not bind to a plasma membrane receptor?
nitric oxide
When the calcium was removed from the extracellular solution, _______.
no transmitter was released
Neurons that release __________ have adrenergic synapses.
norepinephrine
Demyelination results from issues associated with myelin producing cells. Which of the following is an example of a myelin producing cell in the CNS?
oligodendrocytes
Unmyelinated axons are _____.
only partially surrounded by myelin
Which of the following is NOT associated with an inhibitory postsynaptic potential (IPSP)?
opening of chemically gated ion channels that lead to depolarization
What happens by the end of hyperpolarization?
potassium channels close and the membrane returns to resting state (-79mV) so that it is able to fire another action potential
What causes repolarization of the membrane potential during the action potential of a neuron?
potassium efflux (leaving the cell)
The neurotransmitter GABA blocks presynaptic voltage-gated calcium channels. Consequently, GABA produces _____.
presynaptic inhibition
How do action potential propagation speeds in myelinated and unmyelinated axons compare?
propagation speeds are faster in myelinated cells
What is phase 2 of action potentials?
repolarization - sodium channels close and potassium channels open
Myelin limits the movement of ions across the axon membrane, so the action potential "jumps" from node to node along the axon. This is an example of what type of propagation?
saltatory
The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.
saltatory propagation
Which neurotransmitter is associated with a person's emotional states and moods and is linked to depression?
serotonin
The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?
sodium (Na+)
The sodium-potassium exchange pump transports potassium and sodium ions in which directions?
sodium ions are transported out of the cell; potassium ions are transported into the cell
What occurs during depolarization?
sodium ions flow into the cell
The addition of the effects of release of neurotransmitter from multiple synapses at the same time on the same neuron is __________.
spatial summation
The small space between the sending neuron and the receiving neuron is the
synaptic cleft
One communication pathway in the central nervous system (CNS) has three neurons and another pathway has five neurons. If the neurons are identical, what process determines which pathway transmits the impulses faster?
synaptic delay
When you take a pain reliever, which of the following best describes, in general terms, how this affects the threshold of neurons?
taking a pain reliever increases the threshold
What characterizes depolarization, the first phase of the action potential?
the membrane potential changes from a negative value to a positive value
In a myelinated axon, action potential regeneration occurs at the what?
the nodes (where myelin is absent)
The repolarization phase of an action potential results from ____.
the opening of voltage-gated K+ channels
The cranial and spinal nerves make up what part of the nervous system?
the peripheral nervous system
In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?
the previous axon segment is refractory
If a signal from a sending neuron makes the receiving neuron more negative inside,
the receiving neuron is less likely to generate an action potential
The frequency of action potentials is _______.
the reciprocal of the interspike interval, and measured in hertz
During the action potential, the rapid decrease in sodium permeability and increase in potassium permeability is responsible for _______.
the repolarization phase
In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________.
the sodium concentration is higher outside the cell than inside the cell and the potassium concentration is higher inside the cell than outside the cell
What component of a nerve cell puts the Na+ and K+ back where they belong after an action potential?
the sodium potassium pump
During the relative refractory period, _______.
the stimulus must be above threshold to generate an action potential
What is the electrochemcial gradient of an ion?
the sum of the electrical and chemical gradients for that ion
During an action potential of a neuron, what directly causes the different channels to open and close?
the transmembrane potential
The membranes of neurons at rest are very permeable to ___ but only slightly permeable to ___.
they are very permeable to K+ but only slightly permeable to Na+
When calcium ions enter the synaptic terminal,
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
Tumors that originate within the central nervous system (CNS) are due to __________.
uncontrolled divisions of neuroglia (neurons cannot divide in adults)
What happens when membrane potential reaches +30mv?
voltage gated sodium channels close and voltage gated poatssium channels open
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
voltage-gated Ca2+ channels
The generation of an action potential in a neuron requires the presence of what type of membrane channels?
voltage-gated channels
What kind of channels open and close during an action potential?
voltage-gated channnels (which alter permeability of membrane to sodium and potassium)
What is primarily responsible for the brief hyperpolarization near the end of the action potential?
voltage-gated potassium channels taking some time to close in response to negative membrane potential
What channels are most directly responsible for the properties of the axon that lead to action potential generation?
voltage-gated sodium channels
During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential?
voltage-gated sodium channels begin to inactivate (close), and voltage-gated potassium channels begin to open
What happens just after an axon is depolarized to threshold?
voltage-gated sodium channels open
Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation?
without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes
