Physiology Practice Chapter 8
The rearrangement of connections at synapses, which occurs throughout life, is termed
C. Plasticity
When multiple, possibly even conflicting signals reach a neuron, the neuron evaluates the signals and may respond or not. This property is called?
C. Postsynaptic integration
Cells that form supportive capsules around cell bodies
C. Satellite cells
To increase the amount of neurotransmitter released onto a postsynaptic cell, the presynaptic cell would have to
C. Send action potentials with higher frequency.
The region where the axon terminal meets its target cell is called the
C. Synapse
Caffeine, nicotine, and alcohol all have effects on
C. Synaptic activity
What stops the rising phase of the action potential?
C. The Na+ inactivation gate closes
Identify the FALSE statement
C. The amplitude of the action potential depends on the amplitude of the graded potential that precedes it
The total amount of neurotransmitter released at the axon terminal is directly related to
C. The total number of action potentials
The site of information integration in the nervous system is the
C. Trigger zone
The term axonal transport refers to
C. Vesicle transport of proteins and organelles down the axon
Which is/are the most common inhibitory neurotransmitter(s) of the CNS?
D. A and B (GABA and glycine)
When the neuron is at rest, which statement is true
D. A and B (The activation gate is close and the inactivation gate is open)
Information coming into the central nervous system is transmitted along _________ neurons.
D. A and B (afferent and sensory)
The resting membrane potential results from
D. A and B (uneven distribution of ions across the membrane and differences in membrane permeability to Na+ and K+)
When voltage-gated Na+ channels of a resting neuron open,
D. A and C (Na+ enters the neuron and the neuron depolarizes)
Graded potentials bcan
D. A and C (act as signals over short distances and cause or prevent an action potential)
When comparing action potentials to graded potentials, an important distinguishing characteristic is
D. A and C (only graded potentials can undergo summation and the rate of action potentials is limited by the refractory period)
Ion concentrations are first significantly affected after ______ action potential(s)
D. A few thousand
If the sodium-potassium pumps in the cell membrane of a neuron fail to function, over time
D. All of the above (the extracellular concentration of potassium ion will increase, the intracellular concentration of sodium ion will increase and the membrane resting potential will become more positive than normal)
Once the stimulus alters the receptor on the cell's membrane, what happens next?
D. Any of the above could happen next (Ion channels open allowing ions to enter or exit, the membrane permeability is altered and a second messenger is activated on the inside of the cell)
Once the action potential reaches the axon terminal, what happens next?
D. Any of the above could happen next (exocytosis of the neurocrine, release of the neurotransmitter into the synaptic cleft and release of a neurohormone into the blood)
The axon is connected to the cell body by the
D. Axon hillock
Presynaptic facilitation occurs when
D. Calcium channels in the presynaptic membrane remain open longer
In terms of embryonic origin, neurons are most closely related to _______ cells.
D. Epithelial
Clusters of nerve cell bodies in the peripheral nervous system are called
D. Ganglia
Which ion(s) is/are higher in concentration inside the cell compared to outside?
A. Potassium
All of the following must occur before a second action potential can begin, EXCEPT
A. the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments
Tom's father suffers a stroke that leaves him partially paralyzed on his right side. What type of glial cell would you expect to find in increased numbers in the damaged area of the brain that is affected by the stroke?
D. Microglia
The point during an action potential when the inside of the cell has become more positive than the outside is known as the
D. Overshoot
The afferent and efferent axons together form the
D. Peripheral nervous system
When sodium channels open during an action potential, the opening is caused by
D. Presence positive charge
Cells in the PNS that form myelin
D. Schwann cells
Cells that myelinate only one axon each; multiple cells per axon
D. Schwann cells
Repair of damaged neurons can be assisted by certain neurotrophic factors secreted by
D. Schwann cells
How would blocking retrograde transport in an axon affect the activity of a neuron?
D. The cell body would not be able to respond to changes in the distal end of the axon
The Nernst equation predicts
D. The membrane potential resulting from permeability to a single ion
Tetrodotoxin is a toxin that blocks voltage-gated sodium channels. What effect does this substance have on the function of neurons?
D. The neuron is not able to propagate action potentials
Inactivation of the sodium channel is possible because
D. There is more than one gate that can close the channel
If an electrode is placed in the middle of a resting axon and an above-threshold voltage is applied, action potentials
D. Will start at that point and travel in both directions in the axon
An influx of Na+ ions depolarizes the membrane of an axon
True
If the graded potential increases in amplitude, then the frequency of the action potentials fired also increases
True
The absolute refractory period is important in unidirectional propagation of action potentials
True
During childhood, growth and development of the brain PRIMARILY occurs by increasing
E. B and C (neuron size and number of dendrites and synapses)
The primary problem in hyperkalemia is that
E. B and C (neurons are harder to excite because their resting potential is hyperpolarized and neurons respond too quickly to smaller graded potentials)
Myelin is formed by
E. C and D (Schwann cells and oliogodrocytes)
Which of the following is NOT a known drug effect on synaptic function?
E. Change the type of neurotransmitter found in the synaptic function?
Inhibitory neurotransmitters of the CNS act by opening _______ channels
E. Cl- or K+
These glial cells may be a source of treatment for neural degenerative disorders.
E. Ependymal cells
Learning and memory are thought to be due to a synaptic phenomenon known as
E. Long-term potentiation
The collection of axons that carries information between the central nervous systems and the peripheral effectors is called the
E. Nerve
Which is NOT a neuroeffector junction? The junction between a neuron and a(n)
E. Neuron
Cells in the CNS that form myelin
E. Oligodendrocytes
Cells that myelinate several axons
E. Oligodendrocytes
The sodium-potassium exchange pump
E. Requires ATP to function
Which of the following does NOT influence the time necessary for a nerve impulse to be conveyed by a particular neuron?
E. Whether axon is sensory or motor
Which is the correctly written Nernst equation?
A. 61/z x log [ion]out / [ion]in
An increased threshold is associated with the ________ refractory period
A. Absolute
The term hyperkalemia specifically indicates too much potassium in which fluid compartment?
A. Blood
(Matching) Astrocytes
A. CNS
(Matching) Ependymal cells
A. CNS
(Matching) Microglia
A. CNS
(Matching) Oligodendrocytes
A. CNS
A damaged neuron has a better chance of survival and repair if the _______ is/are undamaged?
A. Cell body
The brain and spinal cord together compose the
A. Central Nervous System
Which type of synapse is most prevalent in the nervous system?
A. Chemical
In the membrane of a resting nerve cell, when chemically gated Cl- channels open,
A. Cl- ions enter the cell
Contribute(s) most to membrane surface area of cell
A. Dendrites
Receive(s) most of the incoming synapses
A. Dendrites
Where most graded potentials originate
A. Dendrites
Cells that are a source of neural stem cells
A. Ependymal cells
Cells that create a selectively permeable epithelial layer to separate fluid compartments of the CNS
A. Ependymal cells
Anterograde and retrograde axonal transport are forms of _______ transport
A. Fast
Can involve ion channels regulated by chemicals
A. Graded potential
May be hyperpolarizing
A. Graded potential
Originate(s) on dendrites and cell bodies
A. Graded potential
Size increase if stimulus strength increases
A. Graded potential
How would the absolute refractory period be affected if voltage-gated sodium sodium channels remain inactivated?
A. It would be longer than normal
The basis of neural integration is
A. Linear addition of postsynaptic potentials overlapping in time and space
When more action potentials arrive at the axon terminal, how are neurotransmitters affected?
A. More molecules are released into the synapse
Excitatory neurotransmitters of the CNS usually act by opening _______ channels
A. Na+
The rising phase of the action potential is due to
A. Na+ flow into the cell
A chemical synapse ALWAYS includes _________. 1. axon terminal 2. presynaptic cell 3. synaptic cleft 4. postsynaptic cell 5. dendrite
B. 1, 2, 3, 4
The following are steps involved in transmission at the cholinergic synapse 1. Chemically regulated ion channels on the postsynaptic membrane are activated 2. Calcium ions enter the axon terminal 3. An action potential depolarizes the axon terminal at the presynaptic membrane 4. Acetylcholine is released from storage vesicles by exocytosis 5. Acetylcholine binds to receptors on the postsynaptic membrane The correct sequence for these events is:
B. 3, 2, 4, 5, 1
The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated 2. Voltage-regulated potassium channels open and potassium moves out of the cell, initiating repolarization 3. Sodium channels regain their normal properties 4. A graded depolarization brings an area of an excitable membrane to threshold 5. A temporary hyperpolarization occurs 6. Sodium channel activation occurs 7. Sodium ions enter the cell and further depolarization occurs The proper sequence of events is:
B. 4, 6, 7, 1, 2, 3, 5
Arrange the following events in the proper sequence 1. Efferent neuron reaches threshold and fires an action potential 2. Afferent neuron reaches threshold and fires and action potential 3. Efferent organ responds by performing output 4. Integrating centers reach decision about response 5. Sensory organ detects change in the environment
B. 5, 2, 4, 1, 3
Originate(s) at the trigger zone
B. Action potential
Require(s) a minimum stimulus to occur
B. Action potential
The all-or-nothing principle states that
B. All stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude.
Highly branched cells that transfer nutrients between blood vessels and neurons
B. Astrocytes
Exocrine glands, smooth muscles, and cardiac muscles are controlled by the
B. Autonomic nervous system
Has/have voltage-gated ion channels
B. Axon
Location of voltage-gated ion channels
B. Axon
May be covered with myelin
B. Axon
Neurotransmitters are released from the
B. Axon terminals
Glial cells communicate primarily using
B. Chemical signals
Ion channel inactivation is
B. Closing of the channel even when the stimulus continues
The pattern of synaptic connectivity where a large number of presynaptic neurons provide input to a single postsynaptic neuron, is known as
B. Convergence
A home satellite dish receives signals from a satellite, allowing your television to display TV shows. Which part of the neuron is analogous to the satellite dish?
B. Dendrites
Microvilli are present on cells that, because of their function, benefit from an increased membrane surface area. Which structure(s) on a neuron provide a comparable benefit?
B. Dendrites
The enteric nervous system is a network of neurons that function in controlling
B. Digestion
Detailed understanding of the cellular basis of signaling in the nervous system has lead to good understanding of consciousness, intelligence, and emotion.
B. False
In order for a synapse to be an effective means of cellular communication, slow removal or inactiviation of neurotransmitter molecules from the synapse is important
B. False
The neurotransmitter though to be involved in learning and memory is
B. Glutamate
Which of the following will increase the conduction rate of action potentials?
B. Increase the diameter of the axon, increase the resistance of the axon membrane to ion leakage
Conduction occurs along an axon because
B. Inflow of Na+ triggers the adjacent channels to open
The inactivation gate
B. Is coupled to the movement of the activation gate, but is much slower
When voltage-gated K+ channels of a resting neuron open,
B. K+ leaves the neuron
In order to signal a stronger stimulus, action potentials become
B. More frequent
Spatial summation refers to
B. Multiple graded potentials arriving at one location simultaneously
If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what happens?
B. Nothing. They will cancel each other out.
(Matching) Satellite cells
B. PNS
(Matching) Schwann cells
B. PNS
The portions of a neuron that extend off of the roughly spherical cell body are usually collectively called
B. Processes
Inhibitory postsynaptic potentials (IPSPs)
B. Results in local hyperpolarizations
Calcium is important in the synapse because it
B. Signals the exocytosis of the neurotransmitter
Autonomic motor neurons are subdivided into the
B. Sympathetic and parasympathetic divisions
When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?
B. Temporal summation
What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT?
B. The permeabilities of the ions
In the first phase of triggering an action potential in a neuron, Na+ ions flow in and
B. Trigger a negative feedback loop
Which of the following is the location where action potentials originate?
B. Trigger zone
The cell body of neurons is generally
C. 10% of the cell volume
In general, the nervous system is composed of which two types of cells?
C. 2 and 4 (neurons and glial)
Inhibition of neural activity can result from
C. A and B (presynaptic and postsynaptic events)
Temporal summation refers to
C. Additional graded potential(s) arriving before previous ones have ceased
The structure on the neuron that transmits electrical signals to trigger the release of neurotransmitters is the
C. Axon
Action potentials occur in the membrane of
C. Axons
Result(s) from influx of sodium
C. Both (graded and action potentials)
The ion necessary to initiate the release of acetylcholine into the synaptic cleft is
C. Calcium
Make(s) proteins necessary for repair of damaged neuron
C. Cell body
Occupy(ies) the least amount of cell volume
C. Cell body
Supported by satellite cells
C. Cell body
Branches that sometimes occur along the length of an axon are called
C. Collaterals
The multiple thin, branched structures on a neuron whose main function is to receive incoming signals are the
C. Dendrites
An excitatory postsynaptic potential (EPSP)
C. Depolarizes a neuron, decreasing the likelihood of an action potential
The tip of an embryonic nerve cell's axon is called a
C. Growth cone
Identify the FALSE statement
C. IPSPs depolarize the membrane
Voltage-regulated channels are located
C. In the membranes of axons
If the resting axon's membrane becomes more permeable to potassium ions
C. It will take a stimulus of larger magnitude to initiate an action potential
The falling phase of the action potential is due primarily to
C. K+ flow out of the cell
The major determinant of the resting potenital of all cells is
C. K+ gradient between the blood and interstitial fluid
These glial cells act as scavengers
C. Microglia
These glial cells may contribute to Lou Gehrig's disease?
C. Mircoglia
When more action potentials arrive at the axon terminal, how is the postsynaptic cell affected?
C. Neurotransmitter release increase, thereby increasing the frequency or magnitude of graded potential in the postsynaptic cell
Interneurons are found
C. Only in the CNS
During the relative refractory period, an initial threshold-level depolarization is usually not sufficient to trigger an action potential. Why?
E. A and B (Only some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss)
Neurotransmitter is stored and released from
E. A and B (axon terminals and axon varicosities)
During the relative refractory period, _____ gates are open
E. A and B (sodium and potassium)
Conduction speed is (or can be) enhanced by
E. A and C (myelin and increasing the temperature)
The absolute refractory period of an action potential
E. A, B and C (ensures one-way travel down an axon, allows a neuron to ignore a second signal sent that closely follows the first and prevents summation of action potentials)
When two of more graded potentials arrive at the trigger zone, which of the follow could happen?
E. A, B, and C (an excitatory and inhibitory signal can cancel each other out, two excitatory stimuli may be additive and summation could occur and two two inhibitory stimuli may be additive resulting in lower excitability)
In response to binding a neurotransmitter, a postsynaptic cell can
E. A, B, and C (open chemically gated ion channels causing graded potentials known as fast synaptic potentials, close ion channels via G proteins and second messenger systems producing slow responses and regulate protein synthesis and affect the metabolic activities of the postsynaptic cell)
The channelopathy known as QT syndrome, is a result of mutation in ________ channels
E. A, B, or C (sodium, potassium and calcium)
Glial cells
E. All of the above (provide structural and metabolic support, guide neurons during growth and repair and help maintain homeostasis of the brain's extracellular fluid)
Choose all the items that are incorrectly matched
E. All of the above are incorrectly matched
Graded potentials may
E. All of the above are true (initiate an action potential, depolarize the membrane to the threshold voltage, hyperpolarize the membrane and be called RPSPs or IPSPs)
Some neurotoxins work essentially the same way as some local anesthetics, which is to
E. B and C (bind to Na+ channels and inactive them and prevent depolarization by blocking Na+ entry into the cell)
Presynaptic facilitation makes a pathway
E. B and C (more likely to be in use, through hyperpolarization of selected neurons and capable of alterations through training and conditioning)
Specialized immune cells that are confined to the CNS
F. Microglia
In spatial summation the same stimulus is repeated until a threshold level of depolarization is reached
False
Schwann cells are the primary type of glial cells associated with the central nervous system.
False
The gaps between Schwann cells are called synapses
False
