Chapter 12 Flashcards
Which of these components is usually absent from a neuron? centrioles dendrites axons cell body
centrioles
The afferent division of the PNS \_\_\_\_\_\_\_\_\_\_\_\_\_. carries motor commands carries sensory information controls skeletal muscle controls smooth muscle
carries sensory information
Which of the following is not a function of the nervous system?
control peripheral effectors
coordinate voluntary and involuntary activities
integrate sensory information
sense the internal and external environments
direct long-term functions, such as growth
direct long-term functions, such as growth
The \_\_\_\_\_\_\_\_ nervous system is composed of the brain and spinal cord. efferent afferent autonomic central peripheral
central
The \_\_\_\_\_\_\_\_ nervous system controls the skeletal muscles. parasympathetic somatic sympathetic autonomic afferent
somatic
The part of the peripheral nervous system that carries sensory information to the CNS is designated efferent. afferent. motor. somatic. autonomic.
afferent.
The efferent division of the peripheral nervous system innervates: heart muscle cells skeletal muscle cells glandular cells smooth muscle cells All of the answers are correct.
All of the answers are correct.
Which of these is not a neuron structural category? pseudopolar unipolar bipolar multipolar
pseudopolar
Most CNS neurons fall into which structural category? multipolar unipolar bipolar anaxonic
multipolar
The axon hillock connects the axon with the \_\_\_\_\_\_\_\_\_\_. synapse cell body (soma) telodendria collaterals
cell body (soma)
The axoplasm of the axon contains which of the following? neurotubules mitochondria neurofibrils vesicles All of the answers are correct.
All of the answers are correct.
Which of the following is not a recognized structural classification for neurons? anaxonic bipolar multipolar pseudopolar unipolar
pseudopolar
The most abundant class of neuron in the central nervous system is multipolar. unipolar. bipolar. pseudopolar. anaxonic.
multipolar.
The rabies virus travels to the CNS via subcutaneous connective tissue. cerebrospinal fluid. anterograde axoplasmic transport. blood vessels. retrograde axoplasmic transport.
retrograde axoplasmic transport.
The site of intercellular communication between a neuron and another cell is the collateral. synaptic terminals. telodendria. synapse. hillock.
synapse.
Neurons that are rare, small, and lack features that distinguish dendrites from axons are called bipolar. anaxonic. unipolar. tripolar. multipolar.
anaxonic.
Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called tripolar. bipolar. unipolar. anaxonic. multipolar.
unipolar.
Neurons that have one axon and one dendrite, with the soma in between, are called bipolar. tripolar. unipolar. anaxonic. multipolar.
bipolar.
Neurons that have several dendrites and a single axon are called unipolar. anaxonic. bipolar. multipolar. tripolar.
multipolar.
\_\_\_\_\_\_\_\_ neurons are the most common class in the CNS. Unipolar Sensory Bipolar Anaxonic Multipolar
Multipolar
\_\_\_\_\_\_\_\_ neurons form the afferent division of the PNS. Visceral sensory Neural sensory Sensory Somatic sensory Motor
Sensory
What is contained inside the synaptic terminals? neuroglia calcium ions neurotransmitter molecules acetylcholinesterase sodium ions
neurotransmitter molecules
The basic functional unit of the nervous system is the ________.
neuron
The basic functional unit of the nervous system are cells called ________.
neurons
Which is the largest and most abundant type of neuroglia? astrocytes ependymal cells oligodendrocytes satellite cells
astrocytes
Which of these types of neuroglia are abundant in peripheral ganglia? oligodendrocytes astrocytes microglia satellite cells
satellite cells
The largest and most numerous of the glial cells in the central nervous system are the astrocytes. oligodendrocytes. satellite cells. ependymal cells. microglia.
astrocytes.
Functions of astrocytes include all of the following, except
maintaining the blood-brain barrier.
responding to neural tissue damage.
forming a three-dimensional framework for the CNS.
guiding neuron development.
conducting action potentials.
conducting action potentials.
Which of the following is a type of glial cell found in the peripheral nervous system? satellite cells ependymal cells microglia astrocytes oligodendrocytes
satellite cells
\_\_\_\_\_\_\_\_ account for roughly half of the volume of the nervous system. Synapses Axons Neuroglia Efferent fibers Dendrites
Neuroglia
The neuroglial cells that participate in maintaining the blood-brain barrier are the oligodendrocytes. microglia. Schwann cells. astrocytes. ependymal cells.
astrocytes.
The function of the astrocytes in the CNS includes which of the following?
guiding neuron development
repairing damaged neural tissue
adjusting the composition of the interstitial fluid
maintaining the blood-brain barrier
All of the answers are correct.
All of the answers are correct.
The myelin sheath that covers many CNS axons is formed by satellite cells. oligodendrocytes. microglia. ependymal cells. astrocytes.
oligodendrocytes.
\_\_\_\_\_\_\_\_ line the brain ventricles and spinal canal. Oligodendrocytes Satellite cells Microglia Astrocytes Ependymal cells
Ependymal cells
Small, wandering cells that engulf cell debris and pathogens in the CNS are called astrocytes. ependymal cells. satellite cells. oligodendrocytes. microglia.
microglia.
The neurilemma of axons in the peripheral nervous system is formed by oligodendrocytes. microglia. astrocytes. satellite cells. Schwann cells.
Schwann cells.
Glial cells that surround the neurons in ganglia are oligodendrocytes. satellite cells. microglia. ependymal cells. astrocytes.
satellite cells.
Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.
white
Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference? Action potential Threshold potential Positive membrane potential Resting membrane potential (RMP)
Resting membrane potential (RMP)
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel? Voltage-gated channels Sodium-potassium ATPases Leak channels Ligand-gated channels
Leak channels
On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?
1. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane. 2. The outside surface of the plasma membrane is much more negatively charged than the inside surface. 3. The inside surface of the plasma membrane is much more negatively charged than the outside surface. 4. The inside surface of the plasma membrane is much more positively charged than the inside surface.
- The inside surface of the plasma membrane is much more negatively charged than the outside surface.
The plasma membrane is much more permeable to K+ than to Na+. Why?
1. There are many more voltage-gated K+ channels than voltage-gated Na+ channels. 2. The Na+-K+ pumps transport more K+ into cells than Na+ out of cells. 3. There are many more K+ leak channels than Na+ leak channels in the plasma membrane. 4. Ligand-gated cation channels favor a greater influx of Na+ than K+.
- There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.
1. The presence of concentration gradients and voltage-gated channels 2. The presence of concentration gradients and Na+-K+ pumps 3. The presence of concentration gradients and leak channels 4. The presence of a resting membrane potential and leak channels
- The presence of concentration gradients and leak channels
What prevents the Na+ and K+ gradients from dissipating? Na+ cotransporter H+-K+ ATPase Na+ and K+ leaks Na+-K+ ATPase
Na+-K+ ATPase
The membranes of neurons at rest are very permeable to \_\_\_\_\_ but only slightly permeable to \_\_\_\_\_. K+; Cl– Na+; K+ Na+; Cl– K+; Na+
K+; Na+
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
only the chemical gradient
only the electrical gradient
Na+ does not move into the cell. Na+ moves out of the cell.
both the electrical and chemical gradients
What is the value for the resting membrane potential for most neurons?
–90 mV
+30 mV
–70 mV
–70 mV
The Na+–K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell.
Both Na+ and K+ are pumped into the cell.
Both Na+ and K+ are pumped out of the cell.
K+ is pumped out of the cell and Na+ is pumped into the cell.
Na+ is pumped out of the cell and K+ is pumped into the cell.
The concentrations of which two ions are highest outside the cell.
K+ and Cl–
Na+ and A– (negatively charged proteins)
Na+ and Cl–
K+ and A– (negatively charged proteins)
Na+ and Cl–
The events that occur at a functioning cholinergic synapse cause _____________ .
strengthening of the synapse
a flow of acetylcholine (ACh) into the synaptic cleft that is removed only by simple diffusion
synaptic delay
loss of transmission of the action potential
synaptic delay
The most abundant intracellular cation is \_\_\_\_\_\_\_\_\_\_ while the most abundant extracellular anion is \_\_\_\_\_\_\_\_\_\_. potassium; chloride sodium; chloride potassium; protein anions sodium; protein anions
potassium; chloride
Which type of ion channel is always open? passive mechanically gated voltage-gated chemically gated
passive
The sodium-potassium exchange pump stabilizes resting potential at about \_\_\_\_\_\_\_\_\_\_. -70 mV -90 mV -10 mV \+66 mV
-70 mV
________ open or close in response to binding specific molecules.
Chemically-gated channels
Activated channels
Leak channels
Voltage-gated and chemically-gated channels
Voltage-gated channels
Chemically-gated channels
\_\_\_\_\_\_\_\_ channels open or close in response to physical distortion of the membrane surface. Mechanically-gated Voltage-gated Leak Active Chemically-gated
Mechanically-gated
Any stimulus that opens \_\_\_\_\_\_\_\_ ion channel will produce a graded potential. a voltage-gated a sodium a chemically-gated a mechanically-gated All of the answers are correct.
All of the answers are correct.
Ions can move across the plasma membrane in which of the following ways?
1. through chemically-gated channels as in neuromuscular transmission 2. through passive or leak channels 3. by ATP-dependent ion pumps like the sodium-potassium exchange pump 4. through voltage-gated channels as in the action potential 5. All of the answers are correct.
- All of the answers are correct.
Voltage-gated sodium channels have both an activation gate and a(n) \_\_\_\_\_\_\_\_ gate. inactivation repolarization threshold ion swinging
inactivation
Where do most action potentials originate? Cell body Axon terminal Initial segment Nodes of Ranvier
Initial segment
What opens first in response to a threshold stimulus? Ligand-gated Cl- channels Ligand-gated cation channels Voltage-gated K+ channels Voltage-gated Na+ channels
Voltage-gated Na+ channels
What characterizes depolarization, the first phase of the action potential?
1. The membrane potential reaches a threshold value and returns to the resting state. 2. The membrane potential changes to a much more negative value. 3. The membrane potential changes from a negative value to a positive value. 4. The membrane potential changes to a less negative (but not a positive) value.
- The membrane potential changes from a negative value to a positive value.
What characterizes repolarization, the second phase of the action potential?
a. Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV. b. Once the membrane depolarizes to a threshold value of approximately -55 mV, it repolarizes to its resting value of -70 mV. c. As the membrane repolarizes to a negative value, it goes beyond the resting state to a value of -80 mV. d. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
d. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
What event triggers the generation of an action potential?
a. The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV. b. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV. c. The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV. d. The membrane potential must return to its resting value of -70 mV from the hyperpolarized value of -80 mV.
b. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What is the first change to occur in response to a threshold stimulus?
1. Voltage-gated Na+ channels change shape, and their inactivation gates close. 2. Voltage-gated Ca2+ channels change shape, and their activation gates open. 3. Voltage-gated Na+ channels change shape, and their activation gates open. 4. Voltage-gated K+ channels change shape, and their activation gates open.
- Voltage-gated Na+ channels change shape, and their activation gates open.
What type of conduction takes place in unmyelinated axons? Continuous conduction Saltatory conduction Electrical conduction Synaptic transmission
Continuous conduction
In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________.
1. both sodium and potassium concentrations are higher outside the cell compared to inside. 2. the concentration of sodium outside the cell is equal to the concentration of potassium inside the cell. 3. the sodium concentration is higher inside the cell than outside the cell and the potassium concentration is higher outside the cell than inside the cell. 4. 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.
- 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.
]The sodium-potassium exchange pump transports potassium and sodium ions in which direction(s)?
Sodium ions are transported out of the cell. Potassium ions are transported into the cell.
Sodium and potassium ions are both transported out of the cell.
Sodium and potassium ions are both transported into the cell.
Sodium ions are transported into the cell. Potassium ions are transported out of the cell.
Sodium ions are transported out of the cell. Potassium ions are transported into the cell.
Leak channels allow the movement of potassium and sodium ions by what type of membrane transport? facilitated diffusion channel-mediated diffusion simple diffusion active transport
channel-mediated diffusion
What is the function of the myelin sheath?
1. The myelin sheath increases the insulation along the entire length of the axon. 2. The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. 3. The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals. 4. The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
- The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the smallest diameters
Myelinated axons with the largest diameter
Unmyelinated axons with the largest diameter
Unmyelinated axons of the shortest length
Myelinated axons with the largest diameter
Where in the neuron is an action potential initially generated?
anywhere on the axon
soma and dendrites
axon hillock
axon hillock
The depolarization phase of an action potential results from the opening of which channels? chemically gated Na+ channels voltage-gated Na+ channels voltage-gated K+ channels chemically gated K+ channels
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________.
the closing of voltage-gated Na+ channels
the opening of voltage-gated Na+ channels
the opening of voltage-gated K+ channels
the closing of voltage-gated K+ channels
the opening of voltage-gated K+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated Na+ channels
slow closing of voltage-gated K+ channels
fast closing of voltage-gated K+ channels
slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential?
100 mV
70 mV
30 mV
100 mV
During propagation of the action potential, __________.
the axon hillock depolarizes the initial segment
local currents depolarize a spot adjacent to the active zone
after threshold is reached, sodium channels open rapidly
All of these events occur during propagation of the action potential.
All of these events occur during propagation of the action potential.
Which of these is the earliest step in the generation of an action potential? Potassium channels inactivate. Sodium channels inactivate. Sodium channels open. Potassium channels open.
Sodium channels open.
The all-or-none principle states that
the greater the magnitude of the stimuli, the greater the magnitude of the action potential.
all stimuli will produce identical action potentials.
all stimuli great enough to bring the membrane to threshold will produce identical action potentials.
only motor stimuli can activate action potentials.
only sensory stimuli can activate action potentials.
all stimuli great enough to bring the membrane to threshold will produce identical action potentials.
A threshold stimulus is the
depolarization necessary to cause an action potential.
electrical current that crosses the synaptic cleft.
hyperpolarization of an axon.
resting potential.
peak of an action potential.
depolarization necessary to cause an action potential.
Which of the following is true about threshold for an action potential?
Voltage-gated potassium channels begin to open.
It is more positive than the resting potential.
Voltage-gated potassium channels begin to close.
Threshold for a typical neuron is approximately -30 mV.
The membrane begins to hyperpolarize.
It is more positive than the resting potential.
Compared to type A axons, type C axons are __________.
smaller diameter
unmyelinated
slower propagating
Type C axons have all of these characteristics.
Type C axons have all of these characteristics.
Which of these axons will conduct an action potential most quickly?
Type C fiber
Type B fiber
Type A fiber
All fibers have the same propagation speed.
Type A fiber
Which of the following does not influence the time necessary for a nerve impulse to be transmitted?
diameter of the axon
whether or not the impulse begins in the CNS
length of the axon
presence or absence of nodes
presence or absence of a myelin sheath
whether or not the impulse begins in the CNS
In a synapse, neurotransmitters are stored in vesicles located in the __________.
presynaptic neuron
synaptic cleft
postsynaptic neuron
presynaptic neuron
The effect of a nerve impulse on a postsynaptic neuron depends on the __________.
quantity of neurotransmitter released
characteristics of the receptor on the postsynaptic neuron
kind of neurotransmitter released by the presynaptic neuron
All of these factors affect what happens at the postsynaptic neuron.
All of these factors affect what happens at the postsynaptic neuron.
A neuron that receives neurotransmitter from another neuron is called an interneuron. the presynaptic neuron. an oligodendrocyte. the postsynaptic neuron. the motor neuron.
the postsynaptic neuron.
Which type of synapse is most common in the nervous system? processing electrical mechanical chemical radiative
chemical
The ion that triggers the release of acetylcholine into the synaptic cleft is sodium. chloride. magnesium. calcium. potassium.
calcium.
Cholinergic synapses release the neurotransmitter serotonin. GABA. adrenalin. norepinephrine. acetylcholine.
acetylcholine.
Which of these neurotransmitters does not bind to a plasma membrane receptor? norepinephrine nitric oxide serotonin GABA
nitric oxide
Which of these neurotransmitters is released at CNS adrenergic synapses? GABA norepinephrine adrenaline serotonin
norepinephrine
Which of the following is not a possible drug effect on synaptic function?
interfere with neurotransmitter reuptake
change the type of receptor found in the postsynaptic membrane
prevent neurotransmitter inactivation
block neurotransmitter binding to receptors
interfere with neurotransmitter synthesis
change the type of receptor found in the postsynaptic membrane
Which of the following is a recognized class of opioid neuromodulators? endorphins dynorphins enkephalins endomorphins All of the answers are correct.
All of the answers are correct.
The neurotransmitter glutamate opens channels that are permeable to sodium ions. What effect does glutamate produce on a postsynaptic neuron? both IPSPs and EPSPs neither IPSPs nor EPSPs IPSPs EPSPs
EPSPs
The neurotransmitter GABA blocks presynaptic voltage-gated calcium channels. Consequently, GABA produces \_\_\_\_\_\_\_\_\_\_. IPSPs presynaptic inhibition EPSPs presynaptic facilitation
presynaptic inhibition
