CHAPTER 2 - Book Review Questions Flashcards
The following statements concern the cytology of a neuron:
(a) The protein molecules projecting from the surface of the microtubules take no part in rapid transport in axoplasm.
(b) The protein molecules that extend through the full thickness of the plasma membrane of a neuron serve as sodium and potassium channels.
(c) Strong experimental evidence suggests that the gates of the sodium and potassium channels are formed by actin molecules.
(d) The size of the nucleolus in a neuron is unrelated to the volume of cytoplasm possessed by neurons.
(e) A synapse is the site where two neurons come together and their membranes are in contact; interneuronal communication occurs.
B is correct.
- The protein molecules that extend through the full thickness of the plasma membrane of a neuron serve as sodium and potassium channels (see Fig. 2-21). A. The protein molecules projecting from the surface of the microtubules take part in rapid transport in axoplasm. C. The gates of the sodium and potassium channels are formed of protein molecules but not actin molecules. D. The large size of the nucleolus in a neuron is related to the very large volume of cytoplasm possessed by certain neurons. E. A synapse is the site where two neurons come into close proximity and where functional interneuronal communication occurs.
The following statements concern the axon:
(a) The initial segment of the axon is the first 500 μm after it leaves the axon hillock.
(b) The nerve impulse generated by a neuron does not originate at the initial segment of an axon but on the dendrite.
(c) The action potential is produced by the sudden influx of Na+ ions into the cytoplasm.
(d) Following the influx of Na+ ions in the production of the action potential, the permeability for Na+ ions increases further, and the permeability for K+ ions ceases.
(e) The spread of the action potential along the microtubules of the axon constitutes the nerve impulse.
C is correct.
- The action potential within an axon is produced by the sudden influx of Na+ ions into the cytoplasm (see Fig. 2-17). A. The Initial segment of the axon is the first 50 to 100 μm after it leaves the axon hillock. B. The nerve impulse generated by a neuron does originate at the initial segment of an axon but not on the dendrite. D. Following the influx of Na+ Ions In the production of the action potential, the permeability for Na+ ions ceases, and the permeability for K+ ions increases; thus K+ ions start to flow from the cell cytoplasm. E. The spread of the action potential along the plasma membrane
of the axon constitutes the nerve impulse.
The following statements concern a nerve impulse:
(a) The refractory period is the duration of the nonexcitable state of the plasma membrane following the passage of a wave of repolarization.
(b) Subthreshold stimuli, when applied to the surface of a neuron, cannot be summated.
(c) Inhibitory stimuli are believed to produce their effect by causing an influx of K+ ions through the plasma membrane of the neuron.
(d) Hyperpolarization can be produced by causing an influx of K+ ions through the plasma membrane.
(e) The axolemma is the site of nerve conduction.
E is correct.
- The axolemma is the site of nerve conduction. A. The refractory period is the duration of the nonexcitable state of the plasma membrane following the passage of a wave of depolarization (see p. 45). B. Subthreshold stimuli, when applied to the surface of a neuron, can be summated. C. Inhibitory stimuli are believed to produce their effect by causing an influx of Cl- ions through the plasma membrane of the neuron. D. Hyperpolarization can be produced by causing an
influx of CI- ions through the plasma membrane.
The following statements concern the structure of a
synapse:
(a) Synapses may be axodendritic, axosomatic, or
axoaxonic.
(b) The synaptic cleft is the space between the
presynaptic and postsynaptic membranes and
measures about 200 nm.
(c) The subsynaptic web lies beneath the presynaptic membrane.
(d) Presynaptic vesicles do not contain the neurotransmitter substance.
(e) All neurons produce and release several types
of transmitter substances at all their nerve
endings.
A is correct.
- The synapses may be axodendritic, axosomatic, or axoaxonic (see Fig. 2-25). B. The synaptic cleft is the space between the presynaptic and postsynaptic membranes and measures about 20 nm. C. The subsynaptic web lies beneath the postsynaptic membrane. D. Presynaptic vesicles may contain the neurotransmitter substance (see Fig. 2-27). E. The majority of neurons produce and release only one principal transmitter at all their nerve endings.
The following statements concern a neuron:
(a) Nerve fibers are the dendrites and axons of a neuron.
(b) The volume of cytoplasm within the nerve cell body always far exceeds that found in the neurites.
(c) Golgi type I neurons have very short axons.
(d) Golgi type II neurons have very long axons.
(e) Golgi type II neurons form the Purkinje cells of
the cerebellar cortex.
A is correct.
- Nerve fibers are the dendrons and axons of a neuron. B. The volume of cytoplasm within the nerve cell body is often far less than the total volume of cytoplasm in the neurites. C. Golgi type l neurons have very long axons. D. Golgi type II neurons have very short axons. E. Golgi type I neurons form the Purkinje cells of the cerebellar cortex.
The following statements concern the neuron organelles and inclusions:
(a) Centrioles are not found in mature nerve cells.
(b) Lipofuscin granules tend to disappear with age.
(c) The Nissl substance fills the axon hillock but is
absent from other areas of the cytoplasm.
(d) Microfilaments contain actin and do not assist
in cell transport.
(e) Mitochondria are found in the dendrites and
axons.
E is correct.
- Mitochondria are found in the dendrites and axons. A. Centrioles are found in mature nerve cells as well as in immature dividing nerve cells. B. Lipofuscin granules tend to accumulate with age. C. The Nissl substance is absent from the axon hillock. D. Microfilaments contain actin and probably assist in cell transport (see p. 42).
The following statements concern dendrites:
(a) A dendrite conveys a nerve impulse away from
the nerve cell body.
(b) Dendritic spines are small projections of the
plasma membrane that increase the receptor
surface area of the dendrite.
(c) The cytoplasm of dendrites does not contain
ribosomes and agranular endoplasmic reticulum. (d) Most dendrites expand in width as they extend
from the nerve cell body.
(e) Dendrites rarely branch.
B is correct.
- Dendritic spines are small projections of the plasma membrane that increase the receptor surface area of the dendrite. A. A dendrite conveys a nerve impulse toward the nerve cell body (see p. 48). C. The cytoplasm of dendrites contains ribosomes and agranular endoplasmic reticulum as well as Nissl granules, microtubules, and microfilaments. D. Most dendrites taper in width as they extend from the nerve cell body. E. Dendrites often branch profusely.
The following statements concern neuromodulators:
(a) Neuromodulators may coexist with the principal (classic) transmitter at a single synapse.
(b) They often diminish and shorten the effect of
the principal transmitter.
(c) They never act through a second messenger.
(d) They have a brief effect on the postsynaptic
membrane.
(e) Acetylcholine (ACh) (muscarinic) is not a good
example of a neuromodulator.
A is correct.
- Neuromodulators may coexist with the principal (classic) transmitter at a single synapse (see p. 54). B. Neuromodulators often enhance and prolong the effect of the principal transmitter. C. Neuromodulators act through a second messenger. D. Neuromodulators may have a prolonged effect on the postsynaptlc membrane. E. ACh (muscarinic) is a good example of a neuromodulator.
The following statements concern the neurobiology
of neuron structures:
(a) A lysosome is a membrane-bound vesicle covered with ribosomes.
(b) A terminal bouton is the postsynaptlc part of
an axon.
(c) A receptor is a protein molecule on the postsynaptic membrane.
(d) Nissl substance is formed of the smooth-surfaced endoplasmic reticulum.
(e) Microtubules provide a mobile track that
allows specific organelles to move by molecular motors.
C is correct.
- A receptor is a protein molecule on the postsynaptic membrane. A. A lysosome is a membrane-bound vesicle that is not covered with ribosomes. B. A terminal bouton is the presynaptic part of an axon. D. Nissl substance is formed of the rough endoplasmic reticulum. E. Microtubules provide a stationary track that allows specific organelles to move by molecular motors.
The following statements concern neuroglia:
(a) Fibrous astrocytes are located mainly in the gray matter of the central nervous system (CNS).
(b) Replacement gliosis follows the death of neurons in the CNS and is due to the proliferation
of astrocytes.
(c) Astrocytes are not involved in the absorption
of y-aminobutyric acid (GABA) secreted by the
nerve terminals.
(d) Oligodendrocytes are responsible for the formation of the myelin of nerve fibers in the
peripheral nervous system (PNS).
(e) A single ollgodendrocyte can form, by means of
its processes, only one internodal segment of
myelin on the same axon.
B is correct.
- Replacement gliosis follows the death of neurons in the CNS and is due to the proliferation of astrocytes (see p. 57). A. Fibrous astrocytes are located mainly in the white matter of the CNS. C. Astrocytes are involved in the absorption of GABA as it is secreted by the nerve terminals. D. Ollgodendrocytes are responsible for the formation and maintenance of the myelin of nerve fibers
The following statements concern the microglial cells:
(a) Microglial cells resemble connective tissue mast cells.
(b) Microglial cells are larger than astrocytes or ollgodendrocytes.
(c) Microglial cells migrate into the central nervous system (CNS) during adult life.
(d) In the presence of damaged neurons, microglial cells become branched.
(e) In degenerative lesions of the CNS, the circulating blood contributes cells to the population of mlcrogllal cells.
E is correct.
- In degenerative lesions of the CNS, the circulating blood contributes cells to the population of microglial cells. A. Microglial cells resemble connective tissue macrophages. B. Microglial cells are smaller than astrocytes or oligodendrocytes (Fig. 2-28). C. Microglial cells migrate into the CNS during fetal life. D. In the presence of damaged neurons, microglial cells round off, lose their branches, and increase in number.
The following statements concern the ependymal cells:
(a) Choroidal epithelial cells do not secrete cerebrospinal fluid (CSF).
(b) Ependymocytes line the ventricular system but do not permit the CSF to enter the extracellular spaces of the nervous tissue.
(c) Tanycytes have short, unbranched basal processes, many of which have endfeet placed on the capillaries of the median eminence.
(d) The ependymal cells form a single layer, and many possess microvilliand cilia.
(e) Ependymal cells are incapable of absorbing substances from the CSF.
D is correct.
- The ependymal cells form a single layer, and many possess microvilli and cilia (see p. 60). A. Choroidal epithelial cells secrete CSF. B. The ependymocytes line the ventricular system but permit CSF to enter the extracellular spaces of the nervous system. C. Tanycytes have long, branching basal processes, many of which have endfeet placed on the capillaries of the median eminence. E. Ependymal cells absorb substances from the CSF.
The following statements concern the extracellular space:
(a) The space is formed by the gaps between the neurons and not the gaps between the neuroglial cells.
(b) The space surrounds the lymphatic capillaries present in the brain and spinal cord.
(c) The space is not continuous with the subarachnoid space.
(d) The space is filled with tissue fluid.
(e) The space is not continuous with the synaptic
cleft between two neurons.
D is correct.
- The extracellular space is filled with tissue fluid. A. The extracellular space is formed by the gaps between the neurons and the neuroglial cells (see p. 60). B. The central nervous system does not have lymphatic vessels. C. The extracellular space is in almost direct continuity with the subarachnoid space. E. The extracellular space is continuous with the synaptic cleft between two neurons.
The following statements concern tumors of neuroglia:
(a) They form about 5% of all intracranial tumors. (b) Apart from the ependymomas, tumors of neuroglia grow slowly and are not highly invasive.
(c) They commonly infiltrate between neurons, causing the minimum disturbance of function.
(d) They are nonmalignant and easily removed surgically.
(e) As they expand, they raise the intracranial pressure.
E is correct.
- As neuroglial tumors expand, they raise the intracranial pressure. A. Neuroglial tumors form about 40% to 50% of all intracranial tumors. B. Apart from the ependymomas, tumors of neuroglia are highly invasive. C. Neuroglial tumors commonly infiltrate between neurons, initially causing the minimum disturbance of function; later, they completely disrupt neuronal activities. D. Neuroglial tumors, apart from ependymomas, are highly malignant and difficult to remove surgically.
The following statements concern neuroglial cells:
(a) They tend to be larger than nerve cell bodies.
(b) Heat increases the action potential in an axon
and reduces the signs and symptoms in multiple sclerosis.
(c) Ollgodendrocytes are found some distance
away from nerve cell bodies and their neurites.
(d) Multiple sclerosis is a disease involving the
oligodendrocyte.
(e) Llke Schwann cells, oligodendrocytes are surrounded by a basement membrane.
D is correct.
- Multiple sclerosis is a disease involving the oligodendrocyte (see pp. 63-64). A. Neuroglial cells tend to be smaller than nerve cell bodies. B. Heat reduces the action potential in an axon and accentuates the signs and symptoms in multiple sclerosis. C. Oligodendrocytes are found close to nerve cell bodies and their neurites. E. Unlike Schwann cells, oligodendrocytes are not surrounded by a basement membrane.
