Neurociencia Basica y Conceptos Farmacologicos Flashcards
QUESTION ONE
An excitatory signal is received at the dendrite of a pyramidal
glutamate neuron. When the signal is released from the incoming
presynaptic dopaminergic axon, it is received as an inhibitory
signal. However, this signal is not integrated properly with other
incoming signals to that neuron. Which is the most likely site at
which the error of integrating this signal with other incoming signals
occurred?
A. Dendritic membrane
B. Soma
C. Axonal zone
D. Presynaptic zone
A – Incorrect. Dendritic membrane is the site of signal detection;
signal
integration does not occur here.
B – Correct. Soma is the site that integrates chemical encoding of
signal
transduction from all incoming signals; improper signal integration
is most likely at this site.
C – Incorrect. Axonal zone is the site of signal propagation; signal
integration
does not occur here.
D – Incorrect. Presynaptic zone is the site of signal output; signal integration
does not occur here.
QUESTION TWO
Which brain imaging technique used in psychiatry research provides
measurements of both structure and function of the human
brain?
A. Electroencephalography
B. Magnetic resonance imaging
C. Positron emission tomography
D. Transcranial magnetic stimulation
A – Incorrect. Electroencephalography, or EEG, may be used to identify
electrical activity in the brain. Electrodes placed around the
scalp provide a general location of electrical activity; however,
EEG does not provide measurements of brain structure.
B – Correct. Magnetic resonance imaging, or MRI, may be used to
measure brain structure and function. Structural MRI (sMRI)
and diffusion tensor imaging (DTI) are types of MRI acquisitions
that can be used to obtain structural measurements of the brain.
Functional MRI (fMRI) is a type of MRI acquisition that measures
brain activity by way of the blood-oxygen-level-dependent
(BOLD) signal.
C – Incorrect. Positron emission tomography, or PET, may be used to
identify chemical activity, which is a measure of brain function;
however, it is not used to provide measurements of brain structure.
PET may be combined with MRI or computerized tomography
to make more specific conclusions about the structural location of
chemical activity in the brain.
D – Incorrect. Transcranial magnetic stimulation, or TMS, is not a neuroimaging
technique. TMS is used to stimulate nerve cells in the
brain and the resultant motor output may provide indirect information
on brain function.
QUESTION THREE
Which of the following are involved in regulating neurotransmission
via excitation–secretion coupling?
A. Voltage-sensitive sodium channels
B. Voltage-sensitive calcium channels
C. Both A and B
D. Neither A nor B
A – Partially correct.
B – Partially correct.
C – Correct. Propagation of an action potential to the axon terminal is
mediated by voltage-sensitive sodium channels. Influx of sodium
through voltage-sensitive sodium channels at the axon terminal
leads to opening of voltage-sensitive calcium channels, also at
the axon terminal. Influx of calcium through the open voltage-sensitive
calcium channels leads to docking of synaptic vesicles and
secretion of neurotransmitter into the synapse.
D – Incorrect.
QUESTION FOUR
Agonists cause ligand-gated ion channels to:
A. Open wider
B. Open for longer duration of time
C. Open more frequently
D. A and B
E. A and C
A – Incorrect. Agonists do not cause ligand-gated receptors to open
wider.
B – Incorrect. Agonists do not cause ligand-gated receptors to open for
longer durations of time.
C – Correct. Agonists cause ligand-gated ion channels to open more
frequently.
D – Incorrect.
E – Incorrect.
QUESTION FIVE
Presynaptic reuptake transporters are a major method of inactivation
for which of the following?
A. Serotonin
B. Serotonin and gamma-aminobutyric acid (GABA)
C. Serotonin, GABA, and histamine
D. Serotonin, GABA, histamine, and neuropeptides
A – Partially correct.
B – Correct. Both monoamines such as serotonin and amino acid
neurotransmitters such as GABA are inactivated primarily via presynaptic
transporters.
C – Incorrect. Histamine does not have a known presynaptic reuptake
transporter and is instead inactivated via enzymatic degradation.
D – Incorrect. Histamine and neuropeptides do not have known presynaptic
reuptake transporters. Histamine is inactivated enzymatically,
and neuropeptides are inactivated by diffusion, sequestration,
and enzymatic destruction.
QUESTION SIX
A neuron is infected with a toxin and causes a rather sudden
inflammatory reaction. You detect a high concentration of cytokines
in the surrounding area. Which process has taken place?
A. Apoptosis
B. Excitotoxicity
C. Necrosis
D. Neurogenesis
E. Synaptogenesis
A – Incorrect. Apoptosis is triggered by a cell’s own genetic machinery,
causing the cell to just “fade away.” The more caustic inflammatory
response from cell death is associated with the neural selection
process of necrosis. Cells that commit suicide (apoptosis) die in a
more benign manner than when they are the victims of homicide
(necrosis).
B – Incorrect. Excitotoxicity is a process of synaptic damage from “overexcitation,”
excessive amounts of which can result in cell death.
C – Correct. Necrosis is the neural selection process in which a cell is
poisoned, suffocated, or otherwise destroyed by a toxin after which
the cell explodes and causes an inflammatory reaction.
D – Incorrect. Neurogenesis is the process of forming neurons.
E – Incorrect. Synaptogenesis is the process of forming synapses
QUESTION SEVEN
Communication between human central nervous system neurons
at synapses is:
A. Chemical
B. Electrical
C. Both A and B
D. Neither A nor B
A – Correct. The communication between neurons at synapses is
mediated by neurotransmitter molecules and is therefore chemical.
B – Incorrect. Although electrical communication occurs within
neurons during the propagation of an action potential, communication
at synapses is chemical.
C – Incorrect.
D – Incorrect
QUESTION EIGHT
A serotonin molecule binds to a 5HT2A receptor causing electrical
impulses to be sent down a GABA neuron’s axon terminal, eventually
releasing GABA to the GABA-A receptor of its postsynaptic
neuron. Which type of neurotransmission does this describe?
A. Classic synaptic neurotransmission
B. Retrograde neurotransmission
C. Volume neurotransmission
D. Signal transduction cascade
A – Correct. Classic synaptic neurotransmission is the most common
and well-known process of neurotransmission. It involves the
anterograde transduction of a chemical signal to electrical impulses
and back to chemical signals for the next neuron.
B – Incorrect. Retrograde neurotransmission is the “reverse” neurotransmission
process in which a postsynaptic neuron communicates
with a presynaptic neuron.
C – Incorrect. Volume neurotransmission is the process of neurotransmission
without a synapse, which is also called nonsynaptic
diffusion.
D – Incorrect. Signal transduction cascade is the larger process of neurocommunication
that involves long strings of chemical and ionic
signals.
QUESTION NINE
A receptor with four transmembrane regions changes conformation
as GABA binds. Which system is this process describing?
A. Ligand-gated ion channel
B. Presynaptic transporter
C. Voltage-sensitive ion channel
– Correct. Ligand-gated ion channels are four-transmembrane region
ion channels that open and close under instruction from bound
neurotransmitters.
B – Incorrect. Presynaptic transporters are twelve-transmembrane
region transporters that bind to neurotransmitters to transport
them across the presynaptic membrane.
C – Incorrect. Voltage-sensitive ion channels are six-transmembrane
region ion channels that open and close under instruction from
charges or voltages as determined by ion flow.
QUESTION TEN
The direct role of transcription factors is to:
A. Cause neurotransmitter release
B. Influence gene expression
C. Synthesize enzymes
D. Trigger signal transduction cascades
A – Incorrect. Transcription factors do not directly cause neurotransmitter
release.
B – Correct. Transcription factors are proteins that bind to promoter
sequences of DNA to turn gene expression on and off.
C – Incorrect. Transcription factors do not directly cause enzyme
synthesis.
D – Incorrect. Transcription factors do not directly trigger signal transduction
cascades.
QUESTION ELEVEN
Which of the following is the most likely impetus for upregulation
of D2 receptors on a striatal dopamine neuron?
A. A bound receptor is taken out of circulation
B. A new receptor is bound and put to use
C. A D2 agonist persistently binds to the receptor
D. A D2 antagonist persistently binds to the receptor
A – Incorrect. A bound receptor is usually taken out of circulation
when the neuron wants to decrease, not increase, the number of
receptors.
B – Incorrect. A new receptor being bound and put to use is a result,
not an impetus, of upregulation.
C – Incorrect. Agonists can mimic neurotransmitter actions, potentially
signaling the neuron to downregulate synthesis of that receptor
type.
D – Correct. Antagonists can oppose neurotransmitter actions, potentially
signaling the neuron to upregulate synthesis of that receptor
type.
QUESTION TWELVE
What is the correct order and direction of ion flow into and out of
a neuron experiencing an action potential?
A. Na+ in, K+ out, Ca2+ in
B. Ca2+ in, K+ out, Na+ in
C. K+ in, Na+ in, Ca2+ in
D. Na+ in, Ca2+ in, K+ out
E. Ca2+ in, Na+ out, K+ out
F. K+ in, Ca2+ in, Na+ out
A, B, C, E, and F – Incorrect.
D – Correct. Sodium enters the cell followed by an influx of calcium;
potassium exits the neuron at the end of the action potential,
restoring the baseline electrical charge in the cell.
QUESTION THIRTEEN
What are the molecular mechanisms of epigenetics?
A. Molecular gates are opened by acetylation and/or demethylation
of histones, allowing transcription factors access to genes,
thus activating them
B. Molecular gates are opened by deacetylation and/or methylation
of histones, allowing transcription factors access to genes,
thus activating them
C. Molecular gates are closed by deacetylation and/or methylation
of histones, preventing access of transcription factors to genes,
thus silencing them
D. A and C
A – Partially correct. Epigenetics is a process that determines whether
a given gene is expressed or silenced. Epigenetic control over
whether genes are activated (i.e., expressed) or silenced is achieved
by the modification of chromatin. Acetylation and demethylation
of histones decompress the chromatin, opening the molecular
gates, allowing transcription factors to get to the promoter regions
of genes and activate them.
B – Incorrect.
C – Partially correct. Methylation of histones can silence genes, whereas
demethylation of histones can activate genes. Methylation of DNA
can result in deacetylation of histones by activating enzymes called
histone deacetylases (HDACs). Deacetylation of histones also has a
silencing effect on gene expression. Methylation and deacetylation
compress chromatin, closing the molecular gates, which prevents
the transcription factors from accessing the promoter regions that
activate genes, thus silencing them.
D – Correct.
QUESTION FOURTEEN
N-methyl-d-aspartate (NMDA) receptors are activated by:
A. Glutamate
B. Glycine
C. Depolarization
D. Glutamate and glycine
E. Glutamate and depolarization
F. Glycine and depolarization
G. Glutamate, glycine, and depolarization
A, B, C, D, E, and F – Incorrect.
G – Correct. NMDA receptors are ligand-gated ion channels that
regulate excitatory postsynaptic neurotransmission triggered by
glutamate. In the resting state, NMDA receptors are blocked by
magnesium, which plugs the calcium channel. Opening of NMDA
glutamate receptors requires the presence of both glutamate and
glycine, each of which bind to a different site on the receptor.
When magnesium is also bound and the membrane is not depolarized,
it prevents the effects of glutamate and glycine and thus
does not allow the ion channel to open. In order for the channel to
open and permit calcium entry, depolarization must remove magnesium
while both glutamate and glycine are bound to their sites.
QUESTION FIFTEEN
Neurogenesis occurs in adults:
A. Only in the dentate gyrus of the hippocampus
B. In the dentate gyrus of the hippocampus and in the olfactory
bulb
C. In the dentate gyrus of the hippocampus, in the olfactory bulb,
and in the lateral nucleus of the amygdala
D. Throughout the brain
A – Partially correct. Although adult neurogenesis does occur in the
dentate gyrus, this is not the only brain region where adult neurogenesis
occurs.
B – Correct. Adult neurogenesis occurs in both the dentate gyrus of
the hippocampus and in the olfactory bulb.
C – Incorrect. Although adult neurogenesis occurs in both the dentate
gyrus and the olfactory bulb, there is no evidence that adult neurogenesis
occurs in the lateral nucleus of the amygdala.
D – Incorrect. Adult neurogenesis occurs only in the dentate gyrus and
in the olfactory bulb
