The Na/K transporter (pump) is blocked by:
none of the above
nAChR channels at the endplate:
open when the nAChR are activated
are non-selective in that they allow positive and negative ions to pass through
Na and K ions pass through them by simple diffusion
also open when serotonin or glutamate is present
choices A & C
As a result of repetitive activity the K concentration immediately outside the nerve terminal rises to 10 meq whereas the K concentration inside decreases to 100 meq. Thus:
a type of presynaptic inhibition results
the nerve terminal is depolarized to -62mV
the incoming action potential at the terminal is decreased in amplitude
the amount of transmitter released is decreased
All of the above
Which of the following statements is/are true:
alkalosis can cause coma
action potential starts at the axon hillock
in the Renshaw circuit activity of one motor neuron result in self-inhibition.
removal of Ca2+from the vicinity of axon causes inhibition of AP conduction
the motor endplate is electrically not excitable
pinocytosis is the reverse of emeiocytosis
demarcation (injury) potential is a monophasic action potential
water is a polar molecule but can cross the cell membrane freely
all of the above
What would happen to a muscle action potential if 50% of membrane sodium channels were blocked?
it would be similar to a pacemaker action potential
it would be similar to a heart ventricular muscle action potential
it would be the same but with no relative refractory period
it would be the same but with no absolute refractory period
it would be of much smaller amplitude
Postsynaptic density (opacity) is due to the presence of ______ in or beneath the membrane:
Multiple sclerosis (MS):
also known as ALS
occurs both in the CNS and PNS
is commonly known as Lou Gehrig’s disease
occurs in the PNS only
The inhibitory postsynaptic potential (IPSP):
is the result of negative ions moving through ligand-gated channels into the neuron
has a brief refractory period
is the cause of stimulus artifact
is a depolarization
The refractory periods (RP):
the absolute RP is due to complete closure and inactivation of Na channels
are due to opening of the delayed rectifier
can be seen in nerve action potentials but not in muscle action potentials
choices A & B
Long-term potentiation (LTP)
is a form of functional synaptic plasticity
is manifested as increased synaptic strength (i.e. increased EPSP)
is same a perforated synapses
choices A, B & C
Release of neurotransmitter (NT) takes place as:
NT molecules in the neuroplasm diffuse across the terminal membrane through the synaptic cleft and onto the postsynaptic membrane.
vesicles containing the NT are released into the synaptic cleft where they diffuse and fuse into the postsynaptic membrane.
NT diffuses through the connexins of the gap junction from the presynaptic to postsynaptic membrane
“Saturday night paralysis” is a proof that A fibers are:
more susceptible to hypoxia than B fibers
more susceptible to pressure than B fibers
more susceptible to hypoxia than C fibers
more susceptible to pressure than C fibers
When an action potential depolarizes a terminal button, Ca2+:
enters the synaptic vesicles
is released into the synaptic cleft
enters the nerve terminal
enters the postsynaptic membrane to generate an EPSP
generates the coated vesicles
In the CNS, a severed or injured axon may undergo Wallerian degeneration but virtually no regeneration takes place because:
astrocytes produce certain chemicals that prevent regeneration
astrocytes produce scar tissue to block regeneration
there are no glial cells to lay the track for a growing axon
Which of the following comparisons between neurons and muscle tissue is false?
resting potential is -90to -100mV in muscle fibers
muscle fibers conduct action potentials at relatively slower speeds
action potentials last longer in muscle fibers
muscle fibers conduct action potentials by saltatory conduction only
How would the plateau action potential be affected if calcium channels were blocked?
it would look like a pacemaker action potential
it would look like a regular (muscle or nerve) action potential
it would not change in any aspect
it would change shape but would have no absolute refractory period
The All-or-nothing rule applies to:
While studying the transport of molecule X across the cell membrane, you discover that as you increase the concentration of B in the extracellular fluid, the rate of transport also initially increases. If the concentration of extracellular X is further increased, the rate becomes constant. Based on this information, which of the following statements best describe this situation?
molecule X is transported from outside to the cytoplasm.
the transport process involves a carrier protein.
the system exhibits saturation.
choices A,B &C
Exocytosis is involved in:
A neurotransmitter release
action of dynein and kinesin
The amplitude of action potential in an axon is dependent on:
SNAREs and synaptotagmin:
SNAREs are proteins that exist only on the vesicles
SNAREs exist on the vesicles as well as on the cytoplasmic side of the nerve terminal
SNAREs bind calcium ion directly
Calcium ions bind synaptotagmin
choices B & D
A drug closes potassium channels of an axon and causes a 15 mV change in the resting membrane potential (RMP). The change is:
similar to EPSP
similar to action potential
similar to IPSP
a reversal potential
a plateau potential
Which of the following statements is/are false?
a single Schwann cell forms a single segment of myelin on peripheral axons
EPP results from opening of acetylcholine-gated channels
presynaptic inhibition requires longer time to develop than postsynaptic inhibition.
synaptic spines are presynaptic nerve terminal
Which of the following statement(s) is false?
action potential starts at the initial segment of the axon
oligodendrocytes are found within the brain.
Na -K pump exists on the myelinated part of a nerve
a single oligodendrocyte can myelinate multiple segments of axon membrane
re-creation of electrical signal across synapses is called transmission
Which of the following is True?
all-or-none law applies to action potential from a single neuron
the ion channels in the synaptic area of all chemical synapses are G-protein dependent
Conduction velocity in myelinated axons depends on whether the nerve is sensory or motor
Phagocytosis is an endocytosis whereas pinocytosis is an exocytosis
Intracellular fluid has more Na+ and less K+ than extracellular fluid
The membranes that most commonly form synapses are the _____and the _____.
choices A and D are correct.
Which of the following is true regarding axoplasmic transport?
The kinesin molecule is involved in retrograde transport.
Retrograde transport involves moving substances from the soma to the axon
The kinesin molecule is involved in anterograde transport
The dynein molecule is involved in anterograde transport.
Which of the following is/are true of oligodendrocytes and Schwann cells?
Schwann cells provide myelin for peripheral nerve cells.
A single Schwann cell wraps a single segment of a peripheral nerve cell.
A single oligodendrocyte can myelinate up to 50 segments of axon membrane.
Oligodendrocytes are found within the brain.
All of the above are correct.
The force that moves sodium ions out of the axon is
the sodium-potassium transporter.
Choose the correct ion channel action with the resulting effect:
entry of a positive ion--hyperpolarization
entry of a negative ion--hyperpolarization
exit of a negative ion--hyperpolarization
exit of a positive ion--depolarization
choices B and D are correct.
The “all-or-none law” refers to the observation that an action potential (AP):
will diminish to near zero when transmitted down a long axon.
is conducted more rapidly down the axon as it reaches the axon terminal.
is produced whenever the membrane potential reaches threshold.
when triggered, the amplitude of AP is the same rate regardless of the inputs to the neuron.
travels only in one direction
The essential event for the release of neurotransmitter from the presynaptic membrane is
the hyperpolarization of the axon membrane.
the activation of the sodium-potassium pumps.
the influx of calcium ions into the axon terminal.
the opening of channels within the microtubules.
the arrival of an EPSF at the axon terminal.
In which portion of a neuron would you expect to find the largest number of small vesicles?
the active (release) zone
just before the axon hillock
the dendritic spines
beneath the postsynaptic membrane
Choose the correct statement about receptors:
ionotropic--more time required to open an ion channel
metabotropic--direct opening of an ion channel
metabotropic--rapid short-lived effects on ion channels
ionotropic--direct opening of an attached ion channel
Which of the following will “neutralize” an EPSP?
opening a chloride channel
allowing intracellular anions to leave the cell
closing a potassium channel
further opening a sodium channel
The process, which blocks the postsynaptic potentials (EPSP and IPSP) induced by most neurotransmitters is:
inhibition of the postsynaptic receptor.
facilitation of transmitter release.
enzymatic degradation of the transmitter molecule.
inhibition of axonal transport.
reuptake of the molecule into the axon terminal.
The absolute refractory period of a neuron
is due to the high negative polarity of the inside neuron.
occurs only during the repolarization phase.
occurs only during the depolarization phase.
occurs during depolarization and the first part of repolarization phase.
The summation of EPSPs from numerous presynaptic nerve fibers converging at the exact same time onto one postsynaptic neuron called
Which of the following is true of the action potential?
During the action potential, the interior becomes even more negative.
The potassium channels are opened at a lower voltage than are sodium channels.
The sodium channels are opened at a lower voltage than are potassium channels.
The action potential requires 5 msec for completion.
The overshoot is due to a prolonged change in sodium conductance.