Synapse Flashcards by Mind Med

Which structure most clearly distinguishes chemical synapses from electrical synapses?

A. Presence of a synaptic cleft
B. Gap junctions
C. Direct ionic continuity
D. Nodes of Ranvier

A. Presence of a synaptic cleft

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The postsynaptic density contains:
A. Voltage-gated Ca2+ channels only
B. Presynaptic vesicle proteins
C. Neurotransmitter receptors and binding proteins
D. Schwann cell nuclei

C. Neurotransmitter receptors and binding proteins

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Fast EPSPs are typically produced by opening of which channels?
A. Na+ or Ca2+ channels
B. Cl– channels
C. K+ channels only
D. Voltage-gated Ca2+ channels exclusively

A. Na+ or Ca2+ channels

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Fast IPSPs are usually generated by:
A. Closure of all cation channels
B. Opening of Cl– channels
C. Activation of NMDA receptors
D. Opening of Na+ channels

B. Opening of Cl– channels

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Which is a main function of dendritic spines?

A. Initiate action potentials
B. Increase surface area for synaptic input
C. Myelinate dendrites
D. Provide structural support to the axon initial segment

B. Increase surface area for synaptic input

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Temporal summation at the synapse refers to:

A. Simultaneous firing of multiple neurons
B. Rapid repeated inputs from the same neuron
C. Slow inhibitory potentials
D. Reduced neurotransmitter release

B. Rapid repeated inputs from the same neuron

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A patient with slow EPSPs in autonomic ganglia is most likely experiencing these due to:

A. Decreased K+ conductance
B. Increased Na+ influx
C. Increased Cl– influx
D. Opening of AMPA receptors

A. Decreased K+ conductance

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Where is the lowest threshold for spike initiation in a neuron?

A. Dendritic spines
B. Soma
C. Axon initial segment
D. Synaptic cleft

C. Axon initial segment

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The principle of convergence in neural networks refers to:

A. One neuron synapsing on many others
B. Multiple neurons synapsing on a single neuron
C. Recurrent inhibition
D. Electrical continuity through tight junctions

B. Multiple neurons synapsing on a single neuron

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Presynaptic inhibition in the CNS commonly involves the neurotransmitter:

A. Glutamate
B. GABA
C. Acetylcholine
D. Dopamine

B. GABA

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The neuromuscular junction typically uses which neurotransmitter?

A. Glycine
B. Dopamine
C. Acetylcholine
D. Serotonin

C. Acetylcholine

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Which autoimmune disease results in destruction of muscle-type nicotinic receptors, producing fatigable muscle weakness?

A. Multiple sclerosis
B. Myasthenia gravis
C. Lambert-Eaton syndrome
D. Polymyositis

B. Myasthenia gravis

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Treatment with anticholinesterase inhibitors improves muscle strength in myasthenia gravis because:
A. Increases muscle mass
B. Prolongs action of acetylcholine at the synapse
C. Blocks Ca2+ influx
D. Inhibits serotonin reuptake

B. Prolongs action of acetylcholine at the synapse

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Lambert-Eaton syndrome involves antibodies against:

A. Postsynaptic acetylcholine receptors
B. Presynaptic voltage-gated Ca2+ channels
C. Na+ channels in nodes
D. GABAA receptors

B. Presynaptic voltage-gated Ca2+ channels

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The “end plate potential” at the neuromuscular junction is mainly caused by:

A. Na+ entry
B. Cl– efflux
C. Ca2+ influx
D. K+ entry

A. Na+ entry

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“Quantal release” of neurotransmitter refers to:

A. ATP as the transmitter
B. Release of fixed packets of transmitter from vesicles
C. Summation at the postsynaptic neuron
D. Continuous leakage from the axon hillock

B. Release of fixed packets of transmitter from vesicles

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Which clinical scenario reflects denervation hypersensitivity?

A. Decreased postsynaptic response after denervation
B. Increased sensitivity to neurotransmitters after loss of nerve supply
C. Slowed postsynaptic potential decay
D. Excessive presynaptic action potentials

B. Increased sensitivity to neurotransmitters after loss of nerve supply

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Tetanus toxin exerts its effect by:

A. Blocking VG Na+ channels
B. Cleaving SNARE proteins for vesicle fusion
C. Activating postsynaptic GABA receptors
D. Inhibiting catecholamine reuptake

B. Cleaving SNARE proteins for vesicle fusion

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Which of the following is characteristic of electrical synapses?

A. Unidirectional conduction
B. Presence of voltage-gated calcium channels
C. Direct ionic passage via gap junctions, allowing faster, bidirectional signals
D. Synaptic cleft of 100 nm

C. Direct ionic passage via gap junctions, allowing faster, bidirectional signals

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Most prominent inhibitory transmitter in the CNS is:

A. Glutamate
B. GABA
C. Acetylcholine
D. Dopamine

B. GABA

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Benzodiazepines potentiate inhibition in the CNS by:

A. Directly stimulating GABA synthesis
B. Increasing Cl– influx via GABAA receptor
C. Blocking NMDA receptors
D. Activating muscarinic receptors

B. Increasing Cl– influx via GABAA receptor

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Which structure is most closely associated with presynaptic vesicle docking and fusion?

A. Ankyrin
B. Synaptobrevin and syntaxin (SNARE complex)
C. Aquaporin
D. Tubulin

B. Synaptobrevin and syntaxin (SNARE complex)

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Serotonin is found in high concentration in:

A. Spinal cord ventral horn
B. Platelets and brainstem raphe nuclei
C. Hippocampus only
D. Skin Langerhans cells

B. Platelets and brainstem raphe nuclei

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Blockade of the 5-HT3 serotonin receptor would mostly affect:

A. G-protein coupled transmission
B. Ligand-gated ion channel transmission
C. Adrenergic neurotransmission
D. Dopamine synthesis

B. Ligand-gated ion channel transmission

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The main mechanism for removal of catecholamines from synaptic cleft is: A. Diffusion only B. Reuptake into presynaptic neuron C. Hydrolysis by acetylcholinesterase D. Polymerization in vesicles

B. Reuptake into presynaptic neuron

Excitotoxic neuronal injury following stroke is mostly due to: A. Excess GABA release B. Glutamate-induced excessive Ca2+ influx C. Monoamine oxidase deficiency D. Endorphin overproduction

B. Glutamate-induced excessive Ca2+ influx

The main action of benzodiazepines is to: A. Open Na+ channels directly B. Facilitate GABAA receptor-mediated Cl– conductance C. Inhibit acetylcholinesterase D. Block dopamine D2 receptors

B. Facilitate GABAA receptor-mediated Cl– conductance

Neuropeptides (e.g., substance P, enkephalins) differ from small-molecule transmitters by: A. Synthesized in axon terminals B. Packaged in large dense-core vesicles and often function as neuromodulators C. Released at strictly myelinated regions D. Remain in the synaptic cleft for hours

B. Packaged in large dense-core vesicles and often function as neuromodulators

Activation of the NMDA receptor for glutamate requires: A. Glutamate and glycine binding with Mg2+ block relieved by depolarization B. G-protein activation alone C. Only Na+ influx D. Direct dopamine binding

A. Glutamate and glycine binding with Mg2+ block relieved by depolarization

Dysfunction of dopamine transmission in the nigrostriatal pathway is most associated with: A. Myasthenia gravis B. Parkinson disease C. Multiple sclerosis D. Epilepsy

B. Parkinson disease

The site of lowest threshold for action potential initiation in a typical neuron is: A. Soma B. Dendritic spine C. Axon initial segment D. Node of Ranvier

C. Axon initial segment

An EPSP is most likely to trigger an action potential if: A. It occurs far from the axon hillock B. It summates with another EPSP in time or space C. Ca2+ conductance is reduced D. K+ channels open simultaneously

B. It summates with another EPSP in time or space

Inhibitory postsynaptic potentials (IPSPs) most commonly result from: A. Increased Na+ influx B. Decreased K+ conductance C. Increased Cl– influx D. Opening of voltage-gated Ca2+ channels

C. Increased Cl– influx

In the CNS, a single subthreshold excitatory input that brings a neuron’s potential just below threshold puts the neuron in the: A. Discharge zone B. Occlusion zone C. Subliminal fringe D. Dead zone

C. Subliminal fringe

Spatial summation requires: A. Repetitive activation of the same synapse B. Multiple synapses activated at the same time C. Activation restricted to the axon terminal D. Myelinated axons only

B. Multiple synapses activated at the same time

Temporal summation results when: A. Several presynaptic neurons activate postsynaptic potentials at once B. One neuron fires repeatedly before the EPSP fully decays C. There is refractory period overlap D. Inhibition and excitation occur together

B. One neuron fires repeatedly before the EPSP fully decays

Functionally, the main difference between chemical and electrical synapses is: A. Both allow bidirectional signaling equally B. Electrical synapses have a synaptic cleft C. Chemical synapses offer more flexibility in signal modulation D. Electrical always cause inhibition

C. Chemical synapses offer more flexibility in signal modulation

Opening of voltage-gated Ca2+ channels in the presynaptic terminal results directly in: A. Membrane depolarization B. Axonal repolarization C. Triggered exocytosis of synaptic vesicles D. Hyperpolarization of the postsynaptic cell

C. Triggered exocytosis of synaptic vesicles

The protein directly responsible for docking synaptic vesicles to the presynaptic membrane is: A. Synapsin B. Synaptobrevin (v-SNARE) C. Syntaxin (t-SNARE) D. Dynamin

B. Synaptobrevin (v-SNARE)

A neuron exhibiting greater than expected response to a transmitter following denervation demonstrates: A. Afterdepolarization B. Denervation hypersensitivity C. Refractory period loss D. Feedforward inhibition

B. Denervation hypersensitivity

Presynaptic inhibition typically decreases neurotransmitter release by: A. Inhibiting NMDA post-synaptic receptors B. Reducing Ca2+ influx into the presynaptic terminal C. Increasing vesicle docking D. Blocking acetylcholinesterase

B. Reducing Ca2+ influx into the presynaptic terminal

In relation to EPSPs and IPSPs, the following is true: A. Only EPSPs can summate B. Both EPSPs and IPSPs are all-or-none C. They algebraically sum to determine whether action potential is reached D. Only IPSPs can be spatially summed

C. They algebraically sum to determine whether action potential is reached

Immediately after vesicle fusion, vesicle membrane proteins are: A. Destroyed by lysosomes B. Degraded C. Recycled via endocytosis for future use D. Remain integrated in the postsynaptic membrane

C. Recycled via endocytosis for future use

The concept of “occlusion” in neural networks describes: A. Increased postsynaptic firing over the sum of individual inputs B. Decreased response due to shared postsynaptic targets by converging presynaptic fibers C. Reduced EPSP amplitude due to voltage-gated channel blockage D. Delayed action potential due to slow Na+ inactivation

B. Decreased response due to shared postsynaptic targets by converging presynaptic fibers

Which scenario most exemplifies direct postsynaptic inhibition? A. Binds GABAA receptor, opens Cl– channels, causing hyperpolarization B. Reduces Ca2+ entry into the presynaptic terminal C. Enhances NMDA receptor activation D. Triggers cholinergic transmission at the neuromuscular junction

A. Binds GABAA receptor, opens Cl– channels, causing hyperpolarization

Vesicle priming and fusion at the synaptic terminal most directly require: A. ATP-dependent actin polymerization B. SNARE complex assembly and Ca2+ influx C. Glycogen hydrolysis D. Endothelial cell signaling

B. SNARE complex assembly and Ca2+ influx

“Slow inhibitory postsynaptic potentials” commonly occur via: A. Increased K+ conductance B. Decreased K+ conductance C. Increased Na+ influx D. Activation of voltage-gated Ca2+ channels

A. Increased K+ conductance

Presynaptic facilitation enhances neurotransmitter release by: A. Closing Ca2+ channels earlier B. Prolonging the presynaptic action potential and Ca2+ influx C. Immediate acetylcholine degradation D. Reducing axonal branching

B. Prolonging the presynaptic action potential and Ca2+ influx

Botulinum toxin’s main clinical effect at the neuromuscular junction results from: A. Blockade of postsynaptic ACh receptors B. Destruction of voltage-gated K+ channels C. SNARE protein cleavage, preventing ACh vesicle fusion/exocytosis D. Desensitization of postsynaptic GABA receptors

C. SNARE protein cleavage, preventing ACh vesicle fusion/exocytosis

What structural feature of myelinated axons enables saltatory conduction? A. Continuous spread of action potentials along the axon B. Action potentials regenerated only at nodes of Ranvier C. Axonal branches with synaptic boutons D. Uniform distribution of voltage-gated ion channels along the length

B. Action potentials regenerated only at nodes of Ranvier

Which protein acts as the calcium sensor triggering vesicle fusion in synaptic exocytosis? A. Synaptobrevin B. SNARE complex C. Synaptotagmin D. NSF (N-ethylmaleimide-sensitive factor)

C. Synaptotagmin

The assembly of the trans-SNARE complex primarily results in: A. Endocytosis of synaptic vesicles B. Formation of a fusion pore by bringing vesicle and presynaptic membranes close C. Breakdown of neurotransmitters in the synaptic cleft D. Opening of postsynaptic ligand-gated channels

B. Formation of a fusion pore by bringing vesicle and presynaptic membranes close

Which statement correctly characterizes peptide neurotransmitters compared to small molecule neurotransmitters? A. Peptides are packaged in small clear vesicles near the synapse B. Peptides act rapidly and with short duration C. Peptides are synthesized in the cell body and transported to terminals D. Peptides are terminated primarily by reuptake through the presynaptic membrane

C. Peptides are synthesized in the cell body and transported to terminals

During synaptic transmission, which process terminates the neurotransmitter signal? A. Influx of Ca2+ into the postsynaptic neuron B. Enzymatic degradation in the synaptic cleft, reuptake by presynaptic neurons, and diffusion away from the synapse C. Opening of voltage-gated potassium channels in the presynaptic neuron D. Activation of postsynaptic voltage-gated sodium channels

B. Enzymatic degradation in the synaptic cleft, reuptake by presynaptic neurons, and diffusion away from the synapse

Which class of receptors typically induces a fast postsynaptic response by directly gating ion channels? A. Metabotropic receptors B. Ionotropic receptors C. G-protein coupled receptors D. Tyrosine kinase receptors

B. Ionotropic receptors

Which subunit of the G-protein complex can directly open ion channels during postsynaptic signaling? A. Alpha subunit B. Beta-gamma subunit C. Gamma subunit only D. Delta subunit

B. Beta-gamma subunit

The phenomenon of post-tetanic potentiation is largely attributed to which of the following? A. Temporary depletion of synaptic vesicles B. Increased residual calcium in the presynaptic terminal after high-frequency stimulation C. Decreased postsynaptic receptor availability D. Inactivation of voltage-gated sodium channels

B. Increased residual calcium in the presynaptic terminal after high-frequency stimulation

Botulinum toxins exert their paralytic effect by targeting which crucial synaptic protein family? A. Voltage-gated calcium channels B. SNARE proteins involved in vesicle fusion C. Postsynaptic neurotransmitter receptors D. Sodium-potassium ATPase pumps

B. SNARE proteins involved in vesicle fusion

The following are true of CAPS, except: A. amplitude increases with increased stimulus voltage B. sum of action potentials that have fire given a stimulation voltage C. size and shape is determined by number of axons stimulated D. all fibers have the same threshold potential

D. all fibers have the same threshold potential

TRUE OR FALSE: Different nerve diameter exhibits different conduction velocities

True

TRUE OR FALSE: conduction velocities can be measured seperately for motor and sensory nerves

True

TRUE OR FALSE: Normal NCV in motor nerves is ~50-60 m/s

True

TRUE OR FALSE: If the membrane potential reaches the threshold voltage (approximately -50mV), voltage-gated Na+ channels are activated and an action potential is initiated.

True

TRUE OR FALSE: The peak of the action potential only reaches about +55 mV

False only reaches about +30 mV

Na+ channels close, but voltage-gated K+ channels remain open. The membrane potential falls back towards the resting membrane potential (becomes more negative) What stage is being described?

Repolarization

TRUE OR FALSE: voltage threshold depends on axon diameter

True

Assume that a supramaximal response is obtained at a stimulus voltage of 20 mA. What would happen to the CAP amplitude if you doubled the stimulation voltage to 40 mA? A. CAP amplitude would decrease in size. B. CAP amplitude would increase a little. C. CAP amplitude would remain the same.

C. CAP amplitude would remain the same.

TRUE OR FALSE: Chemical synapses are bidirectional

False

TRUE OR FALSE: Electrical synapses create a coordinated response

True On the other hand, chemical synapses create an amplified response

Neuropeptides differ from small-molecule transmitters in that neuropeptide vesicles are: A. Produced and released at the nerve terminal B. Reused after release C. Synthesized in the cell body and not reused after fusion D. Always faster acting and released in larger amounts

C. Synthesized in the cell body and not reused after fusion

The sequence of events for classic small-molecule neurotransmitter release begins with: A. Vesicle docking and fusion, then presynaptic depolarization B. Neurotransmitter synthesis in the cell body C. Synthesis at the nerve terminal, vesicular packaging, presynaptic depolarization D. Protein cleavage by the Golgi apparatus only

C. Synthesis at the nerve terminal, vesicular packaging, presynaptic depolarization

What is the most crucial signal that directly triggers synaptic vesicle exocytosis? A. Decreased ATP B. Influx of Ca2+ ions through presynaptic voltage-gated channels C. Opening of potassium channels D. Sodium influx at dendrites

B. Influx of Ca2+ ions through presynaptic voltage-gated channels

Which is the correct order for neurotransmitter release from the presynaptic neuron? A. Vesicle docking → Presynaptic depolarization → Ca2+ entry → Fusion → Release B. Presynaptic depolarization → Ca2+ entry → Vesicle docking/fusion → Neurotransmitter release C. Neurotransmitter synthesis → Receptor binding → Ca2+ entry → Vesicle docking D. SNARE disassembly → Priming → Fusion → Ca2+ influx

B. Presynaptic depolarization → Ca2+ entry → Vesicle docking/fusion → Neurotransmitter release

The SNARE complex necessary for vesicle fusion includes all of the following EXCEPT: A. Synaptobrevin B. SNAP-25 C. Syntaxin D. Synaptotagmin

D. Synaptotagmin

Which presynaptic vesicular protein serves as the calcium sensor for neurotransmitter exocytosis? A. Rab3 B. Synaptotagmin C. Syntaxin-1 D. SNAP-25

B. Synaptotagmin

What is the main purpose of the vacuolar-type H+ pump in synaptic vesicles? A. Activate the SNARE complex B. Pump Ca2+ into the vesicle C. Acidify the vesicle lumen to provide a proton-motive force for neurotransmitter uptake D. Hydrolyze neurotransmitter after release

C. Acidify the vesicle lumen to provide a proton-motive force for neurotransmitter uptake

After Ca2+ influx and initial SNARE complex formation, complexin acts to: A. Trigger spontaneous vesicle fusion immediately B. Tether vesicle and membrane proteins such that fusion occurs only after Ca2+ binds synaptotagmin C. Pump H+ ions out of vesicle D. Cleave neurotransmitters before release

B. Tether vesicle and membrane proteins such that fusion occurs only after Ca2+ binds synaptotagmin

What is the minimum synaptic delay for a neuronal signal to be transferred across a synapse? A. 10 s B. 1 ms C. 0.5 ms D. 100 ms

C. 0.5 ms

In the fusion pore opening step, synaptotagmin’s calcium binding causes: A. SNARE complex disassembly before exocytosis B. Complexin displacement, enabling vesicle-membrane fusion and release C. H+ entry into synaptic vesicle D. Recycling of vesicular transporters

B. Complexin displacement, enabling vesicle-membrane fusion and release

Which presynaptic vesicle protein is a v-SNARE and constitutes part of the "anchor" in vesicle fusion? A. Synaptobrevin B. Synaptotagmin C. Complexin D. SNAP-25

A. Synaptobrevin

Which process terminates neurotransmitter action in the cleft for small-molecule NTs like acetylcholine? A. Only passive diffusion B. Proteolysis/enzymatic breakdown and active uptake C. Reuptake of intact vesicles D. None; NTs persist indefinitely

B. Proteolysis/enzymatic breakdown and active uptake

The phenomenon where a single neuron can release both small, rapid-acting and peptide neurotransmitters from the same synapse is: A. Spatial segregation B. Co-release C. Simple diffusion D. Vesicle recycling

B. Co-release

Which gaseous molecule acts as a neurotransmitter, is synthesized as needed, and diffuses rapidly to affect neighboring neurons? A. Glycine B. Nitric oxide C. Dopamine D. GABA

B. Nitric oxide

Synapse Flashcards

(83 cards)