Synaptic Transmission
An AP reaches the axon terminal, but Ca²⁺ cannot enter. What fails?
Neurotransmitter release
A postsynaptic membrane changes to -65mV. What type of potential caused this?
EPSP
Which synapse allows ions to pass directly between adjacent cells through gap junctions?
Electrical
Which neurotransmitter normally activates the skeletal muscle endplate?
Acetylcholine (ACh)
An autoimmune disease reduces ACh receptors at the NMJ. What is the diagnosis?
Myasthenia gravis
Which ion's entry directly triggers synaptic vesicle fusion?
Ca²⁺
Five synapses produce EPSPs simultaneously. What type of summation occurs?
Spatial summation
A signal must rapidly synchronise many cells. Which type of synapse is better suited?
Electrical
What enzyme normally terminates ACh signalling at the NMJ?
Acetylcholinesterase (AChE)
A toxin occupies postsynaptic ACh receptors, preventing ACh binding. What is it?
Curare
A vesicle reaches the presynaptic membrane but cannot fuse. Which proteins are most likely affected?
SNAREs
One synapse repeatedly produces EPSPs before the previous effect fades. What type of summation occurs?
Temporal summation
One neuron distributes its signal to many downstream neurons. What circuit pattern is this?
Divergence
An AP reaches a motor neuron terminal. What ion enters to promote ACh release?
Ca²⁺
A toxin prevents ACh release from motor neuron terminals, causing paralysis. What condition results?
Botulism
Ca²⁺ enters the axon terminal normally, but vesicles cannot fuse. Which process is disrupted?
Exocytosis
If Cl- channels opened on the postsynaptic membrane, what would happen to the RMP? Would it be more or less likely to fire?
Hyperpolarise
Less likely
Many neurons provide input to a single downstream neuron. What circuit pattern is this?
Convergence
ACh is released normally, but its action persists unusually long. What process is impaired?
ACh breakdown
A substance inhibits AChE, causing ACh to accumulate at the NMJ. What could have caused this?
Organophosphate
A presynaptic AP occurs, Ca²⁺ enters normally, and vesicles fuse, but no postsynaptic response occurs. What has most likely failed?
Neurotransmitter binding
At −70 mV, EPSPs are +8, +7 and +6 mV. IPSPs are −4 and −3 mV. Does an AP occur at −55 mV?
No
−70 + 21 − 7 = −56 mV
The patellar reflex involves sensory input, processing within the CNS, and a motor response. Which type of neuron is involved between the sensory and motor pathways?
Interneuron
Why does inhibiting AChE increase activation of the remaining ACh receptors?
More ACh remains
A patient has fewer ACh receptors, causing endplate potentials to repeatedly fall below threshold. What explains the weakness?
Myasthenia gravis