BIO 322 – 2026/2027 Final Exam
(Graded A+) 100% Correct Answers
What is the result of a long, strong psp (from summed inputs) on a motor neuron? - Causes the
motor neuron to fire a sustained train of APs whose frequency depends on how depolarized the
spike-initiating zone becomes and on the refractory period of the neuron
What affects the amount of depolarization (summation) at the spike-initiating zone? - Relative timing
and magnitude of excitatory and inhibitory synaptic currents and where those currents originate
Where are APs generated in motor neurons? - At the spike-initiating zone (just beyond axon hillock)
What is characteristic of the spike-initiating zone in order to generate APs? - Has a lower threshold
for producing APs (has a higher density of voltage-gated Na+ channels)
How are psp's conducted from the synapse to the spike-initiating zone? - With decrement
(electrotonically)
What determines how much current decays over distance for ps neuron? - Length constant
What two things influence how much control individual synapses have on the spike-initiating zone? -
The location of synapses (in relation to length constant) and initial size of synaptic currents
How are excitatory synapses in the CNS different from the NMJ? - NMJ: one AP in the muscle fiber for
each AP in the motor neuron
Excitatory CNS: activation of a single axon terminal that synapses onto a motor neuron releases few
quanta and depolarizes little (need simultaneous input from many excitatory presynaptic terminals)
What determines the production of an AP for motor neurons in the CNS? - Integration of all inputs
(excitatory and inhibitory = summation)
Spatial summation - Integration at spike-initiating zone of psp's from many different presynaptic
neurons
, Temporal summation - Membrane of spike-initiating zone integrates psp's that arrive within a very
small time window, which could have been generated by a train of APs along a single presynaptic
axon
What are the two major types of neurotransmitters? - Small (acetylcholine) and large (amino acids
such as glutamate/glycine)
What type of transmission do modified amino acid neurotransmitters (epinephrine, norepinephrine,
serotonin) act by? - Slow, indirect
What type of neurotransmitter is GABA? - Inhibitory
What type of neurotransmitter is glycine? - Inhibitory
Where does acetylcholine neurotransmitter function? - At the vertebrate NMJ
What is the ubiquitous excitatory neurotransmitter in the vertebrate CNS? - Glutamate
How are chemical synapses characterized? - By structural and phys specialization in the presyn axon
terminal and in the membrane of the postsyn cell
How are signals transmitted at chemical synapses? - By release of neurotransmitter into synaptic cleft
that bind to postsynaptic membrane receptors
What are the two classifications for chemical synapses? - Fast, direct or slow, indirect
Describe fast, direct chemical synapses - Transmitter receptor proteins include both binding site for
neurotransmitter and an ion channel
Describe slow, indirect chemical synapses - Transmitter receptor proteins act through intracellular
messenger systems (G proteins) to affect the conductance through ion channels
How are neurotransmitter molecules packaged? - Packaged into synaptic vesicles that cluster at
active zones on the inner surface of the presynaptic membrane
(Graded A+) 100% Correct Answers
What is the result of a long, strong psp (from summed inputs) on a motor neuron? - Causes the
motor neuron to fire a sustained train of APs whose frequency depends on how depolarized the
spike-initiating zone becomes and on the refractory period of the neuron
What affects the amount of depolarization (summation) at the spike-initiating zone? - Relative timing
and magnitude of excitatory and inhibitory synaptic currents and where those currents originate
Where are APs generated in motor neurons? - At the spike-initiating zone (just beyond axon hillock)
What is characteristic of the spike-initiating zone in order to generate APs? - Has a lower threshold
for producing APs (has a higher density of voltage-gated Na+ channels)
How are psp's conducted from the synapse to the spike-initiating zone? - With decrement
(electrotonically)
What determines how much current decays over distance for ps neuron? - Length constant
What two things influence how much control individual synapses have on the spike-initiating zone? -
The location of synapses (in relation to length constant) and initial size of synaptic currents
How are excitatory synapses in the CNS different from the NMJ? - NMJ: one AP in the muscle fiber for
each AP in the motor neuron
Excitatory CNS: activation of a single axon terminal that synapses onto a motor neuron releases few
quanta and depolarizes little (need simultaneous input from many excitatory presynaptic terminals)
What determines the production of an AP for motor neurons in the CNS? - Integration of all inputs
(excitatory and inhibitory = summation)
Spatial summation - Integration at spike-initiating zone of psp's from many different presynaptic
neurons
, Temporal summation - Membrane of spike-initiating zone integrates psp's that arrive within a very
small time window, which could have been generated by a train of APs along a single presynaptic
axon
What are the two major types of neurotransmitters? - Small (acetylcholine) and large (amino acids
such as glutamate/glycine)
What type of transmission do modified amino acid neurotransmitters (epinephrine, norepinephrine,
serotonin) act by? - Slow, indirect
What type of neurotransmitter is GABA? - Inhibitory
What type of neurotransmitter is glycine? - Inhibitory
Where does acetylcholine neurotransmitter function? - At the vertebrate NMJ
What is the ubiquitous excitatory neurotransmitter in the vertebrate CNS? - Glutamate
How are chemical synapses characterized? - By structural and phys specialization in the presyn axon
terminal and in the membrane of the postsyn cell
How are signals transmitted at chemical synapses? - By release of neurotransmitter into synaptic cleft
that bind to postsynaptic membrane receptors
What are the two classifications for chemical synapses? - Fast, direct or slow, indirect
Describe fast, direct chemical synapses - Transmitter receptor proteins include both binding site for
neurotransmitter and an ion channel
Describe slow, indirect chemical synapses - Transmitter receptor proteins act through intracellular
messenger systems (G proteins) to affect the conductance through ion channels
How are neurotransmitter molecules packaged? - Packaged into synaptic vesicles that cluster at
active zones on the inner surface of the presynaptic membrane
