Cumulative level test: From transmission to regulation: synapses, systems, and the limits of measurement

Check understanding, separately from reading

12 questions · 80% to pass · no timer. This longer test revisits both units in the level. These authored questions assess recognition and application of the taught distinctions, not professional qualification. You may review the lessons and retry. Repeat attempts reuse the question bank; a remembered answer is not proof of transfer to a new situation.

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Question 1

An experiment reports increase in mean evoked response, unchanged failure rate, and unchanged variability relative to the mean. A second experiment reports increase in mean evoked response, doubled failure rate, and raised relative variability. Which pair of explanations fits the two experiments, and what additional measurement separates the remaining possibilities in the first case?Postsynaptic change in quantal size in the first, presynaptic change in release probability in the second; in the first case miniature event amplitude is the measurement that separates quantal size from an increase in the number of release sites.Presynaptic change in the first and postsynaptic change in the second, because presynaptic changes raise the mean while postsynaptic changes raise variability.

Question 2

A cell is held at its chloride reversal potential while receiving strong excitatory drive. Inhibition arriving at the same time produces almost no voltage deflection, yet the excitatory depolarization is smaller and shorter than without it. Explain how both statements hold and what the arrangement implies about circuit stability.The two statements cannot both hold, because a synaptic input with no voltage effect must be functionally silent.The added conductance shunts excitatory current locally, changing the membrane time constant and the fraction of current reaching the integration site without a net voltage deflection; stability comes from conductance rather than from hyperpolarization.

Question 3

A learning protocol produces a lasting increase in one pathway, a smaller decrease in two adjacent, unstimulated pathways on the same dendrite, and no change in a test pathway. Two days later the same protocol produces a much smaller increase. Name the three phenomena and explain why the third does not contradict the first.Associative potentiation at the trained pathway, heterosynaptic depression at neighboring inputs, and metaplasticity, which changes the capacity for further change rather than reversing the earlier weight change.Potentiation, homeostatic scaling, and long-term depression, because any decrease in unstimulated inputs is homeostatic by definition.

Question 4

A study reports that hippocampal inactivation before retrieval impairs memory for material learned one day earlier but not for material learned six weeks earlier, and concludes that the memory moved to cortex. Write the strongest defensible version of the claim and name two alternative explanations the design cannot exclude.The defensible claim is that memories are transferred to cortex within six weeks, since the older memory survived inactivation, leaving no competing explanation.The defensible claim is that retrieval of the younger memory depended on the hippocampus under these conditions while the older memory did not; alternatives include compensation by other structures and a change in retrieval strategy or cue use rather than a change in storage site.

Question 5

A sleep study finds that spindle density correlates with overnight retention of a motor sequence, and a second study finds that auditory cueing during non-rapid-eye-movement sleep preferentially improves retention of cued items. Compare the evidential weight of the two designs and state what neither can support.The cueing design is stronger because the critical event was manipulated by the experimenter with the memory content specified, whereas the correlation is compatible with any factor that covaries with spindle density; neither supports individual prediction or intervention.The correlational design is equally strong because spindle density was measured objectively with a physiological instrument rather than manipulated indirectly through sound.

Question 6

An afferent responds strongly at the onset of a maintained stimulus and then falls to a low steady rate, while a nociceptive afferent under repeated stimulation reduces its threshold. Compare the two and state what each pattern implies for downstream circuits.Both patterns are fatigue of the transducer cascade, which simply limits how long any receptor can signal.Adaptation markedly reduces signaling of sustained innocuous levels while preserving change detection, whereas sensitization increases responding and can support protective guarding of injured tissue.

Question 7

A patient with a focal lesion is impaired on a reaching task requiring fast corrections when the target moves, but performs normally on a slow reach to a fixed target. Damage to which system is most consistent with this pattern, and what does the selective deficit not establish?A system contributing to rapid error correction and sensorimotor adaptation, for example a cerebellar module; the pattern does not establish that the region stores the movement or that it is the only structure that can support it.The primary motor cortex, because slow reaches are simpler and require less cortical output than fast corrections.

Question 8

During a prolonged stand, a person's cardiac output falls and leg blood flow changes while arterial pressure stays within its usual range. Explain the regulation involved, the timescale on which each component acts, and why the single pressure value is a poor summary.Pressure was maintained because the reflex restored cardiac output to its original value, leaving all other variables unchanged.A fast neural reflex raises sympathetic outflow and vascular resistance within seconds while a slower hormonal limb adjusts fluid and metabolic variables over minutes to hours; the unchanged pressure reflects a changed balance among output, resistance, and distribution rather than unchanged physiology.

Question 9

A scalp study reports a larger late component in a memory condition, and the authors attribute the difference to increased synaptic plasticity in a deep structure. Separate the claim into the part the method supports and the part it does not, and identify the measurement that would be needed for the second part.The method supports a larger surface deflection time-locked to the condition with limited spatial inference; the plasticity and deep-source claims need intracranial or invasive measures with their own controls.The method supports both claims because scalp signals are generated by cortical synapses and therefore provide direct evidence about synaptic strength.

Question 10

A region is more active during a task, and patients with damage to the same region perform the task poorly at long intervals after injury but normally soon after injury. State what the two results jointly support and how the timing difference constrains interpretation.The early normal performance shows the region is not required, and the later deficit shows the task was relearned differently after complete compensation.The results jointly support a correlate of the task in that region and a requirement for it in the chronic state; the early normal performance suggests compensation or incomplete damage rather than absence of a role.

Question 11

A researcher wants to claim that a specific rhythm organizes the timing of memory reactivation during sleep in humans. Using the measurement ledger from this level, state which methods can address the timing claim, which can address the localization claim, and what the safest overall conclusion is.Scalp electrophysiology can address the timing of the rhythm and its relation to behavioral retention, imaging can supply a coarse spatial correlate, and the safest conclusion is a time-locked association in the tested protocol because ripple-scale hippocampal events require intracranial recording.Scalp recordings can support both claims directly, because synchronous postsynaptic activity in the hippocampus projects to the scalp at amplitudes comparable to cortical sources.

Question 12

Assemble the level's reasoning into one design. A team wants to test whether a specific synapse type supports a learned avoidance response, and they can use electrophysiology in a preparation, a targeted disruption, and behavior. Write the sequence of claims they should make and the control each claim requires.First, show that the synapse type is active during learning; second, describe its transmitter; third, conclude that the pathway stores the memory, since activity during learning identifies the storage site.First, measure the synaptic change during learning with controls for sensory input and motor output; second, disrupt the same synapse type and confirm that the change is reduced and behavior is impaired relative to a control disruption; third, show that an intervention that restores the change also restores behavior, and report each chain as an inference with its species and preparation named.

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