A sensory signal from the fingertip travels through the spinal cord toward the brain. Which structure receives it before passing it to primary somatosensory cortex?
AHypothalamus
BCerebellum
CThalamus
DAmygdala
The thalamus is the brain's sensory relay hub — all sensory modalities except olfaction synapse in the thalamus before being routed to the appropriate primary cortical area. Each sensory modality has a dedicated thalamic nucleus (e.g., the ventral posterolateral nucleus for touch/pain). The thalamus also gates sensory input, allowing attention to modulate what reaches cortex.
Question 2 True / False
Sensory adaptation — a receptor responding less vigorously to a stimulus that stays constant — indicates a weakness in the nervous system's ability to monitor the environment.
TTrue
FFalse
Answer: False
Adaptation is adaptive, not defective. A constant stimulus (like the pressure of clothing against skin) carries little new information; reducing the neural response to it frees resources for detecting changes, which are far more biologically important. This is why you notice when someone taps your shoulder but stop noticing your shirt after a few minutes of wearing it.
Question 3 Short Answer
Distinguish labeled-line coding from rate coding and explain why both are needed to represent sensory information.
Think about your answer, then reveal below.
Model answer: Labeled-line coding means that which neuron fires specifies the quality of a sensation — C-fibers signal pain, not touch, regardless of how they are stimulated. Rate coding means that how rapidly a neuron fires encodes stimulus intensity — a louder sound causes the same auditory fiber to fire more action potentials per second. Quality (what kind of stimulus) is encoded by which neurons are active; intensity (how strong) is encoded by firing rate.
No single coding scheme could carry all sensory information. Labeled lines give the nervous system a hardwired key for interpreting signal identity, while rate coding provides a continuous analog scale for magnitude. Population coding — patterns across many simultaneously active neurons — adds a further layer of representational richness.