Sensory Receptors, Sensation, Perception, and Neural Pathways

Flashcards covering sensory receptors, sensation, perception, resting membrane potential, stimulus detection, and neural pathways from the provided lecture notes.

What is a sensory receptor?

A specialized cell that can detect stimuli and trigger responses, monitoring both internal and external environments.

What do interoceptors monitor?

The internal environment (e.g., stomach ache, full bladder).

What do exteroceptors monitor?

The external environment (e.g., touching a cold wall, smelling something).

What is a stimulus?

Any detectable change in the environment.

Give an example of a stimulus and explain when it is not a stimulus.

A car backfiring nearby is a stimulus; if it is too far away to be heard, it is not a stimulus.

What is sensation?

Any stimulus processed by or that reaches the central nervous system (CNS).

How does the body prevent nervous system overload from stimuli?

The body filters out most stimuli; only stimuli that reach the spinal cord or brain become sensations.

What is perception?

Conscious awareness of a sensation.

Do all sensations reach our awareness?

No. Not all sensations reach awareness; the body filters out unimportant information.

Provide an example illustrating how a sensation may be filtered before perception.

When getting dressed, you may initially notice clothing against the skin, but you eventually ignore this sensation.

What is the resting membrane potential (RMP) in most neurons?

−70 millivolts.

Define stimulus in terms of RMP.

Anything that alters the resting membrane potential of the receptor or the first-order neuron.

What causes depolarization and hyperpolarization when a stimulus is detected?

Depolarization occurs when sodium channels open; hyperpolarization occurs when potassium channels open.

What are sub-threshold potentials?

Potentials that do not reach the CNS.

Define sensation in terms of RMP.

Anything that alters the resting membrane potential of the second-order neuron; occurs when the first-order neuron fires an action potential.

Define perception in terms of RMP.

Requires the third-order neuron to fire and the information to be processed in the cerebral cortex; if the third-order neuron does not reach threshold, there is no conscious awareness.

What is the role of the thalamus in sensory processing?

It acts as a sensory filter and relay system, determining whether sensations are processed by the CNS or reach awareness.

How many neurons are typically involved in general senses pathways?

Three neurons (first-order, second-order, and third-order).

Describe the first-order neuron in general senses pathways.

Extends from the periphery to the spinal cord; soma is in the dorsal root ganglion.

Describe the second-order neuron in general senses pathways.

Extends from the posterior gray horn up an ascending tract, usually synapsing in the thalamus.

Describe the third-order neuron in general senses pathways.

Usually located in the thalamus and projects to the postcentral gyrus (primary sensory cortex).