Sensory Pathways and the Somatic Nervous System - Flashcards

A set of Q&A flashcards covering the key concepts from the lecture notes on sensory pathways, receptors, and cortical representations.

What is a sensory pathway?

A series of neurons that relay sensory information from sensory receptors to the CNS.

What are sensory receptors?

Specialized cells or neuron processes that monitor specific conditions in the body or external environment.

What information arrives at the CNS via afferent pathways?

Somatic and visceral information.

Where does somatic sensory information go in the CNS?

To the cerebral cortex.

Where does visceral sensory information go primarily?

To the brainstem.

What are efferent pathways?

Somatic motor pathways that exit the CNS and control skeletal muscles.

What is sensation?

Sensory information arriving in the CNS.

What is perception?

Conscious awareness of a sensation and its meaning.

What is receptor potential?

A stimulus-induced change in receptor membrane potential; depolarizing toward threshold and hyperpolarizing away.

What is a receptive field?

Area monitored by a single receptor.

What is a sensory unit?

The sensation generated by a sensory neuron and all its receptors.

What does a larger receptive field imply about localization?

It makes localizing a stimulus more difficult.

What is the two-point touch threshold used to measure?

Tactile acuity; the distance at which two points are perceived as separate.

How does stimulus strength affect receptor potential size?

The size of the receptor potential depends on the strength of the stimulus.

What is sensory adaptation?

The loss of responsiveness at the sensory receptor level in the presence of a constant stimulus.

What are phasic receptors?

Respond with a burst of activity when a stimulus is first applied but quickly adapt to the stimulus.

What are tonic receptors?

Maintain a high firing rate as long as the stimulus is applied; slow-adapting.

What are exteroceptors, proprioceptors, and interoceptors?

Exteroceptors detect external environment; proprioceptors monitor body position; interoceptors monitor visceral organs and functions.

What are nociceptors?

Free nerve endings with large receptive fields that detect tissue damage.

What kinds of pain are described in nociception?

Fast pain, slow pain, acute pain, chronic pain, and visceral pain (which can be referred).

How do opioids block pain?

Through descending inhibition via enkephalin interneurons; exogenous opioids bind opiate receptors to reduce nociceptive impulses.

Where are thermoreceptors located and what kind of receptors are they?

Free nerve endings in the dermis, skeletal muscles, liver, and hypothalamus; phasic receptors.

What are mechanoreceptors?

Receptors sensitive to physical stimuli; mechanically-gated ion channels; include tactile receptors, baroreceptors, and proprioceptors.

What do tactile receptors detect?

Touch (shape/texture), pressure, and vibration.

What is the difference between fine touch/pressure receptors and crude touch/pressure receptors?

Fine touch/pressure receptors have small receptive fields and provide detailed information; crude receptors have large receptive fields and poorer localization.

What are free nerve endings and root hair plexus?

Free nerve endings detect touch/pressure (tonic); root hair plexus detects movement near hairs (phasic).

What are Merkel discs (tactile discs)?

Detect fine touch and pressure; tonic receptors with small receptive fields.

What are Ruffini endings (bulbous corpuscles)?

Sensitive to deep pressure and distortion; tonic receptors in the reticular dermis.

What are Pacinian corpuscles (lamellar corpuscles)?

Sensitive to deep pressure and pulsing vibrations; fast-adapting with layered structure.

What are Meissner’s corpuscles?

Sensitive to fine touch, pressure, and low-frequency vibration; phasic receptors.

What are baroreceptors?

Detect pressure changes in blood vessels and parts of the digestive, respiratory, and urinary tracts; free nerve endings in elastic tissues of distensible organs.

What are proprioceptors?

Monitor the position of joints and skeletal muscles; include muscle spindles, Golgi tendon organs, and joint receptors.

What are chemoreceptors?

Respond to substances dissolved in body fluids; monitor pH, CO2, and O2; located in carotid and aortic bodies.

What is the sensory homunculus?

A functional map of the primary somatosensory cortex; body region representation is proportional to sensory neuron density.

What is the motor homunculus?

A functional map of the primary motor cortex; the size of areas reflects the degree of fine motor control (hands, face, tongue are large).