Sensory Pathways & Receptors (Lecture Notes)

Flashcards covering sensory pathways, receptor types, modalities, and cortical maps.

What is the difference between afferent and efferent sensory pathways?

Afferent pathways carry sensory information from receptors to the CNS; efferent pathways carry information from the CNS to skeletal muscles to control movement.

Define sensation.

Sensory information arriving to the CNS.

Define perception.

Conscious awareness of sensation; assigns meaning.

What are general senses?

Temperature, pain, touch, pressure, vibration, proprioception.

What are special senses?

Olfaction (smell), gustation (taste), vision, equilibrium (balance), hearing.

Receptor specificity.

Each receptor has characteristic sensitivity to certain stimuli.

What is a receptive field?

The area monitored by a single receptor; a larger field makes localizing the stimulus harder; measured using two-point touch threshold.

What is a sensory unit?

A sensory neuron and all of its receptors generate the sensation.

Describe a receptor potential.

Stimulus changes the receptor membrane potential; receptors transduce stimulus into action potentials; amplitude depends on stimulus strength; depolarizing moves toward threshold, hyperpolarizing moves away.

What is sensory adaptation?

Loss of responsiveness by a sensory receptor in the presence of a constant stimulus.

Phasic (fast-adapting) receptors.

Normally inactive; burst of activity when stimulus is applied; quickly adapt; APs are generated in response to change.

Tonic (slow-adapting) receptors.

Always active; high firing rate as long as the stimulus is applied; APs change when the stimulus changes.

Sensory receptor classification by location of stimulus.

Exteroceptors: external environment; Proprioceptors: position of skeletal muscles; Interoceptors: visceral organs/functions.

Thermoreceptors: location and characteristics.

Detect changes in temperature; share pathways with pain sensations; located in dermis, skeletal muscles, liver, hypothalamus; phasic in nature.

Chemoreceptors: what they detect and example locations.

Detect substances dissolved in body fluids (chemicals, e.g., pH); located in carotid bodies and aortic bodies.

Mechanoreceptors: general function.

Mechanically-gated ion channels that respond to physical stimuli (mechanical stress, pressure, gravity, position, movement, etc.).

Tactile receptors.

Free nerve endings, root hair plexus, tactile discs, bulbous corpuscles, lamellar corpuscles, tactile corpuscles.

Baroreceptors.

Detect pressure changes in blood vessels and in parts of the GI, respiratory, and urinary tracts; located in elastic tissues of distensible organ walls.

Proprioceptors.

Provide information on the position of joints and skeletal muscles; include muscle spindles, Golgi tendon organ, receptors in joint capsules.

Nociceptors.

Detect tissue damage or physical injury; large receptive fields; located in superficial skin, joint capsules, periosteum, and vessel walls.

Types of pain detected by nociceptors.

Fast, slow, acute, chronic, visceral (referred) pain.

Sensory homunculus.

Functional map of the primary somatosensory cortex; area devoted to a region is proportional to the density of sensory neurons in that region.

Motor homunculus.

Functional map of the primary motor cortex; size of the area corresponds to the degree of fine motor control available.

Fill-in: The sensory information arriving to the CNS is called __.

sensation

Fill-in: Afferent pathways carry __ information to the CNS.

sensory

Fill-in: Nociceptors detect __.

tissue damage