PY 359 Perception - Module 8: The Body Senses Flashcards

Vocabulary flashcards based on lecture notes about the body senses, including tactile perception, proprioception, nociception, thermoreception, haptics, and vestibular senses.

Body Senses

Sense of touch, encompasses skin deformation, muscle stretch, joint angle, pain, temperature, object shape, balance, and acceleration.

Mechanoreceptor

Sensory neuron that responds to mechanical energy, such as pressure, vibration, or movement.

Mechanical Energy

For somatosensation, this refers to the deformation of the skin.

Epidermis

Outer, avascular layer of the skin composed mainly of dead skin cells.

Dermis

Vascular layer of the skin containing connective tissue and housing most receptors.

Hairy Skin

Skin type that covers most of the body's surfaces.

Glabrous Skin

Hairless skin found on the lips, palms of the hands, and bottoms of the feet.

Merkel Cells

Slow-adapting mechanoreceptors with small receptive fields, important for fine manual control.

Meissner Corpuscle

Fast-adapting mechanoreceptors with small receptive fields, highly sensitive to fast movements across the skin.

Ruffini Endings

Slow-adapting mechanoreceptors with large receptive fields, detecting light touch and skin stretch.

Pacinian Corpuscle

Fast-adapting mechanoreceptors with large receptive fields, responding to fast vibrations and enabling detection of very light touch.

Two-Point Threshold

Minimum distance with 75% correct identification of one or two points.

Merkel Cell

Modified skin cell that synapses with a Merkel disk.

Merkel Disk

Specialized nerve ending associated with Merkel cells.

Spatial Event Plots

Neural representation of tactile patterns studied using spatial event plots.

Ruffini Endings

Fluid-filled cylindrical capsule made of Schwann-like cells and collagen fibers, housing SAII nerve endings.

Meissner Corpuscles

Flat, horizontal layers of Schwann-like cells embedded in connective tissue, interwoven with FAI nerve endings.

Pacinian Corpuscles

Oval layers of Schwann-like cells and fluid embedded in connective tissue, containing a central FAII nerve ending.

C-tactile mechanoreceptors (aka CT mechanoreceptors)

Recent discovery, Free nerve endings (i.e., no capsule) only in hairy skin Responds to slow, gentle touch.

Proprioception

Detects positioning and movement of limbs (aka kinesthesis).

Thermoreception

Detects changes in temperature on the skin.

Muscle Spindles

Detects muscle stretch / changes in muscle length.

Golgi Tendon Organs

Detects compression of nerve fiber due to muscle force.

Warm Fibers

Respond to increases in skin temperature between 29 and 43°C.

Cold Fibers

Respond to decreases in skin temperature between 29 and 17ºC.

Pain

The perception and experience of actual or threatened tissue damage.

Discriminative Pain

The sensory component of pain (location, nature, intensity).

Affective Pain

The emotional component of pain, motivates behaviors.

Nociceptive Pain

Pain due to tissue damage or physical trauma.

Neuropathic Pain

Damage to PNS or CNS.

A-delta fibers

Nociceptor Fiber type ,Rapid (2-4 m/sec), First pain (sharp, stinging).

C-fibers

Nociceptor Fiber type ,Slow (1 m/sec), Second pain (dull, throbbing).

Endorphins

Opioid neuropeptides that inhibit pain and often induce pleasure.

Nerve Roots

Bundles of nerves entering the spinal cord together.

Dorsal Column-Medial Lemniscal Pathway

Spinal pathway Nerve fibers carrying neural signals for tactile perception and proprioception.

Spinothalamic Pathway

Spinal pathway Nerve fibers carrying neural signals for nociception and thermoreception.

Ventral Posterior Nucleus

The thalamic nucleus for somatosensory information.

S1

Primary somatosensory cortex

Somatotopic Map

A systematic mapping of the body’s surface onto the cortex.

Tactile Agnosia

Inability to recognize objects by touch.

Haptic Perception

Using touch to perceive and identify objects.

Vestibular Sensation

Sensory processes pertaining to balance and acceleration.

Endolymph

Fluid filling the sensory organs of the vestibular system.

Semicircular Canals

Detect head rotation.

Otolith Organs

Detect linear acceleration and stationary tilt.

Vestibulo-ocular Reflex

A reflex that produces equal, opposite movement of the eyes during head movement.

Primary somatosensory cortex (S1)

Located in postcentral gyrus Contains four parallel strips of cortex, each somototopically organized.

Afferent (sensory) nerve fiber wound around muscle fibers

Afferent (sensory) Located in Embedded within skeletal muscles.

Joint receptors

Detect joint angle only when it is near the limit of normal motion.

Tissue inflammation of Nociceptors and Pain

Signals organism to avoid using body part (faster healing).

anterior cingulate cortex

Site of emotional responses to physical and emotional pain.

Somatotopic Organization in S1

Contains four parallel strips of cortex, each somototopically organized.

Ventral pathway

Begins in Areas 3b and 1 (tactile perception),Combined with proprioception in Area 2 ,Proceeds to S2 → PFC and hippocampus ,Involved in perceiving (S2) and remembering (PFC and hippocampus) object shape and identity

C-tactile mechanoreceptors

Free nerve endings (i.e., no capsule) only in hairy skin.

Dorsal pathway

Terminates in posterior parietal cortex extensively connected to premotor cortex Guides actions that require tactile and proprioceptive info.

Cortical Processing of Temperature

From ventral posterior nucleus, travels to insular cortex Different regions of insula handle different aspects of temperature (location, intensity)

Exploratory Procedures

Lateral motion Texture,Pressure Static contact Hardness Temperature,Weight Enclosure Volume; Global shape Static contact Unsupported holding Volume; Exact shape Contour following Specific function Function test Part motion test Part motion

Skeletal muscles

Smallest unit = muscle fiber Single cell originally made of many cells Contains many contractile protein filaments.

Important regions for visuospatial guidance of movement

Located around intraparietal sulcus.

Tendons

Connect muscles to bones Composed of the muscle’s connective tissue Translate muscle contraction to skeletal movement.

Inflammatory pain

Tissue damage releases chemicals that stimulate pain receptors or reduce their threshold.

Hair Cells of the Semicircular Canals

Gelatinous cupula, which contains embedded stereocilia acceleration moves the endolymph of the canal.

Muscle Spindles Respond to Stretch

Muscle stretched Firing rate Muscle contracted Firing rate.

The Vestibular System

The vestibular nerve joins with the cochlear nerve and carries signals to the vestibular complex of the brainstem.

Thermoreceptors

Receptors sensitive to skin temperatures around 17-43ºC (63-110ºF).

Somatosensory Pathways

Posterior Insula – Ventral Posterior Nucleus (Thalamus) Tactile, proprioceptive, discriminative pain.

Thermoreceptors

Like C-tactile mechanoreceptors, thermoreceptors have free nerve endings.

Many cortical targets:

All cortical regions receiving vestibular input are connected to PIVC .

Muscle Spindles Respond to Stretch

Muscle fiber Y Stretch Signal in afferent nerve fiber from muscle spindle.

The Semicircular Canals

The semicircular canals are sensitive to rotational acceleration.

Hair Cells of the Otolith Organs

During linear acceleration, the heavy otoconia have less momentum and lag behind, distending the gel layer.

Hair Cells of the Otolith Organs

During stationary head tilt, the heavy otoconia are pulled by gravity, distending the gel layer.

slow-adapting mechanoreceptors

Burst of firing at onset of skin deformation Lower-frequency sustained response until end

Fast -Adapting Mechanoreceptors

Fires at onset and offset

SAI Mechanoreceptors: Merkel Cells

High spatial resolution, sustained response Inform fine manual control Respond to slow vibrations.

SAII Mechanoreceptors: Ruffini endings

Low spatial resolution, sustained response Detect light touch Respond maximally to steady pressure

FAI Mechanoreceptors: Meissner Corpuscles

High spatial resolution, transient response Respond to slow vibrations Highly sensitive, esp. to fast movements across skin Thought to detect object slip to maintain grip

FAII Mechanoreceptors: Pacinian Corpuscles

Very low spatial resolution, transient response RF can cover entire hand Respond to fast vibrations Extremely sensitive, enables detection of very light touch

Somatosensory Pathways

The thalamic nucleus for somatosensory information is the ventral posterior nucleus.Signals to anterior cingulate cortex Somatosensory cortex Signals to insular cortex

Paradoxical Heat / Cold

Cold fibers can respond to heat above 50 Celsius, but produce perceived coldness (paradoxical cold)

Paradoxical Heat / Cold

Warm fibers can respond to skin cooling, even as high as 31 Celsius depending on the baseline (paradoxical heat)

Pleasant Touch

Recent discovery: C-tactile mechanoreceptors (aka CT mechanoreceptors) Free (unmyelinated) nerve endings (i.e., no capsule) only in hairy skin Responds to slow, gentle touch

Muscle Spindles

Most important proprioceptor for sensing limb position and movement

Golgi Tendon Organs

Muscle contracted. Signal in afferent nerve fiber from Golgi tendon organ Muscle stretched Weight Y

Thermoreceptors

Like C-tactile mechanoreceptors, thermoreceptors have free nerve endings.

Pressure Cold stimulus

Free nerve endings (dendrites) Generator potential Triggers Nerve impulses Propagate into CNS

REMINDER: Action and Perception: Organization of the Parietal Lobe

Important regions for visuospatial guidance of movement Located around intraparietal sulcus.

The Vestibular System MANY CORTICAL TARGETS:

Parietal insular vestibular cortex (PIVC) Cortical regions receiving vestibular input are connected to PIVC PIVC thought to represent position and orientation of the head.

The Sense of Balance VESTIBULAR SENSATION

Fluid-filled sensory organs are located in the inner ear Filled with endolymph Directly adjacent to cochlea (hearing).

The Vestibulo-Ocular Reflex 89

Vestibular complex sends output to brainstem nuclei controlling eye movements Vestibulo-ocular reflex – a reflex that produces equal, opposite movement of the eyes during head movement

Muscle Spindles Respond to Stretch

Muscle fiber Muscle spindle fiber Muscle stretched Stretch Muscle length

Subregions of Primary Somatosensory Cortex

S1 Area 3a Area 3b Area 1 Area 2.

The Otolith Organs

Otoliths topheavy Linear acceleration and head tilt cause distention of the macula deflection of stereocilia Orientations of stereocilia decompose movement into different directions Otoliths

Joint-

Muscle-Tendon

Pleasant Touch

Mechanized skin stroking: maximal responses to stroking that was rated most pleasant Moderate speed Neutral temperature

Somatosensory Pathways to the Brain

Axons from receptors in the skin collect into nerves

Somatosensory Pathways to the Brain

Nerves cluster increasingly together towards the spinal cord.

Somatosensory Pathways to the Brain:

Bundles of nerves entering the spinal cord together are known as nerve roots. Nerve Roots and Dermatomes

Reflexes of the Spinal Cord

Some axons carrying nociceptive, thermoreceptive, and proprioceptive information synapse immediately in the spinal cord to enable reflex arcs for automatic, protective behaviors.

Cortical Processing of Temperature

From ventral posterior nucleus, travels to insular cortex Different regions of insula handle different aspects of temperature (location, intensity)