Somatosensory System Quiz

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Questions and Answers

Which receptor is primarily responsible for detecting vibrations?

  • Ruffini's Corpuscle
  • Pacinian Corpuscle (correct)
  • Merkel's Disc
  • Meissner's Corpuscle

What term describes the ability of Pacinian corpuscles to quickly cease responding to continuous stimulus?

  • Sustained adaptation
  • Phasic response
  • Tonic response
  • Rapid adaptation (correct)

Which sensory modality is NOT part of the somatic senses?

  • Hearing (correct)
  • Temperature
  • Pain
  • Touch

What characteristic distinguishes fine or discriminatory touch from crude touch?

<p>Localization of sensation (C)</p> Signup and view all the answers

What types of sensations do Ruffini's corpuscles primarily detect?

<p>Deep pressure and stretch (D)</p> Signup and view all the answers

Which of the following describes the concept of spatial discrimination?

<p>The ability to localize touch sensations accurately (D)</p> Signup and view all the answers

What is the role of lateral inhibition in sensory perception?

<p>Reducing the effect of surrounding sensory inputs (A)</p> Signup and view all the answers

Which cutaneous receptor is primarily responsible for detecting light touch?

<p>Meissner's Corpuscle (C)</p> Signup and view all the answers

What determines the effectiveness of two-point discrimination?

<p>The distance between sensory receptors (A)</p> Signup and view all the answers

Which area of the body has the smallest receptive fields?

<p>Face (B)</p> Signup and view all the answers

What is the primary role of lateral inhibition in sensory perception?

<p>To sharpen perception of edges (D)</p> Signup and view all the answers

Which type of receptor changes its firing rate in response to temperature changes?

<p>Thermoreceptors (B)</p> Signup and view all the answers

What is the function of the labelled line code in the somatosensory system?

<p>To identify the location of stimulation (C)</p> Signup and view all the answers

Which of the following best describes spatial discrimination ability?

<p>The capacity to distinguish the location of stimuli (A)</p> Signup and view all the answers

How do receptive fields differ in size across various body parts?

<p>They are smaller and more numerous on sensitive areas (B)</p> Signup and view all the answers

Which process occurs at each relay point in the sensory pathway to enhance signal processing?

<p>Lateral inhibition (D)</p> Signup and view all the answers

Which mechanoreceptors are primarily responsible for sensing stretch around joints?

<p>Golgi tendon organs (C)</p> Signup and view all the answers

What characteristic describes the receptive fields of mechanoreceptors in the somatosensory cortex?

<p>Specific and localized for particular body areas (D)</p> Signup and view all the answers

Lateral inhibition primarily enhances which aspect of sensory processing?

<p>Contrast and resolution of sensory input (D)</p> Signup and view all the answers

Thermoreceptors are mainly responsible for detecting what type of sensory information?

<p>Changes in temperature (D)</p> Signup and view all the answers

The capacity for spatial discrimination in the somatosensory cortex is enhanced by which of the following?

<p>The density of mechanoreceptors (D)</p> Signup and view all the answers

Which layer of the somatosensory cortex is primarily involved in processing specific sensory modalities?

<p>Layer 4 (C)</p> Signup and view all the answers

Which area of the somatosensory cortex is known for integrating information from different sensory systems?

<p>Somatosensory association cortex (B)</p> Signup and view all the answers

Damage to the somatosensory cortex would likely impair which of the following functions?

<p>Localized feeling of touch and proprioception (C)</p> Signup and view all the answers

Flashcards

Thermoreceptors

Receptors that change their firing rate as temperature changes in a specific direction.

Somatosensory System

Part of the nervous system that provides information about body parts stimulated.

Labelled-line code

A system that identifies the location of a stimulus based on which neurons are activated.

Dermatome

The area of the body innervated by a single spinal nerve.

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Receptive Field

The specific area on the body that stimulates a particular sensory receptor.

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Two-point Discrimination

The ability to perceive two simultaneous stimuli as separate.

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Lateral Inhibition

The process of activating some neurons while inhibiting nearby neurons to sharpen sensations.

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Sensory Pathways

The routes that sensory information travels from the body to the brain via the spinal cord.

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Mach Bands

An optical illusion causing perceived edges appear sharper than they actually are.

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Somatosensory System

The system that allows us to perceive touch, temperature, position sense (proprioception), and pain from the skin, joints, muscles, and viscera.

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Sensory Receptors (touch)

Specialized cells or neuron endings in the skin that detect touch.

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Touch (submodalities)

Two types: fine (discriminatory; e.g., two-point discrimination) and crude (itch, tickle; poorly localized).

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Pacinian Corpuscle

A deep-pressure encapsulated receptor; rapidly adapting; good at detecting vibrations.

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Pacinian Corpuscle structure

Encapsulated receptor in the subcutaneous layers, made of a lamellar structure

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Pacinian Corpuscle Function

Detects vibrations and changes in pressure, responding rapidly but only producing a few action potentials to each stimulus.

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Meissner's Corpuscle

Another type of touch receptor in the skin. Thought to detect light touch or fine touch.

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Ruffini's Corpuscle

Found deeper, detects sustained pressure and skin stretching.

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Merkel's Disc

Touch receptor specialized in sustained touch and fine details.

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Primary Somatosensory Cortex

Part of the brain that processes information from the body's senses, like touch, temperature, and pain. It's located in the post-central gyrus and has a map-like representation of the body (homunculus).

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Somatosensory Cortex Organization

The somatosensory cortex is organized in vertical columns, each managing a specific sensory modality (e.g., touch, pressure).

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Somatosensory homunculus

A map-like representation of the body in the somatosensory cortex where different body parts are allocated space based on their sensitivity.

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Secondary Somatosensory Cortex (SII)

A brain region that further processes somatosensory information, receiving input from SI, and also contains a topographic map.

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Somatosensory Association Cortex

A cortical region that integrates information from the primary and secondary somatosensory cortices to form a more complete understanding of what the body is experiencing.

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Body Part Representation in Cortex

Areas of the somatosensory cortex dedicated to specific body parts are proportional to the sensory sensitivity of those parts. Areas like the face and hands occupy more space relative to areas like the back.

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Study Notes

Somatosensory System

  • Somatic senses perceive touch, temperature, proprioception (position sense), and pain.
  • Information comes from skin, joints, muscles, and viscera.

Sensory Receptors

  • Touch receptors are specialized epithelial cells or neuronal endings in the skin.
  • Two main touch submodalities:
    • Fine/discriminatory touch (two-point discrimination)
    • Crude touch (itch, tickle - poorly localized)

Cutaneous Sensory Receptors

  • Four distinct receptor types transduce touch:
    • Pacinian corpuscle
    • Meissner's corpuscle
    • Ruffini's corpuscle
    • Merkel's disc

Pacinian Corpuscle

  • Encapsulated receptor deep in subcutaneous layers of hairy and non-hairy skin.
  • Consists of a group II myelinated fiber encased in a lamellar structure (approximately 1mm in diameter).
  • Rapidly adapting receptor, suited to detecting vibrations.
  • Adaptation results from lamellae adjusting shape during deformation, preventing continuous depolarization for signaling.
  • Frequency of firing reflects vibratory signal intensity.
  • Poorly localizing due to large receptive fields.

Meissner's Corpuscle

  • Consists of group II myelinated fibers in a small capsule.
  • Found densely in fingertips, lips.
  • Rapidly adapting receptor, useful for encoding tapping and flutter.
  • Small receptive fields, enabling two-point discrimination.

Merkel's Discs

  • Unencapsulated mechanoreceptors in non-hairy skin epidermis.
  • Merkel cell enclosed by a nerve ending.
  • Small receptive fields, enabling precise location.
  • Slowly adapting receptors.
  • Ideal for detecting stimulus location.

Ruffini's Corpuscles

  • Nerve terminal in a liquid-filled collagen capsule.
  • Depolarize in response to skin deformation (any input).
  • Slowly adapting receptor.
  • Large receptive fields.
  • Encoding information regarding stimulus magnitude.

Thermoreceptors

  • Located on free nerve endings of myelinated (Aδ) and unmyelinated (C) fibers.
  • Separate receptors for cold (optimum sensitivity at 25°C) and warmth (optimum sensitivity at 45°C).
  • Very cold (<5°C) or hot (>45°C) stimuli activate pain fibers (thermal nociceptors).
  • Receptors transiently change firing rate in response to temperature change direction.

Where is it?

  • Somatosensory system provides brain information about body part being stimulated.
  • Imagine losing touch sensation to understand possible effects.

Sensory Pathways

  • Two primary pathways:
    • Dorsal column pathway: transmitting fine touch, pressure, proprioception.
    • Anterolateral pathway: conveying pain, temperature, and crude touch.

Dermatomes

  • Refers to body areas innervated by neurons in a single spinal nerve.

Clinical Application

  • Examples of clinical scenarios involving spinal cord damage and associated sensory losses.

Brown-Sequard Syndrome

  • Specifically relates hemisection of spinal cord at T12 and resulting pattern of sensory loss.

Thalamus

  • Relay station for all sensory input to the cerebral cortex, except olfaction.

Cortical Processing

  • Different cortical areas involved in processing somatosensory information:
    • Primary somatosensory cortex (SI): post-central gyrus, Brodmann's areas 1, 2, and 3 - topographic map "homunculus".
    • Secondary somatosensory cortex (SII): superior bank of the lateral fissure, another map but more diffuse.
    • Somatosensory association cortex: areas 5 and 7, integrating information from different sensory systems.

Primary Somatosensory Cortex

  • Contra-lateral representation of somatic senses (except fibers from face).
  • Larger areas for lips, thumb, face; smaller areas for other body parts.
  • Columns arranged in vertical column, each for a specific sensory modality - tactile, pain, temperature.
  • Contains orientation and direction-sensitive properties.

Somatosensory Association Cortex

  • Synthesizes primary and secondary input.
  • Involved in complex sensory associations.
  • Stimulating this area can elicit complex body sensations, like the sensation of a tool.

Damage to Somatosensory Cortex

  • Damage can affect drawing, spatial relations and two-point discrimination.

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