Somatic Sensations Overview

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Questions and Answers

Which type of sensory receptor adapts rapidly to stimuli?

  • Meissner's corpuscles (correct)
  • Free nerve endings
  • Merkel’s discs
  • Hair end-organs (correct)

Which sensory receptor is known for adapting very slowly to stimuli?

  • Merkel’s discs (correct)
  • Meissner's corpuscles
  • Free nerve endings
  • Hair end-organs

Which of the following receptors can be found in the cornea?

  • Meissner's corpuscles
  • Hair end-organs
  • Merkel’s discs
  • Free nerve endings (correct)

Which receptor does not rapidly adapt to changes in stimuli?

<p>Merkel’s discs (B)</p> Signup and view all the answers

Which of these receptors can be classified as rapidly adapting?

<p>Both B and C (D)</p> Signup and view all the answers

What condition is indicated by astereognosis?

<p>Loss of the sense of touch (C)</p> Signup and view all the answers

Which part of the nervous system is primarily affected in astereognosis?

<p>Sensory area (D)</p> Signup and view all the answers

What is one of the causes of astereognosis?

<p>Lesion in the sensory area (D)</p> Signup and view all the answers

Which of the following tracts is associated with astereognosis when cut?

<p>Gracile and Cuneate tracts (C)</p> Signup and view all the answers

Tabes dorsalis affects which of the following mechanisms primarily related to astereognosis?

<p>Sensory perception (A)</p> Signup and view all the answers

What is the temperature range for 'cold' sensation in temperature sensation?

<p>10° to 30°C (B)</p> Signup and view all the answers

Which type of receptors are responsible for temperature sensation?

<p>Free nerve endings (B)</p> Signup and view all the answers

Which sensation involves the ability to recognize objects through touch without visual input?

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

Which of the following statements is true regarding temperature sensations?

<p>Cold sensations are detected between 10°C and 30°C. (B)</p> Signup and view all the answers

What type of fibers are responsible for transmitting itching sensations?

<p>Very small type 'C' unmyelinated fibers (A)</p> Signup and view all the answers

Where are rapidly adapting mechanoreceptive free nerve endings located?

<p>Superficial layers of skin (C)</p> Signup and view all the answers

How do pain sensations influence itching?

<p>They suppress itching (B)</p> Signup and view all the answers

Which of the following statements is true regarding mechanoreceptive free nerve endings?

<p>They are very sensitive and rapidly adapting (C)</p> Signup and view all the answers

Which type of sensory fibers are NOT involved in transmitting itching?

<p>Type 'A' delta fibers (C), Type 'A' beta fibers (D)</p> Signup and view all the answers

What does static position sense refer to in proprioceptive sensations?

<p>The conscious perception of the orientation of body parts. (C)</p> Signup and view all the answers

Which of the following is NOT a subtype of proprioceptive senses?

<p>Vestibular sense (A)</p> Signup and view all the answers

How does static position sense primarily function?

<p>Through the conscious awareness of body position. (D)</p> Signup and view all the answers

What role does proprioception play in daily activities?

<p>It helps individuals maintain balance and coordinate movements. (D)</p> Signup and view all the answers

Which statement best describes the relationship between static position sense and motor skills?

<p>Static position sense enhances the ability to perform coordinated motor tasks. (D)</p> Signup and view all the answers

What does tactile discrimination primarily involve?

<p>The ability to differentiate between touch at one or two points (C)</p> Signup and view all the answers

In the context of tactile discrimination, what does 'two-point discrimination' refer to?

<p>The ability to detect touch from two distinct stimuli (B)</p> Signup and view all the answers

Which scenario best illustrates tactile discrimination in action?

<p>Identifying the position of two separate fingertips touching the skin (D)</p> Signup and view all the answers

Which of the following aspects does tactile discrimination NOT encompass?

<p>Judging the weight of an object through touch (C)</p> Signup and view all the answers

How can a person with eyes closed test their tactile discrimination ability?

<p>By feeling simultaneous touches at one or two points (D)</p> Signup and view all the answers

Flashcards

Meissner's corpuscles

Sensory receptors that rapidly adapt to touch.

Merkel's discs

Sensory receptors that adapt very slowly to touch.

Free nerve endings

Sensory receptors found in tissues, like the cornea.

Hair end-organs

Sensory receptors that wrap around hair follicles.

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Adaptation (sensory)

The ability of sensory receptors to decrease responsiveness to a sustained stimulus.

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Tactile discrimination

The ability to distinguish between one or two points of touch with closed eyes.

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Two-point discrimination

A test of tactile discrimination. It measures the smallest distance at which two distinct points of touch can be perceived as separate.

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Closed eyes

The eyes are not used during the test.

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One Point of touch

Feeling one single contact point with the skin.

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Two Separate Points

Feeling two distinguishable points in contact with the skin.

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Mechanoreceptors

Sensory receptors that respond to mechanical stimuli like pressure, touch, and vibration.

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Rapidly Adapting

Sensory receptors that quickly decrease their response to a sustained stimulus, focusing on changes in stimulation.

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Superficial Skin Layers

The outer layers of skin, where receptors like rapidly adapting mechanoreceptors and free nerve endings are mainly found.

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Itch Transmission

Itching sensations are transmitted by small, unmyelinated nerve fibers called type 'C' fibers.

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Proprioception

The sense of body position and movement, which is critical for coordinated actions.

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Static position sense

The awareness of where your body parts are relative to each other while still.

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Proprioceptive Senses

The senses that provide information about the position and movement of the body.

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What is proprioception?

The ability to sense the position and movement of our body parts without relying on sight.

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Static position sense vs. Kinesthesia

Static position sense refers to the awareness of body part positions while still, while kinesthesia focuses on the perception of movement.

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Vibration

A type of sensory perception that detects the rapid back-and-forth movement of a surface against the skin.

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Stereognosis

The ability to identify objects by touch alone, without visual or auditory cues.

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Temperature Sensation

The ability to detect and perceive different temperatures.

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Cold Receptors

Free nerve endings that are sensitive to temperatures between 10° and 30° Celsius.

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Warm Receptors

Free nerve endings that are sensitive to temperatures between 30° and 45° Celsius.

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Sensory area lesion

Damage to the part of the brain that processes touch information, leading to asterognosis.

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Gracile and Cuneate tracts

Pathways carrying touch information from the body to the brain, damage to these leads to asterognosis.

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Tabes dorsalis

Syphilis-induced damage to the dorsal spinal cord, impacting touch sensation and leading to asterognosis.

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What causes asterognosis?

Astereognosis is caused by damage to the sensory area of the brain, or the Gracile and Cuneate tracts in the spinal cord, or by conditions like tabes dorsalis.

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Study Notes

Somatic Sensations Overview

  • Somatic sensations originate from skin and deep tissues.
  • Visceral sensations originate from internal organs (viscera).
  • Special sensations include vision, hearing, smell, and taste.
  • Hypothalamic/organic sensations include thirst, hunger, and fear.

Lecture Objectives

  • Students will learn the classification of sensations.
  • Students will understand somatic sensations.
  • Students will discuss mechanoreceptive sensations.
  • Students will learn about temperature sensation.
  • Students will discuss pain sensation.

Types of Sensations

  • Somatic sensations (skin and deep tissues).
  • Visceral sensations (internal organs).
  • Special sensations (vision, hearing, smell, taste).
  • Hypothalamic/organic sensations (thirst, hunger, fear).

Somatic Sensation Detail

  • Somatic senses collect sensory information from the body.
  • Cutaneous sensations include pain, touch, temperature, and pressure.
  • Deep sensations come from deep structures and include proprioceptive sensation.

Classification of Somatic Sensations

  • Mechanoreceptive senses: tactile and position; stimulated by mechanical displacement.
  • Thermoreceptive senses: detect heat and cold.
  • Pain sense: activated by tissue damage.

Touch Sensation Receptors

  • Pacinian corpuscles (adapt rapidly).
  • Meissner's corpuscles (adapt rapidly).
  • Merkel's discs (adapt slowly).
  • Free nerve endings (e.g., in the cornea).
  • Hair end-organs (adapt rapidly).
  • Ruffini's endings (adapt slowly).

Touch Types

  • Crude touch: poorly localized, A delta fibers.
  • Fine touch: well localized, A beta fibers.

Ascending and Descending Spinal Tracts

  • Dorsal column-medial lemniscus: vibration, conscious proprioception, fine touch.
  • Spinothalamic (anterolateral): crude touch, pressure, pain, and temperature.
  • Spinocerebellar: position of body parts, stance, and flexion.

Types of Fine Touch

  • Tactile localization: ability to determine the point touched on the skin.
  • Tactile discrimination (two-point discrimination): ability to differentiate between one or two simultaneous points of touch.

Features of Tactile Discrimination

  • Most accurate in fingertips, face, lips, and tongue (up to 2mm).
  • Less accurate on the back (8-15mm).
  • High receptor density in sensitive areas correlates with wide sensory cortex representation.

Other Somatic Senses

  • Stereognosis: recognizing objects by touch without vision.
  • Texture of material: identifying material types without vision.
  • Tickling and itch: "annoying" sensations; itch is transmitted by C fibers.

Temperature Sensation

  • Receptors are free nerve endings.
  • "Cold" sensation: 10°C to 30°C.
  • "Warm" sensation: 30°C to 45°C.
  • Tissue damage occurs below 10°C and above 45°C.
  • Thermoreceptors adapt between 20°C and 40°C.

Temperature Sensation Mechanism

  • Stimulation is by change in metabolic activity.
  • Cold receptors are more numerous than warm receptors.
  • Paradoxical cold: feeling cold after a hot shower due to cold receptors firing more initially.

Additional Temperature and Somatic Sensation Details

  • Hypothalamus contains neurons acting as thermo-receptors detecting body temperature from the blood.
  • Sensation of cold from metal compared to wool is due to heat conductivity differences.

Vibration Sense

  • Tests the integrity of the dorsal columns.
  • Pacinian corpuscles detect high-frequency vibrations (30-800 cycles/second).
  • Meissner's corpuscles detect lower-frequency vibrations (2-80 cycles/second).

Stereognosis Details

  • Recognizing objects by touch without vision.
  • Reaches a central area in the brain (areas 5, 7).
  • Loss of stereognosis (astereognosis) due to sensory area lesions or damage to tracts.

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