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Neuro 600 > Class 3: Somatic Sensations > Flashcards

Class 3: Somatic Sensations Flashcards

1
Q

Tactile Receptors

A

Meissner corpuscles
Hair root plexuses
Merkel Discs (Type 1 Cutaneous Mechanoreceptors)
Ruffini Corpuscles
Paciinian (Lamellated) Corpuscles
Itch and tickle receptors (free nerve endings)

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2
Q

Tactile Senstations

A 
Touch 
Pressure 
Vibration
Itch 
Tickle
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3
Q

Touch, pressure and vibration: Detection

A

Sensed by encapsulated mechanoreceptors attached to large diameter myelinated A-fibres

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4
Q

Itch and tickle: Detection

A

Free nerve endings attached to small-diameter unmyelinated C fibres.

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5
Q

Pressure

A

Sustained sensation over a large area.

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6
Q

Which receptors sense pressure?

A

Meissner Corpuscles
Merkel Discs
Pacinian (lamellated) Corpuscles

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7
Q

Vibration

A

Rapidly repetitive sensory signals from tactile receptors

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8
Q

Which receptors sense vibration?

A 
Meissner corpuscles (slow)
Pacinian (lamellated) corpuscles (fast)
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9
Q

Crude Touch

A

The ability to perceive that something has touched the skin, even though its exact location, shape, size or texture cannot be determined

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10
Q

Discriminative Touch

A

Provides specific information about a touch sensation. Location, size, shape, texture of stimulus.

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11
Q

Four types of touch receptors

A

Meissner/Corpuscles of touch
Hair root plexuses
Merkel discs/Type I Cutaneous mechanoreceptors
Ruffinin corpuscles/Tupe II Cutaneous mechanoreceptors

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12
Q

Merkel Discs

A

AKA Type I Cutaneous Mechanoreceptors

Slow adapting, unencapsulated

Saucer shaped, flattened free nerve endings that contact Merkel Cells of stratum basale

Fine touch

Fingertips, hands, lips, external genitalia

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13
Q

Meissner corpuscles

A

AKA corpuscles of touch

Discriminative touch and lower-frequency vibrations

Quick adapting, encapsulated egg-shaped mass of dendrites in dermal paillae of hairless skin.

Fingertips, hands, eyelids, tip of the tongue, lips, nipples, etc.

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14
Q

Hair Root Plexus

A

Rapidly adapting, free nerve endings wrapped around hair follicles.

Detects crude touch – movement that disturbs hairs

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15
Q

Ruffini Corpuscles

A

AKA Type II Cutaneous Mechanoreceptors

Slowly adapting

Elongated, encapsulated receptors
Deep in dermis (especially hands and soles of feet), and in ligaments and tendons

Sensitive to stretch that occurs with movement

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16
Q

Touch: Fast and free

A

Hair root plexus

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17
Q

Touch: Fast and encapsulated

A

Meissner corpuscles

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18
Q

Touch: Slow and free

A

Merkel Discs (Type I Cutaneous Mechanoreceptors)

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19
Q

Touch: Slow and encapsulated

A

Ruffini Corpuscles (Type II Cutaneous Mechanoreceptors_

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20
Q

Receptors for fine touch

A

Meissner

Merkel

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21
Q

Receptors for crude touch

A

Hair root plexuses

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22
Q

Receptors for stretch

A

Ruffini Corpuscles

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23
Q

Lamellated corpuscles

A

AKA Pacinian corpuscles

Detect pressure and quick vibration; maybe tickle
Quick adapting, encapsulated

Distributed throughout body; oval, layered.
Dermis, subQ, submucosa, joints, periosteum, some viscera.

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24
Q

Itch

A

Chemical stimulation of free nerve endings

Ex. bradykinin (vasodilation as a local inflammatory response)

25
Q

Tickle

A

Stimulation of free nerve endings only by someone else

Mediated by lamellated corpuscles

26
Q

Two explanations for Phantom Limb Pain

A
  1. Cerebral cortex interprets peripheral sensations as still coming from limb.
  2. Brain contains networks of neurons that generate sensations of body awareness. Still active, and so create perceptions even without stimuli.
27
Q

Thermal receptors

A

Free nerve endings that have 1mm receptor fields on the skin’s surface.

Adapt quickly but continue to generate low frequencies impulses

28
Q

Cold receptors

A

Stratum basale
Mostly attached to medium diameter, myelinated A fibres (some to small C fibres)

Activate by temperatures between 10º and 40ºC

29
Q

Warm receptors

A

Less abundant than cold.
Located in the the dermis’

Attached to small diameter unmyelinated C fibres

Stimulated between 32º and 48º

30
Q

What temperatures produce pain?

A

Below 10º and above 48º

31
Q

Nociceptors

A

Free nerve endings found in every tissue except the brain

Activated by intense thermal, mechanical or chemical (prostaglandins, kinins, K+) stimuli

Very little adaptiation

May be stimulated by : excessive distension, prolonged contraction, muscle spasms, ischemia

32
Q

Fast/Acute Pain

A

Sharp, pricking, pain that occurs rapidly (0.1 s) after stimuli

Superficial
Medium diameter, myelinated A fibres

33
Q

Slow/Chronic Pain

A

Begin slowly, build in intensity

Chronic, burning, aching, throbing

Can occur both in the skin and in deeper tissues, or internal organs

Small diameter, unmyelinated C fibres

34
Q

Visceral Pain

A

Results from stimulation of nociceptors in visceral organs.

If stimulation diffuse, pain severe

35
Q

Deep somatic pain

A

Stimulation of receptors in skeletal muscles, joints, tendons and fascia

36
Q

Superficial somatic pain

A

Stimulation of nociceptors in skin

37
Q

Referred pain

A

When visceral pain is felt in a location other than where the injury is.

Sometimes in skin overlying affected organ

In general the organ involved and the area where pain in felt are served by the same segment of spinal cord

38
Q

Heart attack pain is often referred:

A

Along skin in left arm

Both supplied by T1-5

39
Q

Pain threshold

A

How strong a stimulus has to be before it elicits pain.

Constant across population

40
Q

Pain tolerance

A

How much pain an individual can endure.

Depends on the person and the situation

41
Q

Neural gating (ascending) pain modulating mechanism

A

Pain perception is the result of the interaction between different neurons.

Modulation of pain at spinal cord level.

42
Q

Central (descending) pain modulating mechanism

A

Grey matter surrounding the central aquaduct in midbrain use enkephalins and endorphins to block pain pathways.

43
Q

Analgesic drugs

A

Block formation of prostaglandins

44
Q

Local anasthetics

A

Like Novocaine

Block conduction of axons of nerve impulses of axons of first order neurons

45
Q

Proprioception

A

Where the body is located in space; where the self ends and the rest of the universe begins.

46
Q

Kinesthesia

A

Perception of body movement

47
Q

Proprioceptors

A

Muscle spindles
Tendon organs
Joint kinesthetic receptors

Embedded in muscles (especially postural) and tendons.

Adapt slowly and only slightly

Weight discrimination, kinesthetic sense, orientation of head, limbs;

48
Q

Proprioceptive information is sent to:

A

Cerebellem and cerebral cortex.

49
Q

Muscle spindles

A

Proprioceptors in skeletal muscles

Slow. Encapsulated
Several nerve endings wrapped around 3-10 intrafusal muscle fibres, plus gamma motor neurons

Monitors changes in length of skeletal muscles,
Participate in stretch reflexes

50
Q

Intrafusal Muscle Fibres

A

Specialized proprioceptive muscle fibres.

Part of muscle spindles

51
Q

Gamma motor neurons

A

Terminate near both ends of intrafusal fibres
Adjust tension in muscle spindle to adjust muscle tension in response to muscle length. How the muscle spindle remains sensitive to stretch even with the muscle has contracted.

More frequent gamma motor signals –> more sensitive muscle spindle

52
Q

Muscle spindle impulses propigate to:

A

Somatosensory region of cerebral cortex (conscious perception of limb position and movement)
+
Cerebellum (coordination of muscle contractions)

53
Q

Extrafusal muscle fibres

A

Ordinary skeletal muscle fibres surrounding the muscle spindle

Innervated by alpha motor neurons

54
Q

The cell bodies of both Alpha and Gamma motor neurons are located in the:

A

Anterior grey horn of the spinal cord (or brain stem, for muscles in the head)

55
Q

Stretch Reflex

A

Stretch of intrafusal muscle fibres –> muscle spindle impulse –> anterior grey horn –> activate Alpha motor neurons –> extrafusal muscles contract

56
Q

Golgi Tendon Organ

A

Proprioceptive receptor.
Senses muscle tension. Slow adapting

Located at musculotendinous junction.

Tendon fascicles entwined by sensory nerve endings, surrounded by connective tissue capsule

In response to overstretch will send signal to CNS which will cause muscle to relax

57
Q

Joint Kinesthetic Receptors

A

Present in and around the capsule of synovial joints.

Free nerve endings and Ruffini corpuscles (Type II mechanoreceptors) in capsule: Pressure

Small pacinian/lamellated corpuscles: acceleration and deceleration

Articular ligaments contain GTO-like receptors that adjust reflex inhibition of agonist in response to excessive strain.

58
Q

Muscle Tension

A

The force that pulls the points of attachment towards each other.
Sensed by GTOs

Neuro 600 (6 decks)

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