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Physiology CNS > Sensory > Flashcards

Sensory Flashcards

1
Q

Crude Touch

A
  • Ventral Spinothalamic pathway & partially dorsal
  • mechanoreceptors
  • FNE and hair end organs
  • mechanical displacement or deformity
  • A delta , C fibers
  • Thalamus
  • Rapid adaptation
  • Cotton wool test

Better felt in dorsum of hand…. Thin skin& hairy end organ

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2
Q

Thermal

A
  • Lateral Spinothalamic pathway
  • Thermoreceptors
  • FNE for hot, FNE & krause end bulb for cold
  • changes in conc. of metabolites that activate or inactivate ion channels
  • C for hot , A delta & C for cold
  • Thalamus for wide degrees, cortex for fine
  • moderate adaptation but hot rapid than cold
  • two test tubes.
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3
Q

Thermoreceptors

A

They are found in spots
Cold spots more than hot by 3-10 times

Cold 10-43. Max 25
Hot. 30-50. Max 45

<15 cold pain 
> 45 hot pain 
The excess change >43 =
\++ TRP Transient receptor potential =
Mediates pain sensation (Thermal nociceptors)

30-50 indifferent sensation

Lips 20
Hands 5
Trunk 2

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4
Q

Paradixical cold sensation

A

Occur at onset of hot temp.

Rise of temp. Above 40 = sudden and rapid increase in frequency of A.P discharged from cold receptors = Cold sensation

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5
Q

Itch(histamine,kinins) & Tickle(cutaneous receptors)

A
  • Ventral Spinothalamic pathway
  • FNE
  • C fibers
  • Thalamus
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6
Q

Crude pressure

A
  • Ventral Spinothalamic pathway
  • cutaneous receptors
  • A delta
  • Thalamus
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7
Q

Pain

A
  • lateral Spinothalamic pathway
  • mechano& chemo& thermo sensitive
  • specific pain sensitive FNE NOCICEPTORS
  • A delta & C
  • tissue damage (noxious)
    Stimulate chemo & decrease threshold of thermo and mechano
  • thalamus & sensory cortex
  • non adapting (tonic)
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8
Q

Fast cutaneous pain

A
  • onset 0.1 sec
  • duration 1 sec
  • no summation
  • machano and chemo
  • A delta
  • Glutamate
  • Neolateral Spinothalamic
  • sensory cortex
  • skin only
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9
Q

Slow cutaneous pain

A
  • onset 1 sec
  • duration long maybe intolerable
  • summated
  • all NOCICEPTORS especially chemo
  • C fibers
  • Substance p
  • Paleo lateral Spinothalamic pathway
  • reticular formation, specific thalamus nuclei, tectum of midbrain
  • skin, deep , visceral structures
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10
Q

Deep pain

A

Same characters of slow cutaneous pain

Severity = parasympathetic Autonomic effects
= Depressor effects

Moderate Ischemia leads to pain due to accumulation of metabolites

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11
Q

Visceral pain

A

Most viscera contain only nociceptors

Same characters of slow cutaneous pain

May lead to:
Depressor Autonomic effects
Rigidity of overlying skeletal muscles
Referred to other structures

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12
Q

Primary hyperalgesia

A

Due to excessive sensitivity of pain receptors

Facilitation of pain receptors by chemicals (decrease pain threshold)

Inflamed skin around injury

Touch is felt painful

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13
Q

Secondary hyperalgesia

A

Due to facilitation of sensory transmission

Convergence facilitation theory

Healthy skin

Exaggerated response
A painful stimulus is felt more painful

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14
Q

Zoster (shingles)

A

After chicken pox infection, the virus varicella zoster remains latent in dorsal root ganglion
After exposure to any form of immune suppression,
Virus reactivates
Multiplies
Pass to skin dermatome innervated by this ganglion

Characterized by severe pain , rash but unilateral and limited to the skin innervated by a dorsal root ganglion

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15
Q

Tic Douloureux

A

Sharp or stabbing type pain occasionally occurs in one side of face or in one or more area of sensory distribution area of fifth cranial nerve
Feels like sudden electrical shock

It’s also called trigeminal neuralgia

By mechanoreceptive stimulus of sensitive trigger areas ( non painful stimulus)

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16
Q

Referred pain

A

Gall bladder……….. Epigastrium and tip of right scapula

Appendix……….. Skin around umbilicus

Renal…………. Back, inguinal region, testis

Cardiac………… Inner aspect of left arm

Gastris……. Bet. Umbilicus & xiphoid process

17
Q

Mechanisms of referred pain

A

Based on dermatomal rule: the pain is referred to dermatomes that share the same embryonic segmental origin

1- convergence projection theory
2- convergence facilitation theory

18
Q

Extra cranial Headache

A

Spasm of scalp & neck muscles

Sinusitis referred behind eyes

Otitis media

Toothache

Errors of refraction due to spasmodic contraction of ciliary muscle and extraocular muscle…… Orbital& retroorbital headache

Spasm of facial & extraocular ms

Excessive exposure to light irradiation

19
Q

Intracranial headache

A

Venous sinuses & tentorium & dura of base of the brain & blood vessels of meninges especially the middle meningeal artery

Referred to:
(Frontal headache)
Frontal part due to supratentorial irritation
(Occipital headache)
Posterior part due to infratentorial irritation

Causes:
1- meningitis, brain tumors, operative trauma
2- low CSF due to removal.20 ml…. Traction of dura
3- Alcohol….. Direct meningeal irritation
4- hypertension…… Stretch of blood vessels
5- Migraine more in female, maybe genetic, it’s localized severe headache due to abnormal vascular phenomenon
Mechanism: tension/emotions…….. Vasospasm of cerebral bl.vessels……. Ischemia…….. Hallucinations…… Bl.vessels become flaccid &pulsate with bl.pressure……. severe headache

20
Q

Pain control system

A

Analgesic system / opiate / stress analgesia

Periventricular area(hypothalamus)….. B endorphin
Periaqueductal gray area(midbrain,pons)…… Enkephaline
Raphe magnus nucleus(pons,medulla)….. Serotonin
Pain inhibitory complex& interneurons (dorsal horn of spinal cord)…… Enkephaline

These enkephalins produce pre& postsynaptic inhibition of pain nerve terminals which will stop release of substance p… Inhibition of pain impulse transmission
This analgesic system inhibits also reticular formation &non specific thalamic nuclei

Gate theory

SGR in layers 2,3 acts as a gate through which pain impulses reach Spinothalamic tract

Thin myelinated A delta & unmyelinated C can be inhibited by nearby neurons that activate interneurons which release ( GABA, Enkephalins, Serotonin)……… Inhibition of pain afferents
( lateral inhibition)
These inhibitory interneurons are stimulated by:
Rubbing skin… ++ Large myelinated AB fibers
Counter irritants
Acupuncture…. Through gate theory & psychogenic excitation of the central analgesia system.

Surgical control

  • Anterolateral Cordotomy… Interruption of pathway
  • Cauterization of specific areas in intralaminar thalamic nuclei…. Removal of slow severe pain only.

Electrical control

++ Of :

  • large SENSORY neurons or selected areas in skin
  • Analgesic system in PVA, PAGA, RMN

MEDICAL CONTROL

  • Antiacids in peptic ulcer
  • bl.vessels dilators in ms claudications
  • corticosteroids in inflammation
  • pain killers
21
Q

Fine touch

A
  • Dorsal column pathway
  • Mechanoreceptors
  • Meissner’s, Merckle’s, Raffini, Pacinian
  • Mechanical displacement or deformity
  • AB type of fibers
  • Somatosensory cortex
  • Rapid adaptation
  • Two marker test for tactile localization
  • weber compass test for tactile discrimination
22
Q

Areas of the body with small threshold distance are characterized by:

A
  • large no. Receptors
  • large no. Afferents
  • large area of representation in cortex
  • high sensory acuity
  • small receptive field
  • less convergence bet. Afferents
23
Q

Proprioceptive sensations

A

POSITION

  • Dorsal column pathway
  • Machanoreceptors
  • Muscle spindle in muscle, golgi tendon in tendons, Raffini in joint capsules
  • Mechanical displacement or deformity
  • AB fibers
  • Somatosensory cortex
  • slow adaptation
24
Q

Pacinian corpuscles

A

They are rapidly adapting receptors, but responsible only for the initial transient signals about the rate of joint movement

25
Q

Vibration

A
  • Dorsal column pathway
  • Mechanoreceptors
  • Meissner’s fron 2 to 80, Pacinian from 30 to 800
  • Mechanical displacement or deformity
  • AB fibers
  • Somatosensory cortex
  • Rapidly adapting
26
Q

Deep pressure

A
  • Dorsal column pathway
  • Mechanoreceptors
  • Ruffini, deep Pacinian
  • Mechanical displacement or deformity
  • AB fibers
  • Somatosensory cortex
  • Slow adaptation
  • Test for pressure sence with arm supported
27
Q

Requirements for Stereognosis

A
  • Intact all sensations
  • intact cortical association areas
  • previous experience (memory of the object)

Physiology CNS (2 decks)

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