Sensory Flashcards
Crude Touch
- 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
Thermal
- 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.
Thermoreceptors
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
Paradixical cold sensation
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
Itch(histamine,kinins) & Tickle(cutaneous receptors)
- Ventral Spinothalamic pathway
- FNE
- C fibers
- Thalamus
Crude pressure
- Ventral Spinothalamic pathway
- cutaneous receptors
- A delta
- Thalamus
Pain
- 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)
Fast cutaneous pain
- onset 0.1 sec
- duration 1 sec
- no summation
- machano and chemo
- A delta
- Glutamate
- Neolateral Spinothalamic
- sensory cortex
- skin only
Slow cutaneous pain
- 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
Deep pain
Same characters of slow cutaneous pain
Severity = parasympathetic Autonomic effects
= Depressor effects
Moderate Ischemia leads to pain due to accumulation of metabolites
Visceral pain
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
Primary hyperalgesia
Due to excessive sensitivity of pain receptors
Facilitation of pain receptors by chemicals (decrease pain threshold)
Inflamed skin around injury
Touch is felt painful
Secondary hyperalgesia
Due to facilitation of sensory transmission
Convergence facilitation theory
Healthy skin
Exaggerated response
A painful stimulus is felt more painful
Zoster (shingles)
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
Tic Douloureux
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)
Referred pain
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
Mechanisms of referred pain
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
Extra cranial Headache
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
Intracranial headache
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
Pain control system
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
Fine touch
- 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
Areas of the body with small threshold distance are characterized by:
- large no. Receptors
- large no. Afferents
- large area of representation in cortex
- high sensory acuity
- small receptive field
- less convergence bet. Afferents
Proprioceptive sensations
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
Pacinian corpuscles
They are rapidly adapting receptors, but responsible only for the initial transient signals about the rate of joint movement
Vibration
- 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
Deep pressure
- Dorsal column pathway
- Mechanoreceptors
- Ruffini, deep Pacinian
- Mechanical displacement or deformity
- AB fibers
- Somatosensory cortex
- Slow adaptation
- Test for pressure sence with arm supported
Requirements for Stereognosis
- Intact all sensations
- intact cortical association areas
- previous experience (memory of the object)
