Lecture 12 Flashcards
‘Describe herpes zonster (‘shingles’)
Chicken pox virus can lie dormant in dorsal root gangions. When recover from virus doenst completely leave system. When immune system is weaknese e.g. stres, re-emergence of virus grows down sensory nerve withion the ganglions it was hiding and causes sensory deficits along dermatome
Symptoms of shingles
allodenia/ hyperpathia (excessive pain), rash with blisters along trunk, shoulder, face. Parastesias along dermatomes. Sometimes pain lasts for years post-pertetic neuralgia treated with anti-viraland analgesics
Describe tabes dorsalis
slow degeneration of the dorsal columns, dorsal roots and gangia of the spinal cord (typically lumbar region- symptoms of legs and feet), outcome of untreated syphilis (10-30 years)
Symptoms of tabes dorsalis
proprioceprivce loss (loss of vibration and touch sensation), parasthesias and allodenia (if starts to affect the dorsal roots and ganglia), tabetic gait
Level of symptoms of tabes dorsalis
if it is just posterior column damaged that level may be preserved, if also involves dorsal horns also affects that level
neuropathy=
nerve disorder
Neuropathies can influence…
axons, myelin or both
Describe type sof neuropathies
- mononeuropathy (focal- injury influences single nerve) e.g. carpal tunnel syndrome
- Polyneuropathy (general- many nerves involved) e.g. due to diabetes, overdose of pyridoxine (vit B6), ganglionopathies (disorder involving ganglions), polyneuritis (inflamation of multiple nerves)
Describe diebetic neuropathy
- typically affect distal limbs, hands and feet
- “glove and stocking” pattern of sensory loss bilaterally
- positiove symptoms include parethesias/allodenia, can also affect motor neurons-> muscle weakness/strength loss
- high glucose levels leed to inflamtion of mnerves and interferes for blood supply to distal nerve endings
- Gradual, progressive onset
- 60% of people with diabetes experience this
Describe overdose of pyridoxine (Vit B6)
-excessive B6 is neurotoxin- degeneration of nerves across the body.
-broad loss of proprioceptive info affecting large (1a) fibers
-progressive
-Normal dose= ~2mg, only need about 200mg to see overdose, can be non-reversable if taken for long time
Describe ganglionopathy
-damage to gangiopns carrying cell bodies
-often due to autoimmune response, to something else and that response starts to attack own system and cell bodies within it.
-Loss of proprioceptive information
Describe polyneuritis
- due to infection or infl;amtion of the nerve
- widespread damage to nerve
- e.g. GL periminat loss of large sensory myelinated fibers of body, loss of senssations, small unmelinated fibers preserved.
- Ian waterman- total body sensory loss, all sensation below neck
Describe location of vestibular system
- part of inner ear found within petrous ridge of temporal bone, canals house vestibular system and cochlea. Vestibular system most posterior, cochlea most anterior
Describe the anatomy of the vestibular system
-made up of bony labarynth, which is filled with perilymph fluid (peri-around). Bony canals and caves make up bony labaryhtn
- within perilymph fluid have membranous inner structure which is filled with endolymph fluid (endo-inside)
What comprises the inner ear
the vestibular system and cochlea
Identify the otolith organs
utricle- has semicircular canals which extend off
saccule- adjacent with cochlea
Identify the 3 semicircular canals
-anterior semicircular canal
-posterior semicircular canal
-horizontal semicircular canal
- each come off and return back to utricle
- 90 degrees to oneanother
Describe the function of the semicircular canals
- When traying to register head movement and generate neural signals- the semicircular canals work in pairs e.g. horizontal canals work together, the anterior canal on one side parallel with the posterior canal on other side, on other side anterior canal pairs with posterior canal on opposite side
Describe ampulla
at one end of each semicircular canal have bulges to form the ampulla adjacent to the utricle
Describe the anatomy of the semi-circular canal
-on floor of ampulla ridge of epithelial cells called crista ampullaris.
-Hair cells embedded in the crista ampullaris
-From hair cells have cilia projecting upwards
-cilia are encased in gelatenous material/mass (cupula)
- hair cell receptors have axons projecting (sending signals) to cell bodies in vestibular ganglion
Describe orientation of cilia
-1 large kinocilium (large and stiff)
-each kinocilium bundles with series of stereocilia (30-40) which lie adjacent to kilocilia and lines up from smallest to largest
Describe movement of stereocilium
-towards kinocilium get excitation, increased firing rate
-stereocilium away from kinocilum get inhibition
