Sensory Disorders Flashcards
(19 cards)
What happens to photoreceptors in the dark?
Na+ channel open and Na+/K+ ATPase pump active. Cell depolarised
What he opens to photoreceptors in the light?
Na+ channel closed and +ve ions build up in synapse. Hyperpolarisation and glutamate release to bipolar cells prevented
What are photosensitive proteins called?
Opsins (rhodopsin/conospin)
How many different opsins are found in the cone cells?
3 opsins:
420nm - blue
534nm - green
564nm - red
Describe rod cells
In the periphery of the choroid layer. Monochrome and low resolution with multiple rod cells converging to one bipolar cell
Describe come cells
Found in the fovea and responsible for colour vision. High resolution with a 1 to 1 synapse with bipolar cells
Where does the optic tract project to?
Lateral geniculate nuclei in the thalamus. Optic radiations then transmit information to visual cortex (superior radiation straight to it, inferior travel round lateral ventricle - Meyer’s loop)
What is a seizure?
Disordered and hyper-synchronised discharge in a network of cerebral neurons
What is a generalised seizure?
Starts simultaneously in both hemispheres
What is a focus seizure?
Starts in a focused area and then spreads
What is an absent seizure?
Brief childhood seizure lasting between 1-30 seconds. Sudden loss and return of consciousness with no aura or post-ictal state. Some involuntary movement
What is a myoclonus seizure?
Sudden, brief, shock-like muscle contractions. Usually bilateral arm jerks worse in mornings. Can be caused by alcohol or sleep deprivation
What is a tonic-clonic seizure?
Sudden onset with gasp and fall. Tonic phase = muscle stiffness Clonic phase = muscle convulsion Post-ictal phase Followed by headache and muscle pain Tongue bitten and incontinence. Noisy breathing
What is a focal (partial) seizure?
Focal onset with spreading
Simple partial - conscious
Complex partial - loss of consciousness
What are the signs of temporal lobe seizures?
Auras
Epigastric rising sensation
Déjà vu
Olfactory and gustatory disruption
What is the use of Na+ channel blockers in epilepsy treatment?
Block Na+ channel to reduce cell excitation. Onset of block is slow due to poor binding, therefore more to stop spread (phenytoin, carbamazepine…)
What drugs affecting GABA are useful in epilepsy treatment?
GABA tansaminase inhibitors (vigabatrin) prevent breakdown of GABA. GABA reuptake inhibitors.
Increase actions of GABA and inhibitory effect by increasing Cl- influx into cell
What are idiopathic epilepsies?
No associated neurological damage and respond well to treatment
What are symptomatic epilepsies?
More treatment resistant with associated neurological deficits
