Test 123  (Physiology)
1. The following are true about an action potential in a nerve fibre: 
a. it occurs when its membrane potential is hyperpolarized

b. it is associated with a transient increase in membrane 
    permeability to sodium

c. there is a decreased in membrane permeability to 

d. it has an amplitude which varies directly to the strength 
    of stimulus

e. it causes propagation of electrical current along the 
   nerve fibre

2. Increased intracranial pressure causes:
a. sixth nerve palsy 

b. cupping of the optic disc

c. absent venous pulsation

d. increased cerebral blood flow

e. increased blood pressure

3. Muscle tone is reduced by:
a. lower motor neurone lesion

b. curare

c. cerebellar lesion

d. lesion of the motor cortex

e. intravenous edrophonium

4. Optic disc swelling occurs in:
a. optic disc drusen

b. hypotony

c. central retinal vein occlusion

d. retrobulbar neuritis

e. posterior uveitis

5. Compared with myelinated nerve fibres, non-myelinated nerve 
    fibres :

a. do not contain Schwann cell sheaths

b. have a higher threshold for stimulation

c. have a longer refractory period 

d. transmit impulses at a lower frequency

e. are found only in sensory nerve fibres

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