Test 121  (Physiology)

1. Smooth muscle: 

a. has a longer action potential than skeletal muscle

b. has a longer action potential than cardiac muscle

c. contains pacemaker cells

d. contains bridges between cells

e. contains no sarcomeres

Answera.T  b.F  c.T  d.T  e.T
The duration of action potential for smooth muscle is about 50ms, that of skeletal muscle is 10ms and 200ms for cardiac muscles.
 

2. Vagal stimulation increases

a. insulin secretion

b. gastric acid secretion

c. bronchodilatation

d. upper lid retraction

e. bile production

Answera.T   b.T  c.F  d.F  e.T
Vagal stimulation causes bronchoconstriction. Upper lid retraction is caused by sympathetic activity.

 
3. The cerebrospinal fluid:

a. is produced by the arachnoid villi

b. production is largely independent of the intracranial 
    pressure

c. has a potassium concentration similar to that of 
    the serum

d. contains polyclonal banding in multiple sclerosis

e. contains increased protein concentration in 
    Guillain-Barre's syndrome.

Answera.F   b.T  c.T  d.F  e.T
CSF is produced by the choroid plexuses in the third, fourth and lateral ventricles. In multiple sclerosis, the CSF contains oligoclonal banding.
.

4. The following are true about lateral geniculate nuclei:

a. layers 1 and 2 are involved in magnocellular pathway

b. layers 3 to 6 contain synapses from Y cells

c. layers 2, 3 and 5 receives fibres from the ipsilateral eye 

d. receive nerve fibres carrying light reflexes

e. fibres from the upper quadrant of peripheral retina
    synapse on the medial aspect of the nuclei

Answera.T  b.F  c.T  d.F  e.T
layers 3 to 6 are involved in parvocellular pathway and therefore contain synapses from X cells. Nerve fibres carrying light reflexes do not synapse at the LGN. 

5. Lesions in the following regions can give rise to 
    light-near dissociation:

a. ciliary ganglion

b. optic nerve

c. Edinger-Westphal nucleus

d. occipital cortex

e. pineal region

Answera.T   b.T  c.T  d.F  e.T
Lesion that affects light reflexes often gives rise to light-near dissociation. Occipital cortex is not involved in light reflex.

 
 

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