Test 101   (nervous system)

1. The following reflexes are used to test brain stem death:

a. Babinski's reflexes

b. accommodation

c. gag reflex

d. vestibular-ocular reflex

e. pupillary light reflex

Answera.F   b.F  c.T  d.T  e.T
Babinski's reflex is used to test upper motor neurone 
lesion.
Accommodation can not be tested as the patient is in deep coma.
The other reflexes involve the brain stem.

2. The following are true about blood-brain barrier:

a. it is permeable at birth

b. it involves tight junction between endothelial cells 
    and end feet processes of astrocytes

c. it is absent in the posterior pituitary

d. it is absent in area postrema

e. it is permeable to glucose and fat-soluble drugs

Answera.T   b.T   c.T   d.T  e.T
The blood-brain barrier is permeable at birth as 
evidenced by passage of bilirubin into the brain.
It is permeable to glucose and fat-soluble drugs but not to anions.

3. True statements about cerebral blood flow:

a. it is controlled mainly by the autonomic nervous system

b. cerebral arterioles constricts when the blood pressure is 
    raised 

c. it is constant in the blood pressure range of 50 to 
   150 mm Hg systolic

d. hypocapnia increases the cerebral blood flow

e. the cerebral vascular responses to PaO₂ are more 
    marked than those induced by PaCO₂. 

Answera.F   b.T  c.T  d.F  e.F
Cerebral blood flow is controlled by myogenic and metabolic factor.
Hypocapnia decreases the cerebral blood flow and hyperventilation is used to decrease cerebral blood flow.
The cerebral vascular responses to carbon-dioxide is more marked than oxygen.

4. Cerebrospinal fluid:

a. is produced mainly by the lateral, third and fourth 
   ventricles

b. enters the subarachnoid space through foramina 
    Lushka and Magendie

c. is reabsorbed mainly into the lymphatics

d. production is dependent of the blood pressure

e. has a normal pressure of 120-180mm H2O

Answera.T  b.T  c.F  d.F  e.T
CSF is reabsorbed mainly into arachnoid villi and into the dura venous sinuses.
CSF production is independent of blood pressure.

5. Right abducent nerve palsy:

a. causes diplopia worse for distance than near

b. causes diplopia worse on right than left gaze

c. causes overaction of the left medial rectus

d. causes contracture of the right medial rectus

c. causes a V pattern esotropia

Answera.T   b.T  c.T  d.T  e.F
The esotropia is worse for distant than near fixation.
The lateral rectus acts as abductor during elevation and paralysis causes a A pattern esotropia.

 
 

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