Test 127 (Miscellaneous)

1.  Lasers used in medicine include:

a. sodium

b. argon

c. carbon dioxide

d. helium

e. neodymium-YAG (yttrium aluminium garnet)

Answera.F   b.T   c.T   d.T   e.T
Carbon dioxide is used for superficial lesion such as in dermatology, as the light produced is infra-red, it needs helium as an aiming beam. YAG laser is also invisible and requires neodymium to provide the aiming beam.
 

2. The following are true about bipolar diathermy:

a. it must always be earthed

b. it should never be used in patients with pacemakers

c. it produces current with a frequency of greater than 
    100Hz

d. it relies on generation of heat energy from electrical 
    energy

e. it produces more heat energy than unipolar diathermy

Answera.F   b.F   c.T   d.T   e.T
Bipolar diathermy does not need to be earthed (ie passive electrode) as the current passes between the two electrode. The frequency is high and thus avoid excitation of skeletal or cardiac muscle. The heat 
energy is proportional to the resistance between 
electrode and therefore more energy is produced 
in bipolar than unipolar diathermy (which uses a plate 
to conduct the current away and hence lower resistance). Pacemaker is not a contraindication in bipolar cautery. 
 

3. On tilting a patient from supine to vertical position:

a. renin secretion is increased

b. the cerebral vascular resistance is reduced

c. cardiac output is reduced

d. the cerebral blood flow is reduced

e. tachycardia occurs

Answera.T  b.T   c.T   d.F  e.T
The cerebral vascular resistance is reduced when 
the patient is tilted to the vertical position but 
autoregulation maintains the cerebral blood flow. 
Cardiac output decreases due to reduced venous return and tachycardiac occurs in the face of reduced stroke volume to increase the output
 

4. The following are true about tight junction:

a. it forms a barrier to water

b. it is found in the blood-aqueous barrier of the ciliary 
    body

c. it is found in the blood-retinal barrier at the apex of the 
    retinal pigment epithelium

d. it is made up of connexons

e. it contains the intracellular protein cingulin

Answera.T   b.T   c.T   d.F   e.T

Tight junction is not permeable to even water or ions.

It is made up of the proteins occludin which is attached to the intracellular protein cingulin.
 

5. EOG (electrooculogram):

a. measures the electrical potential between the front 
    and the back of the eye

b. has a resting potential of 4 mV

c. is abnormal in optic nerve disease

d. is abnormal in Best's disease even before the onset
    of visual symptoms

e. can be measured using the Arden Index which is the 
    ratio of dark trough to light rise.

Answera.T   b.F   c.F   d.T   e.F
The resting potential for EOG in normal subject is 6 mV. It is abnormal in diseases of the retinal pigment epithelium. The Ardex Index is the ratio of light rise to dark trough and in normal subject is more than 165%.

 
 

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