9/11/2013

9/11/2013

Answers:

Wave IV of an auditory brain stem response corresponds to what structure?

A) Olivary complex 

B) Cochlear nucleus 

C) Inferior colliculus 

D) Lateral lemniscus 

E) Eighth nerve action potential

Remember the mnemonic ECOLI.

With regards to the acoustic reflex, which pathway (ipsilateral or contralateral) contain the majority of neurons? Describe the path of that pathway.

The ipsilateral pathway (cochlea--> eighth nerve-->cochlear nucleus-->trapezoid body-->superior olivary complex-->facial motor nucleus-->ipsilateral stapedial muscle) has more neurons. Contralateral pathway crosses brainstem at superior olivary complex to the opposite cochlear nucleus.

MC Questions:

When the thyroid gland enlarges due to illness, it most often extends in what direction?
A) Superior and Anteriorly 
B) Inferior and Anteriorly
C) Superior and Posteriorly 
D) Inferior and Posteriorly 
E) Laterally

Free Response Question:
What is are the two major roles of thyroid peroxidase in the production of thyroid hormone?

Quick Facts:
Metabolism of Thyroid Hormones
-T3 more potent than T4 (3-8 x more potent)
-T4 is primary circulating hormone, but T3 is main peripherally active hormone.
-More T4 secreted than T3 (20:1)
-Most peripheral T3 is from circulating T4 which has lost an iodine.
-Half lifes:
-T4 = 7 days
-T3 = 1 day
-Drugs that inhibit T4-->T3:
-propylthiouracil, amiodarone, ipodate, glucocorticoids and propranolol.

9/10/2013

9/10/2013

Answers:

This tympanogram is type...?

A) Type A 

B) Type As 

C) Type Ad 

D) Type B 

E) Type C

Type B tympanograms are flat and indicate nonmobility of the TM due to middle ear effusion or perforation.

How can you differentiate a type B tympanogram due to middle ear effusion from a type B tympanogram due to perforation?

The ear canal volume will be large if a perforation is present because the middle ear space is included in that volume, however if an effusion is present then EAC volume should be within normal limits (.5cm^3 in kids, 3cm^3 in adults)

MC Questions:
Wave IV of an auditory brain stem response corresponds to what structure?
A) Olivary complex 
B) Cochlear nucleus 
C)Inferior colliculus 
D) Lateral lemniscus 
E) Eight nerve action potential

Free Response Question:
With regards to the acoustic reflex, which pathway (ipsilateral or contralateral) contain the majority of neurons? Describe the path of that pathway.

Quick Facts:
Stapedius Muscle: 
-attached to posterior crus of stapes 
-contracts reflexively at loud noise. 
-always contracts bilaterally even if only one ear stimulated. 
-protects inner ear from damaging intense sound