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.