Exam 3: olfactory and facial nerve pathways

Question 1

What nerve if the facial nerve closely associated with in terms of nuclei?

Answer 1

Abducens nerve

Question 2

T/F: CN7 is both sensory and motor

Answer 2

True

Question 3

What are the four divisions of the facial nerve?

Answer 3

Branchial motor, visceral motor, somatic sensory, visceral (special) sensory

Question 4

What is the role of the branchial motor division of CN7?

Answer 4

efferent supply to IPSILATERAL muscles of facial expression and stepedius

Question 5

What is the role of the visceral motor division of CN7?

Answer 5

preganglionic parasympathetics to lacrimal gland, submandibular and sublingual glands, secretory portions of the soft palate and nasal cavity

Question 6

What is the role of somatic sensory division of CN7?

Answer 6

afferent sensory input from IPSILATERAL part of the outer ear

Question 7

What is the role of the visceral (special) sensory division of CN7?

Answer 7

afferent sensory input involving taste from the anterior 2/3 of the tongue

Question 8

Where is the facial motor nucleus located?

Answer 8

Ventrolateral caudal pons

Question 9

What does damage to the nerve or motor nucleus of CN7 result in?

Answer 9

paralysis of muscles on the same side of the face (ipsilateral)

Question 10

Explain the corneal blink reflex

Answer 10

sensory afferents (pain) of V1 travel to the trigeminal ganglion and most descend to the spinal trigeminal tract and synapse the rostral spinal trigeminal nucleus. Second order neurons travel to both motor nuclei of the facial nerve. Efferent motor neurons travel to orbicularis oculi to cause blink reflex

Question 11

Describe innervation of the facial muscles by corticobulbar fibers

Answer 11

Lower half of face: only innervated by contralateral motor nuclei. Upper half of face: innervated bilaterally by both nuclei

Question 12

What does damage to the corticobulbar (UMN) tracts result in?

Answer 12

muscle weakness to the contralateral muscles of the lower quadrant of the face

Question 13

What does damage to the LMN of the facial nerve result in?

Answer 13

ipsilateral paralysis of the face.

Question 14

What is Bell’s Paulsy?

Answer 14

Paralysis of the ipsilateral face due to LMN lesion of the facial nerve or its nucleus, rapid onset, may be associated with inflammation from herpes, lyme disease, diabetes, AIDS, cancer, usually self resolves

Question 15

What is unique about olfactory sensation in terms of sensing its special stimuli?

Answer 15

It has no specialized receptor cells

Question 16

Where are olfactory receptor membranes found?

Answer 16

primary afferent neurons

Question 17

Describe path of olfactory transduction

Answer 17

1) Activation of receptor protein (olfactants chaperoned through mucus by olfactory binding proteins). 2) Activated receptor stimulates G protein (Golf). 3) Golf activates the effector protein adenylate cyclase III, increasing cAMP. 4) Increased cAMP causes opening of non-specific cation channels resulting in depolarization of neuron.

Question 18

How is the olfactory bulb organized?

Answer 18

In terms of glomeruli

Question 19

What are the afferent and efferent nerves of the olfactory bulb?

Answer 19

Afferent nerves are the nerves that sense the stimulus and come through cribriform plate, efferent nerves form the olfactory tract

Question 20

What part of the olfactory system is spatially organized?

Answer 20

Efferent nerves leading from the glomeruli

Question 21

how are odorants perceived and coded?

Answer 21

by the combination of the olfactory receptor nerves they activate.

Question 22

How does one increase contrast between different smells?

Answer 22

Lateral inhibition by other neurons

Question 23

List the areas that the olfactory tract projects to

Answer 23

Olfactory tubercle, entorhinal cortex, piriform (primary olfactory cortex)

Question 24

Where does the olfactory tubercle project to?

Answer 24

First the amygdala, then the hypothalamus for visceral reactions and homeostasis

Question 25

Where does the Piriform cortex project to?

Answer 25

Both the medial dorsal thalamus (which can also project to orbitofrontal cortex) and the orbitofrontal cortex for conscious perception of the smell

Question 26

Where does the entorhinal cortex project to?

Answer 26

Hippocampus for memory formation

Question 27

What part of the olfactory system are involved in the subconscious?

Answer 27

Entorhinal cortex (hippocampus) and olfactory tubercle (amygdala –> hypothalamus) for homeostasis