12 - Surface Anatomy of the Brainstem

Question 1

where is cranial nerve 5 (trigeminal nerve) located?

Answer 1

pons

Question 2

where is cranial nerve 7(facial nerve) located?

Answer 2

pons

Question 3

where is cranial nerve 8 (vestibulocochlear nerve) located?

Answer 3

pons to medulla separation

Question 4

what tracts would you find the fasciculus gracilis/cuneatus? together what does these form?

Answer 4

ascending tracts - spinal cord

tracts of the posterior funiculus

Question 5

what three major tracts can be found in the ascending tracts of the spinal cord?

Answer 5

tracts of the posterior funiculus

spinocerebellar tracts

spinothalamic tracts

Question 6

what comprises the spinocerebellar tracts?

Answer 6

posterior sphinocerebellar tract

anterior spinocerebellar tract which goes to the cerebellum

Question 7

what comprises the spinothalamic tracts?

Answer 7

lateral spinothalamic tract

anterior spinothalamic tract

Question 8

where does the corticospinal tract begin?

Answer 8

cerebral cortex

Question 9

in the medulla, at the level of the pyramids what percent of the fibers cross and continue into the spinal cord as the lateral corticospinal tract?

what percent of the corticospinal fibers remain ipsilateral?

Answer 9

80%

About 20% of the corticospinal fibers remain ipsilateral and continue into the spinal cord as the anterior corticospinal tract.

Question 10

fibers in the anterior corticospinal tract decussate where?

Answer 10

in the spinal cord

Question 11

where do the additional descending motor fibers begin and end? what name do we give those motor fibers that end in the cranial nerve nuclei?

Answer 11

fibers begin in the cortex and travel to the brainstem (and cerebellum).

corticonuclear fibers

Question 12

where does the anterior spinocerebellar tract enter?

Answer 12

the cerebellum through the superior cerebellar peduncle

Question 13

where does the posterior spinocerebellar tract enter?

Answer 13

the cerebellum through the inferior cerebellar peduncle

Question 14

where does the large corticopontine tract originate and travel to? what is the effect on the postsynaptic neurons?

Answer 14

originates in the cortex and travels to the pons where the fibers synapse.

The postsynaptic neurons send processes into the cerebellum through the middle cerebellar peduncle.

Question 15

In the caudal medulla, what fibers terminate in the nuclei of posterior fasciculi?

Answer 15

Posterior fasciculi, dorsal column pathway

Question 16

Efferent fibers from these nuclei (nucleus gracilis and cuneatus) travel in what structure?

Answer 16

Medial limniscus

Question 17

What fiber type is carried in the corticospinal tract?

Answer 17

Motor fibers

Question 18

Where do these fibers terminate?

Answer 18

Spinal cord based on level they control

Question 19

where are the red nucleus and substantial migration located?

Answer 19

mesencephalon (midbrain), these are not cranial nerve nuclei and both are involved in motor activities through relays in a system known as the extrapyramidal motor system (corticospinal fibers)

Question 20

what space does the reticular formation occupy?

Answer 20

occupying areas of the tegmentum between discreet structures such as the red nucleus and substantia nigra.

Question 21

what are the important functions of the reticular function?

Answer 21

breathing and blood pressure maintenance, through autonomic reflex circuitry.

*remember that separate regions in the medulla regulate the rate of inspiration and expiration. Loss of these cells can result in sleep apnea

Question 22

what are the two discreet groups of reticular nuclei?

Answer 22

medial and lateral

Question 23

what are the medial nuclei of the reticular nuclei?

Answer 23

large neurons; axons form long ascending and descending tracts

Question 24

what are the lateral nuclei of the reticular nuclei?

Answer 24

small neurons; axons usually stay within the brainstem.

Question 25

describe the noradrenergic neurons?

Answer 25

these neurons are in the locus ceruleus that contain norepinephrine silent during sleep, but are slightly active during wakefullnes. They are most active during states that are startling or call for watchfullnes. The noradrenergic neurons may play a role in maintaining attention and vigilance.

Question 26

describe the dopaminergic neurons?

Answer 26

located in the Substantia nigra and Ventral Tegmental Area. Dopamine is the synaptic transmitter. Loss of dopaminergic neurons is involved in Parkinson’s disease. Dopaminergic cells are involved in the initiation of movement, but also influence motivation and cognition.

Question 27

describe the serotonergic neurons?

Answer 27

These cells contain serotonin and are distributed in all levels of the brainstem, concentrated in raphe nuclei. Like noradrenergic neurons, they innervate virtually all parts of the CNS. Firing of serotonergic neurons fluctuates with sleep and wakefulness, indicating that these cells modulate the general activity levels of the CNS (similar to the way noradrenergic neurons function).

Question 28

describe the cholinergic neurons?

Answer 28

use acetylcholine as a neurotransmitter. Cholinergic neurons are found in the reticular formation of the brain stem. From here, they project axons into the thalamus. All cholinergic neurons may be involved in regulating the sleep-wakefullness cycle. Loss of cholinergic neurons, especially in the basal nucleus, is a hallmark of Alzheimer’s disease.