Brain Stem: Pons

Question 1

describe the gross anatomy of the pons

Answer 1

1. basilar pons = ventral surface
2. pontine tegmentum = dorsal surface and floor of 4th ventricle

Question 2

where are ascending sensory tracts generally found in the pons?

Answer 2

tegmental area (dorsal surface)

Question 3

where are descending motor tracts generally found in the pons?

Answer 3

basilar area (ventral surface)

Question 4

list the fiber tracts that are found in the basilar pons

Answer 4

1. transverse pontine (pontocerebellar)
2. corticospinal fiber tract
3. corticobulbar fiber tract

Question 5

what type of info is carried by the transverse pontine (pontocerebellar) tract?

Answer 5

relayed afferent signals to cerebellum via middle cerebellar peduncle

Question 6

what type of fibers is the transverse pontine (pontocerebellar) tract made up of?

Answer 6

commissural and afferent fibers

Question 7

where are the corticospinal and corticobulbar fiber tracts?

Answer 7

run longitudinally through basilar pons

Question 8

what type of info is carried by the corticobulbar tract?

Answer 8

somatomotor from precentral gyrus to the head

Question 9

what type of info is carried by the corticospinal tract?

Answer 9

somatomotor from precentral gyrus prior to decussation of pyramids heading to the body

Question 10

what nuclei are found in the basilar pons?

Answer 10

deep pontine nuclei

Question 11

list the fiber tracts that are found in the tegmental pons

Answer 11

1. facial colliculus
2. S/M/I cerebellar peduncle
3. medial lemniscus
4. medial longitudinal fasciculus
5. spinothalamic
6. trigeminothalamic
7. lateral lemniscus
8. rubrospinal tract
9. tectospinal tract
10. spinal nucleus tract of CN 5
11. descending limbic and hypothalamic fibers

Question 12

what type of info is carried by the facial colliculus

Answer 12

facial nerve CN7 fibers

Question 13

what type of info is carried by the superior cerebellar peduncle?

Answer 13

efferent fibers from cerebellum to brain stem and cortex

Question 14

what type of info is carried by the middle cerebellar peduncle?

Answer 14

afferent fibers from cortex to cerebellum

Question 15

what type of info is carried by the inferior cerebellar peduncle?

Answer 15

afferent fibers from medulla and spinal cord to cerebellum

Question 16

what type of info is carried by the medial lemniscus at the level of the tegmental pons?

Answer 16

touch, pressure and proprioception from the entire body ascending to the cortex

Question 17

what type of info is carried by the spinothalamic tract in the tegmental pons?

Answer 17

somatosensory (pain and temperature) from body

Question 18

what type of info is carried by the trigeminothalamic tract in the tegmental pons?

Answer 18

afferent somatosensory from head to cortex

Question 19

what type of info is carried by the lateral lemniscus in the tegmental pons?

Answer 19

auditory relay circuit to inferior colliculus for auditory reflex movement of head

Question 20

what type of info is carried in the rubrospinal tract?

Answer 20

efferent motor signals to the arms

Question 21

what type of info is carried by the tectospinal tract?

Answer 21

efferent somatomotor signals to muscles of neck and shoulders (head turning reflex)

Question 22

what type of info is carried by the spinal nucleus tract of CN 5?

Answer 22

pain and temperature sensation from head

this transitions into the trigeminothalamic tract (in the medulla)

Question 23

what type of info is carried by the descending limbic and hypothalamic fibers of the tegmental pons?

Answer 23

info that is carried to autonomic control centers in medulla and spinal cord

Question 24

list the nuclei that are located in the caudal portion of the tegmental pons

Answer 24

1. facial nucleus CN 7
2. abducens nucleus CN 6
3. spinal trigeminal nucleus CN 5
4. superior olivary nucleus (not pictured below)
5. trapezoid body
6. M/I vestibular nucleus
7. superior salvatory nucleus

Question 25

what does the facial nucleus of CN 7 control?

Answer 25

muscles of facial expression

Question 26

what does the abducens nucles of CN 6 control?

Answer 26

eye muscles (lateral rectus)

Question 27

what do the superior olivary nucleus and trapezoid body do?

Answer 27

they are relays in the auditory pathway

Question 28

what does the superior salvatory nucles do?

Answer 28

fibers are part of CN7 to lacrima, submandibular, and sublingual salivary glands

Question 29

list the nuclei that are located in the rostral pons

Answer 29

1. main sensory nucleus of CN5 2. motor nucleus of CN 5 3. mesencephalic nucleus CN5 (not pictured below) 4. S/L vestibular nucleus 5. locus ceruleus 6. raphe nuclei

Question 30

what is the main sensory nucleus of CN 5?

Answer 30

continuation of spinal trigeminal nucleus (light touch from face via trigeminal ganglion synapses here)

Question 31

what does the motor nucleus of CN 5 supply?

Answer 31

somatomotor to muscles of mastication

Question 32

what does the mesencephalic nucleus of CN 5 do?

Answer 32

proprioception of jaw (from trigeminal ganglion)

Question 33

what is the locus ceruleus?

Answer 33

part of reticular formation (NE) involved in pain modulation

Question 34

what is the raphe nucleus?

Answer 34

part of reticular formation (serotonin) involved in pain modulation

Question 35

what tracts merge together in the rostral pons to form a single tract to the postcentral gyrus?

Answer 35

medial lemniscus spinothalamic trigeminothalamic lateral lemniscus all merge together into the medial lemniscus