Exam 2: Lecture 12 Brain Stem

Question 1

What is in the brain stem (5)

Answer 1

midbrain, pons, and medulla
- cranial nerve nuclei and tracts for brain to spinal cord and vice versa
- monoamine neurotransmitters

Question 2

Reticular formation

Answer 2

brainstem regions with neurons but lacking clear nuclear boundaries
- involves sleep and other formations
- meshwork of axons and some go dorsal ventral, medial lateral, and some rostral caudal

Question 3

reasons the brainstem changes shape

Answer 3

• Structures (tracts or nuclei) get added
• Structures get smaller and end
• Fiber tracts change size as axons are added or terminate
• Fiber (axon) tracts move ⇒ they start dorsally and end ventrally or cross midline

Question 4

medulla properties (2)

Answer 4

• two halves where the rostral half is covered by part of the 4th ventricle and the cerebellum
• underneath the peduncles

Question 5

how is the medulla different from the spinal cord?

Answer 5

• Spinal trigeminal nucleus
• Spinal trigeminal tract
• Left dorsal funiculus ⇒ there are cell bodies referred to as dorsal column nuclei which is relayed to the thalamus
• Dorsal column nuclei
• Dorsal horn ⇒ this region is gigantic compared to the brainstem because there are innervations the brainstem needs to deal with
• Not really called the dorsal horn anymore, it is called the spinal trigeminal nucleus due to the cranial nerve
• Fewer motor neurons in the medulla ⇒ they only innervate a couple of the muscles

Question 6

pyramidal decussation

Answer 6

where fibers cross the midline between the pyramidal tracts as they bring cortical information down to the spinal cord region from the corticospinal tract
- this is in the medulla => border of the caudal and rostral area

Question 7

pyramidal tracts

Answer 7

stick out in the caudal medulla as a dark fiber area where fibers cross the midline

Question 8

what does the border of the caudal medulla contain? (2)

Answer 8

1. contains the dorsal column nuclei in the mediolateral dorsal part
2. contains the sensory decussation in the middle ventral part

Question 9

medial lesmniscus

Answer 9

where sensory fibers crossing the midline from the dorsal column nuclei extend out and cross the midline as they go up as a pair of axon columns on top of the pyramidal tract (in the caudal medulla)

Question 10

what does the rostral medulla contain? (9)

Answer 10

• sulcus limitans
• 4th ventricle in the central canal where the pyramid decussation was
• STT where their axons make their way up to the cerebellum on the venture-lateral funiculi
• inferior olive on the ventral funiculi area
  pyramidal tracts at the most ventral side in the middle
• vestibular nuclei
• solitary tract and nucleus
• dorsal motor nerve of vagus
• hypoglossal nucleus

Question 11

inferior olive

Answer 11

on the rostral medulla sending its axons into the cerebellum combine with spinocerebellar tract to make the cerebellar peduncles
- also on the surface of the brainstem outside of the pyramidal tracts

Question 12

what is a big difference between the rostral and caudal medulla?

Answer 12

the rostral medulla has an opening beginning for the 4th ventricle but the caudal medulla does not

Question 13

what does the sulcus limitans do?

Answer 13

separates sensory and motor
- sensory includes vestibular nuclei and solitary tract and nucleus
- motor includes dorsal motor nerve of vagus and hypoglossal nucleus

Question 14

what does the dorsal motor nerve of vagus do?

Answer 14

autonomic regulation for parasympathetic nucleus for the thorax and the abdomen

Question 14

what does the solitary tract and nucleus sense?

Answer 14

visceral sensations
- such as taste

Question 15

what does the hypoglossal nucleus do

Answer 15

lets us move our tongue

Question 16

what is contained in the pons? (9)

Answer 16

• 4th ventricle
• pontine nuclei
• pyramidal fascicles/tracts (dark in picture)
  —> cell bodies (light in picture)
• STT
• monoamines
• locus coeruleus
• raphe nuclei
• superior cerebellar peduncle
• middle cerebellar peduncle

Question 17

what is the pontine nuclei?

Answer 17

create the big bulge of the pons ⇒ characterized on the ventral surface by massive amount of cells on top of the brainstem which talk to the cerebellum (dorsal side)

Question 18

what do the middle cerebellar peduncles do?

Answer 18

the mass of axons connecting the two sides of the pons sending information to the cerebellum

Question 19

what are the pyramidal fascicles?

Answer 19

corticospinal fibers plus corticopontine fibers innervating pontine nuclei (in the pons)

Question 20

what does the 4th ventricle look like in the pons?

Answer 20

it looks like a trapezoid on the top of it

Question 21

Spinothalamic tract (STT)

Answer 21

for pain, temperature, itching, etc. in the ventral part of the lateral funiculi of the spinal cord
- it can be seen from the brainstem to caudal medulla all the way up to the pons

Question 22

Locus coeruleus

Answer 22

cell body of the neurons for norepinephrine in the pons
- - part of the monoamine neurons

Question 23

Raphe nuclei

Answer 23

cell body of the neurons for serotonin in the pons ⇒ close to the midline
- part of the monoamine neurons

Question 24

monoamines

Answer 24

(neurotransmitters)
Serotonin
Dopamine
Norepinephrine
Epinephrine

Question 25

what is special about the caudal midbrain?

Answer 25

there is no more cerebellum overhead and no more 4th ventricle
- the superior cerebellar peduncle is sunken down and starting to cross the midline

Question 26

what does the caudal midbrain contain? (3)

Answer 26

• superior cerebellar peduncle (more in the middle under the 4th)
• cerebral aqueduct
• inferior colliculi

Question 27

inferior colliculi

Answer 27

are involved in the auditory system
- superior to the cerebral aqueduct

Question 28

what does the middle midbrain contain? (3)

Answer 28

• superior colliculi
• cerebral aqueduct
• superior cerebellar peduncle directly ventral to the cerebral aqueduct

Question 29

what does the rostral midbrain contain? (2)

Answer 29

Note: it starts to junction with the diencephalon and thalamus
- superior cerebellar peduncle leads to Red nuclei
- cerebral aqueduct

Question 30

superior colliculus

Answer 30

contributes to motor functions that orient the head and eyes toward or away from a stimulus
- Superior to cerebellar peduncle

Question 31

Red nuclei

Answer 31

axons in the rostral midbrain that have crossed and some have ended below the aqueduct
- Some axons go beyond the red nuclei up to the thalamus