brain stem

Question 1

components of brain stem

Answer 1

• long tracts
• cranial nerve nuclei: deal with motor and sensory functions of the head and neck
• cerebellar circuits: related to cerebellum
• reticular formation

Question 2

long tracts include

Answer 2

• dorsal columns
• spinothalamic
• corticospinal

Question 3

brain stem sections

Answer 3

• medulla
• pons
• midbrain

Question 4

medulla includes…

Answer 4

1. decussation of pyramids
2. closed medulla (D.C. nucleus, medial lemniscus)
3. open medulla (inf. olive, cerebellar peduncle)

Question 5

pons includes…

Answer 5

• caudal portion (cerebellum, basis pontis, middle cerebellar peduncle)
• rostral portion (superior cerebellar peduncle)

Question 6

midbrain includes…

Answer 6

• caudal portion (decussation of s.c.p., inf. colliculi)
• rostral portion (red nucleus, cerebral peduncle, sup. colliculi)

Question 7

descending tracts

Answer 7

• lateral CST
• ventral CST

Question 8

ascending tracts

Answer 8

• spinothalamic tract
• dorsal spinocerebellar tract
• ventral spinocerebellar tract
• fasciculus gracilis
• fasciculus cuneatus

Question 9

the pyramidal decussation location

Answer 9

• the lowest part of the medulla
• marks the boundary between the brain stem and the spinal cord

Question 10

where is the reticular formation?

Answer 10

• part of brain stem’s central core

Question 11

the brain stem gives rise to what?

Answer 11

• cranial nerves 3 and 12

Question 12

cross section of closed medulla @ decussation (most caudal, 1st cross section that looks different from spinal cord)

Answer 12

• you can see the decussation of the pyramids
• the corticospinal tract crosses at this level
• the fibers cross over and slice through the gray matter
• the crossing is responsible for voluntary movement (corticospinal/pyramidal tract)

Question 13

what is a distinction between the spinal cord and the closed medulla cross-section? why does this change occur? (1st cross-section above spinal cord)

Answer 13

• the substantia gelatinosa becomes the spinal trigeminal tract and nucleus
• this change occurs because the zone of lissauer receives dorsal roots from spinal segments which are no longer received once you enter the brain.
• in the brain, that area receives cranial nerves thus the name changes because it is now receiving from the trigeminal nerve

Question 14

zone of lissuaer and substantia gelatinosa receive what kind of messages in the spinal cord?

Answer 14

messages of pain and temperature sensation

Question 15

trigeminal tract and nucleus (AKA descending tract of V)

Answer 15

• the tract and synapsing nucleus of the trigeminal nerve (= CN V)
• is an ascending pathway but actually travels in descent toward the brain stem
• the fibers turn downward through the medulla and the pons

Question 16

afferent fibers in spinal cord and brain stem

Answer 16

spinal cord = dorsal roots
brain stem = trigeminal nerve

Question 17

cell body in spinal cord and brain stem

Answer 17

spinal cord = DRG
brain stem = trigeminal ganglion

Question 18

terminals in spinal cord and brain stem

Answer 18

spinal cord = zone of lissauer
brain stem = tract of (spinal) descending V

Question 19

synapse in spinal cord and brain stem

Answer 19

spinal cord = substantia gelatinosa
brain stem = nucleus of (spinal) descending V

Question 20

what signaling does cranial nerve V (trigeminal nerve) carry?

Answer 20

pain and temperature SENSATION from face and head

Question 21

how does the descending V tract and nucleus relate to zone of lissauer and substantia gelatinosa?

Answer 21

same thing, just get signals form head and neck instead of spinal nerves

Question 22

the trigeminal descending pathway

Answer 22

1. pseudounipolar sensory fibers
2. enter the pons
3. fibers descend through the medulla
4. synapse at the nucleus of the descending V
5. pass the midline
6. turn back up to the thalamus and cortex

Question 23

As you ascend in the medulla, what are the differences of what you can see? (2nd cross-section above spinal cord)

Answer 23

• pyramids are above decussation on the ventral surface
• the fasciculus gracilis and fasciculus cuneatus start to turn into nuclei (grey matter)

Question 24

where does the dorsal column (white matter) turn into nuclei (grey matter)

Answer 24

at the pyramids of the closed medulla above the decussation

Question 25

fasciculus gracilis and fasciculus cuneatus are part of

Answer 25

the spinal cord - dorsal column pathways - terminate in the nucleus gracilis and cuneatus respectively

Question 26

nucleus gracilis and nucleus cuneatus:

Answer 26

- contain second order neuron of dorsal column-medial lemniscus pathway - give rise to internal arcuate fibers - project via the medial lemniscus of the thalamus

Question 27

what are internal arcuate fibers?

Answer 27

fibers that arise from the nucleus gracilis and nucleus cuneatus and FORM the contralateral medial lemniscus

Question 28

what is the medial lemniscus?

Answer 28

basically the pathway of the second order sensory neuron where crossing over occurs in dorsal column pathway

Question 29

when does the order of a neuron change?

Answer 29

after synapsing - 1st order prior to synapse - 2nd order after synapse - 3rd order after another synapse

Question 30

where does the medial lemniscus receive neuron signals from?

Answer 30

the contralateral (opposite side) nucleus gracilis and nucleus cuneatus

Question 31

what makes the medulla open in the cross sections?

Answer 31

the presence of the 4th ventricle

Question 32

what is the major change from the closed medulla to the open medulla?

Answer 32

the presence of the inferior olive

Question 33

where is the inferior olive located?

Answer 33

lateral to the pyramids

Question 34

what does the inferior olive do?

Answer 34

- receives input from spinal cord and cortex - then sends signal to cerebellum - function is tied to cerebellar function

Question 35

where do the fibers from the inferior olive go to?

Answer 35

the inferior cerebellar peduncle

Question 36

what is a peduncle?

Answer 36

a structure that connects the cerebellum to the brain stem and cerebrum

Question 37

how does the spinocerebellar tract relate to the inferior olive?

Answer 37

the spinocerebellar tract joins with the inferior olive fibers and they enter the cerebellum via the inferior cerebellar peduncles

Question 38

what pierces the pons?

Answer 38

THE PYRAMIDAL FIBERS PIERCE THE PONS

Question 39

as you ascend in the cross sections, what changes are there as you enter the pons? (caudal pons)

Answer 39

- pontine nuclei - pyramidal fibers of corticospinal tract pierce the pons - middle cerebellar peduncle - cerebellum

Question 40

why does the medial lemniscus appear to move more dorsally as you enter the pons cross-sections?

Answer 40

- the fibers are destined to terminate in the thalamus - are on an angle to approach the thalamus

Question 41

where does the medial lemniscus send signals to?

Answer 41

the ventral posteriolateral nucleus of the thalamus (VPL)

Question 42

changes and structure in the cross-section of rostral pons?

Answer 42

- superior cerebellar peduncle - 4th ventricle gets a little smaller and begins to look like something else... the aqueduct - central tegmental tract

Question 43

changes to the cross section as you enter the caudal midbrain?

Answer 43

- perioaqueductal grey (pain) - cerebral aqueduct - decussation of superior cerebellar peduncle - inferior colliculus

Question 44

how many colliculi are there in the brain?

Answer 44

4 total 2 superior, 2 inferior

Question 45

what changes as you enter the rostral midbrain cross sections?

Answer 45

- red nucleus - superior colliculi - cerebral penduncle

Question 46

what does the cerebral penduncle consist of?

Answer 46

- substantia nigra (nucleus) - crus cerebri (pathway)

Question 47

what does the crus cerebri contain?

Answer 47

all the output of the cerebral cortex going down to the brain stem and spinal cord - pyramidal tract - corticospinal tract also contains input to the cortex and all the stuff that goes to the pontine nuclei LOTS OF AXONS

Question 48

why is the substantia nigra important?

Answer 48

- it has dopaminergic neurons and damage to those neurons can cause Parkinson's disease

Question 49

what is the interpedunclular fossa?

Answer 49

- the space between the 2 cerebral peduncles - 3rd cranial nerve is attached there