Exam 2: Lecture 12 Brain Stem Flashcards
What is in the brain stem (5)
midbrain, pons, and medulla
- cranial nerve nuclei and tracts for brain to spinal cord and vice versa
- monoamine neurotransmitters
Reticular formation
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
reasons the brainstem changes shape
- 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
medulla properties (2)
- two halves where the rostral half is covered by part of the 4th ventricle and the cerebellum
- underneath the peduncles
how is the medulla different from the spinal cord?
- 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
pyramidal decussation
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
pyramidal tracts
stick out in the caudal medulla as a dark fiber area where fibers cross the midline
what does the border of the caudal medulla contain? (2)
- contains the dorsal column nuclei in the mediolateral dorsal part
- contains the sensory decussation in the middle ventral part
medial lesmniscus
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)
what does the rostral medulla contain? (9)
- 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
inferior olive
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
what is a big difference between the rostral and caudal medulla?
the rostral medulla has an opening beginning for the 4th ventricle but the caudal medulla does not
what does the sulcus limitans do?
separates sensory and motor
- sensory includes vestibular nuclei and solitary tract and nucleus
- motor includes dorsal motor nerve of vagus and hypoglossal nucleus
what does the dorsal motor nerve of vagus do?
autonomic regulation for parasympathetic nucleus for the thorax and the abdomen
what does the solitary tract and nucleus sense?
visceral sensations
- such as taste
what does the hypoglossal nucleus do
lets us move our tongue
what is contained in the pons? (9)
- 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
what is the pontine nuclei?
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)
what do the middle cerebellar peduncles do?
the mass of axons connecting the two sides of the pons sending information to the cerebellum
what are the pyramidal fascicles?
corticospinal fibers plus corticopontine fibers innervating pontine nuclei (in the pons)
what does the 4th ventricle look like in the pons?
it looks like a trapezoid on the top of it
Spinothalamic tract (STT)
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
Locus coeruleus
cell body of the neurons for norepinephrine in the pons
- - part of the monoamine neurons
Raphe nuclei
cell body of the neurons for serotonin in the pons ⇒ close to the midline
- part of the monoamine neurons
monoamines
(neurotransmitters)
Serotonin
Dopamine
Norepinephrine
Epinephrine
what is special about the caudal midbrain?
there is no more cerebellum overhead and no more 4th ventricle
- the superior cerebellar peduncle is sunken down and starting to cross the midline
what does the caudal midbrain contain? (3)
- superior cerebellar peduncle (more in the middle under the 4th)
- cerebral aqueduct
- inferior colliculi
inferior colliculi
are involved in the auditory system
- superior to the cerebral aqueduct
what does the middle midbrain contain? (3)
- superior colliculi
- cerebral aqueduct
- superior cerebellar peduncle directly ventral to the cerebral aqueduct
what does the rostral midbrain contain? (2)
Note: it starts to junction with the diencephalon and thalamus
- superior cerebellar peduncle leads to Red nuclei
- cerebral aqueduct
superior colliculus
contributes to motor functions that orient the head and eyes toward or away from a stimulus
- Superior to cerebellar peduncle
Red nuclei
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
