Brainstem Flashcards
what are the three types of function of the brainstem
- acts as a conduit- ascending/descending pathways
- cranial nerve functions via brainstem nuclei
- integrative and modulatory functions through reticulum
what does the brainstem exert neuronal influence over
heart rate
respiration
antigravity and postural muscles
eye movement
head tracking
lower motor neuron excitation
autonomic activation
arousal
sleep
vomiting
what is the location of the brainstem
housed by the POSTERIOR CRANIAL FOSSA
anterior there is:
clivus
nerves and vessels
posterior:
cerebellum and attachments
inferior:
foramen magnum
spinal cord
superior:
tentorium cerebelli
diencephalon
why does the brainstem need a central location
-takes info to and from the cortex
-takes info to and from cerebellum (to correct intended movements)
-cranial nerves
what are the three segments of the brainstem
midbrain
pons
medulla
the three segments have functional differences
name the neuronal types found in the internal part of the brainstem
tegmentum- 3 different kinds- runs theentire length of brainstem
tectum
substantia nigra
crus cerebri- base of pedicles top of midbrain
cerebral aqueduct
periaqueductal grey matter (around aqueduct)- MODULATE PATHWAY FOR INCOMING PAIN
what happens in the pons in the corticospinal tract
the fibers are broken into many bundles
before descending at the pyramids
where do the lateral corticospinal tract terminate
lower motor neurons in the anterior horn of the spinal cord
where do the anterior corticospinal tract terminate
LMNs
what does a brainstem lesion of the lateral corticospinal tract produce
contralateral UMNs signs
what happens to the pathway of the corticobulbar descending tract
carries motor info from motor cortex, go through internal capsule and branch off and innervate different motor nuclei in brainstem
these motor nuclei control facial and neck muscles
innervation is BILATERAL, decussation occurs at the level of the nucleus
what does a brainstem lesion of the corticobulbar tracts produce
usually ipsilateral
effects dependant on where the lesion is
what are the tracts that have descending pathways, where info is generated from the brainstem and not the cortex. they have sensory info coming to them via other pathways (extrapyramidal pathways- NOT CORTOSPINAL TRACTS)
Rubrospinal tract
Tectospinal tract
Vestibulospinal
Reticulospinal
describe the rubrospinal tract
subconscious coordination effect
contralateral pathway
upper limb coordination
describe the tectospinal tract
connects to cervical spinal cord- neck musculature
from superior colliculus (VISUAL oriented control of neck muscles)- inferior are involved in SOUND
describe the vestibulospinal pathway
2 pathways
LATERAL vestibular nuclei- arms (ipsilateral excitatory to extensors, inhibitors to flexors- so when fall you put your arms out)
MEDIAL- head (bilateral neck muscles, so move head away from falling)
info from vestibular cochlear apparatus, vestibular pathway
describe the reticulospinal pathway
mass of dendritic connections
pontine and medullary reticular formations
allow you to stay upright, spring in step
what are the effects of a brainstem lesion in the medial lemniscal pathway
contralateral loss of JPS and discriminating touch
what are the effects of a lesion in the spinal lemniscal pathway (spinothalamic tract)
produces a contralateral loss of pain and temperature sensation
what are the effects of a lesion in the spinocerebellar tract
ataxia
ipsilateral defect
what is ataxia
inability to coordinate self
==cerebellar problem
therefore know it is ipsilateral
what are the reticulum and what are their functions
they are found throughout the brainstem
found in the central tegmentum
diffuse network of nuclei- regulate activity
work predominately in groups of NT related networks
important in regulation of pain sensation, arousal (sleep) of cortex and modulation of descending motor output
what is the final layout of the brainstem in regards to sensory and motor nuclei and how it compares to the spinal cord layout
as the tectum increases-enlarges, it pushes the nuclei from a ventral-dorsal order to a medial-lateral arrangement (what is found in the brainstem)
what is the organisation of the the cranial nerve nuclei
three lateral sensory columns of nuclei
three Medial Motor columns
are cranial nerves mixed
they can be either sensory, motor, mixed
which cranial nerves are sensory
1, 2, 8
which cranial nerves are motor
3,4,6,11,12
which cranial nerves are mixed
5, 7, 9, 10
what rule do the cranial nerves follow
rule of 4
4 in or ABOVE midbrain
4 in pons
4 in medulla
what does the oculomotor nucleus connect to and its function
oculomotor nerve 3
extraocular eye muscles
EXCEPT superior oblique and lateral rectus
what does trochlear nucleus connect to and its function
trochlear nerve
control superior oblique muscle of eye
what does abducens nucleus connect to and its function
abducens nerve
control lateral rectus muscle of the eye
what dies the hypoglossal nucleus connect to and its function
hypoglossal nerve
controls tongue muscle (deviation towards lesion side)
look at cranial nerves and structures they go to!
are there non-cranial nerve nuclei
yes found in different brainstem levels
midbrain
-medial geniculate
-red nucleus
-substantia nigra
-superior colliculus
-inferior colliculus
-reticular formation
pons
-pontine nuclie
-reticular formation
medulla
-olive
-vital centres
-non-vital centres
reticular formation
what are the clues to diagnosing brainstem localisation lesion
midbrain– eye movement
pons– mastication
medulla– swallowing
brainstem lesions usually produce ipsilateral cranial nerve defects
what are some signs there are lesions affecting CONDUCTION
weakness
loss of pain, temp
ataxia
loss of JPS and vibration
what are some signs there are lesions affecting cranial nerve functions
eye muscle weakness
so sensation on face
autonomic dysregulation
problems speaking or swallowing
vertigo
changes in taste and hearing
what are some signs there are lesions affecting the reticular function
uncontrolled movements-choria
tremor
ataxia
autonomic dysfunction
lethargy
locked in syndrome
what is locked in syndrome
PONTINE lesion disrupting all motor traffic to spinal cord and face
sparing midbrain EYE muscle control
what is chorea
writhing movements
how do clues help with diagnosis
signs of both sides (traffic going up and down)
symptoms above and below lesion
look at cranial nerves are involved-gives level in brainstem
work out if medial, lateral, bilateral
if ipsilateral– sympathetic, LMN cranial nerve, limb ataxia
if contralateral– limb/body UMN, loos of pain, temp, fine touch, proprioception
what is lateral medullary syndrome
wallenberg syndrome
medullary lesions starved of blood
characteristics above and below
ataxia on right side (therefore lesion on that side)
lose of pain, dysphagia and temp on other side
ptosis and small pupil also ipsilateral
