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
