CNS 3; The Central Nervous System; Brainstem & Cerebellum
Midbrain bellow diencephalon (top of midbrain)
Pons has close association with cerebellum
Medulla at base of brainstem
Cranial nerves comes from each part of brainstem
Cerebral peduncles (white matter tracts) cortico spinal motor tracts.
Descend through brainstem to reach areas of spinal cord.
Pons are another white matter tract and are a bridge between left and right
cerebellum, this is how cortex singles into cerebellum to get planned motor
movements in and out of cerebellum. Their a relay nuclei from cortex to
Medulla; pyramids with decussation (cortico spinal motor tracts). Once
cerebral peduncles pass through pons, they appear at bottom of medulla.
Decussation (crossing) of pyramidal tracts at bottom that cause left brain to
control right side of body, and right brain to control left side of body. CNS 3; The Central Nervous System; Brainstem & Cerebellum
Features on back of Brainstem
Lateral geniuculate nuclei of thalamus responsible for relay of sight and
medial geniculate nuclei responsible for primary hearing
Superior collicollus; vision reflex relay
Inferior colliculus auditory reflex relay
Cerebellum can see because it is connected to superior collicolus
Cerebellum; complicated motor movement
Connections between cerebellum and brainstem are cerebellar peduncles (3
of them). Visual pathway extend through superior cerebral peduncle. Middle
cerebellar peduncle; cortical information (from pons) ex: what would you
like to move? and inferiror cerebellar peduncle; proprioceptive, position of
muscles and joints
Cerebral peduncles at front, cerebellar peduncles towards posterior
Medulla has columns of sensory fibers. Spinal fibers come up to cortex from
lower limbs and feet, and then adjacent are fibers from upper limbs.
Front is motor, back is sensory.
Cranial Nerves in Brainstem
Most of cranial nerve nuclei are located in brainstem
CN3-CN12 is located in brainstem
Sensory and motor nuclei run along each side CNS 3; The Central Nervous System; Brainstem & Cerebellum
Olefactory tract (I); smell
Optic nerve (III); vision
Trigeminal nerve (V); sensory (face). All sensation from head and neck.
Vagus nerve (X); Internal organs
Function of Cranial Nerves
Functional categories; special sensory and motor autonomic CNS 3; The Central Nervous System; Brainstem & Cerebellum
Nuclei of Brainstem
Besides nuclei that give rise to cranial nerves, the brainstem also have nuclei
Reticular formation; forms core of brainstem is responsible for receiving
sensory information and then signaling to cortex to keep us alert and awake.
This is grey matter.
Substantia nigra (black stuff) is grey matter that releases dopamine, that
facilitates transfer of information through basal ganglia. In Parkinsons, the
neurons in substantia nigra degenerate. Not its hard for brain to get
information from basal nuclei and so routine movements are getting stuck in
basal ganglia when there isn’t any dopamine. This is why people with
Parkinson’s have trouble starting a movement or completing a movement
once they have started.
Red nucleus; motor pathways, flexion. Automatically controls motor
pathways especially related to flexion
Brainstem Reticular Formation
A cigar shaped structure
Responsible for consciousness, sleep and arousal
Input from vision and ascending sensory tracts (touch, pain, temperature).
Reticular formation sends information through neurons to whole cortex in a
diffuse cholinergic and adrenergic (ACh, NE) that enhances cerebral cortex
to become enlightened and wakefulness
Reticular formation also extends downwards and descending motor
projections to spinal cord. Neurons release endogenous opiods (endorphins
and enkephalins) that allow you to control pain (this is one of the two ways
we will learn about regarding pain control)
receives sensory information from same side of body
sensory information comes from cerebral cortex. Unlike learned movements
in basal ganglia, you have to see (using sensory input unlike basal ganglia) in
order to make motor response in relation to object.
Will to make motor movement extends down through pons and left cerebral
cortex has to go down to pons, synapse there, and go to other side (because
cerebellum controls same side of body)
Cerebellum controls joints and muscles.
Colliculi gives vision and balance
Cerebellum has 3 pieces of information to make planned motor movement:
Cerebellum send inform back to contralateral cortex to initiate planned
Left & Right Cerebellums
Cerebellar peduncles are the input and output fibers CNS 3; The Central Nervous System; Brainstem & Cerebellum
1. Frontal cortex notifies cerebellum of intention to make a movement
2. Proprioceptors in muscle and tendons, visual input, vestibular input inform
cerebellum about position of body and limbs
3. Cerebral cortex calculates best way to coordinate movement
4. Deep cerebral nuclei send blueprint to cortex to initiate a coordinated
movement, to spinal cord to maintain posture
Grey matter on outside, white matter on inside.
Deep cerebellar nuclei project output to opposite side in order to give
information to proper cerebral cortex that requested it in the first place
Cerebellar Control; Appendicular vs. Axial
Different parts of cerebellum are responsible for different parts of body
movement CNS 3; The Central Nervous System; Brainstem & Cerebellum
Outside of cerebellum is responsible for appendicular skeleton
o Spinal cerebellum (limb movement)
o Cerebrocerebellum (learning new motor movements) formation of
new neural connections and new neurons (1 in 3 places where this
Vestibulocerebellum; movement of axial skeleton. Allow you to maintain
even posture. Balance and eye movement are controlled by this.
o Ipsilaleral cerebellum for appendicular skeleton knows vision,
vestibular information, proprioception. Sends information to same
side of cortex to thalamus
o Axial skeleton ipsilaleral cerebellum
Disease of Cerebellum
Exposure to organic solvents dissolve the neurons of the cerebellum
Cerebellar dysfunction if affected in midline of cerebellum effects trunk
movement. People who have this disorder are often thought of as being
Attention tremor: Stroke on lateral cerebellum; one side may not be affected,
the affected side (lets say left) cerebellar processing is ipsilaleral so it’s the
left cerebellum, right cerebral cortex in charge of left limb, but its not getting
right information from cerebellum on opposite side.
Test for d