CNS 3 Notes.docx

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Health Sciences
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Cale Zavitz

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CNS 3; The Central Nervous System; Brainstem & Cerebellum Brainstem Overview  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 cerebellum.  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) Cerebellum  2 cerebellum  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: o Vision o Vestibular o Proprioception  Cerebellum send inform back to contralateral cortex to initiate planned motor movement. 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 happens!)  Vestibulocerebellum; movement of axial skeleton. Allow you to maintain even posture. Balance and eye movement are controlled by this.  Ipsilaleral Cerebellum**** 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 drunk.  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. Romberg Test  Test for d
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