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Class 7. Nervous System.docx

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University of Ottawa
Vanessa Taler

Nervous System Divisions of the Nervous System  CNS: brain & spinal cord  PNS: rest of nervous system  Somatic nervous system: operates muscles under voluntary control.  Autonomic nervous system: regulates individual organ function and is involuntary. The Neuron  axon: carries information away from neuron  dendrite: carries information to neuron  myelin: a collection of lipid fats and proteins that sheathes axons The Synapse  where axon & dendrite meet  neurotransmitter: chemicals released in the brain to allow an impulse to pass from one neuron to another  synaptic vesicle: contains & releases neurotransmitter into synaptic cleft  receptor: a structure on the surface of the neuron that selectively receives and binds a neurotransmitter  nearly 90% of the brain is made up of glial cells, which support and protect neurons. There are four types:  Astrocytes have numerous processes that give the cell a star-shaped appearance.  Oligodendrocytes wrap their processes around neurons to create the myelin sheath.  Microglia engulf microorganisms and cellular debris.  Ependymal cells line the fluid-filled cavities of the brain and spinal cord. Aging of the Nervous System  restricted loss of neurons in few cortical areas  remodeling of synaptic connections, some replacement of neurons e.g. in hippocampus  reduced plasticity (ability to remodel synaptic connections)  increased vulnerability to oxidative stress  neuroinflammation increases with atherosclerosis; causal link to selective neuronal death Neuropathology of Cognitive Aging  AD pathology, oxidative stress, neuroinflammation, changes in cerebral microvasculature  CVD + AD pathology = a more likely diagnosis of dementia  “old-old” brains (age 90+) differ from “young-old” brains in their capacity to withstand structural damage  conversion to dementia probably mediated by factors such as very advanced age, cerebrovascular lesions, cortical atrophy, brain reserve Changes in Sleep Patterns  Results of these changes: more difficulty falling asleep possible sleep deprivation, with negative health consequences  Possible reasons: daytime napping physical inactivity fluid/food intake stress/anxiety Disorders of the Nervous System Tremor  Tremor is an unintentional, somewhat rhythmic, muscle movement involving to-and-fro movements (oscillations) of one or more parts of the body.  It is the most common of all involuntary movements and can affect the hands, arms, head, face, vocal cords, trunk, and legs.  Most tremors occur in the hands. Tremor: Types  at-rest tremor: occurs while affected limb is not moving  postural tremor: occurs while posture is being maintained (e.g., while holding cup)  intention tremor: occurs when person attempts goal-directed motion Tremor: Cause  Parkinsonian tremor  essential tremor (most common type of tremor): usually affects upper body is exacerbated by stress or fatigue there is an important genetic influence not associated with any known pathology  metabolic/toxic factors (e.g., lithium, antidepressants, caffeine, steroids, alcohol withdrawal) Parkinson’s Disease  Major symptoms: tremor: trembling in hands, arms, legs, jaw, or head rigidity: stiffness of the limbs and trunk bradykinesia: slowness of movement postural instability: impaired balance Tardive Dyskinesia  Caused by long-term use of drugs for psychiatric disorders, resulting in abnormalities in the dopamin
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