AP 2 final.docx - 1 Neuroglia CNS Astrocytes most abundant...

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1. Neuroglia CNS: Astrocytes- most abundant neuroglia in CNS - Radiating processes that cling to neurons, synaptic endings, and capillaries - Support/brace neurons & anchor them to their nutrient supply - Role in exchanges between capillaries and neurons - Control chemical environment around neurons & calcium concentration - Recycle neurotransmitters Microglial cells- defensive cells in the CNS - Thorny processes touch/monitor neurons - Monitor healthy then migrate toward injured neurons - Can transform into a type of macrophage to eat microorganisms & neuronal debris - Important because immune cells aren’t very permeable through blood brain barrier (tight junctions) Ependymal cells- line cerebrospinal fluid-filled cavities - May be ciliated - Line central cavities of brain and spinal cord - Form permeable barrier between CSF in cavities & tissue fluid bathing CNS cells Oligodendrocytes- processes form myelin sheaths around CNS nerve fibers - What gets damaged in multiple sclerosis PNS: Satellite cells- surround cell bodies in sensory ganglia - Provide support and nutrition to the neuron cell bodies - Protect neurons from heavy metal poisons by absorbing metals and reducing their access to neuron cell bodies Schwann cells- surround all peripheral nerve fibers & form myelin sheaths in thicker nerve fibers - Vital to regeneration of damaged peripheral nerve fibers 2. Autonomic nervous system - Motor function - Conducts impulses from CNS to cardiac muscles, smooth muscles, and glands - Visceral motor (involuntary) 3. Integrative function of the nervous system - Processing and interpretation of sensory input & decides what actions are required - Occurs in the brain or spinal cord
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Brings sensory information together Adds to memory Produces thoughts Makes decision 4. Periods of depolarization Absolute refractory - Volted-gated Na+ channels open, neuron can’t respond to another stimulus - Ensures each AP is an all-or-none event - Enforces one-way transmission of nerve impulses Relative refractory - Follows absolute refractory period - Most Na+ channels have returned to resting stat - Some K+ channels still open - Repolarization is occurring - Threshold for AP generation is elevated -
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