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6-neurophysiology - Lecture Neurophysiology I Overview of...

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Lecture: Neurophysiology I. Overview of Nervous System Organization A. Central Nervous System (CNS) - brain and spinal cord B. Peripheral Nervous System (PNS) – spinal/cranial nerves 1. Sensory (Afferent) Division - TO the CNS a. somatic afferents - from skin, muscle, joints b. visceral afferents - from membranes & organs 2. Motor (Efferent) Division - FROM the CNS a. Somatic Nervous System (Voluntary) - to skeletal muscles b. Autonomic Nervous System (Involuntary) - to organs & glands i. Sympathetic Division ii. Parasympathetic Division II. The Structure of a Neuron (Nerve Cell) A. neuron - special cells of nervous system that carry messages in the form of electrical Impulses B. Supporting Cells of Neurons 1. Support Cells of the CNS (Glial Cells) a. astrocytes - regulate environment around neurons and selective transport from capillaries b. microglia -eat infectious microbes of CNS c. ependymal cells - line cavities of brain and spinal cord, flushing cerebrospinal fluid (CFS) d. oligodendrocytes - form “myelin sheaths” around axons of CNS; increase speed of impulses 2. Support Cells of the PNS a. Schwann cells form "myelin sheaths" around axons; also assist in regeneration of axon b. satellite cells - control chemical environment C. Special Characteristics of Neurons 1. amitotic - "not mitotic"; they cannot reproduce or regenerate after certain point in life 2. longevity - neurons can survive entire lifetime
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3. high metabolic rate - require OXYGEN and GLUCOSE at all times D. Neuron Cell Body (soma; perikaryon) 1. major part from which the processes (axons and dendrites) project; 5-140 micron diameter 2. single large spherical nucleus with nucleolus 3. Nissl Bodies - Rough Endoplasmic Reticulum (rER); make proteins and plasma membrane 4. nucleus - a collection of cell bodies in the CNS 5. ganglion - a collection of cell bodies in the PNS E. Typical Neuron Processes (Dendrites & Axon) 1. dendrites - branching, rootlike extensions off the cell body receptive/input component of the neuron; incoming signals are forwarded to the cell body signals of dendrites are NOT all-or-none action potentials, but are graded potentials that result from summation of inputs 2. axon - extension that carries an all-or-nothing action potential from the cell body to the target; conducting component of the neuron connecting it to other cells or neurons
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