Nervous System - Part 1 PDF

Nervous System- Part 1 Basic structure & function BI 121 Unit 5 Nervous System – 2 parts Nervous system: communication and control system CNS (central nervous system)- brain and spinal cord. PNS (peripheral nervous system)- peripheral nerves that connect CNS to othe...

Nervous System- Part 1 Basic structure & function BI 121 Unit 5 Nervous System – 2 parts Nervous system: communication and control system CNS (central nervous system)- brain and spinal cord. PNS (peripheral nervous system)- peripheral nerves that connect CNS to other body parts. Functions of CNS and PNS Sensory = collect information detects stimuli in/out of body via sensory receptors in PNS. Integration = process and evaluate information sensory impulses/signals taken to CNS; creates sensations, memories, thoughts. Motor = respond to information impulses from the CNS brought to PNS to cause a response with effectors: muscle contraction, gland secretion. Neuron = aka nerve cell Vary in shape and size, but all generally have: 1. Soma 2. Neurofibrils 3. Nissl bodies 4. Dendrites 5. Axon hillock 6. Axons 7. Axon Terminals and Synaptic Knobs Neuron structure (1) 2. Neurofibrils- 1. Soma Bundles of neurofilaments (proteins) extending into axon Cell body. & dendrites. Large nucleus with Function – provides tensile prominent nucleolus. strength, cytoskeleton Neuron structure (2) 3. Nissl bodies- Darkly staining membranous packets containing clusters of Rough ER & free ribosomes. These give gray matter its gray color. 4. Dendrites- Variable # of branches from soma. Function – Receive input and transfer it to cell body LOTS of surface area to receive info! Neuron structure (3) 5. Axon Hillock – Slightly elevated region off soma. Gives rise to axon. Function – conducts messages from soma to axon 6. Axons- One long, cylindrical process off soma. Function –conduct action potentials and then release neurotransmitter at synaptic knobs Quick check - matching 1. Soma a. Connects axon to soma 2. Neurofibrils b. Finger-like extensions off soma 3. Nissl bodies c. These make gray matter look gray 4. Dendrites d. Main body of the neuron 5. Axon hillock e. Long branch extending away from 6. Axon soma f. Give the neuron strength  Axons - Myelinated Fatty, lipid-rich sheaths around axons. Function – insulates axon Formed by: Schwann cells (PNS)- aka. Neurolemmocyte. Elongated, flat cells that ensheath PNS axons with myelin Allows for faster action potential propagation Oligodendrocytes (CNS)- Large cells with slender extensions Extensions wrap around axons of neurons forming myelin sheath Clinical Application – Multiple Sclerosis Autoimmune disease - Immune system attacks myelin in CNS. Scleroses = plaques form in myelin. Signs/Symptoms = vision loss, speech/balance/motor coordination affected. MS vs Lyme disease? Axons - Unmyelinated No myelin sheath; axons not insulated from ECF. Although in PNS, they may still be protected by a Schwann cell, but not wrapped by one (see neurilemma). Axons - Neurilemma Every axon in PNS is shielded from ECF by Schwann cells whether myelinated or not. Portions of Schwann cell with nucleus and most of the cytoplasm comprise the neurilemma sheath. 1 schwann cell can wrap around ~15 axons Axons – Nodes of Ranvier Gaps in myelin sheath; gaps between Schwann cells/Oligodendrocy tes. Helps speed up nerve signal transmission Axon Terminals & Synaptic Knobs Many fine extensions off the end of an axon. Each extension ends in a synaptic knob, close to the receptive end of another cell (separated only by a space/cleft).