Chapter 12 Neural Tissue 5/9/2018 6:13 PM © 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

12-1: Nervous System Divisions Neurons vs. neuroglia Anatomical Divisions of Nervous System Central nervous system (CNS) Spinal cord & brain Integrate, process, coordinate data Peripheral nervous system (PNS) Neural tissue outside CNS Delivers sensory info, carries motor commands Nerves vs. cranial nerves vs. spinal nerves

Functional Divisions of PNS Afferent division Brings sensory info to CNS from receptors Efferent division Carries motor commands from CNS to target organs (effectors) Somatic nervous system vs. autonomic nervous system

12-2: Neurons Structure of Neurons Cell body Dendrites vs. axons Perikaryon contains organelles & neurotransmitters Dendrites vs. axons Axon: axon hillock  telodendria  synaptic terminals Synapse Presynaptic cell  synaptic cleft  postsynaptic cell Presynaptic cell releases neurotransmitters

Classification of Neurons Anaxonic vs. bipolar vs. unipolar vs. multipolar neurons Sensory vs. motor vs. interneurons Sensory = afferent, motor = efferent Intero-, extero- & proprioceptors Interneurons most abundant

12-3: CNS & PNS Neuroglia Neuroglia of CNS Ependymal cells Astrocytes Line passages for cerebrospinal fluid Astrocytes Maintain blood-brain barrier Oligodendrocytes From myelin sheaths around axon Microglia Remove cell debris

Neuroglia of PNS Satellite cells Schwann cells Surround cell bodies Form sheath around axons

12-4: Transmembrane Potential Resting Potential ↑Na+ & Cl- in extracellular fluid (ECF), ↑ K+ in intracellular fluid (ICF) Neuron interior negative compared to outside

Electrochemical gradient for K+ ICF conc. ↑, ECF conc. ↓ (chemical gradient) Electrical gradient opposes K+ movement; small amounts of K+ move into ECF Electrochemical gradient for Na+ ICF conc. ↓, ECF conc. ↑ Electrical gradient draws Na+ into cell Read Table 12-1!!

At resting potential, most gated channels closed Na+ & K+ channels Passive channels always open Chemically gated channels need specific chemicals Voltage-gated channels respond to changes in transmembrane potential At resting potential, most gated channels closed

Graded Potentials Na+ enters cell, transmembrane potential becomes more positive (depolarization) More open channels = more Na+ = more depolarization Repolarization vs. hyperpolarization

12-5: Action Potential Action Potential (Nerve Impulse) All-or-none principle Action potential begins between -60 & -55 mV (threshold) Stimulus triggers action potential, or not at all if doesn’t meet threshold Examine Figure 12-14 (pg 396-397) for steps of action potential Saltatory propagation—impulse jumps from node to node, impulse travels quicker

12-6: Axon Diameter Larger axon diameter = lower resistance Type A fibers—largest myelinated, fastest impulse speed Type B fibers—smaller myelinated, medium impulse speed Type C fibers—smallest & unmyelinated, slowest impulse speed

12-7: Synapses Electrical vs. chemical synapses Most synapses are chemical Excitatory neurotransmitters vs. inhibitory neurotransmitters Cholinergic synapses release ACh ACh releases into synaptic cleft ACh causes depolarization of postsynaptic membrane

12-9: Information Processing Postsynaptic Potentials Excitatory postsynaptic potential (EPSP) Depolarization of postsynaptic membrane Inhibitory postsynaptic potential (IPSP) Hyperpolarization of postsynaptic membrane Temporal vs. spatial summation EPSPs & IPSPs balance polarization