1. Chapter 12 Neural Tissue 5/9/2018 6:13 PM
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2. 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

3. 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

4. 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

6. 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

8. 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

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

10. 12-4: Transmembrane Potential
Resting Potential
↑Na+ & Cl- in extracellular fluid (ECF), ↑ K+ in intracellular fluid (ICF)
Neuron interior negative compared to outside

11. 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!!

12. 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

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

14. 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 (pg ) for steps of action potential
Saltatory propagation—impulse jumps from node to node, impulse travels quicker

15. 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

16. 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

17. 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