chapter 12 intro to the nervous system. the nervous system the most complex system coordinates...

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Chapter 12 Intro to the Nervous System

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Page 1: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Chapter 12

Intro to the Nervous System

Page 2: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

The Nervous System• The most complex system• Coordinates activities of all body systems• Two divisions:

The Central Nervous System (CNS) = brain & spinal cordThe Peripheral Nervous System (PNS) = all neural tissue not included in CNS

Page 3: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Histology of Nervous Tissue

2 cell types:• Neurons

transmit nerve impulses

• Neuroglia:support neurons

Page 4: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Neurons• Very long lived• Amitotic

mature neurons lose the ability to divide

• High metabolic rateneed a large supply of O2 and C6H12O6

Page 5: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Neuron Structure• Cell Body = Soma

contains the usual cellular organelles

Page 6: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

• Dendritesshort, highly branched extensions from the somatransfer information to the cell body

Page 7: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

• Axontransmits information away from the somaends in many branches (axon terminals)

Page 8: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

• Action potentials (nerve impulses) start at the axon hillock & travel along the axon to the axon terminal

• Arrival of action potential causes the release of neurotransmitters across a synapse to the dentrites of the next neuron

• Neurotransmitters can excite or inhibit the next neuron

Page 9: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

• Myelin sheath = lipid-rich covering on axons, myelinated fibers conduct impulses 10-150x faster than unmyelinated fiber

Nodes of Ranvier = gaps between myelin; impulses jump from node to node

Page 10: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Functions of the Nervous System• Sensory Input

Sensory neurons deliver info (stimulus) from sensory receptors to the CNS

• IntegrationInterneurons in the CNS process & interpret sensory stimulus

• Motor Output Motor neurons cause response by carrying info from

the CNS to various effector organs

Page 11: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central
Page 12: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

Sensory Neuron

Interneuron

Motor Neuron

Muscle Contracts

Synapse Synapse

Synapse

Page 13: Chapter 12 Intro to the Nervous System. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central

NERVES

Nerves = bundles of neurons• Can contain all motor neurons, all sensory

neurons, or be mixed