1. Chapter 12 Intro to the Nervous System

2. The Nervous System The most complex system Coordinates activities of all body systems Two divisions: The Central Nervous System (CNS) = brain & spinal cord The Peripheral Nervous System (PNS) = all neural tissue not included in CNS

3. Histology of Nervous Tissue 2 cell types: Neurons transmit nerve impulses Neuroglia: support neurons

4. Neurons Very long lived Amitotic mature neurons lose the ability to divide High metabolic rate need a large supply of O 2 and C 6 H 12 O 6

5. Neuron Structure Cell Body = Soma contains the usual cellular organelles

6. Dendrites short, highly branched extensions from the soma transfer information to the cell body

7. Axon transmits information away from the soma ends in many branches (axon terminals)

8. 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

9. 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

10. Functions of the Nervous System Sensory Input Sensory neurons deliver info (stimulus) from sensory receptors to the CNS Integration Interneurons in the CNS process & interpret sensory stimulus Motor Output Motor neurons cause response by carrying info from the CNS to various effector organs

12. Sensory Neuron Interneuron Motor Neuron Muscle Contracts Synapse

13. NERVES Nerves = bundles of neurons Can contain all motor neurons, all sensory neurons, or be mixed