Nervous System

Topics: Neuron, Nervous system, Action potential Pages: 4 (604 words) Published: January 17, 2015
Nervous System

Functions of the Nervous System
1. Detect changes and feel sensations
2. Initiate responses to changes
3. Organize and store information

1. Central Nervous System – brain and spinal cord
2. Peripheral Nervous System – cranial nerves and spinal nerves (relays info to/from the CNS) - Autonomic Nervous System

Nerve Tissue – neurons (nerve fibers) and specialized cells (Schwann, neuroglia) 1. Neuron cell body contains the nucleus; cell bodies are in the CNS or trunk; protected by bone 2. Axon carries impulses away from the cell body; dendrites carry impulses toward it 3. Schwann cells in PNS:

- Layers of cell membrane form the myelin sheath to electrically insulate neurons - nodes of Ranvier: spaces between adjacent Schwann cells
- Nuclei & cytoplasm of Schwann cells form the neurolemma – essential for regeneration of damaged axons or dentrites

4. Oligodendrocytes: In CNS, form myelin sheaths
- microglia phagocytize pathogens and damaged cells
- astrocytes contribute to blood brain barrier and regulate localized blood flow

5. Synapse: space between axon of one neuron and dendrites or cell body of next neuron - Neurotransmitter carries the impulse across a synapse and is then destroyed by a chemical inactivator; synapses make impulses one way

Types of Neurons – nerve fibers

1. Sensory – carry impulses from receptors to the CNS
- Somatic – from skin, skeletal muscles, joints
- Visceral – from internal organs

2. Motor – carry impulses from CNS to effectors
- Somatic – to skeletal muscle
- Visceral – to smooth muscle, cardiac muscle, glands

Nerves and Nerve Tracts

1. Sensory – made only of sensory neurons

2. Motor – made only of motor neurons

3. Mixed – made of motor and sensory

4. Nerve tract – white matter; a nerve in the CNS

The Nerve Impulse

1. Polarization – neuron membrane has a + charge outside and – charge inside 2....
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