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Nervous System Part 2. Neurons. Function of neurons. Neurons are part of the peripheral nervous system . They carry impulses (signals, messages) through the nervous system. 2. Types of neurons. Sensory neurons (body to brain) Interneurons (within brain & spinal cord)
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Nervous System Part 2 Neurons
Function of neurons • Neurons are part of the peripheral nervous system. • They carry impulses (signals, messages) through the nervous system
2. Types of neurons • Sensory neurons (body to brain) • Interneurons (within brain & spinal cord) • Motor neurons (brain to body)
3. Anatomy of a neuron Direction of Signal
4. Neuron Structure • Dendrites- receive impulse and send it to cell body • Cell body- contains nucleus, ribosomes, etc. • Axon- carries impulse away from cell body to next neuron, muscle, or organ. 1. Myelin- fatty coating insulates axon
5. Connections between neurons • Axons and dendrites do not touch • Synapse/synaptic cleft- space between • Neurotransmitters- chemicals that go from axon to dendrite across synapse.
Pneumonic Device: D C A S N
Pneumonic Device: D ead C ats A lways S mell N asty D racula C an A lways S uck N ecks D rugs C an’t A lways S atisfy N ikki
HW: Write a story about someone who takes in sensory information, makes a decision, and responds. Be sure to include all 3 kinds of neurons as well as the parts of the brain that are involved. Include: brain stem interneuron cerebrum sensory neuron cerebellum motor neuron
6. Neuron at rest • Inside is negative, outside is positive. • Na+/K+ pump moves ions across the membrane, keeping Na+ out • It is “polarized.” + + + + + + + + + + - - - - - - - -- - - - - - - - - -
7. Relaying a signal within a neuron- nerve impulse • Neuron at rest • When impulse is received, Na+ channels open. • Na+ flows into cell making it more positive inside and negative outside (depolarized).
This passes like a wave through the cell. • Na+ channels close, extra Na+ are pumped out, repolarizing the cell. • The cell returns to resting state.
Polarized (resting) Depolarized (activated) Repolarized (resting)
Homework: Do p. 900:1-4