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Nerves

Nerves. Chapter 6 Objectives: 6.5.1-6.5.6. 6.5.1 State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. The nervous system consists of central nervous system

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Nerves

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  1. Nerves Chapter 6 Objectives: 6.5.1-6.5.6

  2. 6.5.1 State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. • The nervous system consists of • central nervous system • (CNS--the brain and spinal cord) • peripheral nerves (communicate motor/sensory signals between the CNS and body) • composed of special cells called neurons that can carry electrical impulses rapidly

  3. List the three major functions of the nervous system. • Sensory input: signal from sensory receptors (eyes) to centers of integration (brain/spinal cord) • Integration: senses are interpreted/body responds • Motor output: movement of the body in response to environmental simulation

  4. 6.5.2 Draw and label the structure of a motor neuron – to be done in class • Dendrites:signals going TOWARDS ‘cell body’ • Cell body:contains nucleus and organelles • Axon:signals AWAY from ‘cell body’ • Myelin sheath:insulating layer that helps the signal travel more efficiently • Nodes of Ranvier:allows for ‘jumps’ of signal transduction (because this is where the ions are allowed to flow across the cell membrane) • Motor end plates:connection between synaptic terminal and the muscle (motor=muscle)

  5. 6.5.3 State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.

  6. 6.5.4 Define resting potential and action potential • Resting potential: potential difference (charge differential) across the membrane Resting potential video • HELPED BY • Gated ion channels: control the flux of ions across the membrane • Depolarization: increase in positive ions, decreasing the membrane potential • Repolarization: active transport pumps ions to their resting potential positions • Refractory Period: neuron is insensitive after it has fired, limits rate the neuron can be stimulated

  7. 6.5.4 Define resting potential and action potential • Action potential: • The electrical potential across the neuron membrane is reversed (shoots to positive), then is restored (back to negative) as the signal passes through. • Action potential is “yes or no”—no differences in strength, it either meets or does not meet Action potential video

  8. 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron. • Non-myelinated: Axon that does not have the myelinated sheath. (ex: sensory neurons) • Ions: Sodium-Potassium pump maintains the membrane potential. 3 Na+ are pumped out, 2 K+ are pumped in (active transport). • The influx/outflux of these ions is what results in the action potential. 1)Na+ channels open and Na+ flows into the cell 2)Depolarization—Na+ rapidly flows in 3)Most positive membrane potential 4)Repolarization—K+ channels open and K+ flows out of the cell 5) Refractory period—Na+ inactivated and neuron can’t respond

  9. 6.5.6 Explain the principles of synaptic transmission. • Synapse: communication connection (open space) between a neuron and a second cell (neuron, muscle cell, gland). • Synaptic transmission: signal through space between neuron and other cell by chemicals • Neuromuscular junction: Connection between neuron and muscle cell Synaptic transmission video

  10. 6.5.6 Explain the principles of synaptic transmission. • Calcium ions (Ca2+) diffuse into the terminal buttons • Vesicles containing neurotransmitter fuse with the plasma membrane and release neurotransmitter • Neurotransmitter diffuses across the synaptic gap from the presynaptic neuron to the postsynaptic neuron • Neurotransmitter binds with a receptor protein on the postsynaptic neuron membrane • This binding results in an ion channel opening and sodium ions diffusing in through this channel • This initiates the action potential to begin moving down the postsynaptic neuron because it is depolarized • Neurotransmitter is degraded by specific enzymes and is released from the receptor protein • The ion channel closes to sodium channels • Neurotransmitter fragments diffuse back across the synaptic gap to be reassembled in the terminal buttons of the presynaptic neuron

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