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Nervous System Part 2

Nervous System Part 2. Reflex Arc Nerve Impulse and Synapse Spinal Cord. Reflex Arc. reflex arcs are specialized neuron pathways conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland). Reflex Arc.

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Nervous System Part 2

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  1. Nervous System Part 2 Reflex Arc Nerve Impulse and Synapse Spinal Cord

  2. Reflex Arc • reflex arcs are specialized neuron pathways • conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland)

  3. Reflex Arc • Simplest reflex arcs are two-neuron arcs--consist of sensory neurons synapsing in the spinal cord with motor neurons

  4. Three-neuron arcs consists of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons Reflex Arc

  5. Nerve Impulse and Synapse • The membrane of each resting neuron has a slight negative charge.

  6. Nerve Impulse and Synapse • A stimulus (change in environment--pressure, temp) triggers the opening of Na+ channels in the plasma membrane of the sensory neuron.

  7. Nerve Impulse and Synapse • Influx of sodium ions on the dendrites positively charges membrane and marks the beginning of a nerve impulse (depolarization). • View animation http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

  8. Nerve Impulse and Synapse • When the impulse (action potential) encounters the insulating myelin, it jumps around it. This is called saltatory conduction and is faster than nonmyelinated travel. • View animationhttp://www.youtube.com/watch?v=pnB_Hc-Qfs0

  9. Nerve Impulse and Synapse • When the impulse reaches the axon terminals, neurotransmitters are released (example: acetylcholine). • Neurotranmitters bind to specific receptor molecules on the next neuron (thereby stimulating an impulse conduction). • View animation http://www.youtube.com/watch?v=90cj4NX87Yk

  10. Coverings and fluid spaces of the spinal cord: Coverings Vertebrae Spinal meninges--the dura mater (outer), the pia mater (inner), and the arachnoid (middle) Spinal Cord • pia: blood vessels • arachnoid: fibrous “spider web” • dura: tough CT

  11. Spaces filled with cerebrospinal fluid--subarachnoid space of meninges (between pia and arachnoid) and subdural space (between arachnoid and dura) Spinal Cord

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