Nervous tissue 2
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The document discusses nerve impulses and nerve fiber types. It explains that nerve fibers maintain a resting potential of around -70 mV due to ion transport mechanisms. When an impulse is initiated, this potential rapidly changes and then repolarizes. Impulse frequency is limited by the sodium-potassium pump recovery time. Impulse speed is affected by factors like temperature, fiber diameter, and myelination. There are three main nerve fiber types - type A fibers are large and myelinated with fast conduction, type B are medium and myelinated, and type C are small and unmyelinated with slow conduction.
Nervous tissue 2
- 1. Nervous system 2 Nerve resting potential and impulse action potentials Nerve fibers types and speed of conduction
- 3. Resting potential Potential for a nerve impulse due to polarized state Relatively negative within nerve -70 mV inside nerve cells due to 3 Na+ ions transported out of cell for every 2 K+ ions transported in to cell
- 11. Nerve impulse frequency Limited by rate of Na+ // K+ repolarization Refractory period neuron cannot generate a new impulse Absolute refractory, 2nd impulse cannot be initiated Relative refractory, 2nd impulse can be initiated with abnormally strong stimulus
- 12. Speed of nerve impulse conduction Affected by: Temperature Heat increases speed of conduction Cold decreases (or stop) speed of conduction Diameter of fiber; The larger the fiber, the faster the speed of impulse Myelination Myelinated nerves much faster speed of conduction
- 15. Nerve fiber types Type A Large diameter, myelinated, short refractory and fast conduction (130 m/sec). Motor (efferent) neurons, touch pressure, temp and proprioception (afferent) receptors
- 16. Nerve fiber types Type B Medium diameter, myelinated, conduction speed not as fast as Type A Smooth muscle and glandular (efferent) innervation and skin and visceral (afferent) receptor
- 17. Nerve fiber types Type C Small diameter, not myelinated. Longer refractory period Slower speed of conduction Sensory (afferent) from skin and ANS efferent to cardiac and smooth muscle