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Neuron Description and Nerve Impulses

Neuron Description and Nerve Impulses. Neuron: Cells of the nervous system specialized to transmit messages throughout the body.

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Neuron Description and Nerve Impulses

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  1. Neuron Description and Nerve Impulses • Neuron: Cells of the nervous system specialized to transmit messages throughout the body. • Neuron Functions: (1) Irritability- The ability to respond to a stimulus and convert it into a nerve impulse. (2) Conductivity- The ability to transmit the impulse to other neurons, muscles, or glands.

  2. Nerve Impulse & Action Potential. Nerve Impulse- A self-propagating wave of depolarization, also called an “action potential”. Action Potential- An electrical event occurring when a stimulus of sufficient intensity us applied to a neuron or muscle cell, allowing sodium ions to move into the cell and reverse the polarity.

  3. Action Potential, Initiation, and Generation: Part 1 The neuron begins in a polarized and inactive state, with fewer positive ions on the inner face of the plasma membrane then the outer surface. Aslong as the inside remains more negative then the outside the neuron will remain inactive. The two major ions in the neuron is Potassium (K+) and Sodium (Na+).

  4. Action Potential, Initiation, and Generation: Part 2 • Many stimuli excite neurons to become active and to cause a shift in the location of potassium and sodium ions. Sending the neuron into a depolarized or active state. This is the beginning of the nerve impulse. The neuron always reacts in the same way (despite stimuli) the permeability properties if the cells plasma membrane changes. • The sodium channels in the plasma membrane of the neuron. The higher concentration of sodium on the outside of the plasma membrane diffuses quickly into the neuron. The inside of a neuron is now more positive while the outside becomes less positive, this is called “graded potential”.

  5. Action Potential: Nerve Impulse • The nerve impulse is an all or nothing response, like firing a gun. Unlike the graded potential the impulse travels along the whole axon, or not at all. It will never stop part way along the axon nor will it die out along with distance traveled. Which is different than the graded response, that may travel a certain distance then stop.

  6. Action Potential: Nerve Impulse Part 2 • Following the nerve impulse the cell repolarizes by activating the sodium potassium pump, using ATP to pump excess sodium ions out of the cell and bring potassium ions back in. Once this begins it will spread across the neuronal membrane. Until the neuron repolarizes another impulse cannot occur. • This series of events may occur faster among cells with a myelin sheets because it can conduct impulses much faster, literally jumping from neuron to neuron.

  7. Credits: Information from Essentials of Human Anatomy & Physiology Information collection: Ricky Pais Power point design: Joseph Watson, Channing Cox, Ricky Pais Power point presentation: Channing Cox, Ricky Pais

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