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Nervous System Notes Part 4

Nervous System Notes Part 4. SOME MORE INTERESTING NERVOUS SYSTEM FACTS. Neurons do not under go mitosis. Neurons are the largest cells in the human body. They can be up to 3 feet long.

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Nervous System Notes Part 4

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  1. Nervous System Notes Part 4

  2. SOME MORE INTERESTING NERVOUS SYSTEM FACTS Neurons do not under go mitosis. Neurons are the largest cells in the human body. They can be up to 3 feet long. Exercise is not just for muscles, studies show that regular exercise improves nervous system functions, especially brain functions.

  3. PROPAGATION OF NERVE IMPULSES • conducting a nerve impulse from one place to another • Resting Membrane Potential • the inactive nerve cell is called POLARIZED • the outside of the cell membrane is positively charged and the inside is negatively charged • there is a higher concentration of sodium ions (Na+) outside the cell membrane and a higher concentration of potassium ions (K+) inside

  4. sodium/potassium exchange pump • sodium can’t get through the cell membrane until a nerve is stimulated • cell membrane more permeable to K+ than Na+ • as K+ “leaks” out of cell it must be pumped back in for the cell to remain polarized (Resting Membrane Potential)

  5. Depolarization and Action Potential • Depolarization • as a stimulus is applied, a “sodium gate” is opened allowing Na+ ions to rush in • this makes the inside of the cell more positive • this is DEPOLARIZATION and creates an ACTION POTENTIAL or nerve impulse

  6. Repolarization • almost immediately the cell will return to its resting potential • the sodium – potassium pump will pump OUT Na+ and pump IN K+ • this REPOLARIZATION restores the membrane to its original electrical conditions (positive outside & negative inside) • until repolarization, no new impulse can be transmitted

  7. The Synapse • a “gap” between neurons • allows action potential to move from one neuron to the next neuron, muscle cell, organ, etc. • How does it work? • neurotransmitters (chemicals) are released after each action potential from the end of the axon

  8. neurotransmitter molecules diffuse across the synaptic gap and bind to receptors on dendrites of the next neuron • this triggers a response or action potential in the next neuron • neurotransmitters are quickly broken down or transported back to the axon for the next impulse

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