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Anatomy unit 2 nervous system nerve impulse notes
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Anatomy unit 2 nervous system nerve impulse notes

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  • 1. ANATOMY Unit 2 Notes: Nerve Impulses
  • 2. (1) What is a Nerve Impulse? • Chain reaction of chemical events, allowing your neurons to send “messages”. • Synonymous Terms: – Neuron Message – Nervous System Response – Depolarization & Repolarization
  • 3. (2) The Basic Steps 1. Neurotransmitter binds to neuron. 2. Depolarization. 3. Repolarization. 4. Repeat #2 and 3 until reaching axon terminal. 5. Release of another neurotransmitter from axon terminal. 6. Regain resting potential.
  • 4. Neurotransmitter Binds Depolarization & Repolarization Down The Axon Release a neurotransmitter + Stimulate next move
  • 5. (3) Resting Potential • “Resting Potential”: The natural state of a neuron when it’s not doing anything. • At Rest There is… – Potassium (K+) on the inside of axon. – Sodium (Na+) on the outside of axon. – More cations on the outside than inside. *This means that the outside is naturally more positive than the inside (making the axon polar).
  • 6. (4) Depolarization • De = without Polar = uneven charge • Depolarization: To remove the imbalance of charge. • What Happens? – Sodium pumps open. – Sodium ions fly thru channels into axon. – Temporarily increases positive charge inside axon, removing polarization.
  • 7. (5) Repolarization • Re = repeat Polar = uneven charge • Repolarization: To regain the charge imbalance. • What Happens? – Potassium pumps open. – Potassium ions fly thru channels out of axon. – Temporarily increases positive charge back on the outside of the axon, regaining polarization.
  • 8. (6) Reaching the Terminals • A neurotransmitter will be released. • This neurotransmitter will: – Bind to another neuron or organ. – Make something else happen (muscle contraction or another nerve impulse).
  • 9. (7) Regaining Resting Potential • Even though the axon is polarized at the end, the ions are on the wrong sides of the axon. • Must actively transport ions: – Sodium must go back out. – Potassium must go back in. • Requires ATP.
  • 10. …Let’s Review All That Again…
  • 11. (8) Myelin Sheath • Where Is It? – Covers the outside of the axon. – Wraps around Na/K pumps. • What Is Its Purpose? – Block some of the Na/K pumps. – Increases the speed of nerve impulse. • How Does It Work? – Just like main-roads versus the freeway. – Main Roads = Axon without myelin sheath. – Freeway = Axon with myelin sheath.