1. Action Potential

2. Action potential begins Sudden change of normal resting negative membrane potential To positive potential Ends by rapid change back to the negative potential. A.P moves along the whole nerve fiber.

5. Stages Of Action Potential

6. Resting Stage. It is the resting membrane potential before the action potential begins. The membrane is "polarized" with -90 millivolts negative membrane potential. Depolarization Stage. The membrane suddenly becomes very permeable to sodium ions.

7. It allows tremendous numbers of positively charged sodium ions to diffuse to the interior of the axon. Inflow of positive Na-ion immediately neutralizes -90 millivolts memb. Potential. Leading to rapidly rising potential in the positive direction.

9. Repolarization Stage Within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions. The sodium channels begin to close The potassium channels open more than normal.

10. Lead to rapid diffusion of potassium ions to the exterior Re-establishes the normal negative resting membrane potential. Which is called repolarization of the membrane.

13. Absolute Refractory Period During the time interval between the opening of the Na + channel activation gate and the opening of the inactivation gate, a Na + channel CANNOT be stimulated. – This is the ABSOLUTE REFRACTORY PERIOD. – A Na + channel cannot be involved in another AP until the inactivation gate has been reset. – This being said, can you determine why an AP is said to be unidirectional.

15. Structural Classification of Neurons Neurons may be: Multipolar, Bipolar or Unipolar Determined by the number of processes attached to the cell body

16. Neurons Most (99%) neurons in the body are multipolar. Bipolar neurons are rare and occur in special sense organs of ear, nose and eye. Unipolar neurons begin as bipolar but processes fuse into one. They are primarily sensory neurons. ex. dorsal root ganglion

17. Neuroglia cells Found in CNS and PNS Perform a supporting function for neurons CNS PNS – Oligodendrogliocytes Schwann cells – Astrocytes Satellite cells – Ependymal cells – Microglia

18. Neuroglia cells

19. Oligodendrogliocytes -CNS Form myelin sheath in CNS Fewer branches than astrocytes

20. Myelin Insulating layer around a nerve Formed by oligodendrocytes in CNS and Schwann cells in PNS Composed of a lipoprotein with phospholipids, glycolipids and cholesterol. Myelination is the process of myelin formation Myelin allows nerve conduction to be 150 x faster than nonmyelinated nerves. This occcurs by “Saltatory conduction” and the impulse jumps from Node to Node.

21. Microglia - CNS Thorny bushes in appearance and the smallest glia Phagocytic function in CNS Originate from monocytes

22. Astrocytes - CNS Star shaped Most numerous Blood brain barrier

23. Ependymal cells - CNS Epithelial cells that line ventricles and central cavities of brain and spinal cord-secrete CSF Ciliated to help circulate CSF

24. Schwann cells- PNS Form myelin sheath around peripheral axons Look like jelly roll with neurolemma cover Node of Ranvier separates each Schwann cell

26. Structure of a Neuron Dendrites: Carry nerve impulses toward cell body. Receive stimuli from synapses or sensory receptors. Cell Body: Contains nucleus and nissl bodies, a form of rough endoplasmic reticulum. Axon: Carry nerve Impulses away from the cell bodies. Axons interact with muscle, glands, or other neurons.