Neurons

Neuron Structure 1. Insert an image of the basic neuron structure that includes cell body, dendrites, and axon. p. 249 Myelin Sheath 2. Insert an image of a neuron with a myelin sheath. 3. What is the myelin sheath made of? Where is it located? What is its function? p. 249 Axons are proteced by the myelin sheath. Myelin sheath is made of shwann cells which contain myelin the myelin sheath devlops when these cells wrap themselves around an axon many times located on a neuron 4. What is the difference between the "gray matter" and "white matter" in the brain? p.249 White matter contains myelinated axons whereas gray matter does not 5. What causes multiple sclerosis? P.249 An attack on the myelin by the body's immune system

Nerve Impulse p.250-252 5. Where are the sodium and potassium ions when the axon is at rest? What is the charge inside the axon? the concentration of sodium ions is greater outside the axon than inside and the concentration of potassium ions is greater inside the axon than outisde. charge is negative in axon 6. Which ions can cross the membrane and enter the axon? potassium or sodium? Potassium 7. What happens to the charge inside the axon when sodium gates open? Where does sodium go? The charge goes from negative to positive the sodium sodium goes into in the axon 8. What happens to the charge inside the axon when the potassium gates open? Where does potassium go? changes from positive to negative the postassium goes outside the axon 9. Look at the graph on page 251. What do you think depolarization means? What do you think repolarization means? depolarization is when charge inside the axon changes from negative to positive

repolarization is when the inside of the axon resumes a negative charge 10. What causes depolarization of the axon? Sodium going into the axon 11. What causes repolarization of the axon? potassium leaving the axon 12. What is an action potential? Action potential is moving voltage across adjacent axons membranes 13. How does the sodium potassium pump reestablish the resting potential during the refractory period? the sodium gates are inable to open. This ensures that the action potential cannot move backward and instead always moves down an axon toward its branches 14. What is a synapse? a region between axon branches and dendrite or the cell body of another neuron 15. What is a synaptic cleft? a small gap that separates the sending neuron to the receiving neuron. 16. What is a neurotransmitter? stored in synaptic vesicles and transmission across a synapase is carried out by molecules

17. Since neuron's don't touch, how is the signal from one neuron transmitted to another neuron? Nerve impulses traveling along an axon reach an axon terminal calcium ions enter the terminal and they stimulate synaptic vesicles to merge with the sending membrane neurotransmitter molecules are released into the synaptic cleft and they diffuse across the cleft of the recieving membrane 18. Insert an image showing an action potential.

19. Insert an image showing a synapse.