neurons+WG

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 The Myelin sheath is made of a type of neuroglia called Schwann cells. It is located in the PNS, and its function is to protect, and that develops when the cells wrap around an axon many times. 4. What is the difference between the "gray matter" and "white matter" in the brain? p.249 Gray matter is gray because its lacking what the what matter has, which are myelinated axons. 5. What causes multiple sclerosis? P.249 It is caused by the loss of myelin from the axons. It is also caused by a defect in one of the genes involved with the growth and maintenance of myelin.

Nerve Impulse p.250-252 5. Where are the sodium and potassium ions when the axon is at rest? When the axons are at rest, the sodium and potassium actively transport Na+ out and K+ into the axon. What is the charge inside the axon? The charge in the axon is negative. 6. Which ions can cross the membrane and enter the axon? Potassium or sodium? Sodium. 7. What happens to the charge inside the axon when sodium gates open? Where does sodium go? The charge inside the axons go from negative to positive. The sodium goes into the axon. 8. What happens to the charge inside the axon when the potassium gates open? Where does potassium go? When the potassium gates open the charge stays negative. The potassium 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 means the increases of voltage. Its also when the Na+ moves to the inside axon. Repolarization is the decrease of voltage. It is when K+ moves to outside axon. 10. What causes depolarization of the axon? Increase of voltage causes it. 11. What causes repolarization of the axon? Decrease of voltage causes it. 12. What is an action potential? When action potential is unmyelinated, the action potential at one locale stimulates an adjacent part of the axon’s membrane to produce an action potential. 13. How does the sodium potassium pump reestablish the resting potential during the refractory period? 14. What is a synapse? A synapse is a region of close proximity, that region being each terminal lying very close to either the dendrite or the cell body of another neuron. 15. What is a synaptic cleft? A small gap at the synapse, that separates the sending neuron from the receiving neuron. 16. What is a neurotransmitter? It is a transmission across a synapse that is carried out by molecules. They are stored in synaptic vesicles in the axon terminals. 17. Since neuron's don't touch, how is the signal from one neuron transmitted to another neuron? This is a process; first the nerve impulses traveling along an axon reach an axon terminal. Secondly the calcium ions enter the terminal, and they stimulate synaptic vesicles to merge with the sending membrane. Lastly the neurotransmitter molecules are released into the synaptic cleft, and they diffuse across the cleft to the receiving membrane, where they bind with specific receptor proteins. 18. Insert an image showing an action potential. 19. Insert an image showing a synapse.