neuron+structure

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 It is made os a lipid substance. It develops when Schwann cells wrap themselves around an axon many times. Because each schawnn cell onl covers a pertion of an axon, the myelin sheath is interrupted. The gaps where the myelin sheath are not present are called nodes of Ranvier. 4. What is the difference between the "gray matter" and "white matter" in the brain? p.249 Long Axons tend to have myelin sheath but chort ones do not. The gray matter in CNS is grey because there is no myelin. The white matter is there because itdoes contain myelin. 5. What causes multiple sclerosis? P.249 Leisons develop that interrupt with the normal conduction of nerve impulses, and various neuromuscular symptoms are the result. 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? They are inside of the axon, and the charge is negative. 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 remains the same, and they diffuse toward the lesser concentration. 8. What happens to the charge inside the axon when the potassium gates open? Where does potassium go? They remain the same but, they diffuse toward the lesser concentration. 9. Look at the graph on page 251. What do you think depolarization means? What do you think repolarization means? Depolarization when the pumps open and the sodium are moving inside of the axon. Replarization is when the pumps release the potassium and it moves to the outside of the axon. 10. What causes depolarization of the axon? The charge on the inside has changed from negative to positive. 11. What causes repolarization of the axon? The charge on the outside has changes from positive to negative 12. What is an action potential? It is when the gates of sodium channels open first, and the Na+ flows into the axon. 13. How does the sodium potassium pump reestablish the resting potential during the refractory period? It restores by moving the potassium back inside and the sodium back to the outside. 14. What is a synapse? Synapses is a junction between neurons consisting of the presynaptic (axon) membrane, the synaptic cleft, and the postsynaptic (usually dendrite) membrane. 15. What is a synaptic cleft? Synaptic cleft is small gap between presynaptic and postsynaptic membranes of a synapses. 16. What is a neurotransmitter? A neurotransmitter is chemical stored at the ends of axons that is responsible for transmission across a synapse. 17. Since neuron's don't touch, how is the signal from one neuron transmitted to another neuron? Transmission comes across a synapses which is carried out by a molecule called neurotransmitters. 18. Insert an image showing an action potential. 19. Insert an image showing a synapse.