BIO SCI 35 Lecture Notes - Lecture 4: Axon Hillock, Saltatory Conduction, Peripheral Nervous System
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24 Feb 2018
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Ligand-gated sodium channels open - the inside gets more positive. Rising phase of the action potential a. b. When reaches threshold - voltage-gated sodium channels open - since the inside got positive. Falling phase of the action potential a. b. c. Voltage-gated potassium channels open - the inside gets less positive. Hyperpolarized - more negative than resting potential - too much potassium flowed out. During this time, impossible for cell to fire again. Sodium-potassium pump brings the cell back to its resting potential. At the site where the action potential is generated, usually the axon hillock, an electrical current depolarizes the neighboring region of the axon membrane. Action potentials travel in only one direction: toward the synaptic terminals. Inactivated sodium channels behind the zone of depolarization prevent the action potential from traveling backwards. Myelination facilitates saltatory conduction of an action potential. Myelin is a cell with a lot of fat.
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Which of the following statements is FALSE? (choose one)
A. | Voltage-gated sodium (Na+) channels open in the dendrites and cell body during a local, graded potential. |
B. | During repolarization, potassium ions are leaving the cell (K+ is diffusing out of the cell), and the inside of the cell becomes more negative |
C. | If someone damaged an efferent motor neuron, they could feel pain, but not respond to move away from the pain |
D. | Myelin serves as electrical insulation and increases the speed at which an action potential travels along the axon |
E. | Movement of ions can be excitatory (if sodium ligand-gated channels bind the neurotransmitter), or inhibitory (if potassium ligand-gated channels bind the neurotransmitter) |