Production of Action Potentials Worksheet

Action Potentials Production of Action Potentials (AP) 1. When excitable cells are at rest, the charge on their membranes is called the ____resting membrane potantial_______ (RMP). 2. In order to reach threshold, the membrane potential must (depolarize/ hyperpolarize). 3. _local (graded)________ potentials may be a depolarization or hyperpolarization; if threshold is reached, the cell will produce action_____________ potentials. 4. The first phase of an action potential is ______depolarization______; the membrane potential becomes positive. The second phase of an action potential is ____repolarization_________; the membrane potential becomes more negative. The third phase of an action potential is ___hyperpolarization_____________; the membrane potential becomes more negative than the RMP. A positive feedback cycle begins when a graded potential reaches threshold. 5. Once threshold is reached, sodium and potassium __voltage________ gated channels open. 6. __sodium_______ voltage gated channels open immediately once threshold is reached; ___potassium______ voltage gated channels take more time before they are open. 7. During depolarization, sodium voltage gated channels are ____open________; potassium voltage gated channels are ____closed_______. 8. During repolarization, sodium voltage gated channels are _____closed________; potassium voltage gated channels are _____open_______. 9. During hyperpolarization, __potassium________ voltage gated channels are closing. 10. During the ___absolute refractory________ period, an excitable cell cannot produce another AP. 11. During the ___relative refractory________ period, an excitable cell can produce another AP only if a stronger than normal stimulus is applied. 12. Explain why another AP cannot be produced during the absolute refractory period. Sodium channels are closed and nonresponsive or already open. 13. Explain why it takes a stronger than normal stimulus to stimulate another AP during the relative refractory period. The membrane is more negative because it is depolarized AP propagation 1. The movement of action potentials down the axon defines AP ___propagation_______________. 2. The form of AP propagation depends on axon structure. Saltatory conduction occurs along __myelinated________ axons; continuous propagation occurs along ______unmylinated______ axons. 3. Myelin consists of ____lipid_____ and ___protein_______. In the CNS, _____alocodendrocytes_______ form the myelin sheath. In the PNS, ________ _schwan cells__________ form the myelin sheath. The myelin segments (internodes) are separated by exposed segments of axon called the ___nodes_____ of ______rhomiez_____. 4. Describe continuous propagation along an unmyelinated axon. Reinitiate APs down the 5. Describe saltatory conduction along a myelinated axon. Jump from node to node, sodium diffuses in first thru node of rhombie, to adjacent nodes and continues until threshold is reached and an AP is produces, but does not change direction because of refractory period. 6. Compare the speeds of saltatory and continuous conduction. Saltatory- faster Stimulus Intensity & AP generation 7. Mechanical or chemical stimuli will generate graded potentials. Graded potentials result when stimuli open either ____chemical________ gated channels or _____mechanical______ gated channels in excitable membranes. 8. If the graded potential is excitatory, then the membrane __depolarizes_________. If the graded potential is inhibitory, then the membrane __hyperpolarize_________. 9. For each ion, determine whether the graded potential is excitatory (depolarizes) or inhibitory (hyperpolarizes). a. sodium- excitatory b. Potassium- inhibiatoy c. Calcium- excita 10. In order to produce action potentials, the graded potentials must be ____frequent________, and strong enough to depolarize the membrane to ______excitatory______. 11. If threshold is reached, ___voltage_________ gated ion channels open, and an action potential is generated.