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4 Cards in this Set
- Front
- Back
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List the characteristics of graded potentials and give examples. |
--Function is to generate action potentials 1. Local currents: currents are generated only at the site of activation and are limited to the surrounding area of the membrane. 2. Vary in size: the amplitude of the potential is dependent on strength of stimulus. 3. Depolarization or hyper polarization: the type of ion producing the graded potential determines whether its depol or hyperpol. 4. Summation: multiple graded potentials can occur and add together to produce a potential of greater amplitude than a single GP. Temporal: high frequencies of APs can produce repetitive stimuli that can summate into a large potential. Spatial: multiple inputs firing simultaneously can summate and produce a late potential. |
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Compare and contrast the properties of action potentials and graded potentials. |
-Graded potentials: do not propagate, amplitude can vary, they can be excitatory or inhibitory, they can sum to generate an AP, do not have a threshold, they are decremental, they do not have refractory periods, and they're not always depolarizing (can hyper polarize).
-Action potentials: does not vary in amplitude (always goes to +30mV), cannot sum, has a threshold, has refractory periods, not decremental, and is always depolarizing. |
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List the events of neurotransmitter release |
1. An AP propagating down the axon arrives at the nerve terminal and depolarizes the nerve terminal. 2. Depol activates VG Ca2+ channels, Ca2+ enters the synaptic terminal and increases the cytosolic Ca2+ concentration. 3. Increased cytosolic Ca2+ causes release of neurotransmitter stored in vesicles into synaptic cleft through exocytosis. 4. NT diffuses across synaptic cleft and binds to and activates receptors on the postsynaptic membrane. 5. NT dissociates from the receptor and is removed from the synapse. |
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List the events of neurotransmission at the neuromuscular junction and describe how action potentials are generated in skeletal muscle |
1. Motor neuron AP travels to neuromuscular jxn. 2. Ca2+ enters VG channels 3. ACh is released into the synapse. Binding of ACh to nicotinic cholinergic receptors on the motor end plate produces an end plate potential (EPP). [Nicotinic receptors are permeable to both Na+ and K+ thus EPPs are due to an increase in both Na+ and K+ conductance] 4. Na+ enters through the channels. The current produced by an EPP spreads via local currents to the surrounding muscle membrane. 5. The local current depolarizes the surrounding muscle membrane to threshold and activates the VG Na+ channels and produces an AP 6. APs propagate in both directions away from the endplate to the ends of the muscle fibers. 7. APs in muscle fibers cause an increase in cytosolic Ca2+ concentration, which causes muscle to contract. 8. ACh degradation |
