Handout 3 Sol

Handout 3 Sol - TA Anna Gruzman E-mail [email protected]

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TA: Anna Gruzman Section 3 E-mail: [email protected] 1/24/10 1. What would cause an increase in the speed of conduction of an action potential? A: - increase diameter (less resistance) - decrease longitudinal resistance (increase longitudinal conductance) - decrease membrane conductance Speed of conduction= longitudinal/ membrane conductance The larger the diameter of the membrane the longer the longitudinal conductance High membrane conductance = more leakage ( degree of permeability of a membrane) 2. Write out the steps for neurotransmitter release at the synapse of a cell starting from the depolarization at the axon terminal. 1. Action potential depolarizes the axon terminal. 2. Depolarization opens voltage-gated Ca++ channels and Ca++ enters the cell 3. Calcium entry triggers exocytosis of synaptic vesicle contents. ( V snares dock at membrane with t-snares=> fusion leads to exocytosis) - v-SNAREs : incorporated into the membranes of transport vesicles during budding, - -SNAREs : located in the membranes of target compartments 4. Neurotransmitter diffuses cross the synaptic cleft and binds with receptors on the postsynaptic cell 5. Neurotransmitter binding initiates a response in the postsynaptic cell http://www.sumanasinc.com/webcontent/animations/content/synaptictransmission.html 3. EPSP: Excitatory Postsynaptic Potentials IPSP: Inhibitory Postsynaptic Potentials Can EPSP or IPSP cause the postsynaptic neuron to produce an action potential? Does this always happen? A: Recall that an action potential requires depolarization which means that only an EPSP would be capable of generating it in a postsynaptic neuron. That being said, a single EPSP is usually not strong enough to invoke an action potential at the postsynaptic neuron. Since, these postsynaptic potentials are graded, however, they can add if they arrive close together (temporal potential) or if more than one synapse sends an action potential to the same postsynaptic neuron (spatial summation) [This summation also applies to IPSP] o EPSP: If the channel is selected for sodium or for calcium then because of the gradients of these ions either sodium or calcium will enter the cell and the result will be an excitation o IPSP: caused by opening of potassium or chloride channels
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4. What do acetylcholinestrase, curare, and botulin toxixn all have in common? What are the similarities and differences in the mechanisms that allow them to achieve this? A: They all prevent the effects of the neurotransmitter acetylcholine. (the most common
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Handout 3 Sol - TA Anna Gruzman E-mail [email protected]

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