d) an IPSP e) none of the above to the axon, beyond the hillock, should result i

Question

d) an IPSP e) none of the above to the axon, beyond the hillock, should result in a) an EPP b) an EPSP c) an AP A resting postsynaptic neuron is innervated by several presynaptic neuros and four IPSP's almost Asss arrive almost simultaneously at the dendrites of the postsynaptic cell. a)be depolarizethfo events are roughly equal in size, the postsynaptic cell should b) be hyperpolarized from its resting state c) be at its resting membrane potential d) cannot be determined from the information provided 34. The example above demonstrates the principle of a) frequency modulation b) amplitude modulation c) all-or-none d) summation 35. Which synapse would have the greatest excitatory (or inhibitory) effect? a) A synapse located far out on a dendrite b) A synapse located closest to the cell body c) It does not matter where the synapse is located 36.A stimulus acts on a receptor that then conveys this information to a sensory neuron. The stimulus is extraordinarily large. In order to communicate the intensity of the stimulus to the central nervous system, the sensory neuron will most likely a) produce an AP which peaks at value higher than+ 40 mV b) conduct the AP along the membrane at a faster speed c) generate a greater number of AP's in a given period of time d) depolarize or repolarize much more quickly e) none of the above 37.Atropine applied directly to the heart willaffect heart rate. This effect can be explained by atropine's ability to a) Stimulate sympathetic neurons b) Block sympathetic transmission c) Stimulate parasympathetic neurons d) Block parasympathetic transmission 38. At the NMJ, DFP causes ACh action to-, so the muscle fiber experiences a) Terminate more rapidly, spastic paralysis b) Terminate more rapidly, flaccid paralysis c) Last longer, spastic paralysis d) Last longer, flaccid paralysis 39.A ligand that opens a chloride channel would the cell. (Chloride's electrochemical gradient is inward.) a) depolarize b) hyperpolarize c) have no effect on the voltage of

Explanation / Answer

32) Acetylcholine action results in end plate potentials at the axon hillock. When acetylcholine is administered at the axon, it binds to channel-shaped receptor molecules on the end plate. Hence, the channels are opened allowing sodium ions to flow into a muscle cell. Acetylcholine is released in quantas. A single quanta causes slight depolarization resulting in a miniature end plate potential (MEPP). Many MEPP summate to form an end plate potential. Actions potential is formed when EPP depolarizes the cell beyond a threshold level.

When there is combined action of acetylcholine and glutamate neurotransmitter, EPSP is formed.

Hence, the right option is a.

33) There is a summation of three EPSPs to depolarize the postsynaptic membrane. The flow of positively charged ions into the postsynaptic cell by opening of the ligand-sensitive channels causes this depolarization. On the other hand, the fours IPSPs will hyperpolarize the membrane in a reverse action. However, successful depolarization or hyperpolarization is a consequence only when the membrane potentials beyond a threshold level. Due to cancellation of effect from 3 EPSP and 3 IPSPs, only effect of one IPSP will be acting on the membrane. This membrane potential may not be beyond the threshold level. Hence, the post synaptic cell will still be at its resting potential.

Hence, right option is c.

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