In the hippocampus, when glutatmate is released into the synaptic cleft, but the postsynaptic cell is NOT depolarized, there is only a small postsynaptic response. Why is this the case? A. Ca++ ions block the NMDA ion channel B. Mg++ ions block the NMDA ion channel C. Glutamate is an inhibitory amino acid neurotransmitter D. There are no NMDA receptors on the postsynaptic cell
In the hippocampus, when glutatmate is released into the synaptic cleft, but the postsynaptic cell is NOT depolarized, there is only a small postsynaptic response. Why is this the case?
| A. |
Ca++ ions block the NMDA ion channel |
|
| B. |
Mg++ ions block the NMDA ion channel |
|
| C. |
Glutamate is an inhibitory amino acid neurotransmitter |
|
| D. |
There are no NMDA receptors on the postsynaptic cell |
Neurons are the basic structures and functional units of the nervous system. The axon or the nerve fiber is a single, elongated, tubular extension that conducts action potentials away from the cell body and eventually terminates at other cells. The fundamental task of the neuron is to receive, conduct and transmit signals. These cells have the ability to respond to a stimulus by producing an electrical signal or action potential. A rapid and large changes in membrane potential of nerve cells during which the potential actually reverses so that the inside of the cell transiently becomes more positive than the outside, caused by membrane depolarization, is called as action potential. Action potentials allow nerve impulses to travel long distances within the body.
Calcium has a crucial role in the release of chemical neurotransmitters such as nicotinic acetylcholine and muscarinic acetylcholine at the synaptic transmission. Depolarization of the presynaptic neuron causes more Ca2+ influx into the cell from extracellular region by opening the Ca2+ gated ion channel. This influx cause increased Ca2+ ions in the preganglionic synaptic region, and the Ca2+ ions interact with other synaptic proteins to induce the release of chemical neurotransmitters from vesicles. During an action potential, movement of sodium ions occur through voltage-gated Na+ channels down their electrochemical gradients. As influx of Na+ increase, by a stimulus, the membrane is depolarized
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