The Process of Neurotransmission - Free Essay

Living organisms derive their emotional responses, thoughts, feelings, sensations, motor responses, memory and learning, and all functions and dysfunctions of the brain from the communication between nerve cells. Nerve cells, known as neurons, are highly differentiated and specialized for their role. They need to maintain communication for an organism to maintain its senses. However, neurons do not communicate through physical contact with each other. Rather, electrical impulses are sent between the synapses between them. Chemical messengers (neurotransmitters) are essential for this transfer of impulses, a process known as neurotransmission. The process of neurotransmission is understood through the concept of the synapse, the chemical events at a synapse, the types of neurotransmitters, and the activating receptors of the postsynaptic cell.

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The Concept of the Synapse

The synapse is the communication point between two neurons. Charles S. Sherrington's examination of reflections allowed him to infer the extent of synapses and many of their properties (Süudhof, 2008). Because automatic arc transmission is slower than the transmission of equivalent axon length, Sherrington surmised that a process at the synapses impedes transmission. Graded potentials like EPSPs allow positively charges ions while IPSPs allow negatively charged ions to summate their effects. Temporal summation is the summation of graded potential from stimuli at a separate time. Spatial summation is the summation of potentials from distinct locations, inside the nervous system. An inhibition is significant as excitation is an active brake that subdues excitation; therefore, it is not just the absence of excitation. Stimulation at the synapse builds a fleet graded potential in the postsynaptic cell, an excitatory graded potential (depolarizing) EPSP. An inhibitory graded potential (hyperpolarizing) IPSP, or an EPSP happens when the gate opens to permit sodium to go into the neuron's membrane. When the gate opens to let the potassium out or allows the chloride in an IPSP has occurred. The balance between EPSPs and IPSPs increases or decreases at the neurons' frequency of action potentials thence EPSPs on a neuron compete with the IPSPs

Chemical Events at a Synapse

Understanding chemical events at a synapse are essential to understanding the nervous system. Each year, researchers discover more details about synapses, their structure, and the link between these structures and their functions. These are the most important events: the neuron synthesizes chemicals that act as neurotransmitters. It synthesizes the smallest neurotransmitters at axon terminals and neuropeptides in the cell body. The action potential crosses the axon. At the presynaptic terminal, an action potential allows calcium to enter the cell. Calcium releases neurotransmitters from the terminals to the synaptic cleft, the space between the presynaptic and postsynaptic neurons. The released molecules diffuse through the cleft, bind to the receptors, and modify the postsynaptic neuron activity. Neurotransmitter molecules disconnect from their receptors. Neurotransmitter molecules maybe return to the presynaptic neuron for recovery or release. Most postsynaptic cells send reverse messages to control the subsequent delivery of presynaptic cell neurotransmitters.

Most synapses work by transferring a neurotransmitter from the presynaptic cell to the postsynaptic cell. Otto Loewi demonstrated this point by electrically stimulating the heart of a frog and then transferring fluids from the stimulated heart to another frog's heart. Loewi discovered that this transfer of these fluids would modify the reactivity of the heart muscle.

Types of Neurotransmitters

At the synapse, a neuron releases a chemical that can affect another neuron. These chemicals are called neurotransmitters. Hundreds of chemicals are suspected to be neurotransmitters (Borodinsky et al., 2004). These are the main categories,

The concept of Sherrington's synapse was simple: Input creates excitation or inhibition; that is, on / off. When Eccles took photos of individual cells, he selected board cells, which generated short EPSP and IPSP, only activated/deactivated. The discovery of chemical transfer to the synapses did not initially change this. Researchers discovered more neurotransmitters and asked, "Why does the nervous system use so many chemicals when they all deliver the same type of message?" Finally, they found that the news was more complex and diverse. The outturn of a neurotransmitter depends on its receptor on the postsynaptic cell. If the neurotransmitter is bound to its receptor, the receptor can open a channel with an ionotropic effect or achieve a slower but more sustainable effect, a metabotropic effect.

Various drugs, including LSD, nicotine, and opiates, exert their behavioral effects by binding to receptors on the postsynaptic neuron. After a neurotransmitter, numerous transmission molecules re-enter the presynaptic cell through transport molecules in the membrane. These refer to reuptake, which allows the presynaptic cell to recover its neurotransmitter. Stimulants and many antidepressants inhibit this process (Beuming et al., 2008; Schmitt & Reith, 2010; Zhao et al., 2010) Postsynaptic neurons send chemicals to receptors to inhibit the subsequent release of neurotransmitters. The cannabinoids in marijuana mimic these chemicals (Kreitzer & Regehr, 2001; Wilson & Nicoll, 2002) or GABA (Földy, Neu, Jones, & Soltesz, 2006; Oliet, Baimouknametova, Piet, & Bains, 2007). Hormones are released into the blood to impact receptors in the body. Its behavior is like that of a metabotropic synapse.

Conclusion

The process of neurotransmission involves the role of the synapse, chemical events at a synapse, types of transmitters, and the activating receptors of the postsynaptic cells. Communication between neurons occur at the synapse. When stimulation reaches the synapse, it builds a fleet graded potential in the postsynaptic cell. Neurons synthesize neurotransmitters, the smallest at the axon and the neuropeptides in the cell body. The resulting action potential at the presynaptic terminal permit calcium release of neurotransmitters that diffuse through the cleft and bind to their receptors. There are different types of neurotransmitters, whose chemical compositions determine how the receptors are activated. Variations in chemical compositions relate to the numerous messages that need to be transmitted from one neuron to another.

References

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