Neurons are tiny specialized cells that make up a human’s nervous system and brain. Similar to other other cells in the human body, neurons possess a nucleus, and other organelles, but these nerve cells complete a more particular task.
A neurons purpose is to transport certain messages and information throughout the body. These reports contribute to tasks being done both internally and externally. In a human, there are three specific types of neurons (motor neurons, sensory neurons, and interneurons) that have their own specialized tasks. Motor neurons are responsible for the contraction of muscles and glands. Sensory neurons detects external stimulus and can act on that stimuli by transferring the detection message to motor neurons. Interneurons communicate with both motor or sensory neurons and send the information to the brain.
Although these three neurons complete three different tasks, they all operate in similar ways. Every neuron possesses a dendrite, this receives messages from either a sensory receptor or another nerve cell. The message is then sent through the cell body to the axon, which sends that information to the next dendrite of a neuron. The nucleus plays a key roll in the operation as it provides that energy needed to complete a transfer of information. Some neurons may include myelin sheath; sheets of fatty tissue that wraps around the axon that provide both protection and help to speed of the transfer process.
(Black: Sensory neuron, Yellow: Motor neuron, Orange: Interneuron)
When a message is being transferred through an axon, a specific technique is used, this is called Action Potential. This is a abrupt electrical impulse that moves down the axon. These impulses are caused by the trading of negative and positive ions (sodium and potassium) through the membrane of the axon. Action potential requires four different phases. This first phase is resting potential, when more positive ions sit outside the axon membrane giving the internal axon a negative charge, this means that the negatively charged centre is “polarized”. A certain threshold is required to start the process of action potential and when this stimulus has been given, depolarization happens. Depolarization causes the membrane of the axon to open, allowing positive sodium ions to enter. After this, the inside of the axon must become negatively charged again, this is called repolarization. This cause the membrane of the axon to once agian open allowing the positive potassium ions to escape. Repolarization causes the next segment of the axon to start the depolarization process. The progression of depolarization and depolarization sends action potential down the axon.
When the message has reached the end of the axon, the message must be transferred. A synapse is the structure that allows this transfer of information to occur. Axons of nerve cells have “axon terminal buttons” which are placed very close to a dendrite, without touching. The space between the two branches is called synaptic gap and this is where the information is relocated. The messages are held in synaptic vesicles which burst when the meet the end of the axon button, releasing neurotransmitters into the synaptic gap. These neurotransmitters then attach themselves to the receiving neuron (dendrite). When the message is received by the dendrite, the message is either classified as excitatory or inhibitory. Excitatory is when the information stimulates action potential on the new neuron and inhibitory does the opposite but restraining the action potential.
Neurotransmitters fit into the receptor like a “lock and key”, but sometimes certain chemicals can interfere with transfer of neurotransmitters, these are called NT disruptors. NT disruptors can either be agonist or antagonist. Agonist disruptors not only act as neurotransmitters, but boost the action of it. Antagonist disruptors block the binding of neurotransmitters to receptors all together.
Citations:
Astrologer Parshant Kapoor. Astrologer Parshant Kapoor, astrologerparshant.wordpress.com/category/motor-neuron-disease-treatment-by-ayurveda/.
Jalan, Mahak. “What Would Happen If Our Neurotransmitters Stopped Working?” Science ABC, Science ABC, 19 Sept. 2018, www.scienceabc.com/humans/what-is-a-synapse-defnition-neurotransmitter-how-do-they-work.html.