Anatomy of the Neuron The Anatomy of the Neuron The nervous system represents the body parts involved in generating, transmitting, and receiving chemical and electrical signals. Researchers estimate that the human body comprises 86 billion neurons grouped into either motor, sensory, or interneurons (Maurício, 2017). The neurons work together to transmit information from different parts of the body to and from the brain.
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A neuron is divided into three major parts: the cell body, the axon, and the dendrites. The nerve cell body contains the nucleus and other components of a human cell, including the mitochondria (Harding et al., 2019). The cell body has branch-like protrusions referred to as the dendrites, which increase the surface area for connection with other neurons. The axon is the tube-like structure that transmits electrical signals from the cell body to the neuron's end. The myelin sheath covers the axon reducing electrical impulses' dissipation (Harding et al., 2019). Nerve impulse conduction occurs in phases. The first phase is called the resting potential, whereby the neuron is not activated. The second phase is called the action potential, whereby the neuron is activated, leading to a change in polarity (Harding et al., 2019). A short-term electrical change occurs in the neuron permitting the flow of electrical impulses from one neuron to another. The action potential has three stages: depolarization, repolarization and refractory phase (Boron & Boulpaep, 2020). During depolarization, sodium ions get into the neuron until the excitement threshold is reached. Repolarization begins when potassium ion channels open leading to the expulsion of positively charged potassium ions out of the cell. The purpose of expulsion is to restore the normal voltage of the negatively charged membrane potential of the cell (Boron & Boulpaep, 2020). During the refractory phase, the sodium-potassium pump returns potassium ions to the inside of the cell while expelling the sodium ions, eventually achieving a resting potential. The Major Components of the Subcortical Structures Subcortical structures refer to extensive neuronal formations in the brain including basal ganglia, diencephalon, limbic structures, and pituitary gland. These neuronal connections are classified into different compartments involved in specific roles. The diencephalon, for instance, comprises the hypothalamus, the thalamus, the subthalamus and the epithalamus (Singh, 2020).
The limbic system, on the other hand, comprises the amygdala, the hippocampus, and the hypothalamus. These neuronal formations are involved in complex activities like hormone production, memory, pleasure, and emotion (Geddes, & Andreasen, 2020). The Components Involved in Learning, Memory, and Addiction The amygdala, the hippocampus, and the caudate-putamen are the primary components responsible for learning, memory, and addiction (Singh, 2020). These parts are also involved in cognitive control and motivation. Addiction occurs when chemical substances enter the brain resulting in the loss of control over impulses. Such substances cause intense stimulation of the reward system making the brain crave the reward of the substance. The Neurotransmitters Located in the Nigra Striatal Region of the Brain Dopamine and GABA are the main neurotransmitters located in the nigra striatal region of the brain. Whereas GABA inhibits neuronal actions, controlling fear and anxiety (Gedde & Andreasen, 2020), Dopamine controls movement, emotional limbic activities, and cognitive functions. The Function of The Glial Cells in the Central Nervous System Glial cells are non-neuronal cells involved in the protection of neurons. These cells are not involved in the conduction of electrical impulses. Glial cells form the myelin, which offers support to the neuron besides maintaining ion hemostasis (Von-Bernhardi, 2016). They are also involved in the transportation of xenobiotics and metabolites. The Synapse and Nerve Impulses Synapses are the small spaces separating two neurons that allow them to send electrical signals to adjacent neurons. Communication between two neurons occurs when chemicals are released by one of the neurons and cross the synaptic cleft to the adjoining neuron stimulating
the post-synaptic receptors (Byrne, 2019). The synapse comprises the presynaptic ending, the postsynaptic ending, and the synaptic cleft. The dendrites are the parts of the nerve cell that form the synapse. Nerve impulses travel from the pre-synaptic to the post-synaptic neuron across the synapse (Byrne, 2019). Transmission occurs in one way since neurons have neurotransmitter vesicles going in one direction. Neuroplasticity As noted by Grande, Tribble, and Kim (2020), neuroplasticity is a term describing the process through which brain neuronal networks undergo functional changes due to growth and reorganization. The reorganization occurs in specific neuronal pathways resulting in new connections. Reorganizations may also occur in a group of neuronal pathways leading to systematic adjustments. Neuroplasticity is associated with abnormal sensory stimulation, traumatic injuries, and reaction to developmental problems and new information (Grande, Tribble & Kim, 2020). Neuroplasticity is considered a vital though a complex element of the human brain. Research shows that some brain neuronal networks can perform unique actions without affecting their ability to undergo reorganization. These networks may deviate from their normal functions once a person is exposed to traumatic or challenging incidences. For instance, the brains of young fathers and young mothers undergo characteristic neuronal reorganization in preparation for parental duties (Grande, Tribble & Kim, 2020).
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