A neuron is the basic functional unit of the nervous system that transmits chemical and electrical impulses and consists of the cell body or soma, dendrites, axon, and pre-synaptic terminal. Soma incorporates mitochondria, endoplasmic reticulum, Nissl bodies, and nucleus; dendrites are short protrusion of the cell body that receives impulses, while axon conducts impulses from the soma to the pre-synaptic terminal, where neurotransmitters are stored (Amidei & Trese, 2019).
Dendrite activation leads to altered cell membrane permeability, resulting in sodium entering the cell and potassium moving out, causing depolarization and generation of action potential transmitted via saltatory conduction through the axon’s nodes of Ranvier (Amidei & Trese, 2019). Then, the action potential is followed by the return of potassium back into the cell and electric repolarization, when the membrane potential becomes hostile again. Finally, the transmission of the impulse across the axon causes neurotransmitter release in the nerve terminal, where it binds receptors on the postsynaptic terminal, activating or inhibiting the next neuron.
The human brain can be subdivided into two significant components, the cerebral cortex and subcortical structures. Subcortical structures include the thalamus, hypothalamus, basal ganglia, pituitary gland, cerebellum, and brainstem (Camprodon & Roffman, 2016). The hippocampus, a component of the medial temporal lobe of the cerebral cortex, plays an essential role in learning, memory formation, and the development of addiction (Camprodon & Roffman, 2016). Dopamine and GABA are the two neurotransmitters in the nigrostriatal pathway that participate in motor control.
Neuroglial cells are the major supporting elements in the central nervous system that provide nutrition, protection, and myelination to neurons. Glia cells play a significant role in normal brain functioning because schizophrenia and mood disorders are associated with reduced glial volume (Camprodon & Roffman, 2016). The two large categories of glia are microglia and macroglia (Camprodon & Roffman, 2016). The former act as phagocytic cells, cleaning up the cell debris, while the latter include oligodendrocytes and astrocytes that participate in nerve myelination and maintain the synaptic environment, respectively.
The particular regions between two neurons are called synapses, which substantially exceed the number of nerve cells in the brain and are crucial for inter-neuronal chemical communication. Neurotransmitters, released in the pre-synaptic terminal of the first neuron, bind to the receptors located post-synaptically on the second neuron, resulting in activation, inhibition, or other modulation of its function (Camprodon & Roffman, 2016). The final effect on the second neuron depends on the type of neurotransmitter sent by the first neuron’s pre-synaptic terminal.
Evolutionarily, brain plasticity evolved since it was critical for survival because those who could learn and adapt to changing circumstances of the environment were able to pass their genes. Research shows that mastering certain tasks through repetition and practice causes activation of specific brain regions, leading to learning, memory formation, and skill acquisition (Teixeira-Machado et al., 2019).
Depending on an experience, activity, and age, different pathways can be involved in neuronal plasticity: adrenergic, dopaminergic, and cholinergic – which also vary between individuals (Voss et al., 2017). For example, the cholinergic system is essential for modulating learning attention and memory; and the dopaminergic system is vital for improving visual perceptivity in the sensory cortex during critical periods of brain maturation (Voss et al., 2017). Overall, neuroplasticity is the ability of the central nervous system to adapt to intrinsic alterations or extrinsic changes.
References
Amidei, C., & Trese, S. (2019) Neuroanatomy and physiology. In I. Oberg (Ed.), Management of adult glioma in nursing practice (pp. 1-20). Springer.
Camprodon, J. A., & Roffman, J. L. (2016). Psychiatric neuroscience: Incorporating pathophysiology into clinical case formulation. In T. A. Stern, M. Fava, T. E. Wilens, & J. F. Rosenbaum (Eds.), Massachusetts General Hospital Psychopharmacology and neurotherapeutics (1st ed., pp. 1-19). Elsevier.
Teixeira-Machado, L., Arida, R. M., & de Jesus Mari, J. (2019). Dance for neuroplasticity: A descriptive systematic review. Neuroscience & Biobehavioral Reviews, 96, 232-240. Web.
Voss, P., Thomas, M. E., Cisneros-Franco, J. M., & de Villers-Sidani, É. (2017). Dynamic brains and the changing rules of neuroplasticity: Implications for learning and recovery. Frontiers in Psychology, 8, 1-11. Web.