The Anatomy of the Basic Unit of the Nervous System, the Neuron

The basic unit of the nervous system is the neuron, a nerve cell that consists mainly of two parts: the dendrites and the axon (or axoneme). The dendrites are branches that extend from the cell body and receive signals from other neurons. The axon projects from the cell body and sends signals to other cells. The electrical impulse travels along this pathway by conduction, which is a chemical reaction between the signal source, presynaptic terminal, and the destination, or postsynaptic terminal (Camprodon & Roffman, 2016). The net result of an electrical impulse travelling along an axon pathway is that it causes neurotransmitters to be released in response to specific stimuli at particular locations along its length. For example, if one end of an axon were stimulated, neurotransmitters would be released at another end of the same axon; if both ends were stimulated simultaneously at different locations within the same neuron, neurotransmitters would be released at both ends of that neuron’s axon.

The subcortical structures are the brain’s most complex structures. They include the thalamus, hypothalamus, hippocampus, amygdala, and basal ganglia (Camprodon & Roffman, 2016). The subcortical structures consist mostly of the following:

1. Thalamus; this is a pair of enormous, egg-shaped structures that act as a switchboard for the brain’s incoming sensory input. It processes and filters incoming sensory information and sends it to the appropriate cortical areas for further processing.
2. Hypothalamus; the hypothalamus is a small but crucial region that plays a central role in regulating the autonomic nervous system, the endocrine system, and various behaviours such as eating, drinking, and sexual behaviour.
3. The basal ganglia; is a group of interconnected structures involved in controlling voluntary movement and regulating motivation, reward, and addiction.
4. Amygdala; amygdala is a small almond-shaped structure that processes emotions, particularly fear and anxiety. It also plays a role in social behaviour and decision-making.
5. Hippocampus; the hippocampus is a seahorse-shaped structure that forms and consolidates memories, particularly long-term declarative memories. It is also involved in spatial navigation and other cognitive processes.
6. Brainstem; brainstem is the most primitive part of the brain and controls many of the body’s automatic functions, such as breathing, heart rate, and blood pressure. It also serves as a conduit for information between the brain and the rest of the body.

The hippocampus, located in the medial temporal lobe, plays a role in learning and memory. It also plays a role in addiction because it is one of many brain regions that regulate how much alcohol or drugs people take when they consume them. The hippocampus consolidates short-term and long-term memory and encodes, arranges, and retrieves memories (Camprodon & Roffman, 2016). Studies have suggested that the hippocampus plays a role in developing and maintaining addiction and learning to associate a reward with a particular stimulus. Furthermore, the hippocampus is responsible for the extinction of cravings and drug-seeking behaviour in addicts, making it an important component of addiction treatment and management.

The two key neurotransmitters located in the nigra striatal region of the brain that play a major role in motor control are dopamine and Acetylcholine.

1. Dopamine is synthesized in the substantia nigra, a region within the midbrain, and is involved in several important functions, including movement, motivation, and reward. In the nigra striatal region, dopamine is released by neurons in the substantia nigra and acts on receptors located on the neurons in the striatum. Dopamine neurons in the nigra striatum are essential for controlling motor activity (Camprodon & Roffman, 2016). Loss of dopamine-producing neurons in the substantia nigra is thought to have a role in some movement disorders, including Parkinson’s disease.
2. On the other hand, Acetylcholine is synthesized in neurons located in the basal forebrain and projects to the striatum. It involves several important functions, including attention, learning, and memory. In the nigra striatal region, Acetylcholine acts on receptors located on neurons in the striatum and plays a key role in regulating motor activity (Camprodon & Roffman, 2016). Studies have shown that an imbalance in the dopamine and acetylcholine systems can lead to motor dysfunction, and drugs that modulate these neurotransmitters are used to treat movement disorders.

The nigra striatal dopamine and acetylcholine systems are significant therapeutic targets in movement disorders because of their pivotal roles in motor regulation.

Glial cells are involved in the central nervous system (CNS) in various ways. One way they function is by protecting neurons, which means they can be important for maintaining their health. Another way glial cells help neurons is through their ability to help maintain electrical signals during brain activity (Camprodon & Roffman, 2016). Glial cells also help protect neurons from damage by removing harmful substances from the brain and removing damaged neurons from the brain.

The axon made up of neurons terminates in a specialized point called a synapse, which connects to the dendrites or cell bodies of neighbouring neurons. The axon of a presynaptic neuron releases chemical messengers called neurotransmitters, which attach to particular receptors on the dendrites or cell body of a postsynaptic neuron. In response to this binding, the postsynaptic neuron receives an electrical signal that stimulates or inhibits the cell, depending on the specific neurotransmitter and receptors in play (Camprodon & Roffman, 2016). To restate, the synapse is where the axon of the dendrites or cell body and the presynaptic neuron of the postsynaptic neuron exchange information. Unlike other types of neuronal communication, synaptic transmission can only move from the presynaptic to the postsynaptic neuron.

In simple terms, the brain can adapt and restructure a person’s life in response to new information and experiences. This process involves the creation of new neural connections and the strengthening or weakening of existing ones, which can lead to changes in behavior, perception, and cognitive function. For example, a person who suffers a stroke may undergo rehabilitation involving repetitive physical therapy, promoting the brain’s ability to form new neural pathways and relearn lost motor skills (Camprodon & Roffman, 2016). Learning a new language or musical instrument can also stimulate neuroplasticity, resulting in the growth of new neural connections and improved cognitive abilities.

Reference

Camprodon, J. A., & Roffman, J. L. (2016). Psychiatric neuroscience: Incorporating pathophysiology into clinical case formulation. In T. A. Stern, M. Favo, T. E. Wilens, & J. F. Rosenbaum. (Eds.), Massachusetts General Hospital psychopharmacology and neurotherapeutics (pp. 1–19). Elsevier.