Nervous System Paper

The nervous system is a complex network that allows an organism to interrelate with its surroundings. It is made up of various components, including motor and sensory components. The nervous system is broadly categorized into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is chiefly made up of the brain and the spinal cord, whereas the PNS encompasses nerves and ganglia external to the brain, including cranial nerves, spinal nerves and their roots, peripheral nerves, and neuromuscular junctions (Stern et al., 2016).

Nervous System Paper

Nerve tissue is the principal constituent of the nervous system and mainly comprises the neurons and the supporting glial cells. In the subsequent sections of this paper, the neuron, subcortical structures, neurotransmitters, glial cells, and synapses shall be discussed.

Neuron

The neuron is the basic unit of the nervous system. Neurons are polarized signal transmitting cells (Ludwig et al., 2022). They are classified as pseudo-unipolar, unipolar, bipolar, and multipolar based on the neurites. The neurons do not endure mitosis. However, their effect can be inhibitory, excitatory, or modulatory, while their function can be secretory, motor, or sensory (Ludwig et al., 2022).

The neurons are mainly composed of the soma, the axon, and the dendrites (Ludwig et al., 2022). The soma contains organelles such as the nucleus, mitochondria, Golgi apparatus, lysosome, and smooth endoplasmic reticulum, among others. It also has Nissl substance, pigments such as melanin and lipofuscin, and cytoskeletal components such as microfilaments. The soma contains genetic information, sustains the structure of the neuron, and furnishes energy to propel cellular activities.

The axon is a projection from the soma along which action potential travels to deliver intercellular signals. It has no Nissl substance as it lacks an ordinary rough endoplasmic reticulum. As the nerve fiber exits the cell body, it is structurally and physiologically divided into the axon hillock, the initial segment, the axon proper, and the axonal termination (Ludwig et al., 2022).

The axon principally carries nerve impulses away from the cell body. Additionally, the axon has a cytoskeleton network composed of microtubules and neurofilaments. On the other hand, the dendrites are thin, branching projections from the soma that receive impulses from adjacent neurons. They contain Nissl substance, the cytoskeletal framework of microfilaments, and spines that stretches the number of synapses to adjacent neurons.

Nerve impulses are conveyed via action potentials. Neurons ordinarily have a resting membrane potential of -60mV. Upon stimulation, depolarization occurs as a result of the opening of voltage-gated sodium channels with a subsequent influx of sodium ions (Holland et al., 2019). The soma end of the axon becomes depolarized first and travels unidirectionally towards the axonal terminal.

What are the major components that make up subcortical structures?

Subcortical structures refer to a collection of heterogeneous neural formations deep within the brain (Ji et al., 2019). According to Ji et al. (2019), the major components of subcortical structures include the following:

  • Diencephalon- thalamus, subthalamus, epithalamus, and hypothalamus
  • Pituitary gland
  • Basal ganglia
  • Limbic structures- hippocampus and amygdala.

Which component plays a role in learning, memory, and addiction?

Learning, memory, and addiction involve the mesocorticolimbic circuit (Volkow et al., 2019). The circuit comprises the following;

  • Hippocampus
  • Amygdala
  • Dorsal striatum- caudate and putamen
  • Nucleus accumbens
  • Prefrontal cortex.

What are the two key neurotransmitters located in the nigra striatal region of the brain that play a major role in motor control?

Neurons of the substantia nigra can be categorized into substantia nigra pars compacta, and substantia nigra pars reticulata, which produce dopamine and GABA, respectively. Dopamine usually stimulates movement, while GABA can enhance or inhibit movement based on the input signal.

Glia cells

Glial cells are non-neuronal cells that form a supporting framework in the CNS. They include astrocytes, ependymal cells, oligodendrocytes, and microglia (Verkhratsky et al., 2019). Astrocytes form the blood-brain barrier, provide physical support, participate in nerve tissue repair, and remove excess neurotransmitters (Verkhratsky et al., 2019).

Oligodendrocytes myelinate axons in the CNS, including the optic nerve. Meanwhile, ependymal cells are simple columnar glial cells that line the ventricles and are involved in CSF production. Finally, microglia are phagocytic cells and are involved in the inflammatory response.

Synapse

Synapses refer to the intersection across which action potentials are transferred from a presynaptic to a postsynaptic structure (Südhof, 2018). Synaptic transmission is the communication between two neurons and involves neurotransmitter release (Südhof, 2018). Synapses can be chemical or electrical. Similarly, synapses can be classified based on the structures between which they signal.

For instance, axodendritic synapses transmit signals between axons and dendrites, axoaxonic synapses transmit signals between axons, axosomatic synapses transmit signals between axons and the cell body, and dendrodendritic which transmit signals between dendrites (Südhof, 2018). Chemical synapses transmit signals between neurons distinguished by a cleft via a neurotransmitter. In contrast, electrical synapses transmit signals between adjacent neurons joined by a gap junction via the movement of ions.

Neuroplasticity

Neuroplasticity encompasses adaptive functional and structural alterations to the brain following an internal or external insult (Digrazia, 2021). Neuroplasticity is a unique process that the brain deploys in an attempt to restore function following brain damage (Digrazia, 2021). An example of neuroplasticity includes circuit changes that originate after learning a novel skill.

Conclusion

The neuron is the basic component of the nervous system. It is composed of a cell body, axon, and dendrites. Subcortical structures include limbic structures, the pituitary gland, the diencephalon, and the basal ganglia. The hippocampus, amygdala, dorsal striatum, and prefrontal cortex are among the structures involved in learning, memory, and addiction. The glial cells of the CNS include astrocytes, oligodendrocytes, microglia, and ependymal cells. Finally, synapses can be chemical or electrical in nature.

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