The neuron essay

The neuron essay

Question 1

The neuron is the basic unit of the nervous system. It is a specialized cell responsible for receiving, processing, and transmitting information in the form of electrical impulses (Huffman, Dowdell, & Sanderson, 2017). There are different types of neurons based on their structures and functions. Most neurons have three main features: dendrites, the cell body, and an axon. The dendrites are the receptive regions of the neuron. They are short, branched extensions from the cell body, which receive information from other nearby cells. The cell body, or soma, contains the nucleus which serves as the control center of the cell (Rizzo, 2015). The cytoplasm of the cell body contains organelles such as lysosomes, Golgi bodies, and neurofibrils. The neurofibrils, a network of threads, extend into the axon which is the fibre part of the cell through the axon hillock. The axon is a long process that starts out as singly but may branch out towards the end into multiple extensions known as axon terminals.

Neurons communicate using electrical impulses that are transferred through neural and endocrine signaling. The axon terminals of one nerve cell contact with dendrites of other neurons (Rizzo, 2015). Electrochemical information in form of action potential received by the dendrites from neighboring neurons first flows to the soma. If the cell body receives enough stimulation, it passes on the information to the axon, which passes it along to the terminal buttons (Huffman, Dowdell, & Sanderson, 2017). Axons of neurons are surrounded at specific regions by Schwann cells. The cells form a fatty myelin sheath which is essential to the insulating of nerve cells and speeding transmission of neural impulses. The gap between neuron and another cell is known as a synapse. At the terminal buttons, the signal is transmitted from pre-synaptic cell to the post-synaptic cell through an electrical or chemical synapse (Chambers, Huang, & Matthews, 2015).

Question 2

The brain is the organ responsible for coordinating the activity of other body systems through complex sensory, motor and higher functions (Chambers, Huang, & Matthews, 2015). It is divided into four main regions: the brainstem, diencephalon, cerebrum, and cerebellum. The brainstem comprises of three smaller regions: the medulla oblongata, the pons varolii, and the midbrain (Rizzo, 2015). Medulla oblongata contains centres for the control of cardiac, respiratory, and vasomotor activities. It also regulates vomiting, coughing, breathing, and blood pressure. The pons functions with the medulla oblongata to control rate and depth of respiration (Starr, Evers, & Starr, 2015). The midbrain serves in regulation of body temperature, vision, hearing, alertness, motor control, and sleep and wake cycles.

The second main region of the brain, the diencephalon, is divided into two main areas, the thalamus and hypothalamus (Rizzo, 2015). The thalamus functions in memory control and the hypothalamus governs behavior such as thirst and hunger to ensure homeostasis (Starr, Evers, & Starr, 2015). Other areas of the diencephalon are the optic tract and optic chiasma, the infundibulum, mammilary bodies, and the pineal gland. Thirdly, the cerebrum, also known as telencephalon, is the largest part of the brain. It is divided into three areas: right and left cerebral hemispheres, basal ganglia, and the limbic system. The right and left cerebral hemispheres facilitate sensory perception and initiation of voluntary movement and regulate control language, thinking, memory, and planning (Chambers, Huang, & Matthews, 2015). The basal ganglia take part in coordination of posture, muscle tone, and fine motor control. The limbic system is involved in higher functions of emotion, behavior, and long-term memory. The fourth part, the cerebellum, functions in coordination of motor activity for maintaining posture, moving limbs, and spatial orientation.

Question 3

Neuroimaging is a vital tool for studying the structure and function of brain for purposes of research and clinical care. Brain research is supported by imaging techniques such as CT scan and ultrasound used singularly or in combination to explore brain functioning. The Computer Assisted Tomography (CT) scan was developed in the 1970s through the computerization of the x-ray. Advantages of the CT scan include three-dimensional images, use with or without contrast agents, is less time-consuming, and has few contraindications (Asbury & Detre, 2019). It is applicable in emergency situations for identification of abnormalities in brain structure due to head injury, hemorrhagic shock, and aneurysms. However, the method is risky due to the ionizing effects of radiation. Ultrasound is beneficial since it can be used in neonates.

Magnetic Resonance Imaging (MRI) is beneficial because it produces three dimensional images of tissues without interference. MRI is a safe method since it is completely non-invasive and radiofrequency has no ionizing effect on tissue (Papadelis, Grant, Okada, & Preissl, 2015). Unlike other methods it can be used to visualize regions of extensive blood-brain barrier by using exogenous contrast agents (Asbury & Detre, 2019). Positron Emmission Tomography (PET) and Single Photon Emission Computer Tomography (SPECT) are also used for brain imaging, but they use exogenously administered radioisotopes to emit gamma rays (Asbury & Detre, 2019). The ionizing radiation makes these methods harmful to children. PET is particularly beneficial because it allows for repeated studies to be conducted over short time intervals and it has extremely high sensitivity.

Question 4

In a study conducted involving 100 subjects, 69 per cent of all concussions resulted into visual problems affecting accommodation, convergence, or saccadic and smooth pursuit movements (Armstrong, 2018). The frontal and temporal lobes are the most affected regions of the brain when an individual suffers traumatic brain injury. These regions are in close proximity to the skull. Frontal lobe injuries increases position errors, extends latency in saccadic tasks, and reduces the number of self-paced saccades (Armstrong, 2018). Damage to the temporal lobe on the right hemisphere affects nonverbal visual memory. Severity of the injury determines the extent to which brain functioning is affected. In severe cases of TBI, the damage can be permanent.

The larger proportion of vision and related activities is coordinated in the occipital lobe of the brain. The occipital lobe receives and processes visual information, and also has areas that assist in perception of shape and colors. Therefore, injury to this region will deform visual fields and affect the size, shape, and color of objects. Injury to the peristriate region interferes with discrimination of color and movement. When one side of the occipital lobe is damaged, homonomous loss of vision occurs in both eyes, with similar “field cut”. Furthermore, occipital lobe injury can cause simultanagnosia, characterized by difficulty to observe multiple objects at the same time. Severe injury to the occipital lobe can cause blindness even when the eyes and their neural connections are intact (Huffman, Dowdell, & Sanderson, 2017). In severe head injury such as skull fracture, the optic chiasma is affected, causing loss of ganglion cells in the retina. As a result, color mediation is affected and an individual injury experiences difficulty identifying colors. Injury to the brainstem is indicated by signs such as nystagmus and fixations of pupils to light because eye reflexes are controlled in the midbrain.