Function of the Brain and Nervous System in Human Physiology

Introduction

The brain acts to control the way a person feels, think, learn, remember, mover talk and perform other physical as well as psychological action through the help of the nervous system. In this report, the role and function of different parts of the brain and nervous system are to be explored to understand their way of working and support in human body.

The brain is the part of the central nervous system (CNS) which is divided into forebrain, diencephalon, midbrain and hindbrain. The forebrain is divided into telencephalon and diencephalon (Valkenborghs et al., 2019). One of the largest parts of the forebrain is cerebrum. It is composed of left and right hemisphere with its involvement in functions such as interpreting touching, supporting hearing and vision, formation of speech, reasoning, supporting emotional expression, learning and fine control of body movement (Heimer et al., 2019). The part located under the cerebrum is the cerebellum which supports functions such as maintaining posture and balance along with coordination of muscle movement (Agostinelli et al., 2019). The brainstem is the relay centre which connects the cerebellum and cerebrum to the spinal cord and supports the body to perform automatic function such as heart rate management, breathing, temperature control, digestion, coughing and others (Casas-Alba et al., 2019). The brain is composed of ventricles which are hollow fluid-filled cavities and within them choroid plexus is present that is ribbon-like structure that makes the cerebrospinal fluid (CSF) colourless. The CSF acts as cushion around the brain to protect it from any injury (Benghanem et al., 2020).

The telencephalon represents the cerebral cortex which has distinct fissures and divided into 4 lobes which are frontal, parietal, temporal and occipital lobe. Each lobes of the brain work in a complex coordination to support different functioning in the body. The frontal lobes function to support judgement, behaviour, planning, speech, intelligence, self-awareness and other development. The parietal lobes functions to support interpretation of language and words, identification of sense and tough, interpretation of signal from sensory and memory, motor, vision and other action. The temporal lobe functions to support language understanding, memorising, sequencing and organisation and hearing whereas the occipital lobe supports the interpretation of light, colour and movement of vision in coordination with other lobes (Clowry et al., 2018). The cerebrum surface is known as cortex which has been formed of millions of folds. The cortex consists of grey matter on the outer side and white matter on the inner side. The folding of the cortex increases surface area of the brain which allows increased number of neurons to be present for its better functioning (Kubíková et al., 2018).

The diencephalon contains the hypothalamus, pituitary gland, thalamus, pineal gland, basal ganglia and limbic system. The hypothalamus is present on the third ventricle of the brain and functions to support the autonomic system of controlling hunger, blood pressure, sexual response, hormone secretion and others (McElvain et al., 2021). The pituitary gland is present at the base of the skull in a small pocket known as Sella turcica. It remains connected with the hypothalamus and acts as the master gland for supporting sexual development, muscle and bone growth and stress management (Linsler et al., 2017). The pineal gland functions regulating circadian rhythm and internal clock of the body through secretion of melatonin and is located behind the third ventricle of the brain. The thalamus has the function to act as relay station in the brain for most information within the cortex and it has a role for sensation, memory, alertness and other. The basal ganglia include the putamen, caudate and globus pallidus which works with the cerebrum to support fine motor functions (Tan et al., 2018).

The midbrain is located in the middle of the brain connecting the hindbrain to the forebrain. It supports eyelid movement and eye along with contains cerebral aqueduct that is the canal connecting the third and fourth cerebral ventricles. It consists of tectum, cerebral peduncle and subustantia nigra. The tectum supports auditory functioning, cerebral penduncle supports endocrine and automatic functioning in the brain and aid in motor function. The subustantia nigra act as to support the production of dopamine as neurotransmitter in the brain and regulated mood along with voluntary actions (Caggiano et al., 2018). The hindbrain is composed of metencephalon (upper part) which contains the cerebellum and pons and myelencephalon (lower part) which is present just above the spinal cord. The different cranial nerves such as abducent, trigeminal, facial, and vestibulocochlear nerves are present in the metencephalon and myelencephalon contains hypoglossal nerves and others (Falkner et al., 2020). The hindbrain mainly functions to support balance, movement and relay of sensory data (Falkner et al., 2020).

In regard to basic structural difference, the Central nervous system (CNS) is mainly composed of brain and the spinal cord. The bones of the spinal vertebrae and skull acts to encase all the CN neurons and group of neurons within the CNS is known as nuclei (Lochhead et al., 2020). However, Peripheral nervous system (PNS) consists of all the nervous tissues and neurons such as sensory neuron and motor neurons. The neurons in the PNS are seen to travel along the top of the brain, muscles, organ and skin tissues. In PNS, the ganglion represents a group of cell bodies while the nerve is known as bundle of neurons (Briani et al., 2019). In contrast, the Sympathetic nervous system (SNS) mainly composed of two neuron sets are cell bodies which are present within the spinal cord and soma which resides in the ganglia present on the outside of the CNS (Sata et al., 2018). However, the Parasympathetic nervous system (PSNS) is mainly composed of sacral spinal nerves and cranial nerves with preganglionic neuron developing either from the sacral spinal cord or brain (Orimo et al., 2018).

In regard to division, CNS is divided into forebrain, midbrain, hindbrain and diencephalon (Sata et al., 2018). However, PNS is divided into autonomic nervous system and somatic nervous system (). The SNS and PSNS are two parts of the autonomic nervous system (Briani et al., 2019). The key function of CNS is to analyse and organise information to be processed for transmission through the nervous system for allowing the body to react accordingly. The damage of any nerve in the CNS leads to global effect on the body (Sata et al., 2018). However, PNS key function is to abide by the commands of the CNS transmitted through nervous signals. The PNS function respond to the command sent by the CNS by altering the motor output. The damage of any nerve in PNS leads to create localised impact on the body (Briani et al., 2019). The SNS functions to prepare and support individuals during stressful situation. It increases heart rate, respiration, raises blood flow rate to the muscles and others to support the body to fight with the stressed condition (Sata et al., 2018). In comparison, the PSNS functions to support relaxed and digestion response of the body. It mainly works to stimulate digestion, active metabolism, decrease respiration, reduce heart rate and others to normal to make the body remain stable (Orimo et al., 2018).

In the CNS, the glial cells include astrocytes, oligodendrocytes, ependymal cells and microglial cells together which acts to support enhanced internal body environment and neuron functioning. The astrocytes function to provide nutrients to the neurons and act in providing structural support to the nerves and maintain extracellular environment. The oligodendrocytes act in formation of the myelin sheath and the microglia acts to scavenge dead cells and pathogens from the body. The ependymal cells help in production of cerebrospinal fluid that support as cushion for the neurons in the brain. The glial cells in the PNS involve Schwann cells that help in formation of the myelin sheath and satellite cells along with assist in production of nutrient and giving structural support to the neurons (Pogoda and Janmey, 2018). In contrast, the neuron consists of three different part that are body, axon and dendrites. The axon is covered by the myelin sheath with its terminals connecting with other neurons. The neuron contains nucleus in the soma part of the body and develop dendrites which connects with axon terminals of neurons to transmits received nerve signals to specific part of the body (Krauss et al., 2019). The overall function of the glial cells is to support and protect neuron functioning and regulate homeostasis (Pogoda and Janmey, 2018). However, the function of the neuron is to transmit signals from one part of another through the neurons (Krauss et al., 2019).

The neurons communicate with one another through action potential that is the electrical impulse and chemical neurotransmitters (Abdul Kadir et al., 2018). In normal condition, the inner side of the cells is more negative compared to the outside meaning the inner part contains -70 mV charge which is also referred as the resting membrane potential. The action potential is not static within the nerve cells and is continuously fluctuation on the basis of input from the axons (Ling et al., 2020). The action potential on reaching the presynaptic terminal cause neurotransmitters to be released into the synaptic cleft from the neuron. On travelling to the synaptic cleft, the transmitters get attached to the neurotransmitter receptor present in the postsynaptic side and on the basis of the release of the neurotransmitter which is dependent on the neuron releasing it, particular positive ions (Na+, K+, Ca+) or negative ions (Cl-) is to travel through the neuron channel along the membrane span (Deemyad et al., 2018).

In resting stage, the sodium (Na+) and chloride (Cl-) ions are present in high amount in the extracellular fluid and increased amount of calcium (Ca+) and potassium (K+) ions are present in the internal fluid. The neuron is more permeable to K+ allows it to selectively move outside creating a lower concentration gradient inside the nerve cell compared to the outside which also leads to depolarisation. This led the ions to move from higher to lower gradient to stabilise the action potential allowing nerve signals to gradually pass through one neuron to another (Ling et al., 2020).

The neurotransmitters act to relay messages by travelling from one cell to another and attaching to specific nerve receptors present on the target cells. The excitatory neurotransmitters such as glutamate encourages cells to take action in response to the signal received due to which they are to be effectively managed so that they do not disrupt the normal functioning of the body (Reddy et al., 2018). It impacts the behaviour of a person to be excited and perform strenuous actions such as acetylcholine triggers increased heartbeat, enhances muscle contraction and others to support excitatory behaviour (Choudhury et al., 2018). The inhibitory neurotransmitters like gamma-aminobutyric acid (GABA) and serotonin acts in lowering the target cells efficiency in taking actions and it affects the behaviour of a person to be reduced to calmness from excited state (Tu et al., 2020). The serotonin and GABA acts as mood regulator to support pleasure and happiness feeling and behaviour in person (Giannini et al., 2019). The Modulatory neurotransmitters shows capability to influence large number of neurons at the same time and it acts to influence chemical messengers such as dopamine and acetylcholine in the body (Giannini et al., 2019).

Conclusion

The above discussion informs that brain is developed of many complex parts and function to support movement, behaviour and additional physical and mental actions in the body. The communication of nerve signals through action potential and neurotransmitters lead to support body movement and functioning.

Recommendations

The recommendation developed from report is that to promote happy mood and behaviour in person, the enhanced expression of mood stabiliser aa inhibitory neurotransmitters through application of exercise and pharmacotherapy is to be promoted. Moreover, the other recommendation is that effect actions are to be taken to support enhance functioning of central nervous system and peripheral nervous system as they are the key support system for healthy functioning of organs and body.

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