The Function of Nervous System

Question: Describe the structure and the function of the nervous system. Answer: 1.1 Structure of the Central Nervous System and Sensory, Connector and Motor Neurons The Central Nervous System is considered as the processing center of the entire nervous system. The CNS plays a crucial role in receiving and sending information o the peripheral nervous system. Brain and Spinal Cord are the key components of the CNS (Woolsay et al., 2013). The CNS is located within the dorsal body activity in a way that the brain is located in the cranial activity and the spinal cord within the spinal canal. The brain remains enclosed within the skull and is protected by the cranium and is primarily divided into three major portions of the forebrain, midbrain, and the hindbrain. The spinal cord is a cylindrically shaped bundle of nerve fibers that remains connected with the brain. The spinal cord starts from the foramen magnum and terminates roughly in; level with the first or the second lumbar vertebra and thus occupies the upper section of the vertebral canal (Whoolsey et al., 2013). Neurons are considered as the key unit of the nervous system. Structurally neurons consist of nerve processes that are finger-like projections that extend from the body of the nerve cell (Nieuwenhuys et al., 2014). The nerve p[processes thus primarily consist of axons dendrites that play a crucial role in the process of condition and transmission of nerve impulse. Structurally neurons are broadly classified as the motor, sensory and the connecting neurons (interneurons). Motor neuron helps in carrying information from the CNS to the other organs while sensory neurons assist in sending information from the internal organs to then CNS. The connecting neuron lies in between the sensory and the motor neuron and thereby plays a key role in transmitting signals between the sensory and the motor neurons. 1.2 Transmission of Nerve impulse and Role of Chemical transmitters Transmission of nerve impulse takes place from one neuron to another by the formation of a resulting electric charge across the membrane of the neuron. The membrane of an unstimulated neuron gets polarized that helps in creating a difference in electric charge between the outside and then inside of the neuron membrane. This process is known as the synaptic transmission and in this process; the signaling molecules called the chemical transmitter's plays a key role in transmitting the nerve impulse from one end of the neuron to another. This is considered as an essential process that helps in providing communication between the two adjacent neurons. In respond to the threshold action potential generated, a chemical transmitter is released at one end of the pre-synaptic terminal (Nieuwenhuys et al., 2014). The released neurotransmitter then moves across the synapse to get bind with the receptor of the postsynaptic neuron either in an inhibitory or excitatory way. This binding is associa ted with producing a short-term change which includes a change in the membrane potential also known as the postsynaptic potentials or may also initiate long-term changes by suitable activation of various kinds of signaling cascades. Each neuron can have almost 15,000 connections with the adjacent neurons (McDonald Sears, 2015). 1.3 Comparison between Voluntary and Reflex Action and Role of Autonomic Nervous System Voluntary actions are initiated in the brain (cerebral cortex region) due to the formation of a particular thought. In case of initiating voluntary actions, impulse first passes to the motor area located at the lateral side of the cerebral cortex and then the spinal cord. Impulse thus passes over to the motor neuron and thereby produces a significant effect on the opposite side of the body which emphasizes on the fact that the right side of the brain controls the left side of the body and vice versa. This leads to slowing down of the various kinds of the long synaptic pathway. Reflex action, on the other hand, is initiated by stimulation of a particular receptor. Impulse thus generated first passes to the dendrite and axons of the sensory neuron, and the via Synapse goes to the relay neuron located in the grey matter near the center position of the spinal cord (McDonald Sears., 2015). This, in turn, is associated with passing the impulse directly to the motor neuron which carries the impulse to the effectors that are related to producing an action on the same side of the body. Only three cells and two synapses are involved which in turn is associated with showing a quicker response, and thus the secondary information passes up to the spinal cord to the brain and thus then subject gets aware of the event. The primary role of the autonomic nervous system (ANS) is that it helps in regulating the function of the internal organs such as the heart, intestines, and the stomach. ANS also constitutes an important part of the peripheral nervous system and thus also remains associated with controlling some of the muscles of the body (Kierman Rajakumar, 2013). 1.4 Effect of Nicotine on transmission of Nerve impulse Nicotine is considered as one of the potent stimulators for transmitting nerve impulse in ganglia of the autonomic nerve system. At small doses, nicotine stimulates the ganglionic transmission while at high doses it just produces an opposite reaction. Nicotine stimulates the adrenal cortex to release a compound knows as catecholamines (Midlekauff, 2014). The Catecholamines thus released in small doses helps in better transmission of the nerve impulse between the two neuron ends. Thus, it can be stated that nicotine affects the neurotransmission by causing an increase in the action potential in the post-synaptic neuron which in turn is associated with causes more dopamine to get released per vesicle (Hebebrand Verhulst, 2014). 100% (NORMAL) More than 350% (PRESENCE OF NICOTINE) References Hebebrand, J., Verhulst, F. (2014). Prenatal risk factors and postnatal central nervous system function.European child adolescent psychiatry,23(10), 857. Kiernan, J., Rajakumar, R. (2013).Barr's the human nervous system: an anatomical viewpoint. Lippincott Williams Wilkins. McDonald, W. I., Sears, T. A. (2015). The effects of experimental demyelination on conduction in the central nervous system.Brain,93(3), 583-598. Middlekauff, H. R., Park, J., Moheimani, R. S. (2014). Adverse effects of cigarette and noncigarette smoke exposure on the autonomic nervous system: mechanisms and implications for cardiovascular risk.Journal of the American College of Cardiology,64(16), 1740-1750. Nieuwenhuys, R., Hans, J., Nicholson, C. (2014).The central nervous system of vertebrates. Springer. Woolsey, T. A., Hanaway, J., Gado, M. H. (2013).The brain atlas: a visual guide to the human central nervous system. John Wiley Sons.