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Neurons: Their Structure and Function

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Neurons: Their Structure and Function The human central nervous system contains a vast complex of information processing circuits formed by interconnecting networks of nerve cells. Together the brain and spinal cord constitute the central nervous system, which is kept in contact with the receptors and effectors of the rest of the body by the peripheral nervous system. The nerves of the peripheral nervous system convey messages to and from the spinal cord. Afferent nerves run towards the spinal cord and have a sensory function, whereas efferent nerves run away from it and have a motor function. If for example you pricked your finger with a pin, the afferent nerves would carry this information about the sensation to the spinal cord, while the efferent nerves would bring about the movements of muscle groups, thereby bringing the limb into action and to withdraw. Another component of the nervous system is the autonomic nervous system, which is concerned with controlling the body's involuntary activities. These include such functions as the beating of the heart, movements of the gastrointestinal tract, and the secretion of sweat. The person most directly responsible for the acceptance of the neuron constituting an integral part of the nervous system was Ramon y Cajal (Jones, 1981). Ramon y Cajal was able to describe the shapes and distributions of individual neurons in many different parts of the nervous system. ...read more.


These protein molecules constitute more than 20% of the membrane of a typical neuron and present on the neuron many of the characteristics that distinguish it from other types of cells and also other neurons (Alberts & Raff, 1994). Different proteins can have different properties, and because of the presence of particular types of proteins with specific characteristics it brings about certain neurons having a particular functional feature (Brodal, 1992). Despite there being a wide array of proteins they can be grouped into three categories based on characteristics, capabilities and function. The first being transport proteins. Transport proteins mediate the transfer of ions across the cell membrane. Within the category of transport proteins there are proteins known as ion channels that by the process of diffusion allow the passive flow of ions through the membrane. Another is the ion pump protein that expends energy to move one or more ions across the membrane against a concentration gradient in a process known as active transport. The second type of protein is the signalling protein. Signalling proteins are necessary for the transporting of information from one cell to another. An important type of signalling protein is the receptor, which has a high binding ability for other molecules and is used to respond to messages. A further type of signalling protein is the guanine nucleotide protein that initiates biochemical reactions that lead to a neuron's response to a signalling molecule. ...read more.


The nodes of Ranvier are separated sections of the axon that are covered by a myelin sheath. The nodes of Ranvier and the myelin sheath help to increase the speed of the action potential. The axon potential then arrives at the axon terminal which results in the release of neurotransmitters. Neurotransmitters then cross the synaptic cleft and activate receptors on the membrane of the postsynaptic neuron. This can then cause the postsynaptic neuron to fire a nerve impulse. After the neuron has fired it then returns to its resting value of -70 millivolts. In electrical transmission, the current flow generated by an impulse in the presynaptic neuron spreads directly into the next neuron. This may result in the initiation of an impulse in the postsynaptic neuron. The most notable feature with the electrical synapse is its speed compared to the chemical transmission. There are several types of neurons in which action potentials are not generated. These cells operate on a passive potential and are known as non-spiking neurons (the word spike is another name for action potential). These types of non-spiking neurons can be found in the sensory neurons that operate over short distances, such as the ones found in the visual systems (Young, 1989). The ability of the neuron to transmit information is the functional basis of all the nervous system. The minute building block of the neuron that leads to the nervous system and eventually to human consciousness is extremely complex. Its unique structure and function enable the human mind to think, feel see and act. ...read more.

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