The Nervous System - 1486 Words

The nervous system is made up of 2 main parts - the spinal cord and the brain. These two parts combine to make the central nervous system and the sensory and motor nerves which form the peripheral nervous system. Neurons process information in the form of electrical signals, namely nerve impulses, which travel along the axon. Charged ions are not able to enter plasma membranes which make neurons have a difference in ion concentration between the inside and the outside of a neuron. This prevents the passive diffusion of Potassium and Sodium ions from areas of high concentration to areas of low concentration. Proteins which act as ion channels and ion pumps are attached to plasma membranes. This allows the ions to be transported across†¦show more content†¦Voltage-gated ion channels maintain the concentrations of different ions inside and outside of the neuron cell. An action potential takes place when a neuron sends information through an axon, away from the cell body. The transmission of the information flows through a synapse. At the synaptic terminal, an electrical impulse causes the movement of vesicles containing neurotransmitters towards the pre-synaptic membrane. The vesicle membrane merges with the pre-synaptic membrane releasing the neurotransmitters into the synaptic cleft, a space which is between the pre-synaptic and post-synaptic endings. When a neurotransmitter binds to a receptor, the post-synaptic cell s likelihood of firing an action potential can be increased or decreased. When neurotransmitter molecules are stuck to receptors located on a neuron s dendrites, the part of a neuron which receives signals from other neurons, ion channels are opened. At an excitatory synapse, the opening of ion channels enable positive ions to enter the neuron and results in the loss of difference in the charge between the inside and the outside of the membrane, this is called depolarization. Sodium channels open first and sodium ions rush into the neuron. When potassium channels open, potassium ions rush out of the cell and the depolarization is reversed. Sodium ion channels begin to close which results in the action potential to go past -70 mV because the