homeostasis and the nervous system the nervous system helps to maintain equilibrium in the body by its response to internal and external stimuli drinking water example you see a glass of water this image is processed in your brain which then sends an impulse to your bicep to bring the water glass to your mouth nervous system has two main divisions the central nervous system which consists of the brain and spinal cord and the peripheral nervous system which is made of sensory neurons which bring information in to your central nervous system and motor neurons which carries information out the motor neurons have two main divisions somatic nervous system controls voluntary movements so skeletal muscles and the autonomic nervous system controls involuntary movements things like digestion and breathing the autonomic nervous system is further divided into sympathetic which is fight-or-flight and parasympathetic which is rest and digest there's two main cells in the nervous system the glial cells are non conducting they are used for support and metabolism of the nerve cells they help to hold neurons close together the word glial means glue and then neurons are conducting they carry the nerve or electrochemical impulse nerves are bundles of neurons so here we see a big nerve cell made of many many neurons parts of a neuron dendrites have receptors to receive stimulation into the neuron the cell body contains the nucleus the myelin sheath is fatty protein used for insulation it speeds up transmission if a neuron has a myelin sheath then it is referred to as white matter because myelin is made of a fatty protein and fat is white the node of ranvier is the gap between the cells of the myelin sheath where saltatory conduction occurs the axon endings or knobs contain synaptic vesicles filled with neurotransmitters Schwann cells are glial cells that form the myelin sheath the axon is an extension of the cell body it carries the impulse the nucleus contains DNA direction of nerve impulse travels from the cell body to the axon endings the speed of nerve transmission is increased by two things a bigger axon diameter and a myelin sheath around the axon the Schwann cells wrap around the axon forming the myelin sheath here we see a Schwann cell and wraps and wraps and when it's done wrapping it is called the myelin sheath the myelin sheath insulates the axon to prevent the loss of charged ions which increases the speed of transmission myelin is like the plastic coating that covers copper wires in a home the plastic coating insulation prevents electrical signals from inappropriately leaking out of one wire and into another like an axon energy is carried faster through a transmission cable with a bigger diameter covered with more insulation in axons the myelin sheath speeds the electrical signals along that's because glial cells force a signal to jump from one spot on the axon to the next as it hops between glial cells the signal moves faster it's kind of like flying from one spot instead of taking the train so it flies as it's traveling through the myelin sheath and then it slows down at the node of ranvier so we have saltatory conduction as it jumps from one node to the next the nodes of ranvier are the gaps between the myelin sheath they allow for ions to diffuse in and out of the neuron propagating or moving the electrical signal down the axon although the nerve impulse is slower at the nodes of ranvier the exchange of ions is required to regenerate the action potential through saltatory conduction son might unmyelinated neurons the movement of action potential is slower because there's continuous conduction along the entire length of the axon vs. Salta coin sul to Tory conduction carries the nerve impulse faster m/s is an autoimmune disease in which the body's own immune system breaks down the myelin sheath on the neuron due to destruction of the myelin sheath there is inefficient nerve transmission so here we see the healthy nerve the nerve transmission is through the entire length of the axon versus the damaged nerve it stops at the point of scarred myelin there are three types of neurons sensory interneuron and motor neuron in the peripheral nervous system we have sensory neurons which are myelinated they carry information from sensory receptors or al factors to the central nervous system in the central nervous system we have inter neurons which are unmyelinated they integrate and interpret information and transmit information from sensory to motor neurons they also carry the impulse to the brain and back motor neurons are myelinated they carry information from the central nervous system tewi factors which include glands and muscles within the spinal cord we have two types of cells the outer part is myelinated which is called white matter and the in part is uninterpreted myelinated and is referred to as gray matter the reflex arc information coming into the spinal cord and coming out quickly is involuntary and unconscious it synapses at the spinal cord it does not require the brain and the purpose is to make quick responses there's five parts to reflex arc first is the effector or sensory receptor which converts stimulus into nerve impulses sensory neuron carries information into the central nervous system the inter neuron carries it from the sensory neuron to the motor neuron which carries it to the efactor the muscle or gland that responds so the order is effector sensory neuron inter neuron motor neuron an effector which spells a sign in the spinal cord remember we have white matter which has myelin and gray matter which has no myelin as the inter neuron sends information to the motor neuron for quick response it also carries information to the brain about what just happened