The Nervous System T. Zack Crawford

Function To transmit signals between different parts of the body, whether it be voluntary or involuntary action. In the human body, the nervous system is split into two parts: the central and peripheral nervous systems The central nervous system includes only the brain and spinal cord while the peripheral nervous system includes the nerves and ganglia connecting the central nervous system to appendages and organs.

A simple reflex When your body receives a stimulus, a receptor in your nervous system will recognize this stimulus and then send it to your central nervous system. Your CNS will recognize this stimulus and initiate a chemical response. This response travels through a motor nerve which then causes a response in an effector.

The Central Nervous System Cerebral Hemespheres – The left and right regions of the brain bilaterally separated by the 'median plane' The Diencephalon – The posterior region of the forebrain, between the cerebral hemespheres. It contains the epithalamus, dorsal thalamus, subthalamus, and hypothalamus. The Brainstem – The posterior part of the brain structurally joining to the spinal cord. The Cerebellum – The region of the brain known for its involvement in motor control.

The Nerve Impulse A nerve impulse is an electrical current that travels along a neuron to pass a message through the body Inside a neuron, a resting membrane potential is maintained between the inside and outside of the cell membrane by sodium-potassium pumps. The active transport by the pumps send sodium out of the cell and potassium into the cell creating a net negative charge inside, and a net positive on the outside.

The Nerve Impulse cont... The impulse begins when a stimulus disturbs the membrane on the dendrite of a neuron causing voltage gated sodium channels to open. Sodium ions flow into the cell causing a change in the net charge along the membrane of the cell. If the change is greater than the threshold, depolarization will occur in that area of the cell. This depolarization causes more nearby sodium channels to open, moving the depolarization along the membrane. This is called action potential. As the depolarization travels along the membrane, sodium channels close and potassium channels open allowing resting potential to be actively restored. This is called the refractory period.

Neurotransmitters At the end of an axon, the membrane will depolarize and calcium ions enter the cell through gated ion channels. The calcium ions cause a neurotransmitter to be released into the synapse between a neuron and another cell. The neurotransmitter will bind to receptors on the target cell and an excitation or inhibition will occur in the target cell.

Multiple sclerosis An inflammatory disease where the fatty myelin sheaths around the axons of the brain and spinal cord are damaged. The cause could be genetic, environmental, or infectious. Symptoms include almost any neurological symptom such as muscle weakness, spasms, difficulty with movement or balance, or acute/chronic pain. MS more commonly appears in women, especially over the age of thirty. It is most commonly found in North America and Europe with prevalence between 2 and 150 per 100,000 people. There is no common cure for MS, however several therapies focusing on returning function have shown to be helpful.

Meningitis Meningitis is inflammation of the protective membranes covering the brain and spinal cord, usually caused by infection. It can be life threatening due to its proximity to the central nervous system. Symptoms most commonly include severe headache, rigid neck, and fever. Meningitis most commonly occurs in third world countries especially in Africa. Children are at the highest risk of mortality, 20-30% of infected newborns may die from bacterial meningitis. If showing symptoms, treatment with wide-spectrum antibiotics should be immediately administered while confirmatory tests are conducted.

Resources http://en.wikipedia.org/wiki/Nervous_system http://en.wikipedia.org/wiki/Central_nervous_system http://en.wikipedia.org/wiki/Peripheral_nervous_system http://medicalcenter.osu.edu/patientcare/healthcare_services/nervous_system/about/Pages/index.aspx http://en.wikipedia.org/wiki/Neuron http://outreach.mcb.harvard.edu/teachers/Summer05/JerryHalpern/Reflexes.pdf http://en.wikipedia.org/wiki/Cerebellum http://en.wikipedia.org/wiki/Brain_stem http://en.wikipedia.org/wiki/Diencephalon http://en.wikipedia.org/wiki/Cerebral_hemispheres http://en.wikipedia.org/wiki/Nerve_impulse http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html http://www.dummies.com/how-to/content/understanding-the-transmission-of-nerve-impulses.html http://en.wikipedia.org/wiki/Neurotransmitter https://en.wikipedia.org/wiki/Multiple_sclerosis https://en.wikipedia.org/wiki/Meningitis