The Nervous System

Central Nervous System  All nerves encased in bone make up the central nervous system (CNS). The central nervous system is responsible for processing information and directing the body.  Brain =organ of thought & nervous coordination enclosed in the skull  Spinal cord = reaching from the base of the brain through the neck & spinal column transmits messages between the brain & the peripheral nervous system

Peripheral Nervous System  The Peripheral Nervous System (PNS) is made up of all nerves that are not encased in bone; its main function is to carry information to & from the CNS.  Somatic = controls skeletal muscles, interacts with outside environment  Autonomic = regulates internal organs, breathing, blood vessels  Sympathetic = prepares body for emergency; mobilizes energy resources  Parasympathetic = reserves body’s energy; returns body to normal, resting state after an emergency

Neurons & Transmission of Information  Neuron = specialized cell that conducts impulses (sends messages) through the nervous system  contains 3 major parts--cell body, dendrites, & an axon  Cell body = contains the nucleus & carries out the metabolic (life-sustaining) functions of the neuron  dendrites = receivers of signals from other neurons (look like tree branches)  axon = tail-like extension of the neuron that transmits signals to the dendrites or cell body of other neurons or to the other muscles or glands  axon terminal = sends messages to other neurons by releasing a neurotransmitter that travels across the gap between two neurons  myelin sheath = fatty coating wrapped around some axons that acts as insulation & enables impulses to travel much faster

 Note: neurons are not connected to each other--separated by tiny, fluid-filled gaps called synaptic clefts  Synapse = junction where the axon terminal of the sending neuron communicates with a receiving neuron across the synaptic cleft  Neurotransmitters = chemical that is released into the synaptic cleft from the axon terminal of the sending neuron, crosses the synapse, & binds to appropriate receptor sites on the dendrites or cell body of the receiving neuron & influences the other cell

 receptor site = site on the dendrite or cell body of a neuron that will receive only specific neurotransmitters  variety of neurotransmitters = regulate actions of glands, muscles, learning, memory, sleep, emotions, relief from pain, etc.  Two types of neurons:  A sensory neuron is a nerve cell that relays impulses from a receptor such as those in the eye or ear to a more central location in the nervous system.  Also known as receptors  A motor neuron is a nerve cell that sends impulses from a central area of the nervous system to an effector such as a muscle  Also known as effectors

NeurotransmitterNormal FunctionProblems Associated with Imbalance Substances that affect the Action of this N.T Dopamine Affects brain processes that control movement, emotional response, and ability to experience pleasure and pain ADHD, Parkinson’s Disease, Schizophrenia Cocaine, Amphetamines, other stimulants Serotonin Regulates the development of serotonergic neurons and specific tissues Depression, anxiety, irregular appetite, and pain sensations Antidepressants, antipsychotics, anti-migraine drugs, and ecstasy Norepinephrine (aka adrenaline) Increases heart rate, increases blood pressure DepressionImipramine, desipramine, reboxetine ** These are anti- depressants Acetylcholine Activates musclesAlzheimer’s DiseaseTHC, Donepezil, Galantamine, Rivastigmine, Tacrine, Nicotine GABA Contributes to motor control, vision, and many other cortical functions. Also regulates anxiety Spastic Cerebral Palsy, Anxiety, and Epilepsy Alcohol Endorphins Transmit electrical signals within the nervous system Stress and painMorphine, Codeine, Heroin, other opiate drugs Glutamate Key molecule in cellular metabolism Stroke, amyotrophic lateral sclerosis (Lou Gehrig’s Disease), Autism, Mental retardation, and Alzheimer’s Disease Ketamine, and PCP

How Nervous System Works- 5:44 youtube