The Nervous System: The Basic Structure Main Idea: Learning about the nervous system helps us know how messages that are sent to the brain cause behavior.

How the Nervous System Works Controls emotions, movements, thinking, and behavior Two Parts: –Central Nervous System (the brain and spinal cord) –Peripheral Nervous System (the smaller branches of nerves that reach the other parts of the body)

Central Nervous System Brain Spinal Cord – nerves that run up and down the length of the back and transmit most messages between the body and brain

Peripheral Nervous System Nerves of the peripheral system conduct information from the bodily organs to the central nervous system and take information back to the organs.

Peripheral Nervous System Somatic: controls voluntary muscles Autonomic: controls involuntary muscles –Sympathetic: expends energy Prepares the body for dealing with emergencies or strenuous activity Speeds up the heart to hasten the supply of oxygen and nutrients to body tissue Increases the blood pressure and suspends some unneeded activities like digestion. –Parasympathetic: conserves energy Works to enhance the body’s ability to recover from strenuous activity Reduces heart rate and blood pressure

Neurons The long, thin cells of nerve tissue along which messages travel to and from the brain

Neurons – Basic Parts Cell Body –Nucleus –Produces Energy needed to fuel neuron activity Dendrites –short thin fibers that stick out from cell body –Receive impulses (messages) from other neurons and send them to the cell body Axon –Long fiber that carries the impulses away from the cell body toward the dendrite of the next neuron –Can be short or several feet long Myelin Sheath –White, fatty substance that insulates and protects the axon –Speeds the transmission of impulses –If missing, such as in multiple sclerosis, it can cause erratic and uncoordinated behavior Axon Terminals –Small fibers that branch out at the end of the axon that are positioned opposite the dendrite of another neuron Synapse –Space between the axon terminals of one neuron and the dendrite of another neuron –Junction between neurons where the messages are transmitted from one neuron to the other Click to explore the parts:

Neurotransmitters Chemicals released to transmit messages from one neuron to another They can excite the next neuron They can inhibit the message from traveling to the next neuron

Types of Neurotransmitters Norepinephrine –Involved in memory and learning Endorphin –Inhibits pain Acetylcholine –Involved in memory and movement Dopamine –Involved in learning, emotion, arousal, and movement Serotonin

Chemical Imbalances Undersupply –Acetylcholine = Paralysis and Alzheimer’s disease –Dopamine = Parkinson’s disease –Norepinephrine and Serotonin = Depression Oversupply –Dopamine = Schizophrenia