The Nervous System

Interesting Facts Each side of the brain controls the opposite side of the body. Your brain is full grown by age 6-7 (in size). It weighs about three pounds. Your brain is made mostly of water. (85%)

Healthy Habits Exercise Do challenging activities that make you think read, read, read Lift things carefully – use your legs, not your back

What are the functions of the NS? Collects information about the body’s internal and external environment Processes that information Responds to it

Your nervous system has two divisions… Peripheral Nervous System Central Nervous System Spinal cord Brain Links the CNS to body 12 pairs of Cranial nerves Surrounded by bones Somatic Autonomic

Gathers info and sends it to the CNS Searching for a pen in your bag… PNS Gathers info and sends it to the CNS Searching for a pen in your bag… PNS Gathers info from hand Input CNS Processes the info and forms a response CNS YES? Pen found NO? Pen not found Output PNS Carries the response to glands and muscles PNS Keep searching Stop Searching

How does this communication work? The messages are carried by electrical signals called These impulses are transmitted by cells called IMPULSES NEURONS

3 Types of Neurons Specialized in location and structure Sensory - carries impulses from the sense organ (hand) to CNS Interneuron - conducts impulses between sensory and motor Motor - carries impulses from brain + spinal cord to muscles and glands

sensory neuron motor neuron interneuron

Structure of a Neuron dendrites Cell body Nucleus of schwann cells Node of ranvier Node of Ranvier axon Axon terminals

Function of the neuron parts: Cell body – contains nucleus, receives signals from other neurons, Axon – conducts nerve impulses away from the cell body Axon terminal – end of the axon Node of ranvier – gaps where there is no myelin sheath Schwann cells – forms the myelin sheath Dendrites – extensions leading toward the cell body

Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us. Bill Watterson, cartoonist, "Calvin and Hobbes" US cartoonist (1958 - )