Download Introductory Assignment to the Nervous System

 What organ coordinates most of the activities of the nervous system?  Through what part of the body do most messages reach or leave the brain?  The brain and spinal cord form what part of the nervous system?  What connects the central nervous system to muscles and sense organs throughout the body?  What carries signals throughout the nervous system?  Name some parts of a nerve cell, or neuron.  What do we call the tiny space between neurons over which signals must pass from neuron to neuron?  What do we call the electrical signals that have reached the end of an axon and have become chemical signals?  What special nerve cells allow us to see, hear, feel, taste, and smell the world around us?  What special nerve cell allows us to move?  Anything that brings about a response Examples * stimulus – step on nail * response – jerk foot up * stimulus – see bright light * response – squint Eyes  Basic units of the nervous system Axon tips  Dendrites reach out and “grab” sensory information and send it to the cell body  Axons carry the message away from the cell body to another neuron  sensory neurons – receive sensory info from environment and send it to the brain or spinal cord  interneurons – in the brain and spinal cord, they decide what to do with the message from the sensory neuron  motor neurons – carry reaction message away from the brain toward muscles  Neurons do not touch. Messages are transferred by chemicals jumping across the gap between two neurons, called a synapse. Sensory neurons in the ear hear breaking glass. The brain takes the message from the sensory neurons and decides if a response is necessary. The brain decides the response should be to cover eyes with hands. This message leaves the brain via a motor neuron. The motor neuron deadends in a muscle, telling the muscle to contract and jerk up the arms. Example taken from an issue of National Geographic, p. 528  Central is brain and spinal cord, only  Peripheral is all nerves outside the brain and spinal cord. It connects the body to the brain and spinal cord.  Sensory neurons travel toward the brain or spinal cord for message interpretation.  Motor neurons travel away from the brain or spinal cord for responses. • Spinal cord’s diameter gets larger and larger as you go up the back toward the brain. • Spinal nerves have both sensory and motor neurons, so messages travel in two directions  somatic – nerves that go to the skeletal muscles, so voluntary  autonomic – involuntary (sympathetic and parasympathetic)  Involuntary, automatic responses to stimuli  Controlled by spinal cord, not brain  Leaving out the brain enables the body to react faster

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Download Introductory Assignment to the Nervous System