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Section 35-2: The Nervous System

Section 35-2: The Nervous System. The Nervous System: Main Function. The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli. A. What are some specific functions of the Nervous System?.

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Section 35-2: The Nervous System

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  1. Section 35-2: The Nervous System

  2. The Nervous System: Main Function • The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli.

  3. A. What are some specific functions of the Nervous System? • 1. Receives sensory messages from the external environment • 2. Organizes information and integrates it with already stored information • 3. Sends out messages to muscles and glands, producing movement and secretions • 4. Allows for consciousness

  4. B. What makes up the Nervous System? • The basic unit of structure and function of the nervous system is a neuron (nerve cell).

  5. Pictures of Neurons

  6. C. What are the 3 Main Types of Neurons? • 1.Sensory Neurons(sensory = of the senses) -receive information from receptors in sense organs • 2. Interneurons(inter- = between) -relay messages between neurons • 3. Motor Neurons (motor = causing motion) -give instructions to effectors (glands or muscles)

  7. Nucleus Axon terminals Cell body Myelin sheath Axon Nodes Dendrites D. What is the Structure of a Neuron? 1. Cell body: Contains the nucleus and other cell organelles 2. Dendrites: Short, branched extensions of the cell body *Function: receive stimuli* 3. Axon: long, thin extension of the cell body *Function: sends nerve impulses away from the cell body* (Remember “A” for away!)

  8. E. How do Neurons Communicate? • “The brain is a monstrous, beautiful mess. Its billions of nerve cells - called neurons – lie in a tangled web that displays cognitive powers far exceeding any of the silicon machines we have built to mimic it.” -William F. Allman

  9. Steps for How Neurons Communicate • 1. Dendrites receive the signal (action potential) which then travels down to the axon of the first neuron. • 2. When the signal reaches the end of the axon, the axon releases chemicals called neurotransmitters. ex. acetylcholine, norepinephrine, dopamine, serotonin • 3. Neurotransmitters enter into the space between the 2 neurons, called the synaptic cleft. • 4. Neurotransmitters bind to receptors on dendrites of the next neuron thereby passing on the signal.

  10. The Synapse = junction between two neurons Section 35-2 Direction of Impulse Dendrite of adjacent neuron Axon Receptor Vesicle Axon terminal Synaptic cleft Neurotransmitter

  11. Another Diagram of a Synapse

  12. Synapse Animation Synaptic Transmission • Click the image to play the video segment.

  13. Threshold • Strength of impulse is always the same • It is an all or nothing response: An impulse either occurs or does not occur (like dominoes) • Minimum level of stimulation to cause an impulse is called the threshold

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