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THE NERVOUS SYSTEM

THE NERVOUS SYSTEM. DEFINITION. the body’s communicator electrical & chemical changes relay messages nerves are strings of neurons (special cells) that pass on messages ( neural impulses ) to one another (take messages in at one end & send message out another end). PARTS OF A NEURON.

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THE NERVOUS SYSTEM

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  1. THE NERVOUS SYSTEM

  2. DEFINITION • the body’s communicator • electrical & chemical changes relay messages • nerves are strings of neurons (special cells) that pass on messages (neural impulses) to one another (take messages in at one end & send message out another end)

  3. PARTS OF A NEURON • dendrites: branched fibers that RECEIVE message to pass through cell body (soma) • message is passed on to axon: single fiber that carries message after passing through dendrite & soma along to other neurons • action potential– electrical charge of the message

  4. PARTS OF A NEURON, PART II • terminal buttons are activated at end of axon & want to pass message along BUT… • neurons are separated by a synapse (gap) so… • electrical impulse is converted into chemical message that activates neurotransmitters – chemicals that transfer the messages across synaptic gap • picked up by dendrites to start all over again!

  5. TYPES OF NEURONS • sensory or afferent neurons– send message from sensory receptor cells to central nervous system • motoror efferent neurons– deliver messages from CNS to muscles & glands • interneurons– communicate between neurons

  6. TRACTS • ascending tractcarries sensory messages to brain • descending tractcarries motor impulses & messages to the body (from brain)

  7. 2 MAIN BRANCHES OF NERVOUS SYSTEM • central nervous system (CNS)= brain & spinal cord: coordinates all bodily functions by processing neural messages & sending commands to body • peripheral nervous system = connect CNS to body: smaller branches of nerves & nerve fibers that communicate messages between CNS & body

  8. BREAKDOWN OF PERIPHERAL N.S. • somatic nervous system controls voluntary acts (tapping foot, walking, etc) • autonomic nervous systemare involuntary acts (digestion, breathing, etc.)

  9. BREAKDOWN OF AUTONOMIC N.S. • sympathetic system– reactions to emergencies & strenuous activity; “fight or flight” • parasympathetic system– conserves energy, helps body behave normally, monitors routine activities, & calms body after sympathetic arousal

  10. SPINAL CORD • CNS sends/receives messages through spine & PNS • spinal cord is also responsible for reflexes that do not involve the brain (it’s too busy!)(i.e. knee-jerk)

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