the nervous system
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
THE NERVOUS SYSTEM
THE NERVOUS SYSTEMDEFINITIONthe bodys 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 NEURONdendrites: 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 messagePARTS OF A NEURON, PART IIterminal 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!
TYPES OF NEURONSsensory or afferent neurons send message from sensory receptor cells to central nervous system
motor or efferent neurons deliver messages from CNS to muscles & glands
interneurons communicate between neurons
TRACTSascending tract carries sensory messages to brain
descending tract carries motor impulses & messages to the body (from brain)
2 MAIN BRANCHES OF NERVOUS SYSTEMcentral 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
BREAKDOWN OF PERIPHERAL N.S.somatic nervous system controls voluntary acts (tapping foot, walking, etc)
autonomic nervous system are involuntary acts (digestion, breathing, etc.)
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
SPINAL CORDCNS sends/receives messages through spine & PNS
spinal cord is also responsible for reflexes that do not involve the brain (its too busy!)(i.e. knee-jerk)