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 from senses  passes to cell body (soma)
message is passed to axon: long single fiber that carries message
myelin sheath – insulates/protects axon; controls speed of impulses
action potential – message’s electrical charge

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 (brain can understand these)
picked up by dendrites to start all over again!

5. HOW NEURONS WORK VIDEO

6. TYPES OF NEURONS
sensory 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

7. AFFERENT VS. EFFERENT NERVES

8. ascending tract carries sensory messages to brain
TRACTS
ascending tract carries sensory messages to brain
descending tract carries motor impulses & messages to the body (from brain)

9. 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

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

12. 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

13. BREAKDOWN IMAGE

14. 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)

15. SUMMARY VIDEO
Additional Nervous System Video Link:
(1:30min)