1. Part 1 Biology 12

2.  Neurons  Gathers & transmits electro-chemical signals DID YOU KNOW????  Neurons cannot be repaired  Some last a life time  Approximately 1000 die each day!!!

3.  http://outreach.mcb.harvard.edu/animation s/actionpotential.swf http://outreach.mcb.harvard.edu/animation s/actionpotential.swf  http://people.eku.edu/ritchisong/301notes2.htm http://people.eku.edu/ritchisong/301notes2.htm

4.  A nerve is a bundle of neurons attached by connective tissue

5.  Average number of neurons in the human brain = 100 billion  Nerve “highway” in the human body contains 100 billion neurons  1000 impluses/sec  Longest is about 1 meter (Where?) – human  Length of giraffe primary afferent axon (from neck to toe) = 15 feet  Average number of neurons in the octopus brain = 300 million

6.  SENSORY  Carries signals FROM periphery (outside) TO central nervous system for processing  Information FROM environment  NOTE: detect external stimuli (light, sound, touch, heat, smell, & taste) or internal conditions (blood pressure, CO 2 level & muscle tension)

7.  MOTOR  Carries signals FROM central nervous system TO body part (e.g. muscles, skin, glands)  Response to sensory  Movement

8.  INTERNEURONS  Connects sensory or motor neurons to central nervous system  Carries messages in-between neurons  Majority of neurons in the brain are interneurons

9.  The three interconnected functions of the nervous system are carried out by three types of neurons Sensory input Sensory receptor Sensory neuron Integration Interneuron Brain and spinal cord Central nervous system (CNS) Motor neuron Motor output Peripheral nervous system (PNS) Effector Figure 27.2

11.  Cell Body  Contains all organelles, including a nucleus  Dendrites  Projections off cell bodies  Make connections with other cells

12. Figure 27.3 Dendrites Cell body Nucleus Cell body

13.  Axon  Long cable like projection off cell body  Sends messages (nerve impulses)  Myelin Sheath  Fatty protein that covers/insulates most nerves  Increases speed of transmission  Formed by Schwann cells  Nodes of Ranvier  Exposed axon between myelin sheath

14. Figure 27.3 Dendrites Cell body Nucleus Axon Myelin sheath Nodes of Ranvier Cell body

15.  Synaptic knob  End of axon branches  Comes near dendrites of adjacent neurons  Passes messages across synapse (the space between neurons)

16. Figure 27.3 Signal direction Dendrites Cell body Nucleus Axon Supporting cell Myelin sheath Signal pathway Nodes of Ranvier Synaptic knobs Cell body

17.  Moves in only one direction  From dendrite to cell body, axon, then synaptic knob

18. Figure 27.3 Signal direction Dendrites Cell body Nucleus Axon Supporting cell Myelin sheath Signal pathway Nodes of Ranvier Synaptic knobs Cell body

19.  Draw a motor neuron  Label  Cell body  Nucleus  Dendrites  axon  Myelin sheath  Schwann cells  Node of Ranvier  Synaptic knob

20. Synaptic knob