Nervous System ppt

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Part 1 Biology 12

 Neurons  Gathers & transmits electro-chemical signals DID YOU KNOW????

 Neurons cannot be repaired  Some last a life time  Approximately 1000 die each day!!!

 http://outreach.mcb.harvard.edu/animation s/actionpotential.swf

 http://people.eku.edu/ritchisong/301notes2 .htm

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

 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

 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)

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

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

 The three interconnected functions of the nervous system are carried out by three types of neurons

Sensory input Sensory neuron Integration Sensory receptor Motor neuron Motor output Interneuron Effector Peripheral nervous system (PNS) Brain and spinal cord Central nervous system (CNS)

Figure 27.2

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

Nucleus Dendrites Cell body Cell body

Figure 27.3

 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

Dendrites Cell body Nucleus Axon Myelin sheath Nodes of Ranvier Cell body

Figure 27.3

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

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

Figure 27.3

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

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

Figure 27.3

Draw a motor neuron

Label

    Cell body Nucleus Dendrites axon     Myelin sheath Schwann cells Node of Ranvier Synaptic knob

Synaptic knob

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