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The Nervous System
Why is the nervous system important?
Nervous System Structure
• Central Nervous System (CNS)
• Spinal Cord
• Peripheral Nervous System (PNS)
• Sensory – carries impulses to
• Motor – carries impulses from CNS
• Somatic Nervous System – voluntary
• Autonomic Nervous System - involuntary
• Nerve Cells – Neurons (~100 billion neurons in the human
• Dendrites – branched projections of a neuron that act to
conduct the electrochemical stimulation received from other
neural cells to the cell body or soma
• Soma – the cell body, contains the nucleus
• Axon – long, slender projection of a neuron that conducts
electrical impulses away from the soma
• Myelin Sheath – electrically insulating layer around the axon,
increases the speed of impulses
• Schwann Cell – part of PNS, help nerve development and
regeneration, form myelin
• Node of Ranvier – Tiny gaps between Myelin Sheath, action
• Axon Terminals – The end branches of an axon, separated
from neighboring neurons by a synapse
Activity 1: Neuron Model
Multiple students hold “dendrites” = ropes
One student holds the “Soma” = container
One student moves the “action potential” = plastic tube
One student hold the axon terminal = container filled with
• With a larger class there could be multiple neurons
Activity 2: How fast can you process information?
• One person holds the yard stick up
• Second person is being tested at how fast they can
respond to the yard stick falling
• The first person will release the yard stick and the second
person will catch it. They will record where their hand grabs
the yard stick.
• Using this formula: t = √2y/g , y = distance in inches, g =
gravity constant: 385.8 in/sec^2 one can calculate the time
it took to process the information and react to the object
• Variation with sound and dim lighting
• Record data
Activity 3: How sensitive is your skin?
• Put sand paper in order from most coarse to most fine
(ideally more variety)
• Use corkboards and toothpicks to measure touch receptors
on your skin.
• Measure the distance in which you can no longer feel two
spots touching your skin.
• Measure different areas on your body.
• Fill out data sheet and graph and answer analysis questions.
• Campbell, Neil A., Reece, Jane B., 2005. Biology. Pearson
Education Inc., San Francisco, CA. pgs 1011-1044