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The Nervous System
The Nervous System
the electrochemical (chemical reactions brought about by electricity) communication system of the body
Neuron
cells of the nervous system
(brain, spinal cord, nerves)
Neurons perform three basic tasks:receive informationcarry informationpass information to the next neuron
Neuron Development
birth 3 months 2 years
Parts of the Neuron
Dendrites DETECT
Parts of the Neuron
Parts of the Neuron
Parts of the Neuron
Parts of the Neuron
Dendrites DETECT
Axons ANNOUNCE
Neurons
Neural Communication:
The Neural Impulse
Action Potential
brief electrical charge that travels down the axon
All-or-None Principle
if a neuron fires it will always fire at the same intensity
doesn’t matter if there is a strong or weak stimulation
Refractory Period
“recharging phase” when a neuron, after firing, cannot generate another action potential
once complete the neuron can fire again
Resting Potential
neuron is at rest & capable of generating an action potential
neuron is set and ready to fire
How are the 3 phases of neuron
communication like a toilet?
Action potential – when you flush an “impulse” is sent down the sewer
pipe
Refractory period – delay after flushing when the toilet can
not be flushed again
Resting Potential – toilet “charged” when there is water in the tank and is capable
of being flushed again
All-or-none-principle – always flushes with the
same intensity no matter how much force you apply to the handle
Review Questions(think! don’t say the answer out loud…yet)
1. What are the three phases of communication within a neuron?
2. What is the all-or-none principle?
Communication Between Neurons
“How do messages travel from one neuron to the next?”
Synapse
neurons do not come into contact with each other
Synapse - tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron
Neurotransmitters
chemical messengers
travel across the synapse
fit into receptor sites on the dendrite of the next neuron
Neurotransmitters
can stay only in receptor sites designed to fit their shape
serve two functions:1. Excitatory Effect
2. Inhibitory Effect
Excitatory Effect
makes it MORE likely that the receiving neuron will generate an action potential
Inhibitory Effect
makes it LESS likely that the receiving neuron will generate an action potential
Neurotransmitters
Review Questions(think! don’t say the answer out loud…yet)
1. How do messages travel from one neuron to the next?
2. How do neurotransmitters that have an excitatory effect impact neurotransmission? What about an inhibitory effect?
Neurotransmission Simulation
http://www.brainexplorer.org/neurological_control/Neurological_Neurotransmission.shtml#
The Central & Peripheral Nervous Systems
The Nervous System
Central Nervous System (CNS)
brain & spinal cord
brain: where most information processing takes place
spinal cord: main pathway information follows as it enters & leaves the brain
Spinal Cord
Divisions of the Nervous System
Peripheral Nervous System (PNS)
all the nerves that feed into & branch out from the brain & spinal cord
Divisions of the Nervous System
Somatic Nervous System
contains: motor nerves
controls: voluntary movements of skeletal muscles
Divisions of the Nervous System
Autonomic Nervous System
Controls: glands & muscles of the internal organs
monitors the automatic functions (breathing, blood pressure, and digestive processes)
Divisions of the Nervous System
Sympathetic Nervous System
controls: arousal
fight-or-flight response prepares the body to deal with threats or challenges
Divisions of the Nervous System
Parasympathetic Nervous System
controls: calming
brings the body back to a relaxed state
Divisions of the Nervous System