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 information carry information pass information to the next neuron
Neuron Development birth3 months2 years
Parts of the Neuron Dendrites DETECT
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 gical_control/Neurological_Neurotran smission.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