The Nervous System

The Nervous System the electrochemical (chemical reactions brought about by electricity) communication system of the body

Neuron receive information carry information 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 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 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 Refractory period – delay after flushing when the toilet can not be flushed again

Review Questions (think! don’t say the answer out loud…yet) What are the three phases of communication within a neuron? 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: Excitatory Effect 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) How do messages travel from one neuron to the next? 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