Neural and Hormonal System Mod 3 Part 1

Stinger  1.) What do you know about how messages travel from the brain to the rest of the body?  2.) Do you know any names of hormones or neurotransmitters? (List if you do.)

Systems  Systems are often part of larger systems  Bio-psycho-social system: your body, mind, and society  Biological psychologists: psychologists who study links between biology, behavior, and mental processes  Sleep and dreams  Depressionand schizophrenia  Hunger and sex  Stress and disease  Information systems of humans and other animals are similar

Neurons and neural impulsess  What are neurons and how do they trasmit information?  Neurons  Nerve cells  Building blocks of the nervous system  Cell body, axon and dendrite  Denfrtie: bushy fibers that receive information  Axon: fibers that transmit information to neurons, muscles, and glands  Can be very long  Motor neurons like giant redwoods  Myelin sheath  Insulates axons of some neurons  Speeds impulses  Prevents misfire or cross fire  Multiple Sclerosis is a disease of myelin degeneration  Slower than electricity, but measured in microseconds

The Neuron

A more complex view

Action Potential  Neurons fire when  Receives signal from sense receptors stimulated by pressure, heat or light  Stimulated by chemical messages from neighboring neurons  Action potential: brief electrical charge that travels down the axon  Based on exchange of ions  Negative inside/positive outside  Resting potential  Selectively permeable: only lets certain transmitters in through certain gates  Firing involves the first bit of the axon to open, then the positively charged particle moves down the axon gate by gate  Depolarization area by area  Refractory period  Axon rests, pushing positively charged particles back out  It can fire again only after resting

Phases of the Action Potential

Action Potential in Action

Chemical Reactions  Excitatory chemicals push neurons accelerator  Inhibitory chemicals keep neuron from firing  Threshold: minimum intensity to cause neuron to fire  Excitatory chemicals must overcome inhibitory chemicals  Action potential moves down the axon and can trigger multiple other reactions  More excitatory chemicals does not equal a bigger reaction, but it may cause more neurons to fire.

Stop and Review  What are the parts of a neuron?  How does chemical information move down an axon?  What is necessary to send a chemical message down an axon?  What is a refractory period?  How do neurons communicate with each other?

Homework  Complete Charts  Neuron  Synapse  Axon  Action Potential  Read Pages 54-64