We only use about 10% of our brains True or False? We only use about 10% of our brains

False We use 100% of our brains

100 billion 900 billion

IV. Biological Bases of Behavior 8 – 10 % Neuroanatomy Functional Organization of Nervous System Neural Transmission Endocrine System Genetics Evolutionary Psychology

Nucleus Dendrites Cell Body (Soma) Myelin Sheath End Bulb Enlarged Vesicles (storing Nts) End Bulb Neurotransmitters

End Bulbs at

http://outreach.mcb.harvard.edu/animations/synaptic.swf http://outreach.mcb.harvard.edu/animations/actionpotential.swf

The Neural Impulse – The Electrochemical transfer of information Resting Potential – when no information is being exchanged the neuron is polarized: overall neg. charge inside / pos. charge outside of the axon

When stimulated the neuron’s axon becomes depolarized – Sodium (Na +) flows in, temporarily changing the charge (becomes more positive inside) at a point along the axon creating an action potential

The action potential fires down the length of the axon, sending energy to the terminal button Behind the action potential the axon becomes polarized again

Action potentials follow the all-or-none law: it fires or it doesn’t – the energy is always the same The strength of the stimulus depends on the rate of action potentials (faster rate = stronger feeling)

The action potential’s energy causes the release of neurotransmitters (chemical messengers) The neurotransmitters cross the synapse, to possibly bind at receptor sites of the adjacent neuron, muscle fiber, or organ

http://www. sumanasinc http://www.sumanasinc.com/webcontent/animations/content/actionpotential.html http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

Part II: Postsynaptic Potentials After the release of the neurotransmitters they may attach to a receptor site of the adjacent neuron, muscle fiber, or organ creating a postsynaptic potential (PSP) – a change in voltage at the receptor site

PSP’s can be either excitatory or inhibitory Excitatory – increases the chance of another action potential (at the adjacent neuron) by increasing the voltage Inhibitory – decreases the chance by decreasing the voltage at the receptor site

PSP’s do NOT follow the all-or-none law PSP’s do NOT follow the all-or-none law! Excitatory and inhibitory PSP’s can cancel each other out If there are enough excitatory PSP’s to reach the threshold another action potential is created (or the muscle/organ responds) Inhibitory actions are important to slow down or stop processes in body and brain Some neurotransmitters are returned to the terminal button for reuse – this is called reuptake.