Brain As you might imagine, larger animals have larger brains. However, this does not mean that animals with larger brains are smarter than animals with smaller brains. For example, a larger brain is necessary to control larger muscles in larger animals and a larger brain is necessary to process more sensory information from the skin in larger animals - this has nothing to do with intelligence. Possible human ancestor lived 3 million years ago.. Female, little under 4 feet, apelike head, protruding jaw, uneven teeth, Skull held brain roughly 1/3 the size of modern day humans 1/2 million years ago…Homo erectus (man, upright) brain size doubled that of Lucy’s. HomoSapien: Wise Human Our species began about 400,000 years ago. Two possible explanations for brain size change. Accidental changes in gentic instructions and natural selection which means that only those best fitted to their environments will survive. Braintastic!

How Neurons Communicate: The Neural Impulse How Neurons Communicate:

Depolarization: axon opens gate and allows positively charged sodium ions inside each “gate”. Neuron pumps positively charged sodium ions back outside This positive outside/negative inside state is called the resting potential.

All-or-None Principle The principle stating that if a neuron fires it always fires at the same intensity All action potentials are of the same strength. A neuron does NOT fire at 30%, 45% or 90% but at 100% each time it fires.

Communication Between Neurons How Neurons Communicate:

Synapse The tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron The action potential cannot jump the gap

Neurotransmitters A chemical messenger that travels across the synapse from one neuron to the next Can influence whether the second neuron will generate an action potential or not

Neurotransmitters

Excitatory Effect A neurotransmitter effect that makes it more likely that the receiving neuron will generate an action potential or “fire” The second neuron is more likely to fire.

Inhibitory Effect A neurotransmitter effect that makes it less likely that the receiving neuron will generate an action potential or “fire” The second neuron is less likely to fire.