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Unformatted text preview: Chapter 3 Biological Foundations of Behaviour Spike went through head of Phineas Gage, 25 year old foreman o Spoke within a few minutes, was perfectly conscious, but became exhausted from the haemorrhage Nervous system : master control network of nerve cells whose activities underlie your every though, feeling and behaviour Neural Bases of Behaviour Brain is a grapefruit sized mass of tissue that feels like jelly and looks like a greyish gnarled walnut o Our three pound universe Neurons : basic building blocks of the nervous system o linked together in circuits o 100 billion neurons o Chain would cycle earth more than 24 tims o Lose 10 000 each day of life o 3 main parts: Cell body (soma): biochemical structures to keep it alive Dendrites : branchlike fibres that collect messages like antennas Can receive input from up to 1 000 other neurons Axon : conducts electrical impulses away from the cell body to other neurons, muscles or glands Axon terminals: end branches o As many as several hundred Can send messages to as many as 50 000 other neurons o 200 different types of neurons o Supported by glial cells which surround neuron and hold in place Blood-brain barrier : prevents many substances, including toxins, from entering the brain Nerve Conduction: An Electrochemical Process Neurons generate electricity and release new chemicals o Surrounded by cell membrane which protects inner structures and operates as a selective filter o Surrounded by salty liquid environment which carries positive electric charge o Resting potential : -70mV, polarized The Action Potential : nerve impulse, sudden reversal in neurons membrane voltage o Depolarization : shift from negative to positive voltage All or none : Similar to shutter button release of a camera Occurs with maximum intensity or not at all Graded potentials : changes in charge Action potential threshold : -55mV, decrease of only -15mV from the resting potential Ion channels : tiny protein structures in the cell membrane o Influx of +ve charged Na+ ions carries +ve electrical charge into the interior of the cell, and the interior goes from ve to +ve than the outside of the cell = complete depolarization which is the action potential o A wave chain reaction is started along axon o After action potential, Na+ ions trapped inside are pumped back outside, and K- ions pumped back in, restoring normal distribution o Refractory period : membrane is not excitable and cannot discharge another action potential Limits the rate at which APs can be triggered Human limit is 300 impulses per second...
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This note was uploaded on 04/04/2009 for the course PSYCH 1000 taught by Professor Atkinson during the Spring '09 term at UWO.
- Spring '09