Biology of Mind

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Biology of Mind Modules 4, 5 and 6
* Everything psychological is simultaneously biological
* Plato correctly located the mind in the spherical head * Aristotle believed mind was in the heart
* Although heart is the symbol for love, psychology has proven that you fall in love using your brain * 1800s Franz Gall (German psychologist) invented phrenology theory that claims that bumps on our skull could reveal our mental ability and character traits * Biological Psychology – the branch of psychology concerned with the links between biology and behaviour * Biological psychologists sometimes called Behavioural neuroscientist, neuropsychologist, behaviour geneticist, psychological psychologist, bio psychologist … * We are a system of substances, that are composed of even smaller substances (tiny cells make up body organs) * Body’s information system is built from billions of tiny interconnected system of neurones * Sensory Neurones – neurons that carry incoming information from the sensory receptor the brain and the spinal cord for processing – “afferent” * Motor Neurons – the neurons that carry outgoing information from the brain to the muscles and the glands – “efferent” * Interneurons – neurons within the brain and the spinal corf that that communicate internally and intervene between the sensory inputs and the motor outputs * Each neuron consists of a:

* Cell body and branching fibres (the cell’s life support center) * Dendrite fibres – receive information and conduct it toward the cell body * Axon – passes messages away from the cell body to other neurons, muscles and glands * Can be very long projecting several feet into the body * Myelin sheath – a layer of fatty tissue segmentally encasing the fibres of many neurons * Allows for fast impulse transmission among neurons * If myelin sheath degenerates, communication to muscles slow with eventual loss of muscle control * Action potential – brief electric charge that travels down a neuron’s axon (neural impulse) * Generally an axon is in a negative state, while the fluid outside an axon is in a positive state * Resting potential – the positive outside/ negative inside state of an inert neuron * K+ [ ] in axon < Na+ [ ] outside axon (-70mv) * Axon membrane is Selectively Permeable – does not allow everything inside (selective) * When a neuron fires, the first bit of the axon opens up allowing positively charged sodium ions to enter * That section of the ion becomes depolarized, making the axon’s next channel to open up * During resting period(refractory period) the neurons pump the positively charged sodium ions back outside * Each neuron receives signals from hundreds of other neurons * Excitatory signals – like pushing a neuron accelerator * Inhibitory signals – like pushing its breaks

* Threshold – the level of stimulation required to trigger a natural impulse * If the excitatory signal minus inhibitory signal exceeds a min intensity (-60mv) * How neurons communicate: Before thought that axon of one cell fused with dendrites of another, but Sir Charles Sherrington noticed that it takes a long time for the signal to travel. Therefore concluded that there is a gap * Synapse – the junction between the axon tip of the sending neuron and the dendrite of the receiving cell * Synapse gap (synaptic cleft) – the tiny gap at the junction (less than a millionth inch wide) * When action potential reaches the terminal’s at the axon, release of chemical messenger is triggered (neurotransmitters) * Soon the neurotransmitters cross the synapse gap and bind to the receptor site on the receiving neuron * For an instant the receptors unlock the channels at the receiving site and electrically changed atoms flow in , exciting or inhibiting...
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