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PSYC 100 - 3 Biological Bases of Behaviour.docx

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PSYC 100
Peter Graf

Biological Bases of Behaviour Biological psychology – branch of psychology which studies links between biology and behaviour Neuron – a nerve cell; basic building block on the nervous system • Soma (cell body) – contains nucleus and support systems, DNA • Dendrite – tree-like branches that receive information from other neurons (input) • Axon – neuron's tail; long fibre that passes info to other neurons (output) • Myelin sheath– fatty substance on some axons; speeds up neural transmissions (insulator) • Terminal Branches of Axon – form junctions with other cells and contain synaptic vesicles • Synaptic vesicles – sac-like structures that contain neurotransmitters • Synapse (synaptic gap or cleft) – the tiny gaps between the sending and receiving neurons Neural networks – clusters of neurons that work together and become strengthened with use Neural Communication – neurons communicate via an electrochemical process Electrical Processes Resting potential – neuron is at rest and Polarized; cell’s inside is more negative than surrounding fluid Action potential – a neural impulse; when stimulated at or above threshold, the cell becomes depolarized as positively charged sodium ions rush into the cell. The neuron has now ‘fired’ • Threshold – level of stimulation required to trigger a neural impulse All-or-nothing response – neuron either fires completely or it does not fire; impulse is the same every time Refractionary Period – for 1/1000 of a second after firing, the cell cannot fire again Chemical Process 1. When the action potential reaches the terminal buttons on the ends of the terminal branches, it causes the synaptic vesicles to release neurotransmitters into the synapse 2. The neurotransmitters then bind to receptor sites on the receiving neuron 3. After neurotransmitters have done their job, they may be destroyed by other chemicals released into synapse; or reuptake may occur Reuptake – neurotransmitters are reabsorbed by the sending neuron and recycled for future use Neurotransmitters – chemicals held in the terminal buttons that travel in the synaptic gap between neurons; some are excitatory (excite the next cell into firing) or inhibitory (inhibit from firing) Problems associated with an excess / Neurotransmitter Function deficit Motor movement Acetylcholine Lack -> Alzheimer’s disease (muscle, learning, memory) Motor movement and alertness Lack -> Parkinson’s disease Dopamine (learning, attention, emotion) Excess -> schizophrenia Mood control Serotonin Lack -> depression (mood, hunger, sleep, arousal) Lack -> depression Norepinephrine Control alertness and arousal Excess -> manic symptoms GABA (gamma- Inhibitory neurotransmitter Lack -> tremors, seizures, insomnia aminobutytic acid) Glutamate Excitatory neurotransmitter Excess -> overstimulate brain (migraines) Endorphins Pain control and pleasure Involved in addictions Drugs and Neurotransmitters Agonists – drugs that are so similar to a neurotransmitter that they can mimic its effects or they may block reuptake of a neurotransmitter Antagonists – drug molecules that inhibit a neurotransmitters release or they may occupy the receptor site on the receiving neuron, blocking neurotransmitter from binding Nervous system –body's electrochemical communication system; contain central and peripheral • Central nervous system – central sensing parts of the body; all nerves within bone o Brain o Spinal cord – bundle of nerves that run through the center of the spine; transmits information from the rest of the body to the brain • Peripheral nervous system – the body's sense receptors, muscles, and glands; all other nerves o Somatic (Skeletal) nervous system – voluntary behaviours; motor cortex sends impulses o Automatic – self regulation of internal organs and glands  sympathetic – arousing – pupils dilate, HR, BP, respiration increase, and digestive processes slow down  parasympathetic – calming – slowing down body after a stress response Nerves – sensory and motor axons carrying peripheral nervous system info bundled into electric cables 3 types of Neurons 1. Sensory (afferent) neurons – of the peripheral NS take incoming sensory information to the spinal cord and brain 2. Motor (efferent) neurons – take information from the spinal cord out to muscles and glands 3. Interneurons – in CNS; communicate with each other, connect the sensory and motor neurons The Simple Reflex Reflex – an automatic response to stimuli done by the spinal cord; does not involve the brain • simple reflex involves afferent (sensory) neurons carrying sensory information to the spinal cord • Interneurons connect the afferent neurons to the efferent (motor) neurons The Brain Phineas Gage – in an accident that damaged the front part of his brain; affected his behaviour and personality; concluded that parts of the brain damaged are involved in emotional control Lesion – brain tissue destruction or removal; can be used for natural or experimental purposes EEG (electroencephalogram) – amplified recordings of brain wave activity CT or CAT (computed tomography scan) – x-ray photos of slices of brain; shows structures, not functions PET (positron emission tomography scan) – visual display of brain activity that detects where a radioactive form of glucose is being used while the brain performs certain tasks MRI (magnetic resonance imaging) – uses magnetic fields and radio waves to see structures within brain fMRI (functional MRI) – allows us to see where oxygen is being used in the brain while various tasks are being performed Structure and Function of the Brain Brainstem (reptilian brain) – oldest; hindbrain and midbrain; responsible for automatic survival functions • Hindbrain – top part of the spinal cord; life support system o Medulla – base of brainstem; controls regulatory systems you don’t think about (heartbeat, breathing) o Pons – dreams centre; controls facial expressions o Cerebellum - "little brain"; coordinates voluntary movement; balance; stores learned, implicit memories • Mid-brain – coordinates simple movements with sensory information o Reticular formation – neural network within the brainstem; controls arousal, attention Forebrain – controls what we think of as thought and reason • Thalamus – brain's sensory switchboard; gets messages from reticular formation; relays sensory information to appropriate part of the brain for further processing Limb
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