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Chapter 3

Chapter 3: Biological Foundations of Behaviour

6 Pages

Course Code
Psychology 1000
Shauna Burke

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Chapter 3: Biological Foundations of Behaviour 1 Neurons • neuron: nerve cells that constitute the basic building blocks of the nervous system - supported by glial cells - > manufacture protein, absorb toxins/waste - myelin sheath - > protective covering 1) cell body: contains biochemical structures & nucleus carries genetic info 2) dendrites: small branching fibres that extend from soma of neuron & receives messages from adjacent neurons 3) axon: extension from one side of neuron cell body that conducts nerve impulses to other neurons, muscles or glands - blood brain barrier: specialized lining of cells in brain’s blood vessels that screen out foreign substances while letting nutrients pass through to neurons ElectricalActivity: 1) At rest, neuron has electrical resting potential due to distribution of (+) & (-) charged ions inside/outside neuron. • When stimulated, flow of ions in/out through cell membrane reverses electrical charge of resting potential, producing action potential (nerve impulse). 2) Original distribution of ions=restored, neuron at rest. • resting potential: internal difference of approx. 70 millivolts Action Potential: • action potential: sudden reversal in neuron’s membrane voltage (-70 - > +40) • depolarization: shift from (-) to (+) voltage • absolute refractory period: recovery when cell membrane is not excitable & cannot generate another action potential resting - > action potential: 1) Na+ channels open & Na+ ions flood into axon 2) Na+ channels close, K- channels open, allows K- ions to exit, restores resting potential • all-or-none law: action potentials occur at uniform/max. capacity or don’t occur at all Chapter 3: Biological Foundations of Behaviour 2 • action potential threshold: intensity of stimulation (excitatory - inhibitory) needed to produce action potential graded potentials:change in electrical potential of neuron that’s proportional to intensity of • incoming stimulation, not sufficient to produce action potential • myelin sheath: fatty insulating substance on axon of some neurons that increases speed of neural transmission Synaptic Transmission: • synapse: microscopic space b/w neurons where nerve impulse is biochemically transmitted • synaptic cleft: tiny gap b/w axon terminal of one neuron & dendrite of next neuron Neurotransmitters: • neurotransmitter: chemical substances released from axons of one neuron, travel across synaptic space, bind to specially keyed receptors in another neuron, where they produce a chemical reaction (either excitatory or inhibitory) • synaptic vesicles: chambers within axon that contain neurotransmitter substance • receptor sites: protein molecules on neurons’dendrites or soma, specially shaped to accommodate specific neurotransmitter molecule Excitation, Inhibition & Deactivation: 1) Excitation: depolarize polysnaptic cell membrane, stimulating inflow of Na+ & other (+) ions, fire action potential 2) Inhibition: hyperpolarize polysnaptic cell membrane, stimulating outflow of K ions & other (-) ions 3) Deactivation: neurotransmitter molecule binds to receptor, continues to activate or inhibit neuron until it is deactivated • reuptake: transmitter molecules are reabsorbed into presynaptic axon terminal Specialized Transmitter Systems: Chapter 3: Biological Foundations of Behaviour 3 Neurotransmitter Major Function Disorders glutamic acid - excitatory - learning, memory GABA - inhibitory - Huntington's disease - anxiety, motor control acetylcholine (ACh) - excitatory -Alzheimer’s disease - muscle movement, memory norepinephrine - excitatory/inhibitory - depression - learning, memory, - stress/panic disorders wakefulness, eating serotonin - inhibitory - depression, sleeping - mood, sleeping, eating, - eating disorders arousal, pleasure, pain dopamine - excitatory/inhibitory - Parkinson’s disease - voluntary movement, - schizophrenia emotional arousal, learning, motivation, pleasure endorphin - pain -insensitivity to pain - pain hypersensitivity, immune problems Peripheral Nervous System: • Somatic NS - sensory neurons: transmit messages from eyes, ears, other sensory receptors - motor neurons: send messages from brain, spinal cord to muscles •Autonomic NS - controls glands & smooth muscles - respiration, circulation, digestion - emotions, stress 1) Sympathetic NS: activation/arousal, fight-or
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