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Chapter 3

Chapter 3 - biological bases of behavior.docx

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PSYC 1010
Rebecca Jubis

Chapter 3 – Biological bases of behaviour Communication in the nervous system Nervous tissue: the basic hardware Cells in the nervous system fall into 2 major categories: Glia and neurons Neurons – individual cells in the nervous system that receive, integrate, and transmit information o Links that permit communication within the nervous system  Soma (cell body) - contains the cell nucleus and much of the chemical machinery common to most cells  Dendrites – parts of a neuron that are specialized to receive information  Axon – a long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands o Wrap around myelin sheath – insulating material, derived from glial cells, that encases some axons o Speeds up transmission of signals that move along axons o Axon ends in a cluster of terminal buttons – small knobs that secrete chemicals called neurotransmitters o Synapse – junction where information is transmitted from one neuron to another Glia – cells found throughout the nervous system that provide various types of support for neurons  contribute to information processing in the nervous system The neural impulse: using energy to send information The neuron at rest: a tiny battery  Neural impulse – complex electrochemical reaction that allow to transmit signals  Resting potential of a neuron – stable, negative charge when the cell is inactive  No messages are being sent The action potential  Action potential – very brief shift in a neuron’s electrical charge that travels along an axon o Absolute refractory period – the minimum length of time after an action potential during which another action potential cannot begin  very short 1-2 milliseconds The all-or-none law  Its like a gun, it either the neuron fires or it doesn’t action potentials are all the same size  But neurons can still convey information about the strength of a stimulus The synapse: where neurons meet Sending signals: chemicals as couriers  Synaptic cleft – microscopic gap between the terminal button of one neuron and the cell membrane of another neuron o Neuron that sends signal across the gap = presynaptic neuron o Neuron that receives the signal = postsynaptic neuron  Neurotransmitters – chemicals that transmit information from one neuron to another (stored in synaptic vesicles) Receiving signals: postsynaptic potentials  When neurotransmitter and receptor molecule combine, reactions in the cell membrane causes a postsynaptic potential (PSP) – voltage change at a receptor site on a postsynaptic cell membrane (do not follow all-or-none law)  2 types of messages sent cell to cell: o Excitatory PSP – positive voltage shift that increases the likelihood that the postsynaptic neuron will fire action potentials o Inhibitory PSP – negative voltage shift that decreases the likelihood that the postsynaptic neuron will fire action potentials o Depends on which receptor sites are activated in the postsynaptic neuron  Reuptake – process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane  allows synapses to recycle their materials Acetylcholine  Agonist - a chemical that fools the action of a neurotransmitter  but some fail to produce PSP  Antagonist – chemical that opposes the action of a neurotransmitter  block the action of a natural transmitter by occupying its receptor sites Endorphins – internally produced chemicals that resemble opiates in structure and effects Organization of the nervous system – 2 types  peripheral & central Peripheral nervous system  Peripheral nervous system - made up of all those nerves that lie outside the brain and spinal cord o Nerves – bundles of neuron fibres (axons) that are routed together in the peripheral nervous system Divided into somatic and autonomic Somatic nervous system  voluntary  Somatic nervous system – made up of nerves that connect to voluntary skeletal muscles and to sensory receptors o carry information from receptors in the skin, muscles, and joints to the CNS  Afferent nerve fibres – axons that carry information inward to the CNS from the periphery of the body  Efferent never fibres – axons that carry information outward from the CNS to the periphery of the body Autonomic nervous system  involuntary  Autonomic nervous system - made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands  controls functions that people don’t normally think about ex. Heart rate, digestion, perspiration Divided into 2 branches  Sympathetic division – branch of the autonomic nervous system that mobilizes the body’s resources for emergencies  creates fight-or-flight response  Parasympathetic division – branch of the autonomic nervous system that generally conserves bodily resources saves energy and promotes digestion Central nervous system (CNS)  Central nervous system – consists of the brain and the spinal cord  Cerebrospinal fluid (CSF) – nourishes the brain and provides a protective cushion for it The spinal cord  Spinal cord connects the brain to the rest of the body through the peripheral nervous system  Extension of the brain The brain  Fills the upper portion of the skull  Integrate information from inside and outside the body, coordinate actions, talk, think, remember, plan, create, dream Looking inside the brain: research methods Electrical recordings  Electroencephalograph (EEG) – device that monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp  outputs brain waves on paper and the pattern of brain waves illustrates different mental activity Lesioning  Lesioning – involves destroying a piece of the brain o To observe what happens when specific brain structure in animals are purposely disables Electrical stimulation of the brain (ESB)  ESB – involves sending a weak electric current into a brain structure to stimulate (activate) it o Able to systematically map out many functions of the brain Transcranial magnetic stimulation (TMS)  TMS – new technique that permits scientists to temporarily enhance or depress activity in a specific area of the brain o Magnetic field that penetrates the brain  non-invasive method to investigate brain function o CON  cannot be used to study deep areas of the brain Brain imaging procedures  CT scans (least expensive)  to look at abnormalities in the brain structure  PET (positron emission tomography  can scan brain function (mapping out brain activity over time)  Magnetic resonance imaging (MRI) – better 3D images of the brain structure (enhance version of CT scans)  Functional magnetic resonance imaging (fMRI) – maps out activity like PET The brain and behaviour – hindbrain, midbrain, forebrain Hindbrain  Hindbrain – the cerebellum and 2 structures found in the lower part of the brainstem: the medulla and the pons o Medulla – attaches to the spinal cord o Pons – bridge of fibres that connects the brainstem with the cerebellum o Cerebellum – little brain  key role in organizing sensory information that guides movements  drinking damages the cerebellum and disrupts motor skills Midbrain  Midbrain – the segment of the brainstem that lies between the hindbrain and the forebrain o Integrates sensory
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