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Chapter 3

Chapter 3.docx

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York University
PSYC 1010
Jennifer Steeves

Chapter 3: The Biological Bases of Behaviour  Communication in the Nervous System o Nervous Tissue: The Basic Hardwire  Neurons are individual cells in the nervous system that receive, integrate, and transmit information  The soma, or cell body, contains the cell nucleus and much of the chemical machinery common to most cell  Dendrites are the parts of the neuron that are specialized to receive information  The axon is a long, thin fiber that transmits signals away from the soma to other neurons or to muscles or glands  Myelin sheath is the insulating material, derived from glial cells, that encase some axons  Terminal buttons, which are small knobs that secrete chemicals called neurotransmitters  A synapse is a junction where information is transmitted from one neuron to another  Glia are cells found throughout the nervous system that provide various types of support for neurons o The Neural Impulse: Using Energy to Send Information  Resting potential of a neuron is its stable, negative charge when the cell is inactive (~70mV)  Action potential is a very brief shift in a neuron’s electrical charge that travels along the axon  Absolute refractory period is the minimum length of time after action potential during which another action potential cannot begin  Relative refractory period o Neuron can fire but threshold for firing is elevated  All or Nothing Rule  Either a neuron fires or it doesn’t  You can only vary the rate of the AP’s o The Synapse: Where Neurons Meet  Synaptic cleft, s microscopic gap between the terminal button of one neuron and the cell membrane of another neuron  Neurotransmitters – chemicals that transmit information from one neuron to another  PSP: post synaptic potential, a voltage change at a receptor site on a postsynaptic cell membrane  An excitatory PSP is a positive voltage shift that increases the likelihood that the postsynaptic neuron will fire action potentials  Inhibitory PSP is a negative voltage shift that decreases the likelihood that the postsynaptic neuron will fire action potentials  Synaptic Transmission  1. Synthesis and storage of neurotransmitters molecules in synaptic vesicles 1  2. Release of neurotransmitters molecules into synaptic cleft  3. Binding of neurotransmitters at receptor sites on postsynaptic membrane  4. Inactivation (by enzymes) or removal (drifting away) of neurotransmitters  5. Reuptake of neurotransmitters sponged up by the presynaptic neuron  Elimination of old synapses appears to play a larger role in the sculpting of neural networks than the creation of new synapses  The elimination of old or less active synapses is called synaptic pruning  One neuron stimulating another neuron repeatedly produces changes in the synapse; learning has taken place o Neurotransmitters and Behaviour  Monomines  Dopamine, norepinephrine, and serotonin  Acetylcholine  Activates motor neurons controlling skeletal muscles  Contributes to the regulation of attention, arousal, and memory  Some Ache receptors stimulated by nicotine  Dopamine  Contributes to control of voluntary movement, pleasurable emotions  Decreased levels associated with Parkinson’s Disease  Over-activity at DA synapses associated with Schizophrenia  Cocaine and amphetamines elevates activity in DA synapses  Norepinephrine  Contributes to modulation of mood and arousal  Cocaine and amphetamines elevate activity at NE synapses  Serotonin  Involved in regulation of sleep and wakefulness, eating, aggression  Abnormal levels contribute to depression and obsessive compulsive behaviour  Prozac and similar antidepressants drugs affect serotonin circuits  GABA  Serves as widely distributed inhibitory transmitter  Valium and similar antianxiety drugs work at GABA synapses 2  Endorphins  Resemble opiate drugs in structure and effects  Contribute to pain relief and perhaps to some pleasure emotions  Glutamate  Has excitatory effects  Best for contribution to learning and memory  Organization of the Nervous System o The Peripheral Nervous System  Is made up of all those nerves that lie outside the brain and spinal cord  Nerves are bundles of neuron fibers (axons) that are routed together in the peripheral nervous system  Somatic Nervous System  Is made up of nerves that connect to voluntary skeletal muscles and to sensory receptors  Afferent nerve o Are axons that carry information inward to the central nervous system from the periphery of the body  Efferent nerve o Axons that carry information outward from the central system to the periphery  Autonomic Nervous System  Is made of nerves connect to the heart, blood vessels, smooth glands, and glands  Involuntary  Sympathetic o Mobilizes the body’s resources for emergencies  Parasympathetic o Conserves the bodily resources 3 Efferent Sympathetic Peripheral Autonomic Nervous Nervous Systems System (Involuntary) System Paeticmpath (Voluntary) Afferent o The Central Nervous System  Consists of the brain and spinal cord  Spinal Cord  Extension of the brain  Brain  Hindbrain o Reticular formation o Cerebellum o Pons o Medulla  Midbrain o Reticular formation  Forebrain o Thalamus o Hypothalamus o Limbic System o Cerebrum  Looking Inside the Brain: Research Methods o Electrical Recordings  EEG  Device that monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp  Good for understanding brain-behaviour relationships  Used for diagnosis of brain damage and neurological disorders 4 o Lesioning  Case study method  H.M. Epilepsy as a child  Treatment: portions of his brain removed o Medial temporal lobe (hippocampus and amygdala)  Suffered from amnesia o Anterograde  No new memories  Limitations studying patients who have suffered brain damage  Subjects are plentiful  Cant control the location or severity of the subjects brain damage  Variations in subjects history  Involves destroying a piece of the brain  Done by inserting an electrode into the brain structure and passing a high frequency electric current though it to burn the tissue and disable the structure o Electrical Stimulation of the Brain  (ESB)  Involves sending a weak electric current into a brain structure to stimulate (activate) it  Close enough to activate particular part of the brain  Helps understand many brain-behaviour relationships o Transcranial Magnetic Stimulation  TMS  New technique that permits scientists to temporarily enhance or depress activity in a specific area of the brain  Magnetic coil mounted on a small paddle is held over a specific area of a subject’s head  Coil created a magnetic field that penetrates to a depth of 2cm  By varying the timing and duration of the magnetic pulses, a researcher can either increase or decrease the excitability of neurons in the local tissue  “Virtual lesions”  Limitation  Cant be used to study areas deep within the brain o Brain Imagining Procedures  CT (computerized tomography)  Is a computer enhanced X-ray of brain structure  Multiple x-rays shot from many angles  Entire brain can be visualized  Least expensive  Brain STRUCTURE 5  PET (Position Emission Tomography)  Providing especially valuable  PET scans can examine brain FUNCTION  Mapping actual activity in the brain over time  Radioactively tagged chemicals are introduced in the brain  Serve as markers of blood flow or metabolic activity in the brain, which can be monitored by X-rays  Activity of specific neurotransmitters  MRI (magnetic resonance imaging)  Uses magnetic fields, radio waves, and computerized enhancement to map out brain structure  Provide much better image of brain structure than CT scans  3-D  Great insights about depressive behaviours  fMRI (Functional magnetic resonance imaging)  New variation of MRI technology that monitors blood flow and oxygen consumption in the brain to identify area of high activity  It can map out actual ACTIVITY in the brain over time, but with vastly greater precision  Meta analysis in neuroimaging data  The Brain and Behaviour o The Hindbrain  Cerebellum  Relatively large and deeply folded structure located adjacent to the back surface of brainstem  Coordination movement and sense of equilibrium or physical balance  Organizing sensory information  Damage to it o Disrupts fine motor skills  Medulla  Attaches to the spinal cord, is in charge of largely unconscious but vital functions  Circulating blood, breathing, maintaining muscle tone, and regulating reflexes such as sneezing, coughing, and salivating  Pons  Includes a bridge of fibers that connects the brainstem with the cerebellum  Contains several clusters of cell bodies involves with sleep and arousal 6 o The Midbrain  Concerned with integrating sensory processes such as vision and hearing  Dopamine releasing neurons (originate)  Reticular Formation  Contributes to the modulation of muscle reflexes, breathing and pain perception  Best known for regulation of sleep and arousal o The Forebrain  Largest and most complex region of the brain  Variety of structures such as thalamus and hypothalamus, limbic system, and cerebrum  Thalamus  All sensory information (EXCEPT SMELL) must pass through to get to the cerebral cortex  Made up of cell clusters of cell bodies or somas  Hypothalamus  Regulation of basic biological needs  Homeostasis  Control autonomic nervous system  Link between brain and endocrine system  Regulate biological drives related to survival:
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