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Chapter 3

Textbook Chapter 3 Notes

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Ayesha Khan

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Notes From Reading C HAPTER 3:T HE BIOLOGICAL BASIS OFB EHAVIOUR (PGS.84-135) Communication in the Nervous System Nervous Tissue: The Basic Hardware  Neurons – are individual cells in the nervous system that receive, integrate, and transmit information  Soma (cell body) – contains the cell nucleus and much of the chemical machinery common to most cells  Rest of neuron dedicated to handling info  Dendrites – branches that are specialized to receive info from other cells  Axon – fibre that carries signals away from soma to other cells  Myelin sheath – insulating material that encases some axons, may speed up transmission of information  Terminal Buttons – small knobs at ends of axons that release neurotransmitters at synapses o Synapse – point at which neurons connect. Junction where info is transmitted from one neuron to another.  Gila – are cells found throughout the nervous system that provide various types of support for neurons The Neural Impulse: Using Energy to Send Information  The Nueron at Rest: A Tiny Battery o Neural impulse is a complex electrochemical reaction. o The Resting Potential of a neuron – neuron‟s stable, negative charge when inactive  The Action Potential – voltage spike that travels along axon  Absolute Refractory Period – Brief time after action potential before another action potential can begin  The All or None Law – a neuron either fires or doesn‟t o Its action potentials are always the same. i.e. weaker stimuli don‟t produce smaller action potentials. o They can change the rate of action potentials. A stronger stimulus will make for more rapid action potentials in a shorter period of time. The Synapse: Where Neurons Meet  Sending Messages: Chemicals as Couriers o Synaptic Cleft – a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. o Presynaptic Neuron – sends the signal, postsynaptic neuron receives the signal. o Neurotransmitters – chemicals that transmit info from one neuron to another.  Receiving Signals: Postsynaptic Potentials o Postsynaptic Potential (PSP) – a voltage change at a receptor site on a postsynaptic cell membrane. o Graded – vary in size and increase/decrease the possibility of a neural impulse in the receiving cell in proportion to the amount of voltage change. o 2 Types of Signals:  Excitatory PSP is a positive voltage change that increases the likelihood that postsynaptic neuron will fire action potentials.  Inhibitory PSP negative voltage change that decreases the likelihood that the postsynaptic neuron will fire action potentials. o Reuptake – process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane.  Integrating Signals: Neural Networks 1/6 Notes From Reading C HAPTER 3:T HE BIOLOGICAL B ASIS OFBEHAVIOUR (PGS.84-135) o State of a Neuron is the weighted balance between excitatory and inhibitory PSP‟s. Neurotransmitters and Behavior  Acetylcholine (ACh) o Released by neurons that control skeletal muscles o Contribute to the regulation of attention, arousal, and memory o Agonist – is a chemical that mimics the action of a neurotransmitter o Antagonist – is a chemical that opposes the action of a neurotransmitter  Monoamines – regulate everyday behaviour such as voluntary movements (Parkinson Disease); linked to schizophrenia and psych disorders (depression) o Includes 3 neurotransmitters – dopamine (DA), norepinephrine, and serotonin. o Serotonin involves the regulation of sleep; abnormal levels linked to depression and obsessive-compulsive disorder o Dopamine abnormal levels linked to schizophrenia; dopamine circuits activated by cocaine and amphetamines o Norepinephrine abnormal levels linked to depression; contributes to modulation of mood and arousal  GABA and Glutamate o GABA are inhibitory transmitters that contribute to regulation of anxiety o Glutamate are excitatory transmitters linked to memory process of long-term potentiation  Endorphins – internally produced chemicals that resemble opiates in structure and effects Organization of the Nervous System The Peripheral Nervous System  Peripheral Nervous System – is made up of all those nerves that lie outside the brain and spinal cord (divided into the Somatic NS and Autonomic NS)  Nerves – are bundles of neuron fibres (axons) that are routed together in the peripheral nervous system  Somatic Nervous System – nerves that connected to voluntary skeletal muscles and to sensory receptors. (skin, muscles, joints) o Afferent Nerve fibers are axons that carry info INWARD to the central nervous system from the periphery of the body. o Efferent Nerve Fibers – axons that carry info OUTWARD from the central nervous system to the periphery of the body.  Autonomic Nervous System – nerves that connect to the heart, blood vessels, smooth muscles and glands. (2 divisions) o Separate, yet ultimately guided by the Central Nervous System. o Controls automatic, involuntary functions that people don‟t normally think about, i.e. heart rate, blinking, digestion o Sympathetic Division – branch of the autonomous nervous system that mobilizes the body‟s resources for emergencies (fight-or-flight) o Parasympathetic division – branch of autonomic nervous system that generally conserves bodily resources The Central Nervous System  The Central Nervous System – Consists of brain and spinal cord. Protected by the meninges (meningitis)  Cerebrospinal Fluid – nourishes the brain and provides a protective cushion for it 2/6 Notes From Reading C HAPTER 3:T HE BIOLOGICAL BASIS OFB EHAVIOUR PGS .84-135)  Blood-brain barrier – a semipermeable membrane like mechanism that stops some chemicals from passing between the bloodstream and the brain  Spinal Cord – connects the brain to the rest of the body through the peripheral nervous system. i.e. extension of the brain  The Brain – most important part of the central nervous system Looking Inside the Brain: Research Methods Electrical Recordings  Electroencephalograph (EEG) – monitor the electrical activity of the brain over time, yielding line tracings called brain waves  Used in the clinical diagnosis of brain damage and neurological disorders.  Used to identify patterns of brain activity that occurs when participants engage in a specific behavior. Lesioning  Can‟t control where damage occurs  Also plethora of variables in the person‟s cases.  Lesioning – destroying part of the brain to learn about its function o Usually done through passing a high frequency current into an area to burn tissue and disable structure. Electrical Stimulation of the Brain  Electrical Stimulation of the Brain (ESB) – Sending a weak electric current into a brain structure to stimulate it  Mostly occurs with animals Transcranial Magnetic Stimulation  Transcranial Magnetic Stimulation – is a new technique that permits scientists to temporarily enhance or depress activity in a specific area of the brain Brain imaging Procedure  CT Scan – xray, computer enhanced of brain structure, combining many different x rays at different angles, and creating one detailed, horizontal map of the brain.  PET scans examine brain activity, not structure. Using chemicals introduced to the brain  MRI uses magnetic fields, radio waves, and computerized enhancement to map out brain structure o 3D at high resolution, can monitor blood and oxygen flow to find areas of high activity – both Function and Structure The Brain and Behavior The Hindbrain  Includes the Cerebellum and 2 structures found in the lower part of the brainstem: the medulla and the pons. o Medulla – attached to spine, in charge of unconscious, but important functions like
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