Chapter 4 Book Notes
Chapter 4 Book Notes PSY 320
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This 9 page Bundle was uploaded by Alicia Rinaldi on Sunday September 13, 2015. The Bundle belongs to PSY 320 at University of Miami taught by Dr. Marc Gellman in Spring 2015. Since its upload, it has received 31 views. For similar materials see Drugs & Behavior in Psychlogy at University of Miami.
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Date Created: 09/13/15
Chapter 4 The Nervous System Homeostasis A Homeostasis maintenance of an environment of body functions within a certain range ex temperature blood pressure B Psychoactive drugs in uence homeostasis example alcohol 1 Heavy drinkers have less urine output than infrequent drinkers 2 During alcohol withdrawal heavy drinkers exhibit an increased vasopressin release resulting in greater water retention Components of the Nervous System A Neurons 1 Neuron primary elements of nervous system responsible for analyzing and transmitting information 2 Membrane a thin limiting covering of a cell separates inside from outside 3 4 regions b cell body the central region of a neuron which is the control center dendrites branchlike structures that extend from the cell body and specialize in receiving signals from other neurons i receptors recognition mechanisms that respond to speci c chemical signals ii attached to the end of dendrites axon a thin tube that extends from the cell body and specializes in transmitting signals to other neurons axon terminals bulbous structures at the end region of the axon i neurotransmitterchemical messengers released from axon terminals ii synaptic vesicles small bubbles of membrane that store neurotransmitters Dend rite Axon Terminal Node of Cell body Ranv39er 39 Axon Schwann cell Myelin sheath e Nucleus B Glia 1 Most brain cells are glia they provide rmness and structure to the brain get nutrients in the system eliminate waste form the myelin 2 Myelin a fatty white substance that is wrapped around portions of the axons myelin sheath increases processing speed of neurons 3 Autoimmune disease a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue 4 Multiple sclerosis an autoimmune illness caused by damage to the myelin sheath that wraps axons A wide range of symptoms can accompany this disorder including muscle spasms vision loss severe pain dizziness fatigue and intestinal problems 5 Glia create the bloodbrain barrier a structure that prevents many drugs from entering the brain a BBB is semipermeable allowing sum but not all chemicals to pass through b Psychoactive drugs can pass through BBB Neurotransmission the process of transferring information from one neuron to another at a synapse A Action potential 1 Action potential the electrical signal transmitted along the axon when a neuron res generated by a sequential opening and closing of ion channels in the neuron s membrane 2 Ion an atom or molecule that has a net electrical charge because of a difference in the number of electrons and protons 3 Ion channels a protein in the cell membrane forms a pore that allows the passage of ions from one side of the membrane to the other allow ions to move into the cell 4 Resting potential the voltage maintained by a cell when it is not generating action potentials The resting potential of neurons is about 65 mV 5 Hyperpolarized when the membrane potential is more negative a Potassium K ions and negatively charged organic ions on inside of cell b Sodium Na and chloride Cl ions are on outside of cell 6 Depolarized when the membrane potential is less negaUve a The Na ions moved into the cell 7 review process IV The Nervous Systems A Somatic Nervous System 1 Somatic nerve cells on the quotfront linesquot that interact with external environment 2 Nerves relating to 5 senses and movement of the face and spinal nerves controlling arms and legs 3 Serves voluntary action 4 Acetylcholine neurotransmitter found in the parasympathetic branch in the cerebral cortex acts on receptors that excite the muscle and stimulates muscle contraction B Autonomic Nervous System 1 Autonomic the part of the nervous system that controls involuntary functions such as heart rate 2 many drugs have effect on ANS ex increasing heart rate 3 acetylcholine inhibits heart muscle contraction even though it stimulates other muscle contraction a learn the same neurotransmitter can have different effects depending upon the receptor being activated 4 2 branches a sympathetic a branch of the ANS involved in ight of ght reactions i norepinephrine neurotransmitter that may be important for regulating waking and appetite ii amphetamines stimulate these functions b parasympathetic the branch of the ANS that stimulates digestion slows the heart and has other effects associated with a relaxed physiological state C two systems often oppose each other sympathetic excites the body and parasympathetic relaxes the body C Central Nervous System 1 Central Nervous System brain and spinal cord a b V The Brain Sensory nerves come in motor nerves go out Most of integration of information learning and memory and coordination of activity occur A Chemical Pathways lmplicated ln Reward 1 Dopamine Cells in the nucleus accumbens receive input from dopamine bers that arise in the ventral tegmental area in the midbrain to form the mesolimbic dopamine pathway Nucleus accumbens a collection of neurons in the forebrain that plays an important role in reward and emotional reactions to events Dopamine neurotransmitter found in the basal ganglia and other regions Ventral tegmental area a group of dopaminecontaining neurons located in the midbrain whose axons project to the forebrain especially in the nucleus accumbens and cortex Mesolimbic dopamine pathway one of two major dopamine pathways may be involved in psychotic reactions and in drug reward i Pathway may mediate schizophrenic schizophrenia behavior a mental disorder characterized by chronic psychosis ii Overactivation of dopamine produces hallucinations Malfunctions of neurotransmitter systems lead to disease states which can be effectively treated with drugs that target the affected system Nigrostriatal dopamine pathway one of two major dopamine pathways damaged in Parkinson s disease i cells from the substantia nigra course together past the hypothalamus and terminate in the striatum to form this pathway ii substantia nigra a dopaminerick midbrain structure that projects to the striatum iii hypothalamus a structure found near the bottom of the forebrain lt participates in the regulation of hunger thirst sexual behavior and aggression iv striatum a term used to describe the caudate nucleus and putamen Located in the forebrain it is involved in the initiation of body movements and procedural memory v Parkinson s disease a movement disorder involving damage to andor loss of dopamine neurons along the Nigrostriatal dopamine pathway Major symptoms include tremors rigidity of the limbs postural instability and dif culty initiating movements vi Treatment of Parkinson s putting a dopamine precursor a chemical that is acted on by enzymes to form neurotransmitters in the brain to convert to dopamine we use a precursor because dopamine itself can t cross the BBB 2 Acetylcholine a Nucleus basalis a group of neurons of the basal forebrain that send projections throughout the cortex b Cerebral cortex the outermost layer of the brain c Alzheimer s disease a progressive brain disease that destroys memory and thinking cells i cells in this region are damaged in patients with Alzheimer s ii since cells on this pathway have been implicated in learning and memory 3 norepinephrine a pathways from locus cerueus in brainstem release norepinephrine b stimulant drugs may also take these pathways 4 serotonin a serotonin neurotransmitter found in the raphe nuclei may be important for impulsivity depression b raphe nuclei a group of serotonincontaining neurons found in the brain stem and project widely throughout the brain c roles in control of food intake regulation of body weight aggressiveness and impulsivity suicide 5 GABA gammaamino butyric acid a GABA inhibitory neurotransmitter found in most regions of the brain b not in neat pathwaysbundles c found in CNS exerts generalized inhibitory funcUons 6 glutamate a glutamate excitatory neurotransmitter found in most regions of the brain b stimulation of receptors that respond to glutamate makes cells more excitable c glutamate pathways may be important for expression of psychoactive drug effects 7 endorphins a endorphin opiatelike chemical that occurs naturally in the brain of humans and other animals b play a role in pain relief c found in brain and blood not all functions are known B structures 1 cortex is a layer of tissue that covers the top and sides of the upper parts of the brain a some areas are involved in 5 senses b some areas control muscles motor cortex c higher mental processes reasoning language d less active cortex under sedating drugs 2 basal ganglia subcortical brain structures controlling muscle tone a underneath cortex on each side of brain b critical for speci c aspects of learning 3 hypothalamus a small structure near the base of the brain just above the pituitary gland a link between brain and hormonal output of pituitary b involved in feeding drinking temperature regulation and sexual behavior 4 limbic system connected structures amygdala hippocampus etc a emotion memory for location level of physical activity b involves important mechanisms for behavior control 5 midbrain pans medulla are parts of brain stem that connect the brain to the spinal cord 6 brainstem contains important areas a vomiting center helps survival b rate of breathing can be suppressed by drugs VI Drugs and the Brain A Life Cycle of a Neurotransmitter 1 A drug usually has its effects because its molecular structure is similar to the molecular structure of one of the neurotransmitters 2 Uptake energyrequiring mechanism by which selected molecules are taken into cells 3 A cell that is going to make a particular neurotransmitter needs to bring in the right precursor from outside the cell so it needs a gradient for uptake 4 Synthesis the forming of a neurotransmitter by the action of enzymes on precursors a Enzymes large molecule that assists in either the synthesis or metabolism of another molecule b Attaches to precursor molecule and fragment c They connect and leave enzyme as the neurotransmitter d They are then stored in synaptic vesicles 5 Arrival of action potential causes calcium channels to open 6 Neurotransmitter is released into synapse the space between neurons 7 They bind with receptors on membrane of next neuron postsynaptic cel5important interaction btw drugs and neurotransmitter 8 Depending on the type of receptor the effects can be excitatory or inhibitory 9 2 methods to remove the action potential from the synapse a the neurons that release the neurotransmitters have transporters mechanism in the nerve terminal membrane responsible for removing neurotransmitter molecules from the synapse VII VIII by taking them back into the neuron built into their terminal b enzymes in the synapse metabolize break down or inactivate a neurotransmitter or a drug through enzymatic action the molecules B Examples of Drug Actions 1 Two types of drug actions on neurotransmitter systems a Altering the availability of the neurotransmitter in the synapse Synthesis storage release reuptake metabolism Interference with the transporters that clear neurotransmitters by bringing them back into the neuron from which they were just released Coke and antid s block 1 of these transporters and cause the normally released neurotransmitter to remain in the synapse longer than usual b Directly on the receptor Agonist a substance that facilitates or mimics the effects of a neurotransmitter on the postsynaptic cell heroin Antagonist a substance that prevents the effects of a neurotransmitter on the postsynaptic cell opioid naloxone Chemical Theories of Behavior A Chemicals in brain explain many differences in personalities B Monoamine a class of chemicals characterized by a single amine group monoamine neurotransmitters include dopamine norepinephrine and serotonin 1 Monoamine theory ofmood monoamineenhancing drugs elevate mood and large doses of these drugs can produce manic episodes Brain Imaging Techniques A Structural Imaging magnetic resonance imaging MRI 1 Uses magnets to determine the amount of hydrogen atoms at different locations 2 Atoms are forced to align then allowed to go back to random alignment time is measured 3 Different areas of brain return to normal in different amounts of time and this makes a picture of the brain 4 Pros a b High resolution image of brain s anatomy Noninvasive 5 Cons Provides no information about brain functioning B Functional Imaging 1 PositronEmission Tomography PET Radioactively labeled chemical usually glucose is injected into the bloodstream and a computerized scanning device maps out how much of the chemical is in various brain regions Glucose accumulates in the most metabolically active areas of the brain Produces gamma rays detected by a computerized scanning device to make a colored statistical map of brain activity Pro i Provides us with direct measure of brain activity ii Indirect measure of potential toxicity to speci c neurons Cons i Requires injection of radioactive chemicals ii Doesn t provide information about brain structures 2 Functional MRI fMRI d Uses MRI machine but provides realtime information about changes in brain blood ow as an individual does a task Measures blood oxygen level dependent signal used to create colored map of brain regions ache Pro i Gives realtime information about changes in brain blood ow ii Indirect measure of neuron activity iii Noninvasive Con i Doesn t provide information about anatomy of brain
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