Ch. 3 The Biology & Underlying Behavior Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Neuron: Basic Structure

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neuron: Structure n Axon –Carries messages to other cells n Myelin Sheath –wrap around axon providing insulation n Dendrites –receive messages from other neurons

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Donald Bliss, MAPB, Medical Illustration The Neuron: How the Brain’s Messaging System Works Terminal branches of axon Cell body (the cell’s life support center) Dendrites Myelin sheath Axon Neuronal Impulse

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 Types of Neurons n Sensory (Afferent) – carry messages TO the CNS. n INTERNEURONS – connect sensory with motor neurons (in CNS) n Motor (Efferent) – carry messages FROM the CNS to PNS (muscles, glands, organs)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. n Excitatory messages – chemical secretion that makes it more likely a receiving neuron will fire and action potential will travel down its axon. n Inhibitory Messages –chemical secretion that prevents a receiving neuron from firing

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Neuron Firing n All-or-none law –Neurons are either on or off n Resting State –Negative electric charge within the neuron (-70mv) –Depolarization –Threshold (-65mv)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. n Action Potential –An electric nerve impulse that travels through a neuron, changing the cell’s charge from negative to positive (+40mv) –Hyperpolarization (-71-75mv) is refractory period –Resting State (-70mv)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Clearing the synapse: n REUPTAKE (SSRI’s, SNRI’s) n ENZYME BREAKDOWN n Acetylcholinesterase (ACh)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acetylcholine (ACh) n Effect: mostly Excitatory n Function: Muscle movement; cognitive functioning (MEMORY) n Implicated in Alzheimer’s

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glutamate n Effect –Excitatory n Function –Learning and Memory

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. n Effect –Main inhibitory neurotransmitter n Function: Reduce arousal, anxiety, aggression; Gamma-amino butyric acid (GABA)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dopamine n Location-Midbrain (substantia nigra makes it, sends to basal ganglia above hypothalamus to initiate voluntary movement) n Effect –Inhibitory or excitatory n Function –Too little = Muscle disorders (Parkinson’s disease), too much =mental disorders (schizophrenia)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Di Chiara et al., Neuroscience, 1999.,Fiorino and Phillips, J. Neuroscience, Natural Rewards Elevate Dopamine Levels Time (min) % of Basal DA Output NAc shell Empty Food Sex Box Feeding DA Concentration (% Baseline) Sample Number Female Present

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amphetamine Cocaine Time After Drug Morphine hr Time After Drug % of Basal Release Accumbens Caudate Nicotine Di Chiara and Imperato, PNAS, 1988 Effects of Drugs on Dopamine Release

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Drugs can be “Imposters” of Brain Messages

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Norepinephrine n Adrenal glands n "noradrenalin" n epinephrine aka "adrenalin". n Each is produced by a different enzyme. n Stress, learning and memory

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Serotonin n Effect –Inhibitory n Function –Sleeping, eating, mood, depression

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endorphins n Effect –Primarily inhibitory Function –Pain suppression, pleasurable feelings,

Substance P n Excitatory n Produced in spinal cord n pain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

dopamine transporters

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Clearing the synapse: n REUPTAKE NTX taken back into sending terminal buttons n ENZYME BREAKDOWN n Enzymes break down NTX in synapse n Acetylcholinesterase (ACh)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Drugs and neurotransmitters n Agonists: promote or enhance NTX activity n Antagonists: block the operation of NTX n Neuromodulators: change the NTX effect in some way

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Agonists n Benzodiazepines (anti-anxiety: Valium, Xanax) enhance GABA (primary inhibitory NTX) n (increase ability to bind to receptors) n Anti-depressants block reuptake of seratonin and norepinephrine

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Antagonists n Usually attach to post-synaptic receptors and block the message. n Antipsychotics (Haldol, Risperdol) block dopamine. Endorphins, Morphine blocks Substance P

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neuromodulators n Facilitate or inhibit release of neurotransmitters in the terminal buttons/ vesicle sacs (Presynaptic)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central Nervous System (CNS) n Brain & Spinal Cord n Reflexes (spinal cord) n Sensory (Afferent) Neurons n Motor (Efferent) Neurons n Interneurons

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CNS/PNS

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Neurological disorders n Alzheimer’s Disease- rogue plaques destroy neurons n Lack of Ach – memory loss

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neurological D/Os n Tourette’s Syndrome- involuntary motor and vocal tics

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neurological D/Os n Multiple Sclerosis – demyelination (destroys myelin sheath) n ALS- motor neurons deteriorate (Lose voluntary movement)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. n Today show video on ALSvideo

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neurological D/Os n Parkinson’s Disease- lack of dopamine -- Involuntary movements, muscle rigidity n Michael J. Fox, Mohammed Ali