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CHAPTER 3 Biological Foundations Part I

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Wagner Denton

CHAPTER 3: Biological Foundations Part I Genetics  Most important message: Nature and nurture are inextricably entwined! o Nature (genes) and nurture (social context) interact to affect human behaviour The Nervous System  The nervous system is the body’s electrochemical communication circuitry  Central nervous system (CNS) o Brain & spinal cord  Peripheral nervous system (PNS) o Somatic nervous system o Autonomic nervous system  Sympathetic nervous system  Parasympathetic nervous system Neurons  Are the basic unit of the nervous system  Operate through chemical impulses  Communicate with other neurons through chemical signals  Three types of neurons: o Sensory neurons (afferent neurons) o Motor neurons (efferent neurons) o Interneurons o Hint: SAME (sensory afferent, motor efferent)  Neuron structure When do neurons fire?  Excitatory signals  increase the likelihood that the neuron will fire  Inhibitory signals  decrease the likelihood that the neuron will fire  They do this by affecting the polarization of the cell  Neurons fire (generate an action potential) if the excitatory input reaches a certain threshold  All-or-nothing principle: A neuron fires with the same potency each time (it either fires or does not fire); but how frequently the neuron fires can vary  Action potential: The neural impulse that passes along the axon and subsequently causes the release of chemicals from the terminal buttons How do neurons fire?  Neuronal communication  Resting neurons are more negative inside the cell than outside the cell  Depolarization: sodium channels open, making the inside more positive, potassium ions leave the cell sending the signal  Repolarization: restoring original balance Neurotransmitters  Are chemical substances that carry signals from one neurons to another  Are stored in vesicles (small packages) inside the terminal buttons  Action potentials cause the vesicles to fuse to the presynaptic membrane (membrane of the neuron that is sending the signal) and release their contents into the synapse, where they are received by postsynaptic receptors on the postsynaptic membrane (membrane of the neuron that is receiving the signal)  Common Neurotransmitters o Acetylcholine o Epinephrine o Norepinephrine o Serotonin o Dopamine o GABA How Drugs Work  Agonists  Enhance neurotransmitters’ actions by: o Increasing the release of neurotransmitters o Blocking the re-uptake of neurotransmitters o Mimicking a neurotransmitter (& activating a postsynaptic receptor) o E.g., Cocaine, methamphetamine  Antagonists  Inhibit neurotransmitters’ actions by: o Blocking the release of neurotransmitters o Destroying neurotransmitters in the synapse o Mimicking a neurotransmitter (& blocking neurotransmitter binding) o E.g., Beta-blockers, botox (butolinum toxin) The Bra
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