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Chapter 3

Chapter 3.doc

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Ashley Waggoner Denton

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Chapter 3- Biological foundations • Neurons: basic unit of nervous system, operate through electrical impulses (AP), communicate through chemical signals (NT) • E. O Wilson- 1 neuron is no neuron, 100 billion neurons that interact allows us to be self-directed, able to regulate our behaviour, have ideas, etc. • 3 functions: reception/info collection, conduction/integration, transmission • 3 types: sensory (afferent), motor (efferent), interneurons (outnumber motor and sensory- facilitate transmission of info within CNS) Resting membrane potential: when neuron is at rest, inside is slightly more (-) than outside • polarization creates electrical E needed to fire neuron • AP travels along axon in a wave= propagation • Myelin- fatty insulation that surrounds cell axon • Increases speed of neural impulses by preventing interference from adjacent cells • Deterioration of myelin sheath leads to MS, slows down neural impulses movement, sensation, coordination become impaired • Myelin ↓, axons exposed and eventually break down All or none principle: if the sum of excitatory and inhibitory signals leads to positive change in voltage that exceeds neuron’s firing threshold AP fires • Neuron cannot partially fire, always fires with same potency, rate depends on strength of stimulus 3 major events that terminate NT’s influence in synaptic cleft: 1. reuptake: NT taken back into presynaptic terminal buttons 2. enzyme deactivation: enzyme destroys NT in synaptic cleft 3. autoreception: NT binds with receptors on presynaptic neuron. When excess is detected, autoreceptors signal to stop releasing NT • Same NT can send excitatory or inhibitory postsynaptic signals, depending on receptor’s properties Agonists: drugs that enhance NT actions by blocking reuptake of NT • Can also mimic NT, bind and activate postsynaptic receptor/ ↑ NT effects Antagonists: drugs that inhibit NT’s actions, by blocking release, destroying them in synapse • Can also mimic NT, bind to postsynaptic to block real NT from binding Types of NTs Acetylcholine (Ach) • PNS: Responsible for motor control, contraction of muscles • CNS: higher order- learning, memory, sleeping, dreaming • Drugs that are Ach antagonists cause temporary amnesia • Drugs that are Ach agonists enhance memory • Alzheimer’s= diminished Ach functioning • Botulism (botox)- inhibits release of Ach, causing temporary paralysis Epinephrine: stimulates burst of energy (adrenaline) Norepinephrine: arousal, alertness, and vigilance (a heightened sensitivity to what is going on around you) Serotonin: emotional states, impulse control, and dreaming • Low levels- depression, OCD, eating disorders, obesity • SSRI: selective serotonin reuptake inhibitors Dopamine: motivation, motor control, rewards, pleasure • Brain’s natural reward circuitry- originally evolved for functional/adaptive reasons such as learning/motivation drugs mediated through same mechanisms • Parkinson’s Disease: lack of dopamine- problems with mvt • Research: insert fetal cells, hope that it will produce dopamine GABA: primary inhibitory NT • Epileptic seizures- low levels of GABA • GABA agonists- treat anxiety disorders- help GABA bind more effectively to post- synaptic receptors Glutamate: primary excitatory NT in NS, aid learning and memory by strengthening synaptic connections Endorphins: natural pain reduction and rewards- evolved for survival Substance P: pain perception (helps transmit pain signals to brain), mood states, anxiety • Egyptians- heart is mind’s home • Greeks, Romans- gladiator’s brain injuries unconsciousness and loss of speech • Johan Spurzheim- theory of phrenology- brain operates through functional localization - assess personality traits and mental abilities by measuring bumps on human skull • Karl Lashley- took idea of localization, specific areas involved in motor control/sensory experiences, other parts contributed equally to everything else • Paul Broca: brain regions perform specialized functions • Left frontal area (Broca’s area)- crucial for language • Penfield: developed cures for epilepsy, mapped out sensory/motor responses that occurred when specific brain regions stimulated Spinal cord: carry sensory info to brain, and motor info from brain to body • Grey matter: ganglia (neuronal cell bodies), white matter: axons Brain Stem (Medulla, pons, midbrain): control basic functions of survival- breathing, swallowing, vomiting, urination, etc. • Also contains reticular formation- sleep, arousal Cerebellum: motor learning, motor function- planning, timing of movement • Role in posture, and coordination of hand and eye movements Subco
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