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USC BISC 307L - Exam 2 Study Guide
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I. Autonomic Nervous System1. What is the difference between the efferent and afferent pathways and what to each consist of?A. Afferent = carrying toward CNSSensory system1. Somatosensory (touch)2. Visceral (organs)B. Efferent= carry away from CNS1. Sympathetic (fight or flight)2. Parasympathetic (rest and digest)(3) Enteric (nerves in digestive tract)2. What are the differences that define the sympathetic and parasympathetic divisions?1. Sympatheticincrease respiratory rateincrease heart ratevasodilation in limb muscles and brainvasoconstriction in viscera (intestines, skin)dilation of lung airwaysdecrease secretion in mouth and gutincrease general alertnessopen iris for more lightfright2. Parasympatheticdecrease respiration to restingdecrease heart rate to restingvasoconstriction in limb musclesvasodilation in visceraconstriction of lung airwayssecretion returns to normalalertness returns to normal3. What is the job of the hypothalamus?Ultimate control of eating, water balance, thirst, control temperature, “appetitive behavior”, sex, saltIf damaged, your behavior will be damaged4. Please describe the general pathway for the autonomic nervous system.1. Activity from brainstem (from sensory information) sent to preganglionic neurons at brainstem or spinal cord2. Synapse on autonomic ganglion between the preganglion and the postganglion -which makes a synapse onto target tissue5. What is the synthetic pathway for postganglionic sympathetic synapses?TyrosineDPADopaminenorepinephrineepinephrine6. Describe the action of norepinephrine1. Action potential causes influx of calcium through Ca2+ channelsfusion of vesicles to membrane and exocytosis of NENE released into synaptic cleft binds to adrenergic receptors on the effector cell (usually G protein coupled)ResponsTerminated by usual mechanisms (see below)7. What are the ways in which norepinephrine action can be terminated?1. Carried away by blood vessels2. Degraded by enzymes in extracellular space3. Active transport reuptake of NE into presynaptic membranecan be repackagedor digested by mitochondrial monoamine oxidase8. What are the structural differences between the sympathetic and parasympathetic pathways?1. SympatheticThoracolumbar- middle1. Cervical ganglia (neck)2. Prevertebral sympathetic ganglia chainpreganglionic neurons make synapses onto postganglionic neurons3. Adrenal medulla2. ParasympatheticCraniosacral- at top and bottomPreganglionic axons are very long and usually there is no ganglion or it is embedded into organ9. What was the traditional view as to how the autonomic nervous system worked?Parasympathetic: preganglion uses ACh and binds nicotinic receptors on postganglioncauses fast EPSP and action potential postganglion releases ACh which binds to muscarinic (metabotropic) receptors on target tissuesSympathetic: Same as parasympathetic except postganglion releases norepinephrine which binds to alpha1,2 and beta 1, 2 and ARs (adrenergic)10. What is the new and more accurate view of this pathway?1. At ganglion for both sympathetic and parasympathetic pathways ACh from preganglion is released to bind BOTH nicotinic and muscarinic receptors on postganglionmuscarinic receptors generate slow EPSP (modulation of K+)2. Also peptides are released in addition to ACh at preganglion (cotransmitters)Parasympathetic: postganglionsVIP(vasoactive intestinal peptide-salivary) AND ACh releasedSympathetic: postganglionnorepinephrine AND ACh which co-release ATPbinds to ATP receptors or hydrolyzed to adenosine and binds to purinergic (sweating) receptorsII. Skeletal Muscle- *Learn general structure on your own*1. What is the rate determining step for cross bridge cycling?ATP hydrolysis- ATPase activity determines how fast the muscle contracts2. Describe the 6 steps of the cross bridge cycling1. RIGOR STATE: Myosin head with nothing bound to it-with NO ATP bound has a HIGH affinity for binding ACTIN2. DETACHEMNT: Myosin head binds ATP-lowers affinity for actin and head detaches3. ATPase activity of head hydrolyzes ATP to ADP this energy causes a conformation change in myosin (changes from 45 degrees to 90) ADP and phosphate still attached4. REATTACHMENT: ADP inhibits myosin to bind actin but less so, so head attaches weakly (since at 90 degrees attaches at second molecule) myosin loses affinity for phosphate and it comes off5. Phosphate detachment changes angle from 90 to 45 again pulling thin filament along6. Now myosin has low affinity for ADP and so ADP comes off3. What is an important and unique trait of the neuromuscular junctionACh opens a non specific cation channel causing a large EPSP bringing it to threshold generating a postsymaptic action potential. Reliable and effective. There is a high density of Na+ channels at the T-Tubule so the whole T-Tubule system is depolarized4. What are the two types of receptors for the T-Tubule system1. Dyhydropyridine receptor: voltage sensing protein2. Ryanodine receptor: Ca2+ channel pump which takes Ca2+ out of the cytoplasm and pumps it into the SR lumen. This lowers the concentration of Ca2+ inside cell at rest but when channel opens Ca2+ is released from SR causing contractions5. Explain the pathway of the T-tubule systemT Tubule membrane depolarizedconformational change in dihydropyrindine receptorpulls links to Ca2+ channels opening themcontractionCa2+ sequestered back into the SR and contraction terminates.6. Describe the relaxed and cycling state in relation to how Ca2+ triggers contractionRelaxed: low Ca2+ so Ca2+ is not bound to most of the troponin so tropomyosin is bound to binding site for myosin head for actin (cant bind)Cycling: Calcium rises 10 foldbind troponin causing conformational changetropomyosin moves aside so myosin can bind to actin binding site until Ca2+ resequesteredFall off due to how fast Ca2+ can be resequestered7. Explain the difference between isometric recording and isotonic recordingIsometric: Force length relationship, fix muscles at various lengths and measure the force produced (maximum when optimal overlap between thin and thick filaments)Isotonic: Fixed load on muscle and measure rate of change in length (measure speed for which it shortens)- when load minimal, has fastest velocity8. What is the difference between a concentric and eccentric contraction?1. Concentric: When a muscle is active and it shortens (lifting a small weight)2. Eccentric: When a muscle lengthens as it contracts


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