SKELETAL MUSCLE PHYSIOLOGY IN Rana pipiensANNOUNCEMENTSSlide 3REVIEW: THE SCIATIC NERVETHIS WEEK: SKELETAL MUSCLE PHYSIOLOGYSKELETAL MUSCLE PHYSIOLOGYSKELETAL MUSCLE PHYSIOLOGYSKELETAL MUSCLE PHYSIOLOGYSlide 9SKELETAL MUSCLE PHYSIOLOGYSlide 11SKELETAL MUSCLE PHYSIOLOGYSlide 13SKELETAL MUSCLE PHYSIOLOGYSKELETAL MUSCLE PHYSIOLOGYSlide 16Slide 17Slide 18SKELETAL MUSCLE PHYSIOLOGYSlide 20MUSCLE FIBER TYPESSlide 22Slide 23SKELETAL MUSCLE PHYSIOLOGY IN Rana pipiensBIOL 305LANNOUNCEMENTSMidterm Exam:•Friday, March 15th during lab lecture•No calculators•Format: multiple choice, short ans, essay, fill in blank, T/F•No labs that week!•NO MAKEUP EXAM UNLESS UNIVERSITY APPROVED EMERGENCY•Old midterm will be posted online next week. Use it to TEST what you know. Do NOT memorize answers!!ANNOUNCEMENTS•Study for Midterm:–Background concepts/theory–Experimental results (expected)–Flow of information/experimental set up (be able to draw) –Names & function of all instruments–Anatomy (name of muscles, organs, nerves and organisms) –Lab exercises (handouts), especially the introduction–Observations in lab –Traces produced using LabScribe (be able to draw)–Any/all graphs made (i.e. Excel graphs)–Notes from lab lead off lectureREVIEW: THE SCIATIC NERVEMain Points:–Mixed Nerve–Stimulus Artifact–Threshold–Compound Action Potential–Recruitment–Maximum Recruitment–Conduction Velocity–Bidirectionality–Effect of temperatureTHIS WEEK: SKELETAL MUSCLE PHYSIOLOGYThe Dissection:•Isolation of frog:Instrumentation & Equipment:SKELETAL MUSCLE PHYSIOLOGYThe Stimulus: iWorx Unit Stimulating ElectrodeSKELETAL MUSCLE PHYSIOLOGYThe Response:–Relative force of muscle contraction measured by deflection of force transducer bladeSKELETAL MUSCLE PHYSIOLOGYMotor Unit:–Unit of contraction in intact organisms–Composed of:slice from spinal chordmotor neuron axons in a nerve leading from spinal chordneuromuscular junctionmuscleSKELETAL MUSCLE PHYSIOLOGY“Us” versus Them:•Vertebrate Skeletal Muscle:–A motor neuron innervates a muscle fiber –A muscle fiber is innervated by –AP in motor neuron isSKELETAL MUSCLE PHYSIOLOGY“Us” Versus Them:•Invertebrates (Arthropods):–A motor neuron can innervate a muscle fiber–Multiple motor neurons may innervate– motor neurons existSKELETAL MUSCLE PHYSIOLOGYGastrocnemius Muscle:•In intact organisms, innervated by•Sciatic nerve will be removed in lab•You will stimulate muscle DIRECTLY•Contractile force measured withSKELETAL MUSCLE PHYSIOLOGYTwo Methods to Increase Contractile Force:•Increase Stimulus :•Illustrates•Increase Stimulus : •IllustratesSKELETAL MUSCLE PHYSIOLOGY Recruitment:–As stimulus intensity increases, more muscle fibers reach threshold and contract–The greater number of muscle fibers recruited, the greaterSKELETAL MUSCLE PHYSIOLOGYRecruitment:•A muscle reaches MAXIMUM RECRUITMENT whenSKELETAL MUSCLE PHYSIOLOGYTemporal Summation:•In lab, we’ll also observe the relationship between stimulus frequency and force of contractionSKELETAL MUSCLE PHYSIOLOGYSingle Twitch–Single contraction–If multiple twitches occurSingle twitchSKELETAL MUSCLE PHYSIOLOGYSummation:–Sustained contraction due to–Muscle only–Results inSKELETAL MUSCLE PHYSIOLOGYTetanus:•State of•Muscle does •Results in contraction ofSKELETAL MUSCLE PHYSIOLOGYFatigue:•Some types of muscle fibersMUSCLE FIBER TYPES•Different Muscle Cell Types Differ in Susceptibility to Fatigue (as well as threshold, contractile strength, etc..)•Slow versus Fast Twitch Muscle FibersMUSCLE FIBER TYPESSlow twitch (oxidative; aerobic)MUSCLE FIBER TYPESFast twitch (glycolytic;