BIOL 252 1st Edition Lecture 12 Outline of Last Lecture I Sarcomere II Transferring contractile forces to whole muscles III Nerve Muscle Relationship IV Muscle Contraction and Relaxation Outline of Current Lecture I Relaxation II Muscle Strength III Tension in muscle fibers IV Length tension relationship V Poll Everywhere VI Whole Muscle Contractions VII Muscle Metabolism Current Lecture I II Relaxation a Where does calcium go i Back to the SR b How i Active transport ii Uses ATP to push calcium into ST against concentration gradient c Therefore relaxation dependent on ATP Muscle Strength a Temperature i If you freeze cells molecular activity decreases ii In our bodies temperature constant but if you exercise a muscle temperature rises 1 Has positive effect on contractive strength 2 Warmer muscle stronger b pH i Everything depends on stable pH ii Due to accumulation of lactic acid pH decreases c Calcium concentration d Relative length of muscle cell These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III e Hydration Tension in muscle fibers a Latent period doesn t seem to be anything happening for first few milliseconds i Why is there no contraction ii Between time of electrical stimulation and time calcium finds troponin no visible tension iii Excitation excitation contraction coupling and very beginning of contraction there is tension but not measurable outside of the cell b Contraction phase c Relaxation phase d Why does tension build and then slowly decline Smooth curve i Release of calcium is faster than reuptake ii Slope in contraction is greater than relaxation diffusion vs active transport against concentration gradient e Treppe successive twitches will increase strength of twitches over time i ii f T r e p p Because thereeis a small amount of calcium still left over 1 Baseline calcium level slowly rises 2 AP strength is still the same 3 Due to warming up a As you use muscles temperature increases 4 Baseline tension is the same If you stimulate that further wave summation i Incomplete tetanus result of wave summation ii iii iv v Results when stimuli are close together Baseline of tension rises Each successive twitch builds on tension of previous twitch How do you build tension 1 Releasing calcium from SR a Not releasing all of it only a portion IV V 2 Some is pulled back into SR but before we can pull back to get to tension of 0 release more calcium 2 steps forward 1 step back 3 Increase incrementally the amount of calcium in the cell vi Summation Adding local potentials on top of one another to get to threshold of producing action potential vii Wave summation adding TENSION on top of TENSION viii Know the difference ix At the peak reach tetanus 1 Means that we have plateaued sustained level of contraction 2 What s happening in the cell 3 Not substantially resorbed 4 Completely releasing all of the effective calcium 5 Calcium completely saturating troponin so troponin is bound with calcium binding sites are all open 6 As we introduce more calcium more binding sites open until all open and cannot make stronger contraction by adding more calcium x Fatigue 1 Decrease in tension 2 Category of muscle failure there is not one specific reason Length tension relationship a b Optimal length is somewhere in the middle easiest to contract Which of the following does NOT describe how your body controls strength of muscle contraction a Changing intracellular calcium levels YES b Changing muscle temperature NO i Temperature affects strength but doesn t control it ii Do not intentionally find a way to increase temperature to control strength c Activating more fewer motor units VI VII i What s a motor unit ii More motor units more muscle contracting more strength iii So YES d Change frequency of neuronal action potentials i What is the effect on a muscle ii More contraction more calcium more APs iii So YES e Changing number of myosin binding sites i More cross bridges stronger contraction Whole Muscle Contractions a Contraction is generation of force tension b Isometric contraction i Muscle develops tension but does not shorten ii No movement iii Ex carrying a coffee cup c Isotonic contraction tension remains constant but there is movement i Isotonic concentric contraction 1 Muscle shortens 2 More than 5kg force generated for 5kg weight 3 Ex picking baby up ii Isotonic eccentric contraction 1 Muscle lengthens 2 Less than 5kg force generated for 5kg weight 3 Ex putting baby down Muscle Metabolism a All muscle contraction depends on ATP b Where does ATP come from i Glycolysis 1 Generate 2 ATP NET molecules pyruvic acid 2 O2 aerobic respiration ii Aerobic respiration 1 WITH OXYGEN 2 Glucose molecule generates 36 ATP 3 2 from glycolysis 38 total ATP 4 Without oxygen anaerobic respiration a Examples very strenuous exercise for short time or exercise for a long amount of time 5 More sufficient to have oxygen around iii Phosphagen system 1 Regeneration of ATP 2 ADP 3 Myokinase enzyme a Kinase phosphorylates 4 When muscles are active myokinase takes ADP AMP a Takes one phosphate away b Takes extra P and puts it on ADP ATP 5 2 ADP ATP AMP 6 Creatine kinase a Creatine phosphate creatine kinase when removes P b Adds to ADP c Creatine ATP