BSC 109 1st Edition Lecture 9 Outline of Last Lecture I. Skeletal system consists of connective tissueA. Bone: hard elements of the skeleton1. Functions2. Contains living cells3. Ligaments hold bones together4. Cartilage lends support5. Bone development begins as embryo6. Bones undergo repair7. Skeletal systemOutline of Current Lecture B. Muscles1. Found in every organ2. Helps with movement3. Large proportion of body weight4. 3 types5. Produce movement and generate tension6. Contraction is a fundamental activity7. Sarcomere: contractile unit8. What causes contraction?9. Nerves activate skeletal muscles10. Calcium initiates the sliding filament mechanism11. When nerve activation ends, contractions end12. Muscles require energy to contract and relax13. Activity can vary14. Slow twitch vs. fast twitchCurrent Lectureg. Diseases and disorders of the skeletal systemi. Sprainsii. Bursitis and tendonitisiii. Arthritis (osteoarthritis vs. rheumatoid arthritis)iv. Osteoporosis preventionB. Muscles1. Found in every organ2. Helps with movementThese 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.3. Large proportion of body weight4. 3 types5. Produce movement and generate tensiona. Muscles produce voluntary and involuntary movementb. Many muscles resist movement: posture and blood pressurec. Generate heat6. Contraction is a fundamental activitya. Excitable: contract in response to electrical chemical stimulib. 600+ skeletal musclesc. Synergistic vs. antagonisticd. Origine. Insertion. f. Most are attached with tendons7. Sarcomere: contractile unita. Myosin forms thick filamentsb. Actin forms thin filamentsc. Z-lines: attachment points for sarcomeresd. Rowing motion signals to regulate8. What causes contraction?a. Skeletal muscle activated by a nerveb. Nerve activation increases calcium ion countc. Calcium permits contractiond. When nerve stimulation stops, contractions stop9. Nerves activate skeletal musclesa. ACH is released from motor neuronsb. Electrical impulse transmission along T-tubulesc. Calcium is released from sarcoplasmic reticulumd. Calcium imitates chain of events that cause contraction when it contacts myofibrils10. Calcium initiates the sliding filament mechanisma. Contraction: formation of cross-bridges between thin and thick filamentsb. Calcium must be present for cross bridges to formc. Mitochondria make ATPd. Muscle cells have lots of mitochondria11. When nerve activation ends, contractions enda. Calcium is released from sarcoplasmic reticulumb. Calcium binds to troponinc. Troponin/tropomyosin shifts positiond. Myosin binding site exposede. Sarcomere shortensf. Nerve activation ends, contraction endsg. Calcium pumped back into sarcoplasmic reticulum (via ATP)h. Myosin binding site coveredi. No calcium, no cross bridgesj. Muscle relaxes12. Muscles require energy to contract and relaxa. ATP: principle source of energyb. ATP required for contractionc. ATP required for relaxationd. ATP replenished by many meansi. Creatine phosphateii. Stored glycogeniii. Aerobic metabolism of glucose, fatty acids, and other high-energy molecules13. Activity can varya. Isotonic contraction vs. isometric contractionb. Degree of nerve activation influences forcec. Motor unit: motor neuron and all muscle cells it controls, smallest functional unit of muscle contractiond. Muscle tension: mechanical force that muscles generate when they contracte. Determined by size, number of units, frequencyf. All or none principal: completely contracting or completely relaxingg. Muscle toneh. Recruitment: using additional motor units increases muscle tone14. Slow twitch vs. fast twitcha. Slowi. Contracts slowly, make ATP as needed, lots of mitochondria, lots of blood vessels, not a lot of glycogen, “red” muscle, endurance activities (jogging, swimming, biking)b. Fasti. Contracts quickly, rapidly produce ATP, few mitochondria, lots of glycogen, “white” muscle, anaerobic metabolism, brief high intensity activities (sprinting, weights, tennis)c. Strength training builds up myofibrilsd. Aerobic: high blood supply, lots of mitochondriae. Cardiac vs.