16Homework:Find and print a picture of your favorite athlete (bathing suit preferred to see as many muscles as possible)Hand label the visible muscles on their body using the muscles we discussed in class
17Do Now: Grab your Clicker Take out your HW – athlete pic w/labeled musclesReview names of muscles from hotlist & diagram
28Do Now:Why do you think that muscle- enhancing supplements (steroids, creatine, andro) are so popular at all levels of fitness and athletics (high school, college, pro, etc.) and do you see any problems with this?
29Muscle Tissues Cardiac Smooth Skeletal Involuntary striated muscle DinucleatedCommunicate via intercalated disksNatural contraction cycle determined by pacemaker cellsSmoothLines blood vessels, digestive organs, urinary system, and parts of respiratory systemInvoluntary nonstriated muscleCa+ triggers contractions differently (lacks sarcomeres)SkeletalVoluntary striated muscleMultinucleated cells called muscle fibersControlled by motor nerve cells
30Functions of Skeletal Muscle Produce MovementContractions pull on tendons and move bonesMaintain posture and body positionContinuous contractions maintain postureSupport/protect soft tissuesAbdominal wallFloor of pelvic cavityGuard entrances and exitsVoluntary control of swallowing, defecation, and urinationMaintain body tempSome energy from contractions lost as heat
31Gross Anatomy of Skeletal Muscle Each cell is called a “muscle fiber”Contains several tissues:ConnectiveBlood vesselsNerves – control contractionsSkeletal muscle
32Microanatomy of Skeletal Muscle Sarcolemma – cell membraneSarcoplasm – cytoplasmMyofibrils – bundles of myofilamentsThin filaments – actin proteinsThick filaments – myosin proteinsSarcoplasmic reticulum – smooth ER (stores Ca+)Sarcomeres – repeating units of myofilaments
34Classwork:Draw a flowchart or diagram showing how muscle contraction and relaxation occurs at a cellular level
35Muscle MechanicsMuscle cells pull on collagen fibers producing tension (can only contract!)Amount of tension dependent uponFrequency of neural stimulationLatent period (2msec) – action pot. & release of Ca+Contraction phase (15msec) – cross bridges formRelaxation phase (25msec) – tension, cross bridges and Ca+ decrease# of muscle fibrils activatedMotor unit - # muscle fibrils controlled by singe motor neuronFine control of movement determined by size of motor unitEx. Eye vs. Leg musclesDuring sustained contraction – motor units activated on a rotating basis (some rest/some contract)
36Muscle Tone Tone – resting tension Stabilizes the position of your jointsAny skeletal muscle not stimulated on a regular basis will atrophy – fibers become smaller and weakerInitially atrophy is reversibleExtreme atrophy is permanent
37Energetics of Muscle Activity Active Skeletal Muscle fibril requires 600 trillion ATP/sec!Sources of ATPStored (ADP + Creatine-P ATP)Lasts 15 secAerobic Metabolism (Krebs Oxidative Phosphorylation)Provides 30% of ATP needed during peak exertionAnaerobic Metabolism (glycolysis)Main E sourceLactic acid builds upIneffectiveMuscle Fatigue – no contraction despite stimulationLack of ATP or lactic acid build upRecovery Period – returns to pre-exertion levels
38Muscle Performance Force and endurance depends on: Types of muscle fibersFast Twitch (white)Powerful contractionsFatigue rapidly (few mitochondria)Slow Twitch (red)Extended contraction (many mitochondria)Extensive capillary networkMyoglobin binds O2Physical conditioning ( increase power and endurance)AnaerobicFrequent, brief intense workouts (hypertrophy of muscle fibrils)AerobicSustained low levels of activityCarb-load the day before; drink glucose rich sports drinks
39Muscle Review What muscle do you use to shrug your shoulders? What muscle would be well developed in a trumpet player?What is the most likely cause of a muscle cramp?What muscle do you use to stand on your tippy-toes?What muscle do you use to close your eye-lidsWhat muscle do you use when using a “butterfly” machine?Compare “white” muscles to “red” musclesA friend wants to bulk up his arms. What would you suggest to him?What are the 3 sources of energy for muscles? What limits each?