BIO 1150 1st Edition Lecture 16• Myo-muscle • Statin-stop• Myostatin-stops muscle growthMovement- fundamental characteristic of living things• Cells are capable of shortening and converting Muscle tissue specialized for shortening movementTypes of muscle tissue• Cardiac striated• Smooth-involuntary• Skeletal- voluntary striatedMuscle characteristics• Responsiveness (excitability)- capability of responding to different stimulation with electrical changes across the plasma membrane• Conductivity-local electrical change conducted along the cell• Contractility-shortens when stimulated• Extensibility-capable of being stretchedSkeletal muscle fiber• Sarcolemma- membrane, “sarco= flesh”• Myofibrils- looks like coiled wires, striated (striped)o Sarcomere- 1 unit of myofibrilo Composed of actin and myosin Myosin- thick filament (thick bundle of myosin)• 200-500 myosin in a bundleThese 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. Actin- thin filaments• 2 strands actin• Groove that holds tropomyosin• Troponin complex• Sarcoplasmic reticulum (SR)- used for calcium storage• Ttubule (T=transverse(across))- piece of cell membrane that extends into cell, transmits electricityThe motor unit- motor neuron connects to muscle fiber• Activating a neuron causes muscle contraction• Excitation contraction couplingNeuromuscular junction-synapse of neuron/ skeletal muscleAcetycholine (Ach)- is a neurotransmitter for muscle • Has receptors• Binding of Ach to receptors opens ion channels • Ion entry into fiber causes change in membrane voltage (depolarization= more positive on the inside)Excitation spread- opening of voltage gated channels• APs in the Ttubule reaching the SR induce calcium 2+ release• Cacium binding exposes myosin binding sites on actin• Myosin pulls on actin= contraction• Exposure of myosin binding sites induces myosin binding to actin (cross-bridge formation)Calcium accumulation by SR= active transportMyosin releases from actinMyosin Cycle and ATP Role• Myosin binding on actin induces shape change of myosin head, pulling on actin (pulls trigger “power stroke”)• ATP binds to myosin, releases myosin from actino Rigor mortis- stiffening of muscles after deatho Rigor mortis is proof that ATP relaxes muscles• ATP hydrolosisrecocks myosin head (sets trigger)• ATP is stored in myosin• ATP is used for contraction and relaxation of musclesSliding filaments create contraction vs. relaxationThe limits of muscle performance are oxygen availability and the characteristics of muscle fibersTypes of muscle fibers• Oxidative (slow)-type 1- red, slow and weak, low oxygen supply (ex. Posture muscles)• Gylcolytic (fast)- type 2- white, fast and strong, high oxygen supply (ex. Extraocular muscles)• Mammals- have generally a mix of muscle fiber types• Fish- the type of muscle fiber mix varies in different musclesFish – red muscle is superficial, and not mixed as muchExceptions• Tuna- red muscle is deep• Swordfish- only keep the brain and eyes warmo No sarcomeres in muscle cell – this is to maintain
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