BIOL 1140 1st Edition Lecture 24Outline of Last LectureI. Urine System FunctionII. Urinary System StructuresIII. Kidney StructureIV. Anatomy of a NephronV. Urine FormationVI. Hormonal Control of Functions VII. Problems with Kidney FunctionVIII. Dialysis for Treatment of Kidney FailureOutline of Current LectureI. The Muscular SystemII. Muscles Attached to Bones by TendonsIII. Muscle StructureIV. Muscle ContractionV. Regulation of Muscle ContractionVI. Muscle PlasticityCurrent Lecture I. The Muscular System a. 3 types of muscle in bodyi. Cardiac muscle1. Striated2. Involuntaryii. Skeletal muscle1. Striated2. Voluntaryiii. Smooth muscle1. Non-striated2. Involuntaryb. Responsible fori. Producing movement1. Needed for behavior, communicationii. Posture of the bodyiii. Holds the bones togetheriv. Homeostasis - temperature regulationThese 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.1. Low body temp causes brain to signal to skeletal muscles to increase contractions and increase metabolismII. Muscles Attached to bones by Tendonsa. Origin: end of muscle that is attached to the stationary boneb. Insertion: end of muscle that is attached to a moveable bone across a jointi. Muscle contraction pulls insertion toward originc. Many muscles are arranged in antagonistic pairsi. Muscles work in opposite directions1. Biceps and triceps2. Quads and hamstringsIII. Muscle Structurea. Muscle = group of muscle cells with the same function, origin, and insertioni. Made of a bundle of fascicles1. Fascicles are bundles of myofibers wrapped in connective tissuea. Long, tube-shaped cellsb. Multinucleate c. Contain bundles of long, cylindrical structures called myofibrilsi. Composed of muscle proteins including actin and myosinb. Muscles can be stimulated to contract by motor neuronsi. Each myofiber is controlled by just one motor neuronii. But one motor neuron can control many muscle cells1. Motor unit = all the myofibers controlled by one motor neuron2. Neuromuscular junctiona. Neurons release the neurotransmitter acetylcholinec. Inside a myofibril, actin and myosin proteins lie parallel to each other and partially overlappingi. Actions are attached to the Z discs at the ends of the sarcomereii. Myosin’s lie in the middle of the sarcomere, partially overlapping the actin1. I band (light) composed of actin fibers alone2. A band (dark) composed of myosin fibers with some overlap of actinIV. Muscle Contractiona. During a muscle contraction, each sarcomere shortens a tin amounti. 100,000 sarcomeres in the muscle are arranged end- to- endii. Collective shortening of sarcomeres produces large amount of shortening in the muscleb. Myosin heads can bind to the actin fibersc. Myosin then flexes and changes shapei. Pulls the actin toward center of sarcomereii. Myosin releases actin, reattaches further down, and pulls againiii. During contraction, ~5 cross-bridges are formed per second; myosin and actin length DOES NOT CHANGEV. Regulation of Muscle Contractiona. Actin fibers have 2 other proteins attached:b. Tropomyosin wraps around actini. Blocks formation of cross-bridges when muscle is relaxedc. Troponin is attached to tropomyosini. Has binding sites for calcium ionsd. When Ca++ Is present and attached to Troponin, Tropomyosin shifts out of the way to allow myosin heads to form cross-bridges with actin, initiating a contractione. Calcium is stored in the sarcoplasmic reticulum inside myofiber cellsf. Muscle contraction is initiated by motor neuron signal:i. Acetylcholine is released from motor neurons at the neuromuscular junctionii. Creates electrical impulse along myofiber cell membraneiii. Transmitted along T Tubules1. Cell membrane extensions inside myofiberiv. Causes release of Ca++ from sarcoplasmic reticulumv. Ca++ binds to troponinvi. Tropomyosin shifts to allow cross-bridges to formvii. Actin pulled to center of sarcomere; sarcomere shortensVI. Muscle Plasticitya. Strength training:i. Adds more actin and myosin proteinsii. Increases amount of stored glycogeniii. Does NOT increase number of cellsb. Aerobic training:i. Increases branching of capillaries in muscleii. Increases number of mitochondriaiii. Increase amount of myoglobiniv. Does NOT increase muscle mass or cell