Skeleto-Muscular SystemPhysiology 6.1 NotesNotes:- The skeletal + muscular systems work together too Provide movement + locomotiono Manipulate the environment around uso Protect organs in the torsoo Maintain homeostasis by generating heato Maintain upright posture + bipedal lifePhysiology 6.2 Notes:Vocab:- Osteoblasts: immature bone cells that will be surrounded by bony matrix- Ossification: process of bones forming/maturingo Endochondral: forms within cartilage into longer/thicker boneso Intramembranous: forms flat bones in skull + other small parts.- Osteocytes: mature bone cells surrounded by bony matrix- Osteoclasts: large cells that release acids/enzymes that break down bony matrix and adds calcium + minerals to bloodstream- Osteoblasts: build up bone structure by pulling calcium + minerals from bloodstream.Notes:- Osteoblasts secrete osteoid gels that hardens to form bone matrices that mature into osteocytes by growing longer + thicker.- Bone tissue can either be compact or spongy.o Compact is at ends/edges of bones. Spongy is in the inner canals- Bones require blood supply of nutrients + waste transports like all other tissues.o Central canal of osteon holds blood/nerves and communicate with small canals cut through matrix that can exchange chemicals + blood vessels. - Bones constantly break down and repair itself to accommodate lifestyle over lifespan.- Calcium is added or removed in response to how much stress is placed on them.- Interaction between osteoclasts + osteoblasts can increase or decrease calcium concentrations in the bone. Rebuilding with osteoblasts takes much longer than destruction.- Bones are a storehouse for calcium needed all over the body.- Bone repair is much harder than remodelingo Bone fractures must be aligned and immobilized to redevelop properlyo Closed Reduction = fractures under the skino Open Reduction = skin is cut and may require surgery/screws to fix bones to placeo Compound Fractures = more than one break and most serious.o Limited movement + stress is ideal for healing bones.Physiology 6.4 Notes:Vocab:- Skeletal Muscle: contractile tissue composed of protein arranged around a skeleton to provide movement/support- Antagonistic Pair: opposite muscles that work together to provide controlled movement- Sarcomere: contractile units stacked in tubes inside myofibrils- Actin: Thin filament in sarcomere- Myosin: Thick filament suspended in sarcomere- Sarcolemma: The membrane that connects to motor neurons and surrounds myofibrils. Moderates the release of acetylcholine.- Acetylcholine: Binds to receptors at post synaptic gap to stimulate release of calcium and generate muscular contractions- Sarcoplasmic Reticulum: stores calcium ions to be released when Ach binds to receptors.- Tropomyosin: blocks myosin-binding sites on the thin filament when muscle is at rest- Troponin Complex: Calcium binds to TC to open up actin-active sites.Notes:- Each skeletal muscle has an origin (remains stationary), a belly (main body of fibers), and an insertion (moves during contraction)- Skeletal muscles are made of fascicles which are made of muscle fibers (myofibrils) which are made of even smaller sarcomeres.- Inside myofibrils are sarcomeres made of proteins actin + myosin- Sarcomeres have ends that make up “z disc” zig zag lines along the circumference of the myofibril. Z discs are connected to thin filaments (actin) which are connected to thick filaments (myosin). - Myosin is suspended but slides towards z-discs with triggers from actin and thus creates a chain-contraction that contracts the muscle as a whole.- When a motor neuron sends a signal, the axon terminals near the sarcolemma wrapping of the myofibril release acetylcholine neutransmitterso Acetylcholine triggers the release of calcium inside muscle cello Contraction cycle begins in myofibril until Ach is removed from receptors- In detail, calcium initiates contraction and causes myosin + actin to slide in the “sliding filament model”o Calcium, released when motor neuron releases ACh, binds to thin filament “troponin concept”, exposing “actin active sites”o Myosin heads picks up fresh ATP which releases energy to become ADP.o Myosin heads “actin-binding” site reacts and binds to exposed actin-active siteso A crossbridge is formed and the myosin head will lose its ADPo With low energy, myosin head droops and shifts actin towards center of sarcomere, pulling z-discs inwardsPhysiology 6.5 NotesVocab:- Motor Unit: one motor neuron and set of muscles it controls- All or Nothing Principle: entire motor unit contracts when it receives a strong enough signal form the motor neuron, but if not it doesn’t- Threshold Stimulus: minimal amount of stimulation needed to start contractions.- Summation: buildup of multiple contractions from multiple stimuli/action potentials.- Tetanus: smooth and sustained contraction when there is a quick flow of action potentialNotes:- When the motor neuron breaches the threshold stimulus, calcium is released, causing sarcomeres and entire muscle goes through contraction cycle- Muscle contraction becomes graded when there are rapidly delivered action potentials resulting in muscle summation- Meaningful contractions require multiple stimuli that would not allow the affected muscle cells to relax.- The strength or extent of muscle contraction can be altered because contraction is graded.o Varies at number of fibers contracting and rate of stimulation- Number of muscle fibers in body is set, but through hypertrophy, new myofibrils can increasethickness of