Lecture_22_Musculoskeletal.pptx

GENERAL BIOLOGY II Lecture 22: Sensory Systems Chapter: 38 Musculoskeletal System The musculoskeletal system is made up of: bones & joints muscles cartilage tendons & ligaments other connective tissue Its primary functions include supporting the body, allowing motion, and Muscles Purpose: To move th...

GENERAL BIOLOGY II Lecture 22: Sensory Systems Chapter: 38 Musculoskeletal System The musculoskeletal system is made up of: bones & joints muscles cartilage tendons & ligaments other connective tissue Its primary functions include supporting the body, allowing motion, and Muscles Purpose: To move the body Convert chemical energy to mechanical energy (ATP to Force) Force – push or pull on one object by another Muscles Muscle fiber – individual muscle cell Contain contractile proteins: Actin Myosin Muscles Types: Skeletal Cardiac Smooth Muscles Types: Skeletal Cardiac Smooth Striated Muscles Muscles Organization: Individual muscles made up of muscle bundles Muscle bundles made up of Muscle Fibers Muscle fibers are made up of myofibrils Myofibrils Organization: Thin filament – Actin Surrounded by double helix of Tropomysin Thick filament - Myosin Myofibrils Organization: Z-disc – thin filaments are attached to this protein backbone Sarcomere – contractile unit; area from one z-disc to the next Sliding filament model The myosin head binds ATP, and detaches from actin Hydrolysis of ATP to ADP results in a conformational change in which the myosin head is cocked back The myosin head binds to actin, forming a crossbridge When the myosin head binds to actin, the myosin head releases ADP and Pi. The result is another conformational change in the myosin head, called the power stroke Myofibrils Cross-bridge Cycling Myofibrils Motor unit – a motor neuron and all of the myofibers that connect to it Myofibrils Action potential from nerves connects to the muscles at the motor endplate Cause Sarcoplasmic Reticulum to release Ca+2 Ca+2 binds with Troponin, which moves the tropomysin to expose actin binding sites Myofibrils Process is called excitationcontraction coupling excitation of the muscle cell is coupled to contraction of the muscle Smooth muscle doesn’t have tropomysin, and uses the protein Calmodulin to control cross-bridge formation Muscle Contractions Muscles are arranged in pairs Antagonist muscles – paired muscles that cause the exact opposite movement of each other when they contract Flexion – Muscle contraction that causes a bending movement Extension – Muscle contraction that causes a straightening movement Muscle Contractions Agonists - muscles that contract to provide the main force to move or rotate a bone through its joint ex. Three heads of the triceps brachii Muscle Contractions Muscle length affects the actin-myosin overlap and the force that is can generate Maximizing the number of cross-bridges that can be formed maximizes the muscle power (force) LibreText libraries, Anatomy & Physiology (Boundless), 2024 Muscle Contractions Muscle contraction speed relates to muscle power (force) The slower the contraction, the more the power Muscle Contractions Muscle contraction speed relates to muscle power (force) Isometric contraction – contraction in which the muscle does not change length (ex. If you push with all your might on a wall, neither the wall nor your muscles move) Muscle Contractions Muscle contraction speed relates to muscle power (force) Lengthening contraction – Occurs when the force applied to the muscle exceeds the force that the muscle is producing (ex. when you are setting down a heavy weight, your biceps lengthen as you get close to the floor, even though they’re exerting force) Muscle Contractions Twitch – Muscle contraction of a specific force Rapid stimulus increases contraction strength because Ca+2 doesn’t have time to reabsorb into SR Muscle Contractions Tetanus – long, sustained muscle contraction caused by fatigue or depletion of ATP Muscle Contractions Different type of skeletal muscle fibers exist: Slow-twitch – red; contract slowly, consume ATP slowly; aerobic; used for posture or economical movement Fast-twitch – white; rapidly contact; quickly burn through ATP; anaerobic; used for rapid movement Muscle Contractions Slow-twitch fibers are red because of the prevalence of myoglobin, which is used to carry oxygen to the mitochondria for aerobic respiration Skeleton types: Hydrostatic Animal Skeletons Exoskeleton Endoskeleton Hydrostatic Skeletons Pandai.org 2024 Exoskeletons Exoskeletons Exoskeleton terminology: Chitin – polysaccharide fibers reinforced by proteins Molting – process of shedding a cuticle for growth Exoskeletons Exoskeleton limitations: Animals are vulnerable after molting until the chitin hardens If damaged, the entire skeleton must be regrown Prone to breaking if surface area is large Endoskeletons Endoskeleton terminology: Made of relatively few cells and extracellular matrix (bone, tooth enamel, dentine, tendon, and cartilage) Tendons – specialized connective tissue made of collogen that Endoskeletons Endoskeleton divisions: Axial skeleton – Endoskeletons Endoskeleton divisions: Appendicular skeleton – Endoskeletons Bone production: Formed by osteoblast cells Mineral is called hydroxyapatite (calcium phosphate) Secreted with Osteoclasts – cells that remove bone to reshape it or repair damaged regions Vertebrate Skeletons Types of Bone: Spongy – composed of small plates and rods (trabeculae); found at ends of bone; reduces their weight, and increases the ability to resist deformation from force Vertebrate Skeletons Types of Bone: Compact – form the walls of bone shafts; contains dense mineralized bone and a network of blood vessels; provides strong but brittle structure Vertebrate Skeletons Diaphysis – central shaft of long bones Epiphysis – rounded ends of long bones Vertebrate Skeletons Growth plate – area of cartilage that between the epiphysis and the diaphysis Bones grow in length and diameter. Osteoblasts lay down new layers of bone on the outside, while osteoclasts remove older layers of bone along the marrow cavity Sinai Hospital Baltimore, 2019 Vertebrate Skeletons In mammals and birds, growth continues until maturity, at which point cartilage growth plates are replaced with bone. Amphibians and reptiles can often continue to grow throughout their lives, albeit at a slower pace Sinai Hospital Baltimore, 2019 Vertebrate Skeletons Bone formation: Membranous bones – skull & ribs; embryonically produced by osteoblasts with no soft tissue model Other bones first formed embryonically as cartilage, and later become bone as blood vessels invade the cartilage as fetus matures Joints Joint types: Ball-and-socket – Three-dimensional range of motion; more likely to be dislocated or damaged Hinge – Twodimensional range of motion; more stable For Next Class Complete the Quiz on CANVAS Read Chapter 37: Endocrine System