Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Skeletal muscle
Document related concepts
no text concepts found
Transcript
Ch 39.1 p.718 Ch 39.2 p.720 Ch 39.3 p.727 Skeleton Use Protection Support Movement Storage for ions Production of blood cells Types of Skeletons Hydrostatic- “water standing” can be fluid-filled gastrovascular cavity found in Cnidaria and Platyhelminthes analogy: stiff garden hose Organisms: worms, jellyfish, sea anemones, etc. Earthworms-septa Muscle fibers at base of epidermal cells contract body/tentacles shorten quickly=movement Muscular hydrostat-certain parts are helped to be moved by “fluid contained within certain muscle fibers.” e.g. spider legs, elephant trunks Exoskeleton- outer Organisms: molluscs, arthropods, and vertebrates Primarily for protection against outside predators and environment Calcium Carbonate shell in molluscs that can grow with them. i.e. snails, clams Chitin, a “flexible nitrogenous polysaccharide” in arthropods. i.e. insects allow for flexibility Arthropods must molt vulnerability (during the waiting period while the new exoskeleton hardens and dries) Endoskeleton- inner Organisms: vertebrates and echinoderms e.g. starfish Primarily for support and movement and protection of vital organs Spicules and plates of calcium carbonate Vertebrate endoskeleton=living tissue Grows with animal but molting is not needed Can support weight while leaving space Joints allow for complex movements Movement Muscles = force by contraction Tendons are what attach the muscles and bones Bones = anchorage and levers change size or direction of force by muscles Ligaments are what connect bones and help prevent dislocation Nerves are what send messages from brain to muscles to tell to contract and move at certain times and extents Joints Junctions between bones Parts: Cartilage-smooth tough tissue-bone friction reducer Muscle-for bending, straightening Bones-lever, anchor, and force Synovial fluid-joint lubricator Joint capsule-joint seal and holds in fluid Like a bottle cap Difference in Movements Hip joint Movement in three planes Protraction/retraction, abduction/adduction, and rotation Knee Joint Hinge joint A lot of movement in one plane Flexion/extension What are Muscles? Muscles are bundles of tissue that are attached to bone by tendons and are essential for movement Muscles provide the force for movement by working in antagonistic pairs This means that when one muscle contracts, the other relaxes, and vice versa Muscles are made of muscular tissue and involve three types: Skeletal muscle, or striated voluntary muscle, is responsible for posture, support, and movement. It also helps maintain homeostasis by keeping constant body temperature as well as releasing heat stored in the body by breaking ATP during contractions Smooth muscle, or non-striated involuntary muscle, which contracts automatically. It is found in the digestive tract, respiratory tract, iris, and arrector pilli of the skin Cardiac muscle, which is found specifically in the heart; it is responsible for heart contractions in order to pump blood to the rest of the body Macroscopic Anatomy and Physiology There are about 700 different skeletal muscles in the body, all of which make up about 40% of the body weight of an average human (point out some superficial muscles) Skeletal muscles attach to the skeleton by tendons Muscles shorten when the contract; they cannot lengthen They can only push, not pull, and must therefore work in pairs (ask for volunteers) Rapid stimuli can cause muscles to respond to subsequent stimuli without relaxing completely (fishing pole analogy) Repeated stimulation causes increasing contraction until it reaches the maximum sustained contraction, called tetanus Even when they appear to be at rest, some muscles exhibit tone, which is when some of the fibers are still contracted If all muscles went slack, people would just collapse Microscopic Anatomy and Physiology Structure of skeletal muscles Skeletal muscles are composed of bundles of muscle fiber, containing special components The sarcolemma is a plasma membrane for muscle cells The muscle fibers have modified endoplasmic reticulum, called sarcoplasmic reticulum, which serve as storage sites for calcium ions needed in contractions The sarcoplasmic reticulum contains up to thousands of myofibrils, which are the part of the muscle fiber that contract Myofibrils have light and dark bands (called striations) caused by the placement of protein filaments inside of contractile units called sarcomeres Sarcomeres extend between two dark lines called “Z lines” There are two types of filaments: thick, make of myosin, and thin, made of actin The “I band” is light because it contains only actin The darker “H zone” contains only myosin The “A band” contains overlapping actin and myosin, so it is the darkest Sliding Filament Model Contracted muscle fibers show that sarcomeres within myofibrils are shortened When sarcomeres shortened, the actin slide past the myosin and toward each other The “I band” then shortens and the “H zone” basically disappears *NB: the sarcomere gets shorter, but the filaments themselves remain the same length ATP supplies energy for the reaction; myosin filaments are the ones that actually do the work and break down ATP to form cross-bridges that attach to and pull actin filaments to the center ATP ATP provides the energy for muscle contraction Although muscle cells contain myoglobin, an oxygen-storing molecule, cellular respiration does not necessarily supply all of the needed ATP Therefore cells rely on phosphocreatine, a storage form of high-energy phosphate Phosphocreatine does not directly participate in muscle contraction, but instead regenerates ATP in the following equation: creatine-P + ADP ---> ATP + creatine *NB: Phosphocreatine and creatine phospate are the same After all of the phosphocreatine is used, the mitochondria will then produce the required ATP for muscle contraction If not, then fermentation will occur, which causes the buildup of lactate after a short period of time Hard breathing after exercise gathers the necessary oxygen to complete the metabolism of lactate to restore cells to their original energy state (this is known as oxygen debt) The lactate is transported to the liver, where about 20% of it is broken down into carbon dioxide and water to gain ATP in order to reconvert the remaining 80% of lactase into glucose Muscle Innervation Muscle innervation refers to when muscles are stimulated to contract by motor nerve fibers Nerve fibers have several branches that end in axon terminals that lie very close to the sarcolemma; they are separated by a small gap called the synaptic cleft The entire region is called a neuromuscular junction The terminals contain vesicles that hold the neurotransmitter ACh (acetylcholine), which is released when nerve impulses travel down the motor neuron and to the axon The ACh diffuses into receptors in the sarcolemma which generates impulses that spread into the sarcoplasmic reticulum, causing the release of calcium ions The calcium causes the sarcomere filaments to slide past one another, causing contraction of the sarcomere, resulting in myofibril contraction, then muscle fiber contraction, then contraction of the muscle itself Once ACh is relased into the junction and created a response, it is removed Acetylcholinesterase (AchE) breaks down ACh Bibliography Allott, A. (2001). Biology for the IB diploma standard and higher level. Oxford: Oxford University Press. Anatomy of the Skin. (n.d.). Anatomy of the Skin. Retrieved from http://medicalcenter.osu.edu/patientcare/healthcare_services/skin_con ditions/anatomy_skin/Pages/index.aspx Mader, S. S. (1998). Biology. Boston: WCB/McGraw-Hill.
