Muscle Health and Disease (OCR) - PDF

Muscle Health and Disease Outcome D4, Lesson 2 Muscle Twitch A muscle twitch occurs when stimulated to contract by a nerve It consists of a latent period which is the time in between stimulation from the nerve and the start of contraction Following the latent period is contracti...

Muscle Health and Disease Outcome D4, Lesson 2 Muscle Twitch A muscle twitch occurs when stimulated to contract by a nerve It consists of a latent period which is the time in between stimulation from the nerve and the start of contraction Following the latent period is contraction period followed by a relaxation period Muscle Twitch Results in a maximal, all-or- none contraction However, the strength of the contraction can vary depending on the number of muscle fibres contracting Muscle Twitch When a stimulus reaches a muscle fibre, it twitches If stimuli reach a muscle fibre continuously, the twitches may be added together in a process called summation Muscle Twitch If the muscle is in a state of constant contraction, it is called tetanus On the graph, you cannot see individual twitches, they are fused and blended into a straight line Tetanus continues until muscle fatigues Then no contraction can take place despite being stimulated Muscle Twitch Skeletal Muscle Fibre Types What is the difference between dark meat and white meat on a turkey? Skeletal Muscle Fibre Types What is the difference between dark meat and white meat on a turkey? Two main muscle fibres Skeletal Muscle Fibre Types What is the difference between dark meat and white meat on a turkey? Two main muscle fibres Slow-twitch (Type I) – dark; contain lots of myoglobin and have many surrounding capillaries Skeletal Muscle Fibre Types What is the difference between dark meat and white meat on a turkey? Two main muscle fibres Slow-twitch (Type I) – dark; contain lots of myoglobin and have many surrounding capillaries Fast-twitch (Type II) – light; contain little or no myoglobin and have fewer blood vessels Slow-Twitch Fibres Contract slowly, but resist fatigue Have more endurance Produce most ATP aerobically, so they tire only when fuel supply is gone Glycogen and fat allow the abundant mitochondria to maintain steady, prolonged ATP production Surrounded by dense capillary beds, draw more blood and oxygen Best suited for endurance type activities (e.g. biking, swimming, long distance running) Fast-Twitch Fibres Adapted for rapid generation of power, but fatigue quickly Rich in glycogen Have a large number of sarcomeres Depend on anaerobic energy production, putting them at risk of lactate accumulation Fewer mitochondria and fewer blood vessels Best suited for short-term, power activities (e.g sprinting, tennis, weightlifting) Intermediate Fibres Fast-twitch but have a high oxidative capacity More resistant to fatigue Endurance training increases proportion of fibres Genetics also plays a role The Value of Exercise The depletion of muscle glycogen and the buildup of lactic acid limit exercise Frequent exercise will help muscles increase aerobic capacity Able to perform more exercise before lactic acid production and glycogen production depletion cause muscle fatigue The Value of Exercise Endurance training does not increase size of muscles Only enlarged by frequent periods of high-intensity exercise where muscles work against high resistance Ex. Weightlifting Resistance training thickens fast-twitch muscles fibres so muscle grow by hypertrophy This happens because myofibrils thicken Once myofibrils reach a certain thickness they will spilt The increase in size and number of myofibrils builds muscle Complications of the Muscular System Muscles are generally vulnerable to injuries that result from sudden stress placed on them Muscles are one of the few organ groups whose activity can be impaired through lack of use Regular exercise allows muscles to develop and use energy more efficiently Muscular Atrophy Comes from Greek words meaning “without nourishment” Reduction in the size, tone and power of a muscle Even a temporary reduction in muscle use can lead to atrophy Ex. Having a leg in a cast Atrophy can be reversed, but if muscle fibers start dying, they are not replaced, and it can no longer be reversed Permanent loss of function  Muscular System Disorders Conditi Description on a collective term for several hereditary conditions in which the skeletal muscular muscles degenerate, lose strength, and are gradually replaced by fatty dystroph and fibrous tissue that impedes blood circulation; this, in turn, y accelerates muscle degeneration in a fatal spiral of positive feedback a potentially fatal muscular paralysis caused by a toxin produced by the bacterium Clostridium botulinum; the toxin prevents the release of botulism a muscle-stimulating compound (acetylcholine) released by muscle- related cells of the nervous system, thus leading to paralysis painful muscle spasms triggered by strenuous exercise, extreme cold, cramps dehydration, salt (electrolyte) imbalance, low blood glucose, or reduced blood flow abnormal muscle shortening not caused by nerve stimulation; can contractu result from inability to remove calcium ions from the sarcoplasm or re  Muscular System Disorders Conditio Description n chronic muscular pain and tenderness often associated with fatigue fibromyal and sleep disturbances; can be caused by infectious diseases, physical gia or emotional trauma, or medications a shock-like state following massive crushing of the muscles (as in, for example, the aftermath of an earthquake, the collapse of a building crush following an explosion, or a traffic accident); associated with high syndrome fever, heart irregularities caused by potassium ions released from the muscles, and kidney failure caused by blockage of the renal tubules with myoglobin released by the traumatized muscles delayed pain, stiffness, and tenderness felt from several hours to a day after onset strenuous exercise; associated with trauma to the muscles, disruptions muscle in the myofibrils and sarcolemma, and increased levels of myoglobin soreness and muscle-fibre enzymes in the blood muscle inflammation and weakness resulting from infection or an Common Injuries to Muscular System Torn muscles Stretched tendons Tendons connect muscles to bones Torn ligaments Ligaments connect bones to bones (within joints) Joint sprains Joint dislocation Muscles and Homeostasis Movement is essential for maintaining homeostasis You move to respond to certain types of changes in the environment Ex. When you are sitting in the hot sun, you are able to move to the shade or inside to prevent sunburn and heat stroke The muscular system is connected to all other body systems Muscles and Homeostasis System Relationship to Muscular System Circulator y System Respirator y System Digestive System Excretory System Muscles and Homeostasis System Relationship to Muscular System Skeletal muscle contraction help return venous blood to heart, smooth muscle contractions help move oxygenated blood through Circulator arteries, smooth muscle contraction constrict blood vessels to contain heat when cold and skeletal muscle cause shivering which y System warms up body due to ATP being used, skeletal muscles help squeeze lymph into lymphatic vessels, cardiac muscle pumps blood from heart Respirator Skeletal muscles (intercostal muscles and diaphragm) permit breathing brings oxygen into the body, and gets rid of carbon y System dioxide Contraction of the skeletal muscles in jaw and tongue help to Digestive grind food, smooth muscle contraction of peristalsis help move System food through the digestive tract, both important steps in gaining nutrients from our food Smooth muscle of bladder sphincters helps to regulate excretion Excretory of waste from the body