Muscles, Health, and Homeostasis PDF

10.2 - Muscles, Health, and Homeostasis Muscles, Health, and Homeostasis Even at rest, muscles still contract at some level ○ Tone-continuous: “Low-level” activity of muscles (Ex. maintaining posture) If all fibres within muscles of neck, torso, limbs were to relax, body woul...

10.2 - Muscles, Health, and Homeostasis Muscles, Health, and Homeostasis Even at rest, muscles still contract at some level ○ Tone-continuous: “Low-level” activity of muscles (Ex. maintaining posture) If all fibres within muscles of neck, torso, limbs were to relax, body would collapse Complications of Muscular System Muscles are generally vulnerable to injuries that result from sudden and intense stress Complications of Muscular System Atrophy Muscles are one of few organ groups whose activity can be impaired through lack of use Muscular atrophy result from lack of movement of muscle ○ Atrophy: Reduction in size, tone, and power of muscle ○ Is reversible, however, dead/dying muscle fibres aren’t replaced ○ If muscle fibres die, loss of muscle tissue is permanent Exercise and Muscle Contraction Regular exercise allows muscles to develop and use energy more efficiently Hypertrophy: Increase in size of muscles ○ Regularly used muscles grow due to increase in size of individual muscle fibres ○ Contain more mitochondria ○ Withstand more execution before lactate builds up (fermentation starts) ○ Contain more blood → more blood vessels (white meat vs. dark meat) ○ Stores more glycogen Muscle Twitch Muscle is stimulated to sufficient degree - will contract quietly (“twitch”) If stimuli are given in rapid succession, twitch will build and create full contraction Contraction can continue until muscle expends it energy reserves and becomes fatigued Divided into 3 periods: 1. Latent 2. Contraction 3. Relaxation 1. Latent Period Time period between stimulation and initiation of contraction During this time, Ca2+ ions are leaving sarcoplasmic reticulum and are penetrating myofibrils 2. Contraction Period Time during which muscle shortens Z-lines are pulled closer together 3. Relaxation Period Muscle refers to normal length Actin and myosin filaments slide past each other to resting position Myograms Myogram: Graph that shows force of muscle contraction with time 1. Summation: Successive twitches blend together creating cumulative response 2. Tetanus: Maximum sustained muscle contraction Muscle remains contracted and graph no longer shows individual twitches Ends due to depletion reserves ○ Allows us to stay in one position 3. Fatigue Muscle relaxes even though stimulation continues Fast vs. Slow Twitch Slow twitch (Type I): Muscle fibres contract slowly but resist fatigue - more endurance ○ Reduce energy aerobically as they have large amounts of myoglobin and mitochondria Fast twitch (Type II): Are adapted for rapid generation of power but fatigue quickly ○ Have little to no myoglobin and fewer mitochondria ○ Often depend on anaerobically produced energy Intermediate Fibres Similar to fast-twitch fibres but are more resistant to fatigue Endurance training increases the proportion of these fibres in muscles Heredity is involved in determining proportion of fast-twitch and slow-twitch fibres in our bodies Homeostasis Muscular system allows us to maintain homeostasis Muscle generates heat through use of ATP during contraction and muscles allow blood vessels to contract and dilate to move warm blood throughout body Many of our processes in other body systems rely on movement of muscles to regulate actions