62) Cardiac - heart; striations; NOT voluntary; STEADY contraction Muscle Types1) Skeletal - longest; striations (bands); voluntary control; FAST contraction2) Cardiac - heart; striations; NOT voluntary; STEADY contraction3) Smooth - visceral; NO striations; NOT voluntary; SLOW contraction
7Muscle Function 1) Movement - locomotion; blood pressure; propulsion 2) Support Soft Tissues - support the weight of visceral organs; shield internal tissues3) Maintain Posture & Body Position4) Maintain Body Temperature - energy is used, converted to heat, heat is released5) Guard Entrances & Exits - digestive/urinary openings provide voluntary control
8Muscle Characteristics 1) Excitability - receive & respond to a stimulus2) Contractility - shortening3) Extensibility - stretch or extend4) Elasticity - resume resting length
9Muscle MovementFlexion - the angle between the two bonesExtension - the angle between the two bones
10Abduction - a bone is moved away from the midline of the body Adduction - a bone is moved toward the midline of the body.
11Rotation - a body part partially revolves on its axis
17A sarcomere is the smallest organized functional unit of the myofibril A sarcomere is the smallest organized functional unit of the myofibril. It contains thick and thin filaments (actin and myosin).A myofibril consists of about 10,000 sarcomeres.
20Two Important Proteins Involved inMuscle Contraction
21MyosinMyosin heads are also called cross-bridges. The heads pivots at the base, a key step in muscle contraction.
22Each thick filament consists of about 500 myosin molecules.
23ActinF actin is a twisted strand composed of 300+ G actin molecules. Each G actin contains an active site that binds to a thick filament (myosin). Tropomyosin covers the active sites. Troponin binds tropomyosin and G actin.
34Action Potential is generated & travels along sarcolemma down T-tubules Neurotransmitter is released, diffuses across synapseAction Potential triggers calcium release from SRACh - acetylcholine12Contraction ends, muscle fiber relaxes3SR76Calcium inside SR binds to troponin - changes shape - actin active sites exposed45Removal of calcium by re-uptake into SR after action potential endsAContraction - myosin cross bridges attach, detach from actin. Cross bridges split ATP & store energy.TP
35Types of Skeletal Muscle Fibers Fast Fibers - most muscle fibers in the body; contract in 0.01 second or less; powerful contractionsSlow Fibers - smaller than fast; take 3 times as long to contract; continue contracting after fast muscles are fatiguedIntermediate Fibers - properties between fast and slow fibersMORE
36White Muscles - dominated by fast fibers White Muscles - dominated by fast fibers. Example - chicken breast contain “white meat” because chickens use their wings only for brief intervals.Red Muscles - dominated by slow fibers; extensive blood vessels. Example - chickens walk around all day moving their slow muscle fibers, the “dark meat” in their legs.
37Muscle Hypertophy Athletes & Muscle Builders - Muscle Enlargement Occurs in muscles that are repeatedly stimulated to produce near-maximal tension.Muscles develop more mitochondria, more enzymes, larger glycogen reserves.Fibers have more myofibrils containing more thick and thin filaments.Number of fibers does not change, but the muscle diameter increases.
38Muscle mass of men exceeds that of women because muscle fibers are stimulated by testosterone.