Muscular Tissue

• Cardiac muscle tissue is found only in the heart and is responsible for pumping blood.
• Motion results from the alternating contraction and relaxation of muscles, which make up 40 – 50% of total adult body weight.
• Muscular tissues are produced through sustained contraction or alternating contraction and relaxation.
• Muscular tissues produce body movements and functions by the skeletal muscles, bones, and joints.
• Skeletal muscle contractions stabilize joints and help maintain body positions, such as standing or sitting.
• Postural muscles contract continuously when you are awake.
• Sustained contractions of ringlike bands or smooth muscles (sphincters) are used by muscular tissues to store and move substances within the body.
• The proportions of motor units in a muscle vary with the typical action of the muscle.
• The motor units of a muscle are recruited in the following order: first SO fibers, then FOG fibers, and finally FG fibers.
• Various types of exercises can induce changes in the fibers in a skeletal muscle.
• Endurance-type (aerobic) exercises, such as swimming, cause a gradual transformation of some fast glycolytic (FG) fibers into fast oxidative – glycolytic (FOG) fibers.
• Exercises that require great strength for short periods produce an increase in the size and strength of fast glycolytic (FG) fibers.
• Smooth muscle contractions also move food and substances such as bile and enzymes through the GI tract, push gametes (sperm and oocytes) through the reproductive system passageways, and propel urine through the urinary system.
• Peristalsis is the process that moves substances in the body.
• Peristalsis can stretch considerably and still maintain their contractile function.
• Peristalsis contracts in response to nerve impulses, hormones, and local factors.
• Peristalsis have small amounts of smooth-muscle relaxant (SR).
• Peristalsis is located in the GI tract, uterus, eye, blood vessels, and skins attached to hair follicles.
• The function of Peristalsis is Peristalsis.
• Peristalsis has no striated, central nucleus.
• Peristalsis is controlled involuntarily.
• Caveolae are small pouchlike invaginations of the plasma membrane that contain extracellular Ca2+ for muscular contraction.
• Visceral (single-unit) smooth muscle is found in the skin and walls of hollow viscera and of small blood vessels.
• Muscular tissues maintain normal body temperature through thermogenesis, the process of producing heat as muscular tissues contract.
• Termination of ACh activity is achieved by enzyme acetylcholinesterase (AChE) located on the motor end plate membrane.
• If another nerve impulse releases more acetylcholine, steps 2 and 3 repeat.
• When action potentials in the motor neuron cease, ACh is no longer released, and AChE rapidly breaks down the ACh already present in the synaptic cleft.
• This ends the production of muscle action potentials, the Ca2+ moves from the sarcoplasm of the muscle fiber back into the sarcoplasmic reticulum, and the Ca2+ release channels in the sarcoplasmic reticulum membrane close.
• A skeletal muscle fiber has only one NMJ and it is usually located near the midpoint of the fiber.
• Muscle action potentials that arise at the NMJ propagate toward both ends of the fiber.
• Shivering is an involuntary contraction of skeletal muscles that can increase the rate of heat production.
• Skeletal muscle tissues move bones of the skeleton and are located in the skeleton.
• Potentials in the motor neuron to release enough acetylcholine are referred to as action potentials.
• Oxygen Debt refers to the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise.
• An extra oxygen is used to “pay back” or restore metabolic conditions to the resting levels: to convert lactic acid back into glycogen stores in the liver, to resynthesize creatine phosphate and ATP in muscle fibers, and to replace the oxygen removed from myoglobin.
• Cardiac Muscle metabolism contracts 10-15 times longer than skeletal muscle, has an extensive coronary circulation, and generates ATP primarily through aerobic respiration.
• Smooth Muscle metabolism has a low capacity for generating ATP, primarily through anaerobic respiration.
• Control of Muscle Tension involves Motor Units, which consist of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates.
• A single motor unit may contain as few as 2 or as many as 3000 muscle fibers.
• All of the muscle fibers in one motor unit contract in unison.