THE MUSCULAR SYSTEM CHAPTER 5

THE MUSCULAR SYSTEM CHAPTER 5

MUSCULAR SYSTEM Only tissue capable of shortening or contracting Responsible for both powerful and graceful movements Control movements of eyes, food, and heart Three categories of muscle fibers Skeletal Smooth cardiac

SKELETAL MUSCLE Striated muscle Voluntary Attach to bones Individual cell is referred to as muscle fiber Genetically determined Growth with age

SKELETAL MUSCLE Highly organized Sarcolemma cell membrane Endomysium protective sheath Perimysium strong fibrous membrane Fascicle unit Epimysium thick, tough connective tissue

SMOOTH MUSCLE Also known as visceral muscle Small Spindle shaped Non-striated Involuntary Single nucleus Found in internal organs such as: Stomach Intestines Respiratory passageways bladder

SMOOTH MUSCLE Arranged in layers One layer runs lengthwise Other surrounds the organ in which the muscles are contained Moving food through the digestive system Emptying the bladder Changing diameter of blood vessels Can sustain contraction for long periods of time

CARDIAC MUSCLE Solely in walls of heart Branched Cross-striated Involuntary Arranged in spiral shaped bundles Joined at structures called intercalated discs Enables simultaneous contractions of neighboring cells to produce heartbeat

BEHAVIORAL PROPERTIES Irritability Ability to respond to a stimulus Extensibility Ability to be stretched Elasticity Ability to return to normal length after stretch Contractility The ability to contract or shorten

TENSION Contraction implies shortening We usually use this term when tension has developed in a muscle However, one of three actions can happen: Muscle can shorten Muscle can remain the same length Muscle can lengthen

TENSION Concentric Shortening contraction Eccentric Lengthening contraction Isometric Contraction where no change occurs Agonist Muscle that is the prime mover Antagonist Opposing muscle group

THE MOTOR UNIT Muscle can t develop tension unless stimulated by nerves Motor neuron: nerve that stimulates skeletal muscle Motor unit: single motor neuron and all of the muscle cells it stimulates Considered to be the functional unit of the neuromuscular system

ACTION POTENTIALS Axon: connects the motor neuron cell body with the muscle fibers in a motor unit Axon terminals: axon branches into axon terminals which branch out to individual muscle fibers Neuromuscular Junction: link between axon terminal and muscle fiber Synaptic Cleft: gap between axon terminal and muscle fiber

ACTION POTENTIALS Acetylcholine: neurotransmitter than stimulates muscles Makes sarcolemma temporarily permeable Channels open that allow Na+ ions to invade the muscle fiber, as K+ ions rush out More Na+ enters than K+ exits = positive charge Depolarization: reversal of electrical charge Triggers opening of additional channels in fiber membrane that only allow Na+ to enter This generates an electrical charge called an ACTION POTENTIAL https://www.youtube.com/watch?v=wrv510gulco

SARCOMERE CONTRACTION Glycogen provides the energy for creating action potentials Phosphocreatine in the cell enables transfer of energy to protein filaments actin and myosin Sarcomeres release Ca+ ions which results in a contraction

SKELETAL FIBER TYPES Skeletal muscle fibers may play a big role in which sports people excel in Slow-twitch Contract slowly Fast-twitch Type IIa speed between slow and type IIb Type IIb 1/7 the time required for slow twitch, however they fatigue much faster

FIBER ARCHITECHTURE Way fibers are arranged within the muscle Two major types Parallel Pennate

PARALLEL MUSCLE FIBER Run largely parallel in length Result in 3 shapes Fusiform Bundled Triangular

PENNANTE FIBER Unipennate Aligned in one direction to a central tendon Bipennate Attach to a central tendon Multipennate Attach to a central tendon in more than two directions

STRENGTH, ENDURANCE, POWER Muscular Strength Impossible to measure Multiple muscle groups move a certain amount of resistance Amount of torque joints can make Muscular Power Force x velocity Based on resistance moved and speed Muscular Endurance Ability of muscle to produce tension over a period of time

DIRECTIONAL MOVEMENTS Origin: end of muscle that attached to fixed structure Insertion: end of muscle that attaches to bone that typically moves Ex. Brachialis muscle

MUSCLES OF HEAD & NECK

MUSCLES OF THE TRUNK

MUSCLES OF THE TRUNK

MUSCLES OF UPPER LIMB

MUSCLES OF LOWER LIMB

MUSCLE INJURIES Muscle Strain: when a muscle is stretched beyond its usual limits Grade I Mild, tightness in the muscle the day after Grade II Moderate, pain from a partial tear in the muscle Grade II Severe, tearing of the muscle, loss of function, internal bleeding, and swelling

MUSCLE INJURIES Contusion: bruise or bleeding within the muscle resulting from an impact Ex. Head injuries in football players Myositis Ossificans: occurs when an injured muscle is repeatedly struck Involves the formation of a calcium mass within the muscle After 6-7 weeks the mass is resorbed by the body In some cases a bony lesion can remain in the muscle

MUSCLE INJURIES Tendinitis: inflammation of a tendon usually causing pain and swelling Acute and overuse injuries Can occur with aging as elasticity decreases Can occur in any part of the body Tendinosis: degeneration of a tendon Caused by mircotears in the tendon Increases likelihood of rupture Recovery months to years of minimal use No inflammation

MUSCLE INJURIES Rotational injuries of the shoulder Repetitions of forceful overhead motions Throwing, spiking a volleyball, tennis serve Swimmer s Shoulder Improper motion mechanics contribute to inflammation or tears of muscle and surrounding tendons Treatment: ice, rest, possible surgical repair

MUSCLE INJURIES Overuse injuries to the elbow: inflammation and sometimes microtearing of muscle tendons that cross the lateral and medial side of the elbow. If left untreated the condition can worsen leading to swelling and scarring of the tendons near the elbow Tennis Elbow: lateral epicondylitis Little Leaguer s Elbow: medial epicondylitis

MUSCLE INJURIES Shin Splints: localized pain in the medial lower leg Overuse injury that typically arises from running or dancing on a hard surface Believed to be microdamage to the muscle tendons that attach to the tibia or inflammation of the periosteum of the tibia Treatment Stop activity Ice Stretch achilles and calf Wear proper shoes

MUSCLE DISORDERS Muscular Dystrophy: progressively worsening muscle weakness and loss of muscle tissue May occur in childhood or adulthood Some forms affect a certain muscle group, others affect all muscles Symptoms Intellectual disability Delayed development of motor skills Frequent falling Drooling Drooping of eyelids

MUSCLE DISORDERS Hernia: balloon-like section of the abdominal cavity lining that protrudes through a whole or weakened section of the muscle in the abdomen Can be caused by heavy lifting or by any activity that increase pressure inside the abdominal cavity Most produce no symptoms, some cause discomfort or pain that intensifies with heavy lifting or other activities that produce abdominal strain