Muscular System Muscles are responsible for all types

Muscular System Muscles are responsible for all types of body movement ¢ Three basic muscle types are found in the body ¢ Skeletal muscle l Cardiac muscle l Smooth muscle l

Characteristics of Muscle All Muscle cells are elongated (muscle cell = muscle fiber) ¢ All can contract due to the movement of microfilaments ¢ All muscles share some terminology ¢ Prefix myo refers to muscle l Prefix mys refers to muscle l Prefix sarco refers to muscle l

Types of Muscle

Types of Muscle, cont.

Skeletal Muscle Characteristics ¢ ¢ ¢ Most are attached by tendons to bones Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue

Characteristics of Smooth Muscle ¢ ¢ ¢ Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow organs

Cardiac Muscle Characteristics ¢ ¢ ¢ Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart

Functions of Skeletal Muscles ¢ l l Produce movement Maintain posture Stabilize joints Generate heat

¢ Muscle Fibers blend into a connective tissue attachment l l ¢ Tendon – cord-like structure Aponeuroses – sheet-like structure Sites of muscle attachment l l l Bones Cartilages Connective tissue coverings of each other

Muscle Tissue There are three types of muscle tissue in the body. ¢ Skeletal muscle is the type that attaches to our bones and is used for movement and maintaining posture. Cardiac muscle is only found in the heart. It pumps blood. ¢ Smooth muscle is found in organs of the body such as the GI tract. Smooth muscle in the GI tract moves food and its digested products. ¢

Skeletal Muscle Skeletal muscle attaches to our skeleton. ¢ The muscle cells are long and cylindrical. ¢ Each muscle cell has many nuclei. ¢ Skeletal muscle tissue is striated. It has tiny bands that run across the muscle cells. ¢ Skeletal muscle is voluntary. We can move them when we want to. ¢ Skeletal muscle is capable of rapid contractions. It is the most rapid of the muscle types. ¢ No rhythmic contraction. ¢

Cardiac Muscle ¢ ¢ ¢ ¢ Branching cells One or two nuclei per cell Striated Involuntary Medium speed contractions Cardiac muscle tissue is only found in the heart. Its speed of contraction is not as fast as skeletal, but faster than that of smooth muscle. IT has rhythmic contraction

Smooth Muscle Fusiform cells ¢ One nucleus per cell ¢ Nonstriated ¢ Involuntary ¢ Slow, wave-like contractions ¢ Smooth muscle is found in the walls of hollow organs. *. ¢ *The contractions of smooth muscle are slow and wave-like. ¢ Some has rhythmic contraction ¢

Connective Tissue Wrappings of Skeletal Muscle · Endomysium – around single muscle fiber · Perimysium – around a fascicle (bundle) of fibers Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6. 1 Slide 6. 4 a

Connective Tissue Wrappings of Skeletal Muscle · Epimysium – covers the entire skeletal muscle · Fascia – on the outside of the epimysium Figure 6. 1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 4 b

Skeletal Muscle Attachments · Epimysium blends into a connective tissue attachment · Tendon – cord-like structure · Aponeuroses – sheet-like structure · Sites of muscle attachment · Bones · Cartilages · Connective tissue coverings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 5

Function of Muscles · Produce movement · Maintain posture · Stabilize joints · Generate heat Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 8

Microscopic Anatomy of Skeletal Muscle cell (fiber) · The nuclri are pushed aside by ribbonlike myofibrils · Cells are multinucleate · Nuclei are just beneath the sarcolemma Figure 6. 3 a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 9 a

Microscopic Anatomy of Skeletal Muscle cell (fiber) · Sarcolemma – specialized plasma membrane · Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6. 3 a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 9 b

Microscopic Anatomy of Skeletal Muscle cell(fiber) · Myofibril · Bundles of myofilaments · Myofibrils are aligned to give distrinct bands · I band = light band · A band = dark band Figure 6. 3 b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 10 a

Microscopic Anatomy of Skeletal Muscle · Sarcomere · Contractile unit of a muscle fiber Figure 6. 3 b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 10 b

Microscopic Anatomy of Skeletal Muscle · Organization of the sarcomere · Thick filaments = myosin filaments · Composed of the protein myosin · Has ATPase enzymes Figure 6. 3 c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 11 a

Microscopic Anatomy of Skeletal Muscle · Organization of the sarcomere · Thin filaments = actin filaments · Composed of the protein actin Figure 6. 3 c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 11 b

Microscopic Anatomy of Skeletal Muscle · Myosin filaments have heads (extensions, or cross bridges) · Myosin and actin overlap somewhat Figure 6. 3 d Slide 6. 12 a

Microscopic Anatomy of Skeletal Muscle · At rest, there is a bare zone that lacks actin filaments · Sarcoplasmic reticulum (SR) – for storage of calcium Figure 6. 3 d Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 12 b

Striations in Skeletal Muscle ¢ A- Band- covers the length of the myosin filament ¢ I- Band- covers actin where there is no overlap with myosin ¢ H- Zone- the portion of myosin that does not overlap actin ¢ Z- Line- point where actin filaments anchor

Microanatomy of Skeletal Muscle Each muscle cell is called a muscle fiber. Within each muscle fiber are many myofibrils.

Z line The sarcomere is the functional unit of a muscle cell

H Band The area of the sarcomere has only myosin is called the H band.

Sarcomere Relaxed The part of the sarcomere with only actin filaments is called the I band.

Sarcomere Partially Contracted This sarcomere is partially contracted. Notice than the I bands are getting shorter.

Sarcomere Completely Contracted The sarcomere is completely contracted in this slide. The I and H bands have almost disappeared.

Neuromuscular Components Neuromuscular junction- the point where a motor neuron joins muscle fibers, Motor unit- a motor neuron and all the muscle fibers it innervates, may be few or hundred All or none law-with adequate stimulation, a muscle cell will contract to its fullest extent or not at all

Skeletal muscle activity Muscles have special functions ¢ 1 -Irritability : the ability to receive and respond to stimulus ¢ 2 -Contractility : the ability to shorten ¢ Muscle cell must be stimulated by nerve impulse to contract ¢ There is a gap (synaptic cleft) between the nerve &muscle cell ¢

This gap is crossed by chemical transmitter called Acetylcholine (Ach) ¢ Sarcolemma becomes temporarly permeable to sodium ¢ This upset generates an electric current called action potentiual which is unstoppable leading to contraction ¢

MUSCLE TONE ¢ Relaxed skeletal muscles are always slightly contracted l This state is termed “muscle tone” ¢ Stretch receptors in muscles and tendons are activated l l Spinal reflexes continually activate an alternating subset of motor neurons No active movement produced Muscles kept firm, healthy, and ready to respond to stimulation Helps stabilize joints and maintain posture

MUSCLE CONTRACTIONS ¢ Isotonic contraction ¢ Muscle length changes and moves the load l Cross bridges are moving l Once tension is sufficient to move load, tension remains relatively constant l Bending the knee, rotating the arms and smiling are examples

ISOMETRIC CONTRACTIONS ¢ Tension builds but muscle length remains constant Muscle attempts to move a load greater than the force the muscle is able to develop l Try to lift your car or push against immovable object or trying to lift 400 kg are examples l

Effect of exercise on Muscles are no exceptions to the saying –use it or lose it¢ Regular exercise increases muscle size, strength and endurance ¢ Aerobic exercise (isotonic contraction)results in stronger muscle with greater resistance to fatigue ¢ No increase in size but better heart &lungs ¢

Isometric(Resistance)contra ction Require little time ¢ No special equipment ¢ Leads to enlargement of muscle cell without increase in their number ¢

Energy for muscle contraction ATP store in the muscle supplies energy ONLY for 4 -6 seconds ¢ ATP then comes from 1 -direct phosphorylation of ADPby reaction with creatine phosphate(CP) -No need for oxygen -1 ATP for 1 CP -Provides energy for 15 seconds only ¢

¢ 2 -Anaerobic respiration: glycolysis and lactic acid formation ¢ -No need for oxygen ¢ -2 ATP per glucose ¢ -lactic acid accumulate ¢ - Provides energy for 30 -60 seconds only ¢ -after that muscle become sluggish

3 -aerobic mechanism (oxidative phosphorylation) ¢ Oxygen is needed to oxidize glucose, pyruvic acid, lactic acid, free fatty acids and aminoacids ¢ 36 ATP for 1 glucose ¢ Duration of energy is HOURS ¢

Tetany Sustained contraction of a muscle ¢ Result of a rapid succession of nerve impulses delivered to the muscle. ¢

Tetanus This slide illustrates how a muscle can go into a sustained contraction by rapid neural stimulation. In number four the muscle is in a complete sustained contraction or tetanus.

Muscle fatigue. ¢ Muscle fatigue occurs when an exercising muscle can no longer respond to the same degree of stimulation with the same degree of contractile activity. l Factors for this include an increase in inorganic phosphate, accumulation of lactic acid, and the depletion of energy reserves. l Increased oxygen consumption is needed to recover from exercise (paying off an oxygen debt).

Naming Skeletal Muscle Direction of Muscle Fibers Location Action Skeletal Muscle Origin & Insertion Size Shape Number Of Origins

Naming Skeletal Muscle ¢ Direction of Muscle Fibers l l Relative to the Midline RECTUS means parallel to midline • Rectus Abdominus l TRANSVERSE means perpendicular to midline • Transversus Abdominus l OBLIQUE means diagonal to midline • External Oblique • Internal oblique

Naming Skeletal Muscle ¢ Location l Structure near which a muscle is found l Muscle near l frontal bone = Frontalis l Muscle near the Tibia = Tibialis

Naming Skeletal Muscle ¢ Size l l Relative Size of Muscle MAXIMUS means largest • Gluteus Maximus l MINIMUS means smallest • Gluteus Minimus l LONGUS means longest • Fibularis Longus l BREVIS means short • Fibularis Brevis

¢ Number of Origins l l Number of tendons of origin BICEPS means two • Biceps Brachii l TRICEPS means three • Triceps Brachii l QUADRICEPS means four • Quadriceps Femoris

Naming Skeletal Muscles ¢ Shape l l l Relative Shape of the Muscle DELTOID means having a triangular shape TRAPEZIUS means having a trapezoid shape SERRATUS means having a saw-toothed shape (Serratus Ant. ) RHOMBOIDEUS means having a diamond shape (Rhomboid Major)

Naming Skeletal Muscles ¢ Origin & Insertion l l STERNOCLEIDO MASTOID attaches to the Sternum, Clavicle, and Mastoid Process ILIO COSTALIS attaches to the ilium & ribs

Naming Skeletal Muscles NAME FLEXOR EXTENSOR ACTION EXAMPLE Decrease angle at a joint Flexor Carpi Radialis Increase angle at a joint Extensor Carpi Ulnaris ABDUCTOR Move bone away from midline Abductor Pollicis Longus ADDUCTOR Move bone toward midline Adductor Longus LEVATOR Produces upward movement Levator Scapulae DEPRESSOR Produces downward movement Depressor Labii Inferioris SUPINATOR Turn palm upward/anteriorly Supinator PRONATOR Turn palm downward/posteriorly Pronator Teres

Types of Skeletal Muscle ¢ ¢ Prime mover (Agonist) – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover

Types of body movements l Flexion – Movement that decreases angle between 2 bones.

l Extension – movement that increases angle between 2 bones

l Abduction – movement away from the midline of the body

Muscular System l Adduction – movement towards the midline of the body

Rotation – movement around a longitudinal axis l Circumductioncombination of flexion, extension, abduction, and adduction. seen in ball and socket joints as the shoulder l

l Supination – occurs when palms rotate forward or upward

l Pronation – occurs when palms rotate downward or posteriorly

l Dorsiflexion – standing on heal l Plantar flexion – standing on toes

¢Inversion of the foot: turn the sole medially. ¢Eversion of the foot: turn the sole laterally ¢Opposition: moving the thumb to touch the tips of the other fingers

Axial and Appendicular Muscles Figure 11– 3 a

Axial and Appendicular Muscles Figure 11– 3 b

Divisions of the Muscular System 1. Axial muscles: l l l 2. position head and spinal column move rib cage 60% of skeletal muscles Appendicular muscles: l l l support pectoral and pelvic girdles support limbs 40% of skeletal muscles

Muscles of the face Figure 11– 4 a

Muscles of Facial xpression Figure 11– 4 b

Extrinsic Eye Muscles ¢ Also called extra-ocular muscles Figure 11– 5 a, b

Extrinsic Eye Muscles Inferior rectus Medial rectus Superior rectus Lateral rectus Inferior oblique Superior oblique Figure 11– 5 c

Summary: Extrinsic Eye Muscles Table 11– 3

Muscles of Mastication Figure 11– 6

3 Muscles of Mastication ¢ Masseter: l ¢ the strongest jaw muscle Temporalis: l helps lift the mandible Buccinator ¢ flattens the cheek, hold the food between the teeth ¢

Summary: Muscles of the Tongue Table 11– 5

Muscles of the Pharynx Figure 11– 8

3 Muscles of the Pharynx ¢ Pharyngeal constrictor muscles: l ¢ Laryngeal elevator muscles: l ¢ move food into esophagus elevate the larynx Palatal muscles: l lift the soft palate

Summary: Muscles of the Pharynx Table 11– 6

Anterior Muscles of the Neck Figure 11– 9

6 Anterior Muscles of the Neck ¢ ¢ ¢ Digastric: l from chin to hyoid l and hyoid to mastoid Mylohyoid: l floor of the mouth Geniohyoid: l between hyoid and chin Stylohyoid: l between hyloid and styloid Sternocleidomastoid: l from clavicle and sternum to mastoid Omohyoid: l attaches scapula, clavicle, first rib, and hyoid

Anterior Muscles of the Neck Table 11– 7

Muscles of the Vertebral Column Figure 11– 10 a

Muscles of the Vertebral Column Spinal extensors or erector spinae muscles (superficial and deep) ¢ Spinal flexors (transversospinalis) ¢

Superficial Spinal Extensors ¢ ¢ ¢ Spinalis group Longissimus group Iliocostalis group Deep Spinal Extensors ¢ ¢ ¢ Semispinalis group Multifidus muscle Interspinalis muscles Intertransversarii muscles Rotatores muscles

Spinal Flexors ¢ Neck: longus capitis and longus colli l rotate and flex the neck l ¢ Lumbar: quadratus lumborum muscles l flex spine and depress ribs l

Muscles of the Vertebral Column Table 11– 8 (1 of 2)

Muscles of the Vertebral Column Table 11– 8 (2 of 2)

Oblique and Rectus Muscles Figure 11– 11 a, b

Oblique and Rectus Muscles Figure 11– 11 a, c

Oblique and Rectus Muscles ¢ Oblique muscles: compress underlying structures l rotate vertebral column l ¢ Rectus muscles: flex vertebral column l oppose erector spinae l

Oblique Muscles Cervical region: scalene muscles l flex the neck l Thoracic region: l intercostal muscles (external and internal intercostals): • respiratory movements of ribs l transversus thoracis: • cross inner surface of ribs

Oblique Muscles ¢ Abdominopelvic region (same pattern as thoracic): external oblique muscles l internal oblique muscles l ¢ Transversus abdominis

Rectus Group ¢ Rectus abdominis: between xiphoid process and pubic symphysis l divided longitudinally by linea alba l divided transversely by tendinous inscriptions l ¢ Diaphragmatic muscle or diaphragm: divides thoracic and abdominal cavities l performs respiration l

Summary: Oblique and Rectus Muscles Table 11– 9 (1 of 2)

Summary: Oblique and Rectus Muscles Table 11– 9 (2 of 2)

Functions of Pelvic Floor Muscles 1. 2. 3. Support organs of pelvic cavity Flex sacrum and coccyx Control movement of materials through urethra and anus

Perineum ¢ Muscular sheet forming the pelvic floor, divided into: anterior urogenital triangle l posterior anal triangle l Pelvic Diaphragm Deep muscular layer extending to pubis: l supports anal triangle l

Urogenital Diaphragm ¢ Deep muscular layer between pubic bones: supports the pelvic floor l and muscles of the urethra l ¢ Superficial muscles of the urogenital triangle: l support external genitalia

Muscles of the Pelvic Floor Table 11 -10 (1 of 2)

Muscles of the Pelvic Floor Table 11 -10 (2 of 2)

The Appendicular Muscles Figure 11– 13 a

The Appendicular Muscles Figure 11– 13 b

The Appendicular Muscles Position and stabilize pectoral and pelvic girdles ¢ Move upper and lower limbs ¢

Divisions of Appendicular Muscles 1) Muscles of the shoulders and upper limbs: ¢ Position the pectoral girdle ¢ Move the arm ¢ Move the forearm and hand ¢ Move the hand fingers 2) Muscles of the pelvis and lower limbs

Muscles that Position the Pectoral Girdle Figure 11– 14 a

Muscles that Position the Pectoral Girdle Figure 11– 14 b

6 Muscles that Position the Pectoral Girdle ¢ Trapezius: superficial l covers back and neck to base of skull l inserts on clavicles and scapular spines l ¢ Rhomboid and levator scapulae: deep to trapezius l attach to cervical and thoracic vertebrae l insert on scapular border l

6 Muscles that Position the Pectoral Girdle ¢ Serratus anterior: l l l ¢ Subclavius: l l ¢ on the chest originates along ribs inserts on anterior scapular margin originates on ribs inserts on clavicle Pectoralis minor: l attaches to scapula

Muscles that Position the Pectoral Girdle Tables 11– 11

Muscles that Move the Arm Figure 11– 15 a

Muscles that Move the Arm Figure 11– 15 b

9 Muscles that Move the Arm ¢ Deltoid: l ¢ Supraspinatus: l ¢ the major abductor assists deltoid Subscapularis and teres major: l produce medial rotation at shoulder

9 Muscles that Move the Arm ¢ Infraspinatus and teres minor: l ¢ produce lateral rotation at shoulder Coracobrachialis: attaches to scapula l produces flexion and adduction at shoulder l

9 Muscles that Move the Arm ¢ Pectoralis major: between anterior chest and greater tubercle of humerus l produces flexion at shoulder joint l ¢ Latissimus dorsi: between thoracic vertebrae and humerus l produces extension at shoulder joint l

The Rotator Cuff ¢ Muscles involved in shoulder rotation l supraspinatus, subscapularis, infraspinatus, teres minor, and their tendons

Muscles that Move the Forearm and Hand Figure 11– 16 a

Muscles that Move the Forearm and Hand Figure 11– 16 b

Muscles that Move the Forearm and Hand Originate on humerus and insert on forearm ¢ Exceptions: ¢ the major flexor (biceps brachii) l the major extensor (triceps brachii) l

Extensors and Flexors ¢ Extensors: l ¢ mainly on posterior and lateral surfaces of arm Flexors: l mainly on anterior and medial surfaces

13 Muscles that Move the Forearm and Hand ¢ Biceps brachii: l l ¢ Triceps brachii: l l l ¢ flexes elbow stabilizes shoulder joint extends elbow originates on scapula inserts on olecranon Brachialis and brachioradialis: l l l flex elbow originates on scapula inserts on radial tuberosity

13 Muscles that Move the Forearm and Hand ¢ Anconeus: l ¢ opposes brachialis Palmaris longus: superficial l flexes wrist l ¢ Flexor carpi ulnaris: superficial l flexes wrist l adducts wrist l

13 Muscles that Move the Forearm and Hand ¢ Flexor carpi radialis: l l l ¢ Extensor carpi radialis: l l l ¢ superficial flexes wrist abducts wrist superficial extends wrist abducts wrist Extensor carpi ulnaris: l l l superficial extends wrist adducts wrist

13 Muscles that Move the Forearm and Hand ¢ Pronator teres and supinator: originate on humerus and ulna l rotate radius l ¢ Pronator quadratus: originates on ulna l assists pronator teres l

Tendon Sheaths ¢ Extensor retinaculum: wide band of connective tissue l posterior surface of wrist l stabilizes tendons of extensor muscles l ¢ Flexor retinaculum: anterior surface of wrist l stabilizes tendons of flexor muscles l

The Intrinsic Muscles of the Hand Figure 11– 18 b

Muscles of the Pelvis and Lower Limbs ¢ Pelvic girdle is tightly bound to axial skeleton: l l permits little movement has few muscles Muscles that Position the Lower Limbs 1. 2. 3. Muscles that move thigh Muscles that move the leg Muscles that move the foot and toes

Muscles that Move the Thigh Figure 11– 19 a, b

Muscles that Move the Thigh Figure 11– 19 c, d

Muscles that Move the Thigh Gluteal muscles ¢ Lateral rotators ¢ Adductors ¢ Iliopsoas ¢

Gluteal Muscles (1 of 2) Cover lateral surfaces of ilia ¢ Gluteus maximus: ¢ largest, most posterior gluteal muscle l produces extension and lateral rotation at hip l

Gluteal Muscles (2 of 2) ¢ Tensor fasciae latae: works with gluteus maximus l stabilizes iliotibial tract l ¢ Gluteus medius and gluteus minimus: originate anterior to gluteus maximus l insert on trochanter l

Lateral Rotators ¢ Group of 6 muscles, including: piriformis l obturator l

Adductors ¢ Adductor magnus: l ¢ Adductor brevis: l ¢ hip flexion and adduction Pectineus: l ¢ hip flexion and adduction Adductor longus: l ¢ produces adduction, extension, and flexion hip flexion and adduction Gracilis: l hip flexion and adduction

Muscles that Move the Leg Figure 11– 20 a

Muscles that Move the Leg Figure 11– 20 b, c

Muscles that Move the Leg ¢ Flexors of the knee: l ¢ originate on the pelvic girdle Extensors of the knee: originate on the femoral surface l insert on the patella l

Flexors of the Knee Biceps femoris- Hamstrings ¢ Semimembranosus- “ ¢ Semitendinosus“ ¢ Sartorius: ¢ l ¢ originates superior to the acetabulum Popliteus: l rotates the tibia to unlock the knee

Extensors of the Knee ¢ 4 muscles of the quadriceps femoris: 3 vastus muscles l rectus femoris muscle l

Muscles that Move the Foot and Toes Figure 11– 21 a, b

Muscles that Move the Foot and Toes Figure 11– 21 c, d

Muscles that Move the Foot and Toes ¢ Extrinsic muscles that move the foot and toes include: muscles that produce extension at the ankle l muscles that produce flexion at the ankle l muscles that produce extension at the toes l muscles that produce flexion at the toes l

4 Muscles that Produce Extension at the Ankle Gastrocnemius ¢ Soleus ¢ Fibularis ¢ Tibialis posterior + The Achilles Tendon. The calcaneal tendon (Achilles tendon): ¢ l shared by the gastrocnemius and soleus

Muscles that Produce Flexion at the Ankle ¢ Tibialis anterior: l opposes the gastrocnemius Muscles that Produce Flexion at the Toes Flexor digitorum longum ¢ Flexor hallucis longus: ¢ l oppose the extensors

Muscles that Produce Extension at the Toes Extensor digitorum longum ¢ Extensor hallucis longus ¢ Extensor retinacula: ¢ l fibrous sheaths hold tendons of toes as they cross the ankle

The Intrinsic Muscles of the Foot Figure 11– 22 a

The Intrinsic Muscles of the Foot Figure 11– 22 b, c

Effects of Aging on the Muscular System 1. 2. Skeletal muscle fibers become smaller in diameter Skeletal muscles become less elastic: l 3. 4. develop increasing amounts of fibrous tissue (fibrosis) Decreased tolerance for exercise Decreased ability to recover from muscular injuries

Integration with Other Systems Figure 11– 24