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The Muscular System Chapters 9 & 10.

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Presentation on theme: "The Muscular System Chapters 9 & 10."— Presentation transcript:

1 The Muscular System Chapters 9 & 10

2 Overview Functions: movement maintain posture stabilize joints
generate heat

3 3 Types 1) Skeletal 2) Cardiac 3) Smooth
Striated striated not striated voluntary involuntary involuntary

4 Gross Anatomy made of muscle fibers, blood vessels, nerve fibers and connective tissue

5 CT wrappings surrounding muscle fibers
endomysium – fine layer CT that surrounds each fiber perimysium – collagenic sheath that surrounds each fascicle (bundle of muscle fibers)

6 epimysium –CT that binds several fascicles together to surround the entire muscle
deep fascia – coarser sheet of CT that binds muscles into functional groups

7 Nerve and Blood Supply each muscle contains an artery and one or more veins

8 Attachments origin – attachment to immovable, or less movable, bone
insertion – attached to movable bone in muscles of the limbs, origin typically lies proximal to the insertion

9 Microscopic Anatomy of a Skeletal Muscle Fiber
sarcolemma = plasma membrane sarcoplasm = cytoplasm sarcoplasmic reticulum = endoplasmic reticulum width = um length = up to 30 cm (12 in)

10 Myofibrils there are hundreds to thousands in each muscle fiber, depending on its size account for 80% of volume and organelles are squeezed around them

11 striations formed from where actin and myosin overlap or don’t overlap

12 Sarcomere functional unit of muscle
portion of myofibril between two Z discs

13 Muscle Metabolism energy stored in ATP
comes from cellular respiration, hydrolysis of creatine phosphate and lactic acid fermentation

14 Contraction of Motor Units
a motor unit consists of a single motor neuron and all of the muscle cells it stimulates recruitment = when more motor units need to be stimulated for increased strength

15 small motor units, containing fewer cells, provide precise movements
the advantage of having only a few muscle cells per motor unit is to allow precise movements small motor units, containing fewer cells, provide precise movements muscles of the eye large motor units, containing many cells, provide gross movements movement of thigh

16 muscle tone is achieved by random, asynchronous motor unit contractions that provide a constant state of low-level tension without stimulation, muscle loses tone

17 The Sliding Filament Theory
involves 5 molecules plus Ca+ ions actin myosin tropomyosin troponin ATP

18 The Theory The contraction of a muscle cell occurs as the thin filament slides past the thick filament. During contraction the sarcomere shortens and the thin and thick filaments overlap to a great degree

19 made of myosin filaments
Thick filaments made of myosin filaments myosin head = cross bridge Thin filaments made of actin, tropomyosin & troponin tropomyosin covers actin binding sites in a unstimulated muscle


21 during the contraction of an entire muscle, the cross bridges stagger their binding

22 Smooth Muscle Diameter 3-6 um Length 100-500 um
Lack neuromuscular junctions found in skeletal muscle, but have varicosities that release neurotransmitters into a wide synaptic cleft in the general area of smooth muscle cells Have actin and myosin filaments, but no sarcomeres

23 intermediate filaments are interlaced through the cell much like the threads in a pair of "fish-net" stockings because smooth muscle is not as organized as skeletal muscle, shortening occurs in all directions

24 Cardiac Muscle Has myofibrils that are organized into sarcomeres, but the myofibrils have irregular thickness

25 Major Skeletal Muscles of the Body
There are over 600 skeletal muscles! You will only be held responsible for the names and locations of the 32 shown in the following slides.

26 Head Temporalis – closes jaw, elevates mandible; maintains posture of mandible at rest Masseter – elevates mandible Frontalis – raises eyebrows and wrinkles forehead skin horizontally

27 Head Orbicularis oris – closes lips; purses and protrudes lips
Orbicularis oculi – produces blinking, squinting and draws eyebrows downward Zygomaticus – raises lateral corners of the mouth upward

28 Neck Sternocleidomastoid - prime mover of active head flexion; acting alone, each muscle rotates head towards side and tilts or laterally flexes head to its own side

29 Shoulder Trapezius – stabilizes, raises, retracts and rotates scapula
Deltoid – prime mover of arm abduction

30 Arm Triceps brachii – powerful forearm extensor
Biceps brachii – flexes elbow joint and supinates forearm (movements usually happen at same time)

31 Forearm Brachioradialis – helps with forearm flexion

32 Thorax Pectoralis major – prime mover of arm flexion
Intercostals – elevate and depress ribs to aid in breathing Latissimus dorsi – prime mover of arm extension; medially rotates arm at shoulder

33 Abdomen Rectus abdominis – flex and rotate lumbar region of vertebral column External oblique – aid rectus abdominus in flexing vertebral column; help with trunk rotation and lateral flexion Transverse abdominis – compress abdominal contents

34 Gluteal Region Gluteus maximus – major extensor of thigh; laterally rotates thigh Gluteus medius – abducts and medially rotates thigh; steadies pelvis

35 Thigh Tensor fascia lata – flexes and abducts thigh; rotates thigh medially Sartorius – flexes and laterally rotates thigh; flexes knee Gracilis – adducts thigh, flexes and medially rotates leg, especially during walking

36 Thigh Rectus femoris – extends knee and flexes thigh at hip
Vastus lateralis – extends knee Vastus medialis – extends knee; inferior fibers stabilize patella

37 Thigh Biceps femoris – extends thigh and flexes knee
Semitendinosus – extends thigh at hip; flexes knee Adductor muscles – adduct and laterally rotate the thighs

38 Leg Tibialis anterior – prime mover of dorsiflexion; inverts foot
Gastrocnemius – plantar flexes foot when knee is extended Fibularis longus – plantar flexes foot

39 Other Fun Facts

40 Other Fun Facts Calcaneal tendon = tendon of gastrocnemius = achilles tendon = achilles heel




44 It takes 17 muscles to smile and 43 to frown

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