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