1. Muscle Contractions, Fatigue & Names
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2. Type of Muscle Contractions
Isotonic contractions “same tone”
Myofilaments are able to slide past each other during contractions
The muscle shortens, tension rises
Walking, running, lifting an object
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3. Types of Muscle Contractions
Isometric contractions “same measurement”
Tension in the muscle increases
The muscle is unable to shorten and tension does not exceed resistance
Pushing against a wall with bent elbows
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5. Isometric vs. Isotonic
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6. Concentric-movement causes a muscle to shorten
Eccentric- Muscle lengthens—elongation of muscle
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7. Muscle Fatigue
Muscle fatigue – the muscles inability to contract even though it is being stimulated
Occurs when:
ATP production fails to keep pace with ATP used
Relative deficit of ATP, causing contractures
Lactic acid accumulates in the muscle
Ionic imbalances are present
Result of oxygen debt
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8. Muscle Classification
Prime Mover
agonist
Causes a desired action
Ex: elbow flexion (biceps brachii)
Antagonist
Relaxes when prime mover contracts
Ex: elbow flexion (triceps brachii)
Synergist
Helps the prime mover by reducing unnecessary movements
Fixators
Stabilize the origin of the prime mover
Can immobilize a bone
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9. Muscle Names Muscles are named based on: size shape location action
number of attachments
direction of its fibers
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10. Direction Rectus: parallel to the midline
Transverse: perpendicular to the midline
Oblique: diagonal to the midline
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11. Size Maximus: largest Magnus: large Minimus: smallest Major: larger
Longus: longest
Minor: smaller
Latissimus: widest
Vastus: great
Longissimus: longest
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12. Shape Deltoid: triangular Piriformis: pear- shaped
Trapezius: trapezoid
Platys: flat
Serratus: saw-tooth
Quadratus: square
Rhomboid: diamond-shaped
Gracilis: slender
Orbicularis: circular
Pectinate: comblike
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13. Action Flexor: decreases joint angle Extensor: increases joint angle
Abductor: moves bone away from midline
Adductor: Moves bone closer to midline
Levator: produces superior movement
Depressor: produces interior movement
Supinator: turns palms up
Pronator: turns palms down
Sphincter: decreases size of opening
Tensor: makes body part rigid
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14. Number of Origins Biceps: two origins Triceps: three origins
Quadriceps: four origins
Location:
Pectoralis: chest
Gluteus: buttock
Temporalis: temporal
Brachii: arm
Lateralis: lateral

15. Arrangement of Fascicles
Circular-arranged in rings Convergent-muscle has broad origin & fascicle converge into 1 insertion

16. Arrangement of Fascicles
Parallel- fascicle runs parallel to axis of muscle Fusiform-spindle shaped muscle with large muscle body

17. Arrangement of Fascicles
Pennate: fascicles are short & at angle to a tendon -unipennate- fascicle insert in 1 side of tendon -bipennate-fascicles are on both sides of tendon -multipennate-from multiple directions in tendon

18. Basic Principles of skeletal muscles
1. skeletal muscles produce movement by pulling bones (muscle only pull, they never push) 2. Bones act as levers and joints act as fulcrums for muscles to bring about movement 3. They contract only when stimulated 4. They contract according o the graded strength principle 5. A muscle fiber will follow the all or none principle 6. Muscles that move parts usually do not lie over that part 7. Muscles act in groups rather than singly.

19. Lever Systems A partnership between muscle and bone
Levers- bone/bar that moves on a fixed point
Fulcrum-joint/fixed point
Load-weight or resistance to be moved

20. 1st class 2nd class 3rd class

21. Aging & Muscles Muscles begin to shrink and lose mass
Size of muscle fiber decreases
Tendons become stiffer due to decreased water content

22. 40 Superficial muscles divided into 12 regions
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23. 27 superficial muscles divided into 7 regions
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24. Based on what you know about naming skeletal muscles, what do you predict about the following muscles:
Biceps femoris
Rectus abdominis
Flexor carpi ulnaris
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25. Sternocleidomastoideus
Flexes and Rotates Head
The first muscle we will learn is the sternocleidomastoideus. It is sometime called the sternocleitomastoid. It is the same neck muscle shown on the previous slide. * This muscle has two origins. The first origin is on the sternum manubrium. The second origin is on the clavicle. *The insertion is on the mastoid process of the skull. *Contraction of both sternocleidomastoideus muscles will flex the head. If just on of the muscles contracts, the head will rotate.

26. Masseter Elevates Mandible
The masseter is one of major chewing muscles. *The origin of the masseter is on the zygomatic arch. *The insertion is on the mandible. *Contraction of the masseter will elevate the jaw.

27. Elevate & Retract Mandible
Temporalis
Elevate & Retract Mandible
The temporalis is another chewing muscle. Note how it attaches on the side of skull. *It also elevates the mandible. Also note I did not give the origin and insertion of this muscle. You will only need to know the origin and insertion of a few of the muscles in this unit.

28. Extend Head, Adduct, Elevate or Depress Scapula
Trapezius
Extend Head, Adduct, Elevate or Depress Scapula
The trapezius is a large muscle in the upper back. It attaches to the skull, shoulder and vertebrae of the back. *When this muscle contracts it will cause the head to extend. It will also move the scapula. The direction the scapula moves depends on which part of the trapezius contracts. The trapezius may adduct elevate or depress the scapula.

29. Extend, Adduct & Rotate Arm Medially
Latissimus Dorsi
Extend, Adduct & Rotate Arm Medially
The latissimus dorsi is a large muscle in the back. It is often referred to as a lat. *It has origins on the vertebrae, ilium ribs and scapula. *The insertion is on the humerus. When it contracts it moves the humerus. *It can extend, adduct and rotate the arm medially. This is the main muscle used in movement such as pounding a nail with a hammer.

30. Abduct, Flex & Extend Arm
Deltoid
Abduct, Flex & Extend Arm
The deltoid covers the shoulder and has the shape of a delta. *It has origins on the scapula and clavicle. *The deltoid inserts on the deltoid tuberosity of the humerus. *Contraction of the deltoid will adduct the arm. If only the anterior fibers of the muscle contract it will flex the arm. Contraction of the posterior fibers will extend the arm.

31. Flexes, adducts & rotates arm medially
Pectoralis Major
Flexes, adducts & rotates arm medially
The pectoralis major is a large muscle in the pectoral region of the body. *It has origins on the clavicle and sternum. *The insertion is on the greater tubercle of the humerus. *Contraction of the pectoralis major will flex the arm. It will also adduct and rotate the arm medially. The pectoralis major is used in movements such a climbing, throwing and doing pushups.

32. Biceps Brachii Flexes Elbow Joint
The biceps brachii is located on the anterior side of the upper arm. It is often just called the biceps. There is a biceps femoris in the leg we will study shortly. *The biceps has two origins. One origin is on the corocoid process and the other on the Glenoid cavity of the scapula. The “bi” in biceps refers to the two origins. *It inserts on the radial tuberosity. *Contraction of the biceps will cause flexing at the elbow joint.

33. Triceps Brachii Extends Elbow Joint
The triceps is on the back of the upper arm. *It has three origins. Two origins are on the back of the humerus and one on the scapula. *The triceps inserts on the olecranon. *Movement of the triceps will extend the elbow joint.

34. Rectus Abdominus Flexes Abdomen
Rectus abdominus is a long muscle in the abdomen. *The muscle originates on the pubis. *It inserts on the xiphoid process of the sternum and also on cartilage of the ribs. *When rectus abdominus contracts it will flex the abdomen.

35. External Oblique Compress Abdomen
Another muscle in the abdomen is the external oblique. It has muscle fibers that run in an oblique direction across the abdomen. *Contraction of the external oblique will compress the abdomen.

36. External Intercostals
Elevates ribs
There are two groups of muscles that run between the ribs. The first are the external intercostals. *They will elevate the ribs.

37. Internal Intercostals
Depress ribs
The internal intercostals are also located between the ribs. *They will depress the ribs.

38. Diaphragm Inspiration
This is an inferior view of the diaphragm. This muscle separates the abdominal cavity from the thoracic cavity. *When it contracts it will cause inspiration.

39. Forearm Muscles Flexor carpi—Flexes wrist Extensor carpi—Extends wrist
Flexor digitorum—Flexes fingers
Extensor digitorum—Extends fingers
Pronator—Pronates
Supinator—Supinates
There are several muscles in the forearm that have important movements. *The flexor carpi are used to flex the wrist. *Extensor carpi extend the wrist. *Flexor digitorum flexes the fingers. *Extensor digitorum extends the fingers. *The pronator pronates. *A supinator muscle will supinate.

40. Extends & Rotates Thigh Laterally
Gluteus Maximus
Extends & Rotates Thigh Laterally
The large muscle on the posterior side of the body at the top of each leg is the gluteus maximus. *The gluteus maximus originates on the ilium, sacrum and coccyx. *It inserts on the gluteal tuberosity of the femur. *This muscle will extend and rotate the thigh laterally.

41. Flexes Thigh, Extends Lower Leg
Rectus Femoris
Flexes Thigh, Extends Lower Leg
Rectus femoris is located on the anterior side of the thigh. *It originates on the ilium. *The insertion is on the patella and the tibial tuberosity. *When rectus femoris contracts it will flex the thigh and extend the lower leg.

42. Adducts and Flexes Thigh
Gracilis
Adducts and Flexes Thigh
The gracilis is on the medial side of the thigh. *It adducts and flexes the thigh.

43. Flexes Thigh, & Rotates Thigh Laterally
Sartorius
Flexes Thigh, & Rotates Thigh Laterally
Sartorius is a long, strap like muscle. *It originates on the anterior superior iliac spine of the ilium. *The insertion is on the medial side of the tibia. * Contraction of the sartorius flexes the thigh and rotates the thigh laterally. This is the muscle used when crossing the legs to sit on the floor.

44. Extends Thigh & Flexes Lower Leg
Biceps Femoris
Extends Thigh & Flexes Lower Leg
Biceps femoris is one of the hamstring muscles. *The origin is on the ischial tuberosity. *Biceps femoris inserts on the tibia and fibula. This muscle extends the thigh and flexes the lower leg.

45. Plantar Flexes Foot & Flex Lower Leg
Gastrocnemius
Plantar Flexes Foot & Flex Lower Leg
Gastrocnemius is commonly called the calf muscle. *It originates on the distal end of the femur. *The insertion is on the calcaneus bone of the foot. *It will cause plantar flexion of the foot and also flex the lower leg.

46. Dorsiflexes and Inverts Foot
Tibialis Anterior
Dorsiflexes and Inverts Foot
Tibialis anterior is located on the anterior side of the tibia. *It will dorsiflex and invert the foot.