Chapter 7: The Muscle system

1. Chapter 7: The Muscle system Karyn Borrego Tyler Correa Sabrina Cardona Nicholas Jacinto

2. The three types of muscle Three types of muscle exist in the human body: smooth, cardiac, and skeletal. Each fiber is surrounded by a thin layer or areolar connective tissue called endomysium. Smooth: located in the walls of hollow internal organs and blood vessels; moves materials through organs and regulates blood flow in blood vessels; the fibers of this muscle are narrow, tapered root shaped cells; can sustain prolonged contractions and does not fatigue easily; involuntary

3. Cardiac Muscle • Forms the heart wall. • Fibers are uninucleated , striated, tubular, and branched • Relaxes completely between contractions, which prevents fatigue • Contractions are involuntary

4. Skeletal muscle • Fibers are tubular, multinucleated, and striated • Contractions always simulated • Supports the body • Makes bones and body parts move, constant body temperature and protection; usually found attached to tendons

23. In the Laboratory • Muscles can be studied in the lab • When a muscle fiber is isolated and provided with ATP, it contracts completely along its entire length • Result from the all or nothing law: Law that states that muscle fibers contract maximally or not at all • In contrast, a whole muscle shows a degree of contractions • Isolated and stimulated electronically • Mechanical force of contraction is recorded as a visual pattern called myogram

24. Muscle twitch • Muscle twitch: A single contraction that last for only was fraction of a second • Three parts: • Latent period: period of time between stimulation and initiation of contraction • Contraction period: When the muscle shortens • Relaxation period: When the muscle returns to its former length

25. Myogram • A. Series of twitches • B. Summation • Increased muscle contraction • C. Tetanic Contraction • Maximal sustained contraction • No longer shows individual twitches; rather the twitches are fused and blended completely into a straight line • Continues until the muscle reaches fatigues: Failure of a muscle fiber to continue to contract due to the exhaustion of ATP

26. Fatigue • Gradual weakening that occurs after repetitive use • Reasons why muscles become fatigue • ATP is depleted during constants use • Lactic acid by fermentation • Muscles run out of neurotransmitter, acetylcholine • The brain itself signals a person to stop exercising even if the muscles aren’t fatigued

27. In the body • In the body, muscles are innervated to contract by nerves • Each axon stimulates a number of muscle fibers • Motor Unit: A nerve fiber together with all of the muscle fibers it innervates. • Obeys all-or-none law because the muscles in the motor unit are all stimulated at once; they either contract or do not contract • Tetanic contractions ordinarily occurs in the body because , as the intensity of nervous stimulation increase, more and more motor units are activated • This is known as recruitment • While some muscles are contracting, other are relaxing, which is why muscles rarely experience fatigue • Even when some muscles appear to be resting, they exhibit tone, in which fibers re always contracting. • Muscle tone is important in posture

28. Exercise and Size of Muscles • Muscles not used or used for weak contraction decrease in size or atrophy. • Atrophy: Occurs when a limb is placed in a cast or when the nerve serving a muscle is damaged. • Can cause muscle fibers to shorten, leaving body parts in contorted positions • If nerve stimulation is not replaced, muscle fibers are replaced by fat & fibrous tissue • Forceful muscular activity causes muscles to increase in size as the number of myofibrils within the muscle fibers • Hypertrophy: occurs only if the muscle contracts to at least 75% of it maximum tension • Athletes take anabolic steroids, either testosterone or related chemicals, to promote muscle growth. This causes undesirable side effects

29. Slow-twitch muscle fibers • Muscle fibers metabolize both aerobically and anaerobically but some muscle fiber utilizes one method more than the other to provide myofibrils with ATP • Slow-twitch fibers tend to be aerobic and is referred as Type I fibers • Steadier tug and more endurance despite having motor units with a smaller number of fibers • Helpful in sports such as running, biking, jogging • Tire when fuel supply is gone • Have many mitochondria and are dark in color because they contain myoglobin, respiratory pigment found in muscles • Resistant to fatigue because they have a substantial reserve of glycogen and fat

30. fast twitch muscle fibers • Fast-twitch fibers tend to be anaerobic and is referred as Type II fibers • Designed for strength because their motor units contain many fibers • Provide an explosion of energy and are helpful in sport activities such as sprinting, wrestling and swinging a golf club • Light in color because they have fewer mitochondria, little to no myoglobin, and fewer blood vessels • Develop maximum tension more rapidly than slow twitch fibers and their tension is greater • Vulnerable to an accumulation of lactic acid that causes them to fatigue quickly

31. Basic Principles • Muscle contracts at a joint, one bone remains stationary and the other moves • The origin of a muscle is on the stationary bone and the insertion of a muscle is on the bone that moves • A body part is moved by a group of muscles working together. A prime mover is the muscle that does most of the work. • The assisting muscles are the synergist • Muscles contract, the shorten. Therefore they can only pull; they cannot push. However, muscles have antagonist. Antagonist pairs work opposite one another to bring about movement in opposite directions

32. Naming Muscles • Size • Shape • Direction of fibers • Location • Attachment • Number of attachments • Action

33. Skeletal Muscle Groups The muscles of the body will be grouped according to the region Try to correlate its name with muscles location and action

34. Muscles of the Head • Facial expression and mastication (chewing) • Neck allows the head to move

35. Muscles of Facial Expression • Located in scalp and face • Insert into and move the skin • These muscles communicate emotions to others

36. Muscles of Facial Expressions • Frontalis: Raises the eyebrows • Skin and muscles around the eye • Orbicularis oculi: Closes eye or to blink • Skin around the eye • Orbicularis oris: Closes and protrudes the lips • Skin around the mouth • Buccinator: Compresses cheek inward • Outer surface of maxilla and mandible • Zygomaticus: Raises corner of the mouth • skin and muscle around mouth

37. Muscles of Mastication • Muscles of mastication are used when we chew and bite • Both Massetersand Temporalis insert on the mandible, are synergist and are prime movers for elevating the mandible • Masseters: Closes jaw • Located in the zygomatic arch • Temporalis: Closes Jaw • Located in the temporal bone • Fan-shaped muscle

38. Muscles of the Neck • Swallowing • Moving the head

39. Swallowing • The tongue (a muscle) & the buccinators squeeze the food back along the roof of the mouth to the pharynx • Hyoid: important bone that functions in swallowing , does not articulate with another bone and is attached to the larynx • Suprahyoid Muscles: Lie superior to the Hyoid • Pulls hyoid forward and upward toward the mandible • Infrahyoid Muscles: Lie inferior to the hyoid • Moves the hyoid • Moves hyoid and larynx to their original positions • Epiglottis: Closes the respiratory passages • Small Palatini Muscles: Closes nasal passages • Pharyngeal Constrictor Muscles: Pushes the food into the pharynx; widens the surahyoid muscle

40. Muscles that move the Head Terms • Flexion: Movement that closes the angle at a joint • Extension: Movement that increases the angle at a joint • Abduction: Movement away from the midline of the body • Adduction: Movement towards the midline of the body • Rotation: Movement of a part around its own axis

41. Muscles that move the Head • Sternocleidomastoid: Flexes and rotates the head • Located in the sternum and clavicle • Trapezius: Extends the head and adducts the scapula • Located in the Occipital bone C7 vertebra, all of thoracic vertebra

42. MUSCLES OF THE TRUNK: Thoracic Wall • Primarily involved in breathing • External Intercostal: Elevate rib cage for inspiration during breathing • Located in the superior rib • The Diaphragm: Depress rib cage for forced expiration • Located in the inferior rib • Internal Intercostal: Tenses abdominal wall; lateral rotation of trunk • Located in the lower eight rib

43. Muscles of the trunk: abdominal wall • Protect and support organs within the abdominal cavity • External: Tenses abdominal wall; lateral rotation of trunk • Located in the lower eight ribs • Internal obliques: Tenses abdominal wall; lateral rotation of trunk • Located in the Iliac crest • Transverse abdominis: Tenses abdominal wall • Located in the lower six • Rectus abdominis: Flexes and rotates the vertebral column • Located in the pubic symphysis

44. Muscles of the shoulder • The muscles of the shoulder attach the scapula to thorx • Move the scapula • Also attach the humerus to the scapula and move the arm

45. Muscles that move the scapula • Serratus anterior: Depresses the scapula and pulls it forward; elevates arm above horizontal • Located in the upper nine ribs

46. Muscles that move the arm • Deltoid: Abducts arm to horizontal • Located in the upper nine ribs • Pectoralis major: Flexes and adducts arms • Located in the spine of scapula and clavicle • Latissimusdorsi: Extends and adducts arm • Located in the lliac crest • Rotator cuff: Angular and rotational movements of arms • Located in the scapula

47. Muscles that move the forearm • Biceps brachii: Flexes and supinates the forearm • Located in the scapula • Triceps brachii: Extends the forearm • Located in the scapula and proximal humerus • Brachialis: Flexes the forearm • Located in the anterior humerus

48. MUSCLES THAT MOVE THE HAND AND FINGERS • Flexer carpi and extensor carpi: Move wrist and hand • Located in the humerus • Flexerdigitorum and extensor digitorum: Move fingers • Located in the humerus, radius and ulna

49. Muscles that move the Thigh • lliposoas: Flexes the thigh • Located in the lumbar vertebrae • Gluteus maximus: Extends the thigh • Located in the Posterior ilium • Gluteus medius: Abducts the thigh • Located in the llium • Adducts group: Adducts the thigh • Located in the Pubis

50. Muscles that move the leg • Quadriceps femoris group: Extends the legs • Located in the Ilium and femur • Satoruis: Flexes, abducts and rotates leg laterally • Located in the Iiium • Hamstring group: Flexes and rotates leg medially and extends thigh • Located in the Ischial tuberosity