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The Muscular System. or “Everything you ever wanted to know about Muscles, but were afraid to ask” !!!

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Presentation on theme: "The Muscular System. or “Everything you ever wanted to know about Muscles, but were afraid to ask” !!!"— Presentation transcript:

1 The Muscular System

2 or “Everything you ever wanted to know about Muscles, but were afraid to ask” !!!

3 Did you know that ? -more than 50% of body weight is muscle ! -And muscle is made up of proteins and water

4

5 The Muscular System Muscles are responsible for all movement of the body There are three basic types of muscle –Skeletal –Cardiac –Smooth

6 Info About Muscles Only body tissue able to contract create movement by flexing and extending joints Body energy converters (many muscle cells contain many mitochondria)

7 3 Types of Muscles

8 Three types of muscle SkeletalCardiacSmooth

9 Classification of Muscle Skeletal- found in limbs Cardiac- found in heart Smooth- Found in viscera Striated, multi- nucleated Striated, 1 nucleus Not striated, 1 nucleus voluntaryinvoluntary

10 Characteristics of Muscle Skeletal and smooth muscle are elongated Muscle cell = muscle fiber Contraction of a muscle is due to movement of microfilaments (protein fibers) All muscles share some terminology –Prefixes myo and mys refer to muscle –Prefix sarco refers to flesh

11 Shapes of Muscles Triangular- shoulder, neck Spindle- arms, legs Flat- diaphragm, forehead Circular- mouth, anus

12 Skeletal Muscle Most are attached by tendons to bones Cells have more than one nucleus (multinucleated) Striated- have stripes, banding Voluntary- subject to conscious control Tendons are mostly made of collagen fibers Found in the limbs Produce movement, maintain posture, generate heat, stabilize joints

13 Structure of skeletal muscle Each cell (fibre) is long and cylindrical Muscle fibres are multi-nucleated Typically 50-60mm in diameter, and up to 10cm long The contractile elements of skeletal muscle cells are myofibrils

14 Skeletal muscle - Summary Voluntary movement of skeletal parts Spans joints and attached to skeleton Multi-nucleated, striated, cylindrical fibres

15 Smooth Muscle No striations Spindle shaped Single nucleus Involuntary- no conscious control Found mainly in the walls of hollow organs

16 Smooth muscle Lines walls of viscera Found in longitudinal or circular arrangement Alternate contraction of circular & longitudinal muscle in the intestine leads to peristalsis

17 Structure of smooth muscle Spindle shaped uni-nucleated cells Striations not observed Actin and myosin filaments are present( protein fibers)

18 Smooth muscle - Summary Found in walls of hollow internal organs Involuntary movement of internal organs Elongated, spindle shaped fibre with single nucleus

19 Cardiac Muscle Striations Branching cells Involuntary Found only in the heart Usually has a single nucleus, but can have more than one

20 Cardiac muscle Main muscle of heart Pumping mass of heart Critical in humans Heart muscle cells behave as one unit Heart always contracts to it’s full extent

21 Structure of cardiac muscle Cardiac muscle cells (fibres) are short, branched and interconnected Cells are striated & usually have 1 nucleus Adjacent cardiac cells are joined via electrical synapses (gap junctions) These gap junctions appear as dark lines and are called intercalated discs

22 Cardiac muscle - Summary Found in the heart Involuntary rhythmic contraction Branched, striated fibre with single nucleus and intercalated discs

23 Muscle Control Type of muscle Nervous control Type of control Example Skeletal Controlled by CNS Voluntary Lifting a glass Cardiac Regulated by ANS Involuntary Heart beating Smooth Controlled by ANS Involuntary Peristalsis

24 Types of Responses Twitch- –A single brief contraction –Not a normal muscle function Tetanus –One contraction immediately followed by another –Muscle never completely returns to a relaxed state –Effects are compounded

25 Where Does the Energy Come From? Energy is stored in the muscles in the form of ATP ATP comes from the breakdown of glucose during Cellular Respiration This all happens in the Mitochondria of the cell When a muscle is fatigued (tired) it is unable to contract because of lack of Oxygen.

26 Muscle Fatigue If muscle is continued to be stimulated, the strength of the contraction decreases until eventually it will no longer contract!! When oxygen supplies of muscle run low, the cells switch to anaerobic respiration, but at a cost. This produces lactic acid that makes you sore!!!

27 Muscle Fatigue Oxygen Debt- continued increased metabolism that must occur in cell to remove excess lactic acid that accumulates during prolonged exercise. Labored breathing after exercise is needed to “pay the debt”

28 How are Muscles Attached to Bone? Origin-attachment to a movable bone Insertion- attachment to an immovable bone Muscles are always attached to at least 2 points Movement is attained due to a muscle moving an attached bone

29 Exercise and Muscles Isotonic- ( most normal exercise) produces movement. Muscle shortens and lengthens. Tension on muscle stays the same. Isometric- tension in muscles increases, no movement occurs (pushing one hand against the other)

30 Effects of Exercise on Skeletal muscle Changes correspond to amount of work they do. Prolonged inactivity- muscle mass shrinks--- called disuse atrophy. Exercise- increase in muscle size called hypertrophy. Can be enhanced by strength training- number of fibers stays same but number of myofilaments increase causing increase in mass of muscle

31 Exercise and muscle cont. Aerobic or endurance training- no muscle hypertrophy but get better blood flow, with increased oxygen and glucose delivery to muscle. Increase in mitochondria----- more production of ATP

32 Functions of skeletal muscle Movement Posture (muscle tone)- from “tonic contractions”. Hold muscles in position but do not move any body parts Heat production- reverse hypothermia

33 Movement Muscles pull on bones. Insertion bone moves and origin bone stays put. Muscle responsible for producing any particular movement is called the prime mover. Other muscle that help in producing movement are called synergists. As prime movers and synergists contract, other muscles called antagonists relax

34 Motor Unit Before skeletal muscle can contract, it must be stimulated by nerve impulse(the nerve fiber is a motor neuron) Point of contact between nerve ending and muscle fiber is called the neuromuscular junction A single motor neuron and the muscle cells it innervates is called a motor unit

35 Muscle Stimulus Muscle fiber will not contract until a stimulus reaches a certain level of intensity. This minimal level required for a contraction is called the threshold stimulus When muscle cell is subjected to threshold, it contracts completely. Called “all or none” response. Number of fibers involved changes with load

36 Muscle Attachments Origin Insertion

37 Flexion Types of Musculo-Skeletal Movement

38 Extension

39 Hyperextension

40 Abduction, Adduction & Circumduction

41 Rotation

42 More Types of Movement…… Inversion- turn sole of foot medially Eversion- turn sole of foot laterally Pronation- palm facing down Supination- palm facing up Opposition- thumb touches tips of fingers on the same hand

43 The Skeletal Muscles There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this section we will only study a sample of the major muscles.

44 Sternocleidomastoideus Flexes and Rotates Head

45 Masseter Elevate Mandible

46 Temporalis Elevate & Retract Mandible

47 Trapezius Extend Head, Adduct, Elevate or Depress Scapula

48 Latissimus Dorsi Extend, Adduct & Rotate Arm Medially

49 Deltoid Abduct, Flex & Extend Arm

50 Pectoralis Major Flexes, adducts & rotates arm medially

51 Biceps Brachii Flexes Elbow Joint

52 Triceps Brachii Extend Elbow Joint

53 Rectus Abdominus Flexes Abdomen

54 External Oblique Compress Abdomen

55 External Intercostals Elevate ribs

56 Internal Intercostals Depress ribs

57 Diaphragm Inspiration

58 Forearm Muscles Flexor carpi—Flexes wrist Extensor carpi—Extends wrist Flexor digitorum—Flexes fingers Extensor digitorum—Extends fingers Pronator—Pronates Supinator—Supinates

59 Gluteus Maximus Extends & Rotates Thigh Laterally

60 Rectus Femoris Flexes Thigh, Extends Lower Leg

61 Gracilis Adducts and Flexes Thigh

62 Sartorius Flexes Thigh, & Rotates Thigh Laterally

63 Biceps Femoris Extends Thigh & Flexes Lower Leg

64 Gastrocnemius Plantar Flexes Foot & Flex Lower Leg

65 Tibialis Anterior Dorsiflexes and Inverts Foot


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