1. The Muscular System

2. or “Everything you ever wanted to know about Muscles, but were afraid to ask” !!!
This is the presentation on the muscular system for Human Anatomy and Physiology I at Oklahoma City Community College. I am Dennis Anderson.

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

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
Skeletal
Cardiac
Smooth

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
voluntary
involuntary

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
Skeletal
Cardiac
Regulated by ANS
Involuntary
Heart beating
Smooth
Controlled by ANS
Involuntary
Peristalsis

24. Types of Responses Twitch- Tetanus 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 Insertion Origin
Muscles attach in at least two places in the body. *The origin is the attachment that moves the least. *The insertion is the attachment that moves the most. This diagram illustrates the origin and insertion of one of the neck muscles. Note the origin is on the clavicle and sternum. The insertion is on the skull. When the muscle contracts it will shorten the distance between the origin and insertion. The head will move when this muscle contracts. Remember the insertion is the end of the muscle that moves the most. Since the head moves the attachment on the head is called the insertion. The origin is generally on a larger body part will move the least. The chest does not move when this muscle contract. The bones in the chest are therefore the origin.

37. Types of Musculo-Skeletal Movement
Flexion
You will need to know the action or movement performed for each of the muscles we study. The first type of movement is called flexion. Note the lower leg is being flexed in this diagram. During flexion the angle of joint is decreased. As the knee is flexed, the angle between the lower leg and the thigh is decreased. Flexion of the upper arm is also illustrated in this diagram. Here the angle between the arm and the frontal plane is decreased.

38. Extension
Extension is the opposite of flexion. In extension the angle of a joint is increased. Extension of the lower leg causes an increased angle between the lower leg and the thigh.

39. Hyperextension
Flexion and extension also apply to the neck. When a joint is extended past the anatomical position the movement is called hyperextension.

40. Abduction, Adduction & Circumduction
Abduction refers to moving away from the median plane of the body. Adduction is the opposite movement to abduction. It is moving toward the medial plane. Circumduction refers to inscribing a circle while moving a limb.

41. Rotation
Rotation is turning a bone on its own axis. Moving the head back and forth to indicate “no” is an example of rotation. Note the difference between medial and lateral rotation. In lateral rotation the limb is rotated the lateral side of the body. Medial rotation rotates the limb toward the medial side of the body.

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

44. 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.

45. Masseter Elevate 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.

46. 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.

47. 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.

48. 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.

49. 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.

50. 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.

51. 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.

52. Triceps Brachii Extend 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.

53. 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.

54. 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.

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

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

57. 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.

58. 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.

59. 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.

60. 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.

61. 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.

62. 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.

63. 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.

64. 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.

65. 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.