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ST110 Concorde Career College, Portland

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1 ST110 Concorde Career College, Portland
Muscular System

2 Objectives Define the term muscle.
Describe the functions of the muscular system. List and identify the structures of the muscular system and describe the function of each. Identify the types of muscle.

3 Objectives Understand the physiology of muscle contraction.
Identify muscles according to their action, location, number of divisions, or according to the direction that the fibers run. Describe the mechanism by which the muscular system helps to maintain homeostasis.

4 Objectives Describe common diseases, disorders, and conditions of the muscular system including signs and symptoms, diagnosis, and available treatment options. Demonstrate knowledge of medical terminology related to the muscular system verbally and in the written form.

5 Three Types of Muscle 1. Skeletal 2. Smooth 3. Cardiac


7 Skeletal Muscle - Three Primary Functions
1. Movement of the skeleton 2. Maintenance of posture 3. Generation of heat

8 Anterior View

9 Posterior View

10 Skeletal Muscle

11 Smooth Muscle

12 Cardiac Muscle

13 Muscle Structure Endomysium Perimysium Epimysium


15 Muscle Structure Fascicles - bundles of muscle fibers
Each bundle held together with connective tissue Several bundles encased in tough connective tissue called fascia

16 Microscopic Structure
Each skeletal muscle fiber is one muscle cell. Sarcolemma- electrically polarized membrane covering each fiber. Sarcoplasm- found underneath the sarcolemma and contains the nuclei and mitochondria. Each muscle fiber is further broken down into myofibrils that are composed of myofilaments. Myofibrils: further broken down into sarcomeres- the functioning unit


18 Microscopic Structure
2 types of monofilaments: Myosin- thick filament Actin- thin filament, contains 2 proteins Tropomysoin Troposin The 2 filaments produce striations in skeletal and cardiac muscle. Striations are composed of: I Band (light band) A Band (dark band)

19 Microscopic Structure
Sarcoplasmic reticulum (SR): system of tubules and sacs surrounding each myofibril. Stores and releases calcium ions which regulates the calcium ion concentration with myofibrils. Transverse tubules (T tubules) are attached to surface of SR & have openings to surface of skeletal muscle fiber.


21 Microscopic Structure

22 Muscle Action Skeletal muscle action is stimulated by nerve impulses from the brain and spinal cord. The point where the nerve and the muscle fiber meet is called the neuromuscular junction. A chemical called a neurotransmitter (usually acetylcholine) is released from the nerve stimulates muscle contraction.

23 Muscle Action Dendrites Synapse Synaptic cleft Vesicles
Motor end plate Excitability Action potential



26 Contraction The capacity of muscle to shorten and thicken is called contractility. Muscle fibers contain two types of proteins Actin Myosin

27 Role of Calcium Necessary for muscle contraction.
Calcium is stored in the ER of the muscle cell and is released into the cytoplasm when the cell is stimulated. Calcium exposes the sites on the actin where the crossbridges form with the myosin to cause contraction.

28 ATP Muscle contraction requires energy in the form of ATP.
ATP is produced in the cell by a process called oxidation (“burning”) of nutrients. Oxygen and a nutrient (usually glucose) are necessary to produce ATP. Myoglobin stores oxygen in the muscle. Glucose is stored in the form of glycogen.

29 Muscle Contraction Tone - A property of muscle in which a steady or constant state of partial contraction is maintained. Isotonic contraction - Muscles become shorter and thicker and tone remains the same (movement) Isometric contraction - Muscles remain at a constant length while tension against the muscle increases (no movement).

30 Smooth Muscle

31 Smooth muscle The mechanism of smooth and cardiac muscle contraction is the same as that of skeletal muscles. The difference is in the structure and function of the cells.

32 Smooth Muscle Fiber Structure
Cells are shorter and have single, centrally located nucleus. The cells are elongated and taper at both ends. Myofibrils contain actin and myosin & are randomly arranged, not striated.

33 Smooth Muscle Fiber Structure
Visceral smooth muscle: most common type, located in the walls of hollow organs. 2 layers: Outer-fibers travel in longitudinal Inner- fibers are arranged in a circular pattern The multi-layer arrangement of fibers allows the organ to change in shape and size. EXAMPLE: stomach after a meal (3 layers). Peristalsis- wavelike motion (like intestines)

34 Cardiac Muscle

35 Cardiac Muscle aka myocardial muscle
The only smooth muscle that has striations. Muscle cells are arranged end to end to form fibers that are interconnected. Muscle cells have a centrally located single nucleus and have actin & myosin filaments. Endomysium-located between muscle fibers & contains capillaries and lymphatics.

36 Cardiac Muscle Cells are joined at each end by intercalated disk. This allows for rapid transfer of impulses from cell to cell “all or nothing manner” Myogenic: spontaneous, involuntary contractions of the heart. The rate of contractions is controlled by nerve impulses from the ANS.


38 Cardiac Muscle Electrocardiogram (ECG)-records the rhythmic patter of a heartbeat.


40 Attachments of Skeletal Muscles
Tendons - Attach muscle to bone Aponeurosis - broad and flat tendon

41 Tendons & Ligaments Tendons - attach muscle to bone.
Ligaments - attach bone to bone.

42 Tendons Dense fibrous connective tissue. Consists of parallel fibers held together by tenosynovium. Fibers of the tendon come together with the periosteum of bone. This attatches muscle to bone. Typically inserted at the distal end of bone. Tendinitis Tenosynovitis

43 Tendon Structure

44 Ligaments Fibrous connective tissue consisting of parallel collagenous bundles that bind bone to bone, forming joints.

45 Fascia Aponeuroses: special type of fascia that binds muscle to muscle. EXAMPLE: external abdominal oblique muscle

46 Fascia Fascia – fiberous connective tissue that covers and supports muscle. 3 types- Deep: surrounds muscle to hold them together and provide support. Forms fascial compartments: contain groups of muscles that have nerves and blood vessels. Compartment Syndrome Fasciotomy- surgical incision through a fascia to relieve tension or pressure. Subcutaneous: continuous layer of connective tissue over the entire body. Between skin and deep fascia. Subserous: located between internal layer of deep fascia and the serous membranes.

47 Attachments of Skeletal Muscles
Origin The more fixed and stationary attachment that serves as a basis for action proximal Insertion Movable attachment where effects of contraction are seen distal

48 Terminology of Movement
Agonists - Perform the main action (also called prime movers) Antagonists - Opposite action of the agonist Synergists - Assist prime movers Flexion - Bending Extension - Straightening

49 Extension & Flexion

50 Extension & Flexion Antagonistic muscle pair of the upper arm in action. During extension of the elbow (shown at left), the triceps is contracted and the biceps is relaxed. During flexion of the elbow (shown at right), the triceps is relaxed and the biceps is contracted.

51 Terminology of Movement

52 Naming and Action of Skeletal Muscles
Named by: Action Shape Origin and insertion Location Number of divisions Direction of fibers

53 Naming and Action of Skeletal Muscles
Muscles named for the number of divisions: Posterior view shown at left. Anterior view shown at right.

54 Muscles of the Head and Neck (lateral view)

55 Major Cervical Muscles

56 Muscles of the Arm

57 Muscles of the Arm

58 Muscles of the Trunk Abdomen – Three layers Respiratory muscles
External oblique (outer most) Internal oblique Rectus abdominis Respiratory muscles Intercostal muscles (important for respiration) Diaphragm (separates the thoracic and abdominal cavities)

59 Muscles of the Abdomen

60 Muscles of the Abdomen


62 Muscles of the Leg



65 Muscle Disorders Caused by problems with: Symptoms Vascular supply
Nerve supply Connective tissue sheaths around muscle Muscle bundles Symptoms Paralysis Weakness Degeneration or atrophy Pain Spasms

66 Paralysis The loss of sensation and voluntary muscle movement through disease or injury to its nerve supply Myoparesis Hemiparesis Hemiplegia Cardioplegia Paraplegia Quadriplegia

67 Contracture A muscle shortens its length in the resting state
Lack of exercise Treatment Relengthening

68 Torticollis

69 Cramps Spastic, painful contractions
Irritation caused by lactic acid build-up or inflammation

70 Myasthenia Gravis Easy tiring of muscles and/or muscle weakness
Starts in face Abnormal ACh destruction

71 Torn Muscle

72 Other Disorders Myalgia Myositis Atrophy Muscle pain Inflammation
Decrease in muscle bulk Lack of exercise Electrical current

73 Other Muscle Disorders
Hypertrophy Increase in muscle size Muscle bulking Exercise and weight-lifting Tendinitis Tendon inflammation Muscular dystrophy Genetic Muscle tissue degenerates over time

74 Hypertrophy Variances of muscle size and shape: hypertrophy.

75 Atrophy Variances of muscle size and shape: atrophy.


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