Muscular System Muscles are responsible for all types
Muscular System Muscles are responsible for all types of body movement ¢ Three basic muscle types are found in the body ¢ Skeletal muscle l Cardiac muscle l Smooth muscle l
Characteristics of Muscle All Muscle cells are elongated (muscle cell = muscle fiber) ¢ All can contract due to the movement of microfilaments ¢ All muscles share some terminology ¢ Prefix myo refers to muscle l Prefix mys refers to muscle l Prefix sarco refers to muscle l
Types of Muscle
Types of Muscle, cont.
Skeletal Muscle Attachments · Epimysium blends into a connective tissue attachment · Tendon – cord-like structure · Aponeuroses – sheet-like structure · Sites of muscle attachment · Bones · Cartilages · Connective tissue coverings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 5
Microscopic Anatomy of Skeletal Muscle cell (fiber) · The nuclei are pushed aside by ribbonlike myofibrils · Cells are multinucleate · Nuclei are just beneath the sarcolemma(plasma membrane) Figure 6. 3 a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 9 a
Microanatomy of Skeletal Muscle Each muscle cell is called a muscle fiber. Within each muscle fiber are many myofibrils.
· Myofibril · Bundles of myofilaments · Myofibrils are aligned to give two distinct bands: · I band = light band · A band = dark band Figure 6. 3 b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 10 a
Z line The sarcomere is the functional unit of a muscle cell
Sarcomere Relaxed The part of the sarcomere with only actin filaments is called the I band.
Sarcomere Completely Contracted The sarcomere is completely contracted in this slide. The I and H bands have almost disappeared.
Neuromuscular Components Neuromuscular junction- the point where a motor neuron joins muscle fibers. Motor unit is a motor neuron and all the muscle fibers it innervates(may be few or hundreds). All or none law : with adequate stimulation, a muscle cell will contract to its fullest extent or not at all. So there is no partial contraction of muscle fiber
Skeletal muscle activity Muscles have two special functions: 1 -Irritability : the ability to receive and respond to stimulus 2 -Contractility : the ability to shorten -Muscle cell must be stimulated by nerve impulse to contract -There is a gap (synaptic cleft) between the nerve &muscle cell
This gap is crossed by a chemical transmitter called Acetylcholine (Ach) ¢ Sarcolemma becomes temporarly permeable to sodium which enter the cell so leads to depolarization of the cell. ¢ This upset generates an electric current called action potentiual which is unstoppable leading to muscle fiber contraction. ¢
MUSCLE TONE ¢ Relaxed skeletal muscles are always slightly contracted l This state is termed “muscle tone” l Spinal reflexes continually activate an alternating subset of motor neurons. l No active movement produced but muscles are kept firm, healthy, and ready to respond to stimulation. l Helps stabilize joints and maintain posture.
TYPES OF MUSCLE CONTRACTIONS 1 -Isotonic contraction Muscle length changes(shortens) and moves the load. l Once tension is sufficient to move a load, tension remains relatively constant. l Bending the knee, rotating the arms and smiling are examples
2 -ISOMETRIC CONTRACTIONS ¢ Muscle length remains constant Muscle attempts to move a load greater than the force the muscle is able to develop l Try to lift your car or push against immovable object or trying to lift 400 kg are examples. l
Effect of exercise on Muscles are no exceptions to the saying –use it or lose it¢ Regular exercise increases muscle size, strength and endurance - Isotonic contraction (Aerobic exercise) results in stronger muscle with greater resistance to fatigue. No increase in size but better heart &lungs. -Isometric(Resistance)contraction: Require little time. No special equipments. Leads to enlargement of muscle cell without increase in their number ¢
Energy for muscle contraction ATP store in the muscle supplies energy ONLY for 4 -6 seconds ¢ ATP then comes from 1 -direct phosphorylation of ADP ¢ 2 -Anaerobic respiration 3 -aerobic mechanism (oxidative phosphorylation
Muscle fatigue. ¢ Muscle fatigue occurs when an exercising muscle can no longer respond to the same degree of stimulation with the same degree of contractile activity. l Factors for this include an accumulation of lactic acid, and the depletion of energy reserves. l Increased oxygen consumption is needed to recover from exercise (paying off an oxygen debt).
Naming Skeletal Muscle Direction of Muscle Fibers Location Action Skeletal Muscle Origin & Insertion Size Shape Number Of Origins
Naming Skeletal Muscle ¢ Direction of Muscle Fibers l l Relative to the Midline RECTUS means parallel to midline • Rectus Abdominus l TRANSVERSE means perpendicular to midline • Transversus Abdominus l OBLIQUE means diagonal to midline • External Oblique • Internal oblique
Naming Skeletal Muscle ¢ Location l Structure near which a muscle is found l Muscle near l frontal bone = Frontalis l Muscle near the Tibia = Tibialis
Naming Skeletal Muscle ¢ Size l l Relative Size of Muscle MAXIMUS means largest • Gluteus Maximus l MINIMUS means smallest • Gluteus Minimus l LONGUS means longest • Fibularis Longus l BREVIS means short • Fibularis Brevis
¢ Number of Origins l l Number of tendons of origin BICEPS means two • Biceps Brachii l TRICEPS means three • Triceps Brachii l QUADRICEPS means four • Quadriceps Femoris
Naming Skeletal Muscles ¢ Shape l DELTOID means having a triangular shape l TRAPEZIUS means having a trapezoid shape l SERRATUS means having a saw-toothed shape (Serratus Ant. ) l RHOMBOIDEUS means having a diamond shape (Rhomboid Major)
Naming Skeletal Muscles ¢ Origin & Insertion STERNOCLEIDOMASTOID attaches to the Sternum, Clavicle, and Mastoid Process
• Naming Skeletal Muscles According to Function NAME ACTION EXAMPLE FLEXOR Decrease angle at a joint Flexor Carpi Radialis EXTENSOR Increase angle at a joint Extensor Carpi Ulnaris ABDUCTOR Move bone away from midline Abductor Pollicis Longus ADDUCTOR Move bone toward midline Adductor Longus LEVATOR Produces upward movement Levator Scapulae DEPRESSOR Produces downward movement Depressor Labii Inferioris SUPINATOR Turn palm upward/anteriorly Supinator PRONATOR Turn palm downward/posteriorly Pronator Teres
Types of Skeletal Muscle ¢ ¢ Prime mover (Agonist) – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover
Types of body movements l Flexion – Movement that decreases angle between 2 bones.
l Extension – movement that increases angle between 2 bones
l Abduction – movement away from the midline of the body
Muscular System l Adduction – movement towards the midline of the body
l Supination – occurs when palms rotate forward or upward
Opposition: moving the thumb to touch the tips of the other fingers l Pronation – occurs when palms rotate downward or posteriorly
l Dorsiflexion – standing on heal l Plantar flexion – standing on toes
Axial and Appendicular Muscles Figure 11– 3 a
Axial and Appendicular Muscles Figure 11– 3 b
Divisions of the Muscular System 1. Axial muscles: l l l 2. position head and spinal column move rib cage 60% of skeletal muscles Appendicular muscles: l l l support pectoral and pelvic girdles support limbs 40% of skeletal muscles
Muscles of the face Figure 11– 4 a
Muscles of Facial xpression Figure 11– 4 b
Extrinsic Eye Muscles ¢ Also called extra-ocular muscles Figure 11– 5 a, b
Extrinsic Eye Muscles Inferior rectus Medial rectus Superior rectus Lateral rectus Inferior oblique Superior oblique Figure 11– 5 c
Muscles of Mastication Figure 11– 6
3 Muscles of Mastication ¢ Masseter: l ¢ Temporalis: l ¢ the strongest jaw muscle helps lift the mandible Buccinator flattens the cheek, hold the food between the teeth
Anterior Muscles of the Neck Figure 11– 9
Oblique and Rectus Muscles Figure 11– 11 a, b
¢ Anterior abdominal wall muscles : external oblique muscles l internal oblique muscles l Transversus abdominis l Rectus abdominis: l ¢ Diaphragmatic muscle or diaphragm: divides thoracic and abdominal cavities l performs respiration l
Pelvic Floor Muscles Function 1 -Support organs of pelvic cavity 2 -Flex sacrum and coccyx 3 -Control movement of materials through urethra and anus ¢ Divided into: anterior urogenital triangle l posterior anal triangle l
The Appendicular Muscles Figure 11– 13 a
The Appendicular Muscles Figure 11– 13 b
The Appendicular Muscles Position and stabilize pectoral and pelvic girdles ¢ Move upper and lower limbs ¢
Divisions of Appendicular Muscles 1) Muscles of the shoulders and upper limbs: ¢ Position the pectoral girdle ¢ Move the arm ¢ Move the forearm and hand ¢ Move the hand fingers 2) Muscles of the pelvis and lower limbs
Muscles that Position the Pectoral Girdle Figure 11– 14 a
Muscles that Move the Arm Figure 11– 15 a
Muscles that Move the Forearm and Hand Figure 11– 16 a
Muscles that Move the Forearm and Hand Figure 11– 16 b
The Intrinsic Muscles of the Hand Figure 11– 18 b
Muscles of the Pelvis and Lower Limbs ¢ Pelvic girdle is tightly bound to axial skeleton: l l permits little movement has few muscles Muscles that Position the Lower Limbs 1. 2. 3. Muscles that move thigh Muscles that move the leg Muscles that move the foot and toes
Muscles that Move the Thigh Figure 11– 19 a, b
Extensors of the Knee 4 the quadriceps femoris: 3 vastus muscles l rectus femoris muscle l Flexors of the knee o o o Semitendinosis Semimembrenosis Biceps femoris
Muscles that Move the Leg Figure 11– 20 b, c
Muscles that Flex the Leg (hamstring) Figure 11– 20 a
Muscles that Move the Foot and Toes Figure 11– 21 a, b
Muscles that Move the Foot and Toes Figure 11– 21 c, d
The Intrinsic Muscles of the Foot Figure 11– 22 a
The Intrinsic Muscles of the Foot Figure 11– 22 b, c
Effects of Aging on the Muscular System 1. 2. Skeletal muscle fibers become smaller in diameter Skeletal muscles become less elastic: l 3. 4. develop increasing amounts of fibrous tissue (fibrosis) Decreased tolerance for exercise Decreased ability to recover from muscular injuries
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