The Muscular System 5 Lesson 5.1: Muscle Tissue Categories and Functions Lesson 5.2: Skeletal Muscle Actions Lesson 5.3: The Major Skeletal Muscles Lesson 5.4: Common Injuries and Disorders of Muscles

Muscle Tissue Categories and Functions Chapter 5: The Muscular System Lesson 5.1 Muscle Tissue Categories and Functions

Muscle Tissue Categories Functions skeletal smooth cardiac behavioral properties tension and types of skeletal muscle contractions

Muscle Tissue Categories skeletal voluntary striated smooth involuntary no striations cardiac intercalated disks

Muscle Tissue Categories

Skeletal Muscle Organization Sarcolemma and endomysium surrounds the muscle fiber Perimysium bundles groups of muscle fibers to make up a fascicle Epimysium encloses several fascicles to make up a muscle Aponeurosis connects muscle to other tissues

Skeletal Muscle Organization

Behavioral Properties of Muscle extensibility–stretch elasticity–snap back irritability–respond contractility–shorten

Muscle Tissue Functions tension and types of skeletal muscle contraction agonist–moves bone antagonist–opposes the movement of the agonist

Concentric Contraction agonist contracts, antagonist relaxes

Eccentric Contraction agonist contracts while lengthening, antagonist relaxes

Isometric Contraction both agonist and antagonist contract

Skeletal Muscle Actions Chapter 5: The Muscular System Lesson 5.2 Skeletal Muscle Actions

Skeletal Muscle the motor unit skeletal fiber types muscular strength, power, and endurance

The Motor Unit group of muscle fibers under the control of one motor neuron 100-2000 fibers, depending on size and function of muscle

Generating Action Potentials Acetylcholine crosses the synaptic cleft at the neuromuscular junction (neurotransmitter) Na+ rushes in, K+ rushes out->creates POSITIVE charge (Depolarization) More Na+ enters- Action potential begins

Contraction of the Sarcomeres Fed by glycogen (stored glucose) Triggered by Ca++ release Sarcomeres shorten by actin filaments (heads grabbing) sliding along myosin filaments Number and frequency of action potentials determine speed and force of contraction!

Maximum Tension and Return to Relaxation Action potential always causes entire motor unit muscle fibers to contract- then it must FULLY relax before a new stimulus can be applied All-or-none law Multiple motor units must be stimulated to produce maximum tension Sustained maximum tension=tetanus

Skeletal Muscle Fiber Types Type 1 - Slow-twitch contracts relatively slowly and is resistant to fatigue Type IIa - These fast twitch muscle fibers are also known as intermediate fast-twitch fibers. Moderate fatigue Type IIb - This fast twitch muscle fiber has the highest rate of contraction (rapid firing) of all the muscle fiber types, but it also has the highest rate of fatigue. All muscle fibers in a motor unit are the same type, but not all motor units in a muscle are!

Skeletal Muscle Fiber Architecture parallel fiber arrangements- large range of motion Fusiform- biceps brachii Bundled- rectus abdominus Triangular- pectoralis major pennate fiber arrangements- Oblique attachment gives force, Does not shorten as much Unipennate- abductor pollux Bipennate- rectus femoris Multipennate-deltoid

Muscular Strength Rotary force that muscles can produce at a joint the maximum weight you can lift is a measurement of muscular strength ONLY (no variable for speed)

Muscle Power force x velocity (both force and speed contribute equally, so strength is not the determining factor) how fast you can sprint is a measurement of muscle power

Muscle Endurance Muscle tension/time Can be sustained or cyclical- varies based on activity how far you can run is a measurement of muscle endurance So is rowing Handstands Cycling

Fatigue Opposite of endurance Affected by: Nature of work/exercise done How often the muscle is used Muscle fiber composition Humidity/temperature of enviornment

The Major Skeletal Muscles Chapter 5: The Muscular System Lesson 5.3 The Major Skeletal Muscles

The Major Skeletal Muscles directional motions head and neck muscles trunk muscles upper limb muscles lower limb muscles

Skeletal Muscle Attachments Origin fixed end of a muscle Insertion movable end of a muscle

Sagittal Plane Movements Anterior and Posterior Flexion- forward (except knee) Extension- back to normal position Hyperextension- too far Dorsiflexion- toes toward body Plantar flexion- “gas pedal”- point toes

Frontal Plane Movements Medial and Lateral Abduction- limb lateral Adduction-limb medial Inversion-foot medial Eversion-foot lateral radial deviation- Hand lateral at wrist ulnar deviation- Hand medial at wrist

Transverse Plane Movements Rotational Medial rotation-toward midline Lateral rotation- away from midline Pronation- palm down Supination- palm up

Multiplanar Movements Not in a single plane Circumduction- make a circle Opposition- thumb to any of the other 4 fingers

Head and Neck Muscles All except orbicularis Oris and Platysma are paired

Trunk Muscles- Posture, stability and protection

Upper Limb Muscles- NOT all of them (just the major ones)

Lower Limb Muscles- (just the major ones)

Common Injuries and Disorders of Muscles Chapter 5: The Muscular System Lesson 5.4 Common Injuries and Disorders of Muscles

Muscle Injuries Strain – overstretched muscle (less common in the more flexible, speed at time of injury is a factor as well) grade I- mild: tightness 1 day grade II- moderate: partial tear, temporary weakness and loss of function grade III- severe: torn muscle, loss of function, internal bleeding, swelling. EX: Hamstring strains most common, tend to reoccur, slow to heal (1/3 repeat within 1 year)

Muscle Injuries Contusion – bruised muscle from impact myositis ossificans When an already injured muscle is struck, forms calcium mass over 3-4 weeks. Reabsorbs after 6-7 weeks (usually) Cramps – spasming muscle Numerous causes: electrolyte imbalance, Ca, Mg, K deficiency, dehydration, idiopathic Delayed onset muscle soreness – begins 24-48 hours later, multiple, microscopic tears= pain, swelling and stiffness

Tendon Injuries Tendinitis –inflamed tendon Tendinosis –degeneration of a tendon leading to rupture. No inflammation Val Thoermer/Shutterstock.com

Joint / Stress Injuries Rotational injury at shoulder improper mechanics Overuse of elbow- epicondylitis Medial (little leaguer) tears lateral tears (tennis elbow) tears Shin splints- periosteum Tibial tendons Whiplash- abnormal motion Cervical vertebrae, muscle spasms Attempt to protect spine

Muscle Disorders Hernia - A hernia is the protrusion of an organ or the fascia of an organ through the muscular wall of the cavity that normally contains it. Complications include strangulation Repair with surgery Various causes Heavy lifting Increased abdominal pressure Present at birth 41

Muscle Disorders Muscular dystrophy - a group of inherited, progressive disorders that involve muscle weakness and loss of muscle tissue, varies in severity. No cure.