Muscular System ST 110

Muscle Tissue  Three types Skeletal Smooth Cardiac

Skeletal Muscle  Attaches to bones  Striated (Cross stripes or striations)  Voluntary

Smooth  Located in the walls of internal organs  Nonstriated  Involuntary  Visceral Muscle

Cardiac  Forms the walls of the heart  Striated  Involuntary

Role of Other Body Systems in Movement  It sometimes takes other systems of the body other than the muscular system to create movement Nervous System – Tells some muscles to move The Cerebrum generates nerve impulses for movement

Structure of Skeletal Muscle  Most skeletal muscles attach to two bones that have a movable joint between them  One of the two bones is usually more stationary that the other  A body part moves with the involvement of a group of muscles. No one muscle ever works alone.

Movement  Insertion portion of the muscle is what moves bones  Several muscles contract while others relax to produce movement Prime movers – mainly responsible for producing movement Synergist – help along with prime movers Antagonists – move opposite of prime movers and synergists

Movement  Bending the arm Biceps brachii – prime mover Brachialis – synergists Triceps brachii – antagonists  Straightening the arm Triceps brachii – prime mover Biceps brachii and Brachialis - antagonists

Structure of Skeletal Muscle  Fascia - fibrous connective tissue surrounding muscle groups.  Tendons attach muscles to bones - Dense fibrous connective tissue. Have great strength and don’t break easily.  Ligaments attach bone to bone - slightly elastic and more flexible than tendons.

Microscopic Structure  Sarcolemma  Myofilaments  Myosin  Actin

Microscopic Structure  Sarcomere – Basic functional or contractile unit of skeletal muscle. Very much like the Haversian System in bones Contraction – tightening of a muscle, becomes shorter and thicker Relaxation – Muscle returns to its original form, becomes longer and thinner

Muscle Stimulus  Muscle fibers do not contract until an applied stimulus reaches a certain level of intensity, this is called the threshold stimulus  At this time the muscle fiber contracts completely so its called “all or none”

Motor Unit  Muscles must be stimulated by nerve impulses called motor neurons  The area between the nerve ending and the muscle fiber is called the neuromuscular junction

Functions of Skeletal Muscle  Three basic functions Movement Posture or muscle tone Heat Production

Posture  Tonic Contraction Special type of skeletal muscle contraction that helps us maintain posture Doesn’t move any body parts, it just helps us defy gravity by holding us upright

Heat Production  Muscle fiber contractions produces heat  Energy required to produce a muscle contraction is obtained from the breakdown of ATP. Some energy is lost during these contractions and this is what helps us to maintain our body temperature

Structure of Skeletal Muscle  The muscle attachment at the more stationary bone is called its “origin”  The muscle attachment at the more movable bone is called its “insertion”  The rest of the muscle is called the “body”

Fatigue  When muscles are stimulated repeatedly without adequate periods of rest will cause fatigue

Types of Skeletal Muscle Contraction  Twitch Contraction: Jerky response to a stimulus Seen in muscles during research Play a minimal role in normal muscle activity

Types of Skeletal Muscle Contraction  Tetanic Contraction: A sustained contraction

Types of Skeletal Muscle Contraction  Isotonic Contraction: Produces movement of a joint Muscle changes length The insertion end moves toward the origin

Types of Skeletal Muscle Contraction  Isometric Contraction: Does not always produce movement Sometimes it increases the tension within a muscle but does not shorten the muscle

Effects of Exercise  Prolonged inactivity Muscles shrink in mass “disuse atrophy”  Increased activity Increase muscle size “hypertrophy” Enhanced by strength training

Effects of Exercise  Endurance training (aerobic training) Doesn’t usually cause muscle hypertrophy Increases the number of blood vessels in a muscle with increasing its size Increases number of mitochondria in muscle fibers, which produces more ATP

Skeletal Muscle Groups  Head and Neck Facial Expression  Frontal – raise your eyebrow in surprise and furrow the skin of your forehead into a frown

Skeletal Muscle Groups  Head and Neck Facial Expression  Orbicularis Oris – Puckers your lips “kissing muscle  Zygomaticus – Elevates the corners of the mouth and lips “smiling muscle”

Skeletal Muscle Groups  Head and Neck Muscles of Mastication – among the strongest groups in the body  Masseter – elevates the mandible  Temporal – assists masseter in closing the jaw

Skeletal Muscle Groups  Head and Neck Sternocleidomastoid – rotates and flexes head and neck Trapezius – Extends head and neck

Skeletal Muscle Groups  Muscles that move Upper Extremities Pectoralis major – fan-shaped, attached to the thorax. Flexes upper arm, and helps adduct the arm Latissimus dorsi – Extends the upper arm, and helps adduct the upper arm

Skeletal Muscle Groups  Muscles that move Upper Extremities Deltoid – rounded prominence over shoulder, abducts upper arm. Shaped like an inverted triangle (Greek Letter Delta)

Skeletal Muscle Groups  Muscles that move Upper Extremities Biceps brachii – located on the anterior portion of the upper arm, flexes the elbow. Named for number of divisions

Skeletal Muscle Groups  Muscles that move Upper Extremities Triceps brachii – located on the posterior of the upper arm, extends the elbow. Also named from number of divisions

Skeletal Muscle Groups  Muscles of the trunk Three layers (anterolateral abdominal wall)  External oblique – outermost layer, gets its name for the oblique angle it slants away from the midline

Skeletal Muscle Groups  Muscles of the trunk Three layers (anterolateral abdominal wall)  Internal oblique – middle layer  Transversus abdominis – innermost layer, gets its name from the crosswise alignment

Skeletal Muscle Groups  Muscles of the trunk Rectus abdominis – runs down the midline of the abdomen from the thorax to the pubis. Helps flex the trunk. Gets name from the word rectus meaning straight

Skeletal Muscle Groups  Muscles of the trunk Respiratory Muscles  Intercostal muscles – located between the ribs, aid in breathing by allowing the chest to expand  Diaphragm – Separates the thoracic and abdominal cavities. Helps breathing again by extending the chest cavity

Skeletal Muscle Groups  Muscles that move lower extremities Iliopsoas – Flexes thigh or trunk, postural muscle that keeps the trunk from falling over backward when we stand

Skeletal Muscle Groups  Muscles that move lower extremities Gluteus maximus – outer contour and much of the substance of the buttock. Helps extend the thigh and helps support torso in the erect position. Largest muscle of the buttock

Skeletal Muscle Groups  Muscles that move lower extremities Adductor muscles – Help adduct thigh  Adductor longus  Gracilis  Pectineus

Skeletal Muscle Groups  Muscles that move lower extremities Hamstring muscles – Flex the lower leg  Biceps femoris  Semitendinosus  Semimembranosus

Skeletal Muscle Groups  Muscles that move lower extremities Quadriceps Group – Extend the knee  Rectus femoris  Vastus lateralis  Vastus intermedius  Vastus medialis

Skeletal Muscle Groups  Muscles that move lower extremities Tibialis Anterior - located on the anterior of the lower leg. Dorsiflexes ankle

Skeletal Muscle Groups  Muscles that move lower extremities Gastrocnemius – Calf muscle, plantar flexes ankle, known as the dancers muscle Soleus – located below the calf, plantar flexes ankle

Skeletal Muscle Groups  Muscles that move lower extremities Peroneus Group - located along the sides of the lower leg, plantar flexion  Peroneus longus

Movements of Skeletal Muscles  Flexion  Extension  Abduction  Adduction  Rotation  Supination  Pronation  Dorsiflexion  Plantar flexion

Movements of Skeletal Muscles  Flexion - Decreasing the angle between two bones  Extension – Increasing the angle between two bones

Movements of Skeletal Muscles  Abduction – Moves away from the midline  Adduction – Moves toward the midline  Rotation – Turns a bone on its own axis

Movements of Skeletal Muscles  Supination – turns the palm of the hand upward or forward  Pronation – turns the palm of the hand downward or backward

Movements of Skeletal Muscles  Dorsiflexion – bends the foot upward at the ankle  Plantar flexion – bends the foot downward at the ankle

Medical Specialties  Orthopedic – treats injuries and disorders of the bones, joints, muscles, and tendons  Rheumatologist – treat disorders that involve inflammation of connective tissues

Medical Specialties  Neurologist – treat paralysis patients and other neuromuscular disorders

Pathology  Fasciitis – inflammation of the fascia  Tendonitis – inflammation of the tendons  Adhesion – fibrous tissue that holds together two structures that should be apart

Pathology  Atrophy – weakness or wearing away of body tissues  Myalgia – muscle tenderness or pain  Myositis – inflammation of a skeletal muscle

Pathology  Hernia – protrusion of a part or structure through tissues normally containing it  Myocele – protrusion of muscle

Pathology  Ataxia – the inablility to coordinate muscle activity during voluntary movement  Dystaxia – difficulty in controlling voluntary movement

Pathology  Bradykinesia – extreme slowness in movement  Dyskinesia – impairment of voluntary movement

Pathology  Hyperkinesia – abnormally increased motor activity  Hypokinesia – abnormally decreased motor activity

Repetitive Motion Disorders  Carpal Tunnel Syndrome – the overuse of the tendons in the carpal tunnel become swollen and inflamed. The swelling puts pressure on the median nerve and causes pain, burning, and paresthesia in the fingers and hand

Repetitive Motion Disorders  Epicondylitis – inflammation of the tissues surrounding the elbow. Lateral – tennis elbow Medial – golfers elbow  Plantar Fasciitis

Paralysis  Myoparesis – slight paralysis or weakness of a muscle  Hemiparesis – slight paralysis of one side of the body

Paralysis  Hemiplegia – total paralysis of one side of the body  Cardioplegia – paralysis of the muscles of the heart

Paralysis  Paraplegia – paralysis of both legs and lower part of the body  Quadriplegia – paralysis of all four extremities

Diagnostic Procedures  Electromyography (EMG) – measures the electrical activity with muscle fibers in response to nerve stimulation

Treatment Procedures  Medication Anti-inflammatory Anticholinergic Atropine Muscle relaxant

Treatment Procedures  Physical Therapy  Therapeutic Ultrasound