Muscle Tissue Skeletal Muscle Notes 3 Types of

Muscle Tissue & Skeletal Muscle Notes

3 Types of Muscle Tissue • Skeletal muscle- striated and voluntary (it is subject to conscious control)

• Smooth muscle- not striated and involuntary (we do not consciously control it) – Lines our digestive system and empties our bladder and bowels

• Cardiac muscle- striated and involuntary – Only found in the heart

Functions of Skeletal Muscle • • • Produce movement Maintain posture Support soft tissue Guard entrances and exits Body temperature

THE ANATOMY OF A MUSCLE

Anatomy of Skeletal Muscle • Each muscle is composed of bundles of muscle fibers. • Each muscle fiber (cell) has many nuclei and is a cluster of myofibrils • Myofibrils contain two types of protein filaments that are arranged in a regular, over-lapping pattern – Myosin – thicker filament – Actin – thinner filament

Sarcomere • The functional unit of contraction in skeletal muscle myofibrils • Located between two Z lines • One end of each actin filament is attached to the Z line • Myosin filaments are located between two actin filaments and overlap them on each end

Muscle Tissue Anatomy • Epimysium - outer covering of muscles • Fascicle - a bundle of muscle fibers

Muscle Tissue Anatomy • Perimysium - each fascicle is covered by the perimysium • Endomysium - thin covering around each muscle fiber - Both perimysium & endomysium contain blood vessels and nerve endings

Muscle Tissue Anatomy • Myofibrils - each muscle fiber (muscle cell) contains bundles of myofibrils

• Sarcomere - what gives skeletal muscle its STRIATIONS • A – BAND - area where actin & myosin overlap • I – BAND - area of actin only

CW: Color and Label

Muscle Contractions

Sliding Filament Theory • The myosin filaments pull the actin filaments towards the center of the sarcomere • This shortens the sarcomere which in turn shortens the muscle

• Pink is actin • Blue is myosin The myosin pulls the actin toward the center of each sarcomere which in turn shortens or contracts the muscle

All-or-None Response • The shortening of the sarcomere occurs along the entire length of the muscle fiber • The strength of a muscle contraction depends on – How often the individual muscle fibers are stimulated to contract – How many muscle fibers contract within a given muscle

Skeletal Muscle Contractions • Controlled voluntarily by the nervous system • Motor Unit – a motor neuron (nerve cell) and all of the muscle fibers it controls

Steps to Muscle Contraction Neuron action potential arrives at end of motor neuron 2 ACH is released 3 ACh binds to receptors on motor end plate 4 Permeability of sarcolemma changes (Na rushes in)(an action potential is produced) 5 Muscle action potential sweeps into the T tubules triggering 6 release of Ca from the cisternae of the sarcoplasmic reticulum 7 CA binds to troponin 8 Troponin changes shape and shifts tropomyosin to expose binding sites of actin 9 myosin binds to actin (cross bridge is formend)(ADP released from myosin) 10 Myosin head pivots (pulling actin) 11 Myosin releases from actin (cross bridge is broken)(another ATP binds to myosin) 12 Myosin re-extends into "ready" position (ATP->ADP+Pi)(ADP is bound to myosin)

Energy for Muscle Contractions • Energy for muscle contractions comes from ATP (adenosine triphosphate) • Glucose is converted into ATP by mitochondria during cellular respiration

Two Cellular Respiration Pathways • Aerobic Respiration requires a supply of oxygen in order to take place • Produces the maximum number of ATP molecules (36 -38 ATP’s for each glucose molecule converted) • ATP is used in long continuous exercise (distance running)

Two Cellular Respiration Pathways • Anaerobic Respiration occurs when available oxygen has been depleted • Produces only 2 ATP’s per glucose molecule • Also produces Lactic Acid – causes muscle soreness & fatigue • Typically occurs during short periods of intense exercise

Cellular Respiration Summary (glucose) 2 Lactic acid 36 -38

Oxygen Supply • Oxygen is carried to the muscle cells by red blood cells through the circulatory system

Fatigue • Decrease in the strength of muscle contractions due to repeated stimulation without periods of rest • If continued, muscle will lose ability to contract • Occurs when ATP supply is depleted and oxygen is not replenished fast enough – lactic acid builds up in the muscle fibers

Oxygen Debt & Recovery Period • Oxygen debt – amount of oxygen needed to restore pre-exertion oxygen levels • During recovery (rest) period, oxygen is replenished along and more ATP is produced while lactic acid is broken down

Skeletal Muscles • Attached to bones by tendons • Origin – the end of the muscle attached to the bone that remains stationary during a muscle contraction • Insertion – the end of the muscle attached to the bone that moves during a muscle contraction • The insertion always moves toward the origin

Skeletal Muscles • Attached to the bones of the appendicular skeleton in opposing pairs (flexors and extensors) • Flexors – cause the limb to bend at the joint • Extensors – cause them to straighten

Notes: Naming Muscles

Types of Muscles Prime mover – 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

Naming of Skeletal Muscles Direction of muscle fibers Example: Relative rectus (straight) size of the muscle Example: maximus (largest)

Naming of Skeletal Muscles Location of the muscle Example: many muscles are named for bones (e. g. , temporalis) Number of origins Example: triceps (three heads)

Naming of Skeletal Muscles Location of the muscle’s origin and insertion Example: Shape of the muscle Example: Action sterno (on the sternum) deltoid (triangular) of the muscle Example: flexor and extensor (flexes or extends a bone)

• Types of Movements (terminology) • Origin - where a muscle begins • Insertion - where a muscle ends • Action - motion produced

• Flexion - joint angle gets smaller

• Extension - joint angle gets larger

hyperextension - movement beyond 180 o of joint motion •

• abduction movement away from midline of body

• adduction - movement toward midline of body

Identifying Muscles

Face Muscles Temporalis Closes jaws (chewing) Masseter Closes side of jaws (chewing) Frontalis Raises temporal Bone frontal bone eyebrows and wrinkles forehead horizontally

Face Muscles Orbicularis Closes eye Orbicularis Draws Oculi- encircles eye Oris- encircles mouth lips together Mentalis-chin Raises and protrudes lower lip

Neck Muscles Sternocleidomastoid- attaches to sternum, clavicle, and mastoid process Turns the head and bows the head

Head and Neck Muscles

Anterior Trunk Muscles Pectoralis Pulls Major- upper chest upper arm forward and across the chest Rectus Abdominus-connects pubic bones to ribs and sternum Compresses Flexes contents of abdominal cavity spinal column (sit-ups)

Anterior Trunk Muscles External Oblique- slant downward from lower ribs to pelvic girdle Tenses abdominal wall

Posterior Trunk Muscles Trapezius- triangular muscle extends from the base of skull, cervical & thoracic vertebrae to the shoulder Rotates the scapula (shoulder blade) Latissimus Dorsi- from lower back, around side, to armpit Adducts arm, pulls arm back in swimming, climbing, and rowing

Trunk Muscles

Deep Trunk and Arm Muscles

Arm Muscles Deltoid- covers shoulder joint, connects clavicle and scapula to the humerus Abducts the upper arm (lifts arm) Biceps brachii- in upper arm, connects scapula to radius Flexes upper arm at the elbow, rotates the hand laterally

Arm Muscles Brachialis- beneath the biceps brachii, connects the shaft of humerus to the ulna Strongest flexor of the elbow Brachioradialis- connects the humerus to the radius Aids in flexing the elbow

Arm Muscles Triceps brachii- 3 heads, back of upper arm connects humerus and scapula to ulna Extensor of the elbow

Arm Muscles

Arm Muscles

Upper Leg Muscles Gluteus Maximus- muscle of the hip that forms most of the butt Extends jumping leg at hip, for climbing and Gluteus Medius- from hip to femur and is under the gluteus maximus Steadies the pelvis during walking Good site for intramuscular injections (shots)

Butt Muscles Gluteus Medius Gluteus Maximus Gluteus Minimu s

Upper Leg Muscles Rectus Femoris- one of the quadriceps Extends the knee (like when kicking a ball) and can flex the hip Vastus Lateralis- one of the quadriceps (on the outside of leg) Extends the knee

Upper Leg Muscles Vastus Medialis – one of the quadriceps (toward the inside of body) Extends the knee Sartorius- thin and straplike and the most superficial Synergist to help cross legs

Upper Leg Muscles Biceps Femoris- part of the hamstring group Prime movers of thigh extension and knee flexion.

Muscles of the Pelvis, Hip, and Thigh

Lower Leg Muscles Tibialis Anterior- From upper tibia to tarsals Acts to dorsiflex and invert the foot Gastrocnemius- a two bellied muscle that form the curve of the calf Plantar flexion of the foot. Needed to lift the heel during walking.

Muscles of the Lower Leg

Superficial Muscles: Anterior

Superficial Muscles: Posterior

Diseases of the Muscular System

Muscular Dystrophy Congenital muscle-destroying disease affect specific muscle groups Muscle fibers degenerate & atrophy due to an absence of dystrophin, a protein that helps keep muscle cells intact Most common & serious—Duchenne’s M. D. Mostly in males (diagnosed between 2 -6 yrs) Survival is rare beyond early 30’s X-linked recessive

Myasthenia gravis Rare adult disease caused by antibodies to acetylcholine receptors at the neuromuscular junction which prevents the muscle contraction from occurring Drooping upper eyelids, difficulty swallowing & talking, muscle weakness & fatigue Death occurs when respiratory muscles cease to function

Disorder of Muscle Tissue • Cramps & Spasms - an “over contraction” – can be due to electrolyte imbalance, fatigue, overuse

Hernia - a tear in wall of muscle – can be congenital, or from severe strain

ABDOMINAL HERNIA

• Muscle Tear - aka: “pulled” muscle or strained muscle – caused by overstretching of muscle during activity • muscle fibers actually tear apart Torn Pectoralis Major

• Hamstring Muscle Tear

• Hypertrophy - increase in the size of muscle fibers

• Atrophy - decrease in size of muscle fiber