Because flexing muscles look like mice scurrying beneath the skin, scientists dubbed them, muscles, from the Latin word mus meaning little mouse

Because flexing muscles look like mice scurrying beneath the skin, scientists dubbed them, muscles, from the Latin word mus meaning little mouse

The Muscular System Muscles are responsible for all types of body movement machines of the body Essential function of muscle is contraction or shortening Three basic muscle types are found in the body: differ in structure, location,& how stimulated to contract Skeletal muscle Cardiac muscle Smooth muscle

imilar Characteristics of All Muscle Types Muscle cells are elongated (muscle cell = muscle fiber) Contraction of muscles depends on two types of myofilaments, which are like microfilaments of cytoskeleton All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh

Skeletal Muscle Characteristics Most are attached by tendons to bones Skeletal muscle fibers are cigar-shaped Cells are multinucleate Largest muscle fibers, up to 1 ft in length Striated have visible banding (stripes) Voluntary subject to conscious control

Contract rapidly & w/great force Tires easily must rest after short periods of activity Cells are surrounded and bundled by connective tissue (strength & support) There are several layers that are around skeletal muscle fibers: endomysium, perimysium, fascicle, epimysium

Connective Tissue Wrappings of Skeletal Muscle Endomysium tissue sheath around single muscle fiber (between fibers) Perimysium fibrous membrane around a(bundle) of fibers, called fascicle

Connective Tissue Wrappings of Skeletal Muscle Epimysium the overcoat that covers the entire skeletal muscle Fascia on the outside of the epimysium

Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment, tendons or aponeuroses Tendon cord-like structure Aponeuroses sheet-like structure Sites of muscle attachment: Bones Cartilages Connective tissue coverings

Smooth Muscle Characteristics Has no striations Spindle-shaped cells Single nucleus Involuntary no conscious control Found mainly in the walls of hollow organs

Cardiac Muscle Characteristics Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart

Function of Muscles Produce Movement Maintain Posture Stabilize Joints Generate Heat

Microscopic Anatomy of Skeletal Muscle Cells are multinucleate Nuclei are just beneath the plasma membrane, which is called the sarcolemma ( muscle husk )

Microscopic Anatomy of Skeletal Muscle Sarcolemma specialized plasma membrane Sarcoplasmic reticulum specialized smooth endoplasmic reticulum, for storage of calcium

Microscopic Anatomy of Skeletal Muscle Myofibril Bundles of myofilaments Myofibrils are aligned to give distinct bands I band = light band A band = dark band

Microscopic Anatomy of Skeletal Muscle Sarcomere Contractile unit of a muscle fiber Chains of these units make up myofibrils

Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere: Thick filaments = myosin filaments Composed of the protein myosin Has ATPase enzymes

Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere: Thin filaments = actin filaments Composed of the protein actin

Microscopic Anatomy of Skeletal Muscle Myosin filaments have heads (extensions, or cross bridges) Myosin and actin overlap somewhat At rest, there is a bare zone that lacks actin filaments

Properties of Skeletal Muscle Activity Muscle cells have functional properties that enable them to perform their duties: Irritability ability to receive and respond to a stimulus Contractility ability to shorten (forcibly) when an adequate stimulus is received

Nerve Stimulus to Muscles (structure) Skeletal muscles must be stimulated by a nerve to contract (3 parts) May stimulate a few cells or hundreds of them Motor Unit: One neuron Muscle cells stimulated by that neuron

Nerve Stimulus to Muscles (structure) Neuromuscular Junctions association site of nerve and muscle Synaptic Cleft gap between nerve and muscle Nerve and muscle do not make contact Area between nerve and muscle is filled with interstitial fluid

Transmission of Nerve Impulse to Muscle 1) Neurotransmitter chemical released by nerve upon arrival of nerve impulse The neurotransmitter for skeletal muscle is acetylcholine 2) Neurotransmitter attaches to receptors on the sarcolemma 3) Sarcolemma becomes temporally, permeable to sodium (Na + ) 4) Sodium rushes into the cell upsetting electrical conditions, which generates an electrical current called an action potential

Transmission of Nerve Impulse to Muscle Action potential travels over the entire surface of the sarcolemma, conducting electrical impulse from one end to the other Once started,muscle contraction cannot be stopped 2 things return cell to resting state: 1) diffusion on K + ions out of cell and 2) operation of sodium-potassium pump, which moves Na + and K + ions back to initial positions

The Sliding Filament Theory of Muscle Contraction Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament Myosin heads then bind to the next site of the thin filament

The Sliding Filament Theory of Muscle Contraction This continued action causes a sliding of the myosin along the actin The result is that the muscle is shortened (contracted)

The Sliding Filament Theory

Contraction of a Skeletal Muscle Muscle fiber contraction is all or none Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Graded Responses different degrees of skeletal muscle shortening

Graded Responses Graded Responses can be produced two ways: 1) by changing the frequency of muscle stimulation 2) by changing number of muscle cells being stimulated

Types of Graded Responses Twitch Single, brief, jerky contraction Not a normal muscle function Tetanus (summing of contractions) One contraction is immediately followed by another The muscle does not completely return to a resting state The effects are added

Types of Graded Responses Unfused (incomplete) tetanus Some relaxation occurs between contractions The results are summed Fused (complete) tetanus No evidence of relaxation before the following contractions The result is a sustained muscle contraction

Muscle Response to Strong Stimuli Muscle force depends upon the number of fibers stimulated More fibers contracting results in greater muscle tension Muscles can continue to contract unless they run out of energy

Energy for Muscle Contraction Initially, muscles used stored ATP for energy Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored by muscles ATP only energy source directly used by muscles for power-regenerated continuously After this initial time, other pathways must be utilized to produce ATP (3 pathways)

Energy for Muscle Contraction Direct Phosphorylation Muscle cells contain creatine phosphate (CP) CP is a high-energy molecule After ATP is depleted, ADP is left CP transfers energy to ADP, to regenerate ATP CP supplies are exhausted in about 20 seconds

Energy for Muscle Contraction Aerobic Respiration (95%) ATP from this Series of metabolic pathways that occur in the mitochondria Glucose is broken down to carbon dioxide and water, releasing energy(36 ATP per glucose) This is a slower reaction that requires continuous oxygen

Energy for Muscle Contraction Anaerobic Glycolysis Reaction that breaks down glucose without oxygen Glucose is broken down to pyruvic acid to produce some ATP (2 ATP per glucose) Pyruvic acid is converted to lactic acid

Energy for Muscle Contraction Anaerobic glycolysis (continued) This reaction is not as efficient, but is fast Huge amounts of glucose are needed Lactic acid produces muscle fatigue

Muscle Fatigue and Oxygen Debt When a muscle is fatigued, it is unable to contract The common reason for muscle fatigue is oxygen debt Oxygen must be repaid to tissue to remove oxygen debt Oxygen is required to get rid of accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

Types of Muscle Contractions Isotonic contractions same tone or tension Myofilaments are able to slide past each other during contractions The muscle shortens Ex. bending knee, smiling, rotating arms Isometric contractions same measurement or length Tension in the muscles increases The muscle is unable to shorten Ex. lifting heavy object with arms

Muscle Tone Some fibers are contracted even in a relaxed muscle State of continuous partial contractions = Muscle Tone Different fibers contract at different times to provide muscle tone The process of stimulating various fibers is under involuntary control

Effects of Exercise on Muscle Use it or Lose it Results of increased muscle use: Increase in muscle size Increase in muscle strength Increase in muscle efficiency Muscle becomes more fatigue resistant Aerobic, endurance exercise(stronger, more flexible muscles, fatigue less Isometric, resistance exercise (increase size and strength)

1) All muscles cross at least one joint. 2) The bulk of the muscle lies proximal to the joint crosses 3) All muscles have at least two attachments: the origin and the insertion 4) Muscles can only pull, the never push 5) During a contraction, the muscle insertion moves towards the origin

Muscles and Body Movements Movement is attained due to a muscle moving an attached bone Muscles are attached to at least two points (have aprox. 600 odd muscles) Origin attachment to a immoveable bone Insertion attachment to an movable bone

Types of Ordinary Body Movements Flexion movement decreases the angle of the joint & brings 2 bones closer together (hinge joints knee, elbow, also in ball-and-socket joints) Extension movement that increases the angle, or distance, between 2 bones. (ex. straightening the elbow) If >than 180 o called hyperextension Rotation movement of a bone around its longitudinal axis (ball-and-socket)

Body Movements

Abduction movement of limb away from midline, or median plane, of body- also applies when move fingers and toes apart Adduction opposite of abduction, movement of limb toward body midline Circumduction- combo. of flexion, extension, abduction, and adduction, commonly seen in ball-and-socket joints like the shoulder Proximal end is stationary and distal end moves in a circle

Special Movements Dorsifelxion and Plantar Flexion- up & down movements of foot & ankle, dorsifelxion = standing on heels, plantar flexion = pointing toes (hands & wrists) Inversion and Eversion- movements of foot, inversion turn sole medially, eversion turn sole laterally Supination and Pronation- refer to radius around ulna, supination turn backward, and pronation turn forward Opposition- palm of hand thumb touch tips of other fingers

Types of Muscles Prime mover muscle with the major responsibility for a certain movement Antagonist muscle that opposes or reverses a prime mover ex. biceps prime mover, triceps antagonist in moving elbow 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 (7 criteria) Direction of muscle fibers (rectus-straight, oblique-slanted) Ex: rectus femoris (straight thigh muscle) Relative size of the muscle (maximus, minimus, longus) Ex: gluteus maximus (largest of glutes) Location of the muscle (named after bones) Ex: temporalis

Naming of Skeletal Muscles (7 criteria) Number of origins(bi, tri, quad) Ex: triceps (three heads) Location of the muscles origin and insertion Ex: sternocleidomastoid (sternum & clavicle) Shape of the muscle Ex: deltoid (triangular) Action of the muscle Ex: flexor, extensor, & adductor

Two categories of Head & Neck Muscles: Facial Muscles Chewing Muscles Facial unique because inserted into soft tissues such as other muscles or skin When pull on skin of face allow us to: smile faintly, grin widely, frown, pout, deliver a kiss, etc.

Name Origin Insertion Action Facial: Frontalis Cranial aponeurosis Skin of eyebrows Raises eyebrows Orbicularis Oculi Frontal bone& maxilla Tissue around eyes Orbicularis Oris Mandible & maxilla Skin & muscle around mouth Blinks & closes eyes Closes & protrudes lips (kissing muscle) Buccinator Maxilla & mandible Orbicularis oris Compresses check, holds food between teeth Zygomaticus Zygomatic Bone Skin & muscle at corner of lips Chewing: Raises corner of mouth(smiling muscle) Masseter Temporal Bone Mandible Closes jaw Temporalis (fan shaped) Temporal Bone Mandible Closes jaw

Name Origin Insertion Action Neck: Sternocleidomastoid (two headed, each side of neck) Platysma Sternum & clavicle Connective tissues of chest muscles Temporal bone Tissue around mouth Flexes neck (bowing head, praying) & rotates head Pull corners of mouth inferiorly (downward sag)

Trunk muscles include: Those that move the vertebral column Anterior thorax muscles, move ribs, head, and arms Muscles of the abdominal wall, which help move vertebral column and provide the natural girdle of the abdominal wall 3 regions: anterior, abdominal girdle, and posterior

Trunk Muscles

Anterior Trunk Muscles Name Origin Insertion Action Anterior: Pectoralis major Intercostal Muscles Sternum,clavicle & 1 st -6 th ribs (fan shaped) Deep muscles between ribs Proximial humerus Adducts & flexes humerus Depress rib cage, exhale Abdominal Girdle: natural girdle Reinforces body Plywood look like Rectus abdominis Pubis Sternum & 5 th -7 th ribs Flexes vertebral column External oblique Lower 8 ribs Iliac crest Flexes & rotates vertebral column Internal oblique Iliac crest Last 3 ribs Flexes & rotates vertebral column Transverse abdominis Lower ribs & iliac crest Pubos Compress abdominal contents

Posterior Trunk Muscles Posterior: Deep Trunk Trapezius (diamond or kite shaped muscle mass) Latissimus Dorsi Occipital bone & all cervical & thoracic vertebrae Lower spine & iliac crest Erector Spinae Iliac crests, 3-12, & vertebrae Deltoid (fleshy, triangle-shaped that form rounded shape of shoulders) Scapular spine & clavicle Scapular spine & clavicle Extends neck & adducts scapula Proximal humerus Extends & adducts humerus (power stroke) Ribs,thoracic, & cervical vertebrae Humerus Extends back, bending at waist Abducts humerus

Deep Trunk and Arm Muscles

Fall into 3 groups: 1 st - Arise from the shoulder girdle and cross the shoulder joint to insert into the humerus to move the arm (pectoralis major, latissimus dorsi, and deltoid) 2 nd - Causes movement at the elbow, enclose the humerus and insert on the forearm bones (Biceps Brachii, Brachialis, Brachioradialis, Triceps Brachii) 3 rd - Includes the muscles of the forearm, which insert on the hand bones and causes their movement

Name Origin Insertion Action Biceps Brachii Scapula of shoulder girdle Proximal radius Flexes elbow & supinates forearm Brachialis Deep in biceps Elbow flexion Brachioradialis Humerus Distal forearm Weak of forearm Triceps Brachii boxer s muscle Shoulder girdle & proximal humerus Olecranon process of ulna Flexor Carpi radialis Distal humerus 2 nd & 3 rd Flexor carpi ulnaris Extensor carpi radialis Distal humerus & posterior ulna Humerus metacarpals Carpals of wrist & 5 th metacarpal Base 2 nd 3 rd metacarpal Extensor digitorum Distal humerus Distal phalanges of 2 nd -5 th fingers Extends elbow Flexes wrist & abducts hand Flexes wrist & adducts hand Extends wrists & abducts hand Extends fingers & wrists

Cause movement at hip, knee, and foot joints Among the largest, strongest muscles in body, specialized for walking and balance, many span 2 joints cause movement at both Muscles acting on thigh, massive & help hold body upright against pull gravity Thigh muscles cross knee and cause its flexion or extension & have attachments on pelvic girdle, cause movement of hip Common terms leg = whole limb, anatomically refers to only part between knee and ankle

There are 3 major groups for movement of lower limb: Muscles causing movement at hip joint (Gluteus Maximus, Gluteus Medius, iliopsoas, Adductor ) Muscles causing movement at knee joint (Hamstring Group: biceps femoris, semimembranosus, semitendinosus), satorius, (Quadriceps Group: Rectus & 3 vastus) Muscles causing movement at ankle and foot (Tibialia anterior, Extensor, Fibularis, Gastrocnemius, soleus)

Muscles of the Pelvis, Hip, and Thigh

Muscles of the Lower Leg

Name Origin Insertion Action Gluteus Maximus Sacrum & Ilium Proximal femur Extends hip Gluteus Medius Ilium Proximal femur Abducts thigh Iliopsoas Ilium & lumbar vertebrae Femur Flexes hip Adductor Pelvis Proximal Femur Adduct thigh Hamstring Group: Biceps femoris Semimembrananosus Ischial tuberosity Ischial tuberosity Head of tibia Proximal femur Extends hip & flex knee Extends hip & flex knee Semitendinosus Ischial tuberosity Proximal tibia Extends hip & flex knee sartoius ilium Proximal femur Flexes thigh on hip

Quadriceps Group: Rectus Femoris Pelvis Tibial tuberosity via patella lig. Vastus Lateralis Vasti:Femur Tibial tuberosity via patella lig. Vastus Medialis Vasti:Femur Tibial tuberosity via patella ligament Extend knee & flex hip on thigh Extend knee Extend knee Name Origin Insertion Action Tibialis Anterior Proximal tibia 1 st tarsal & 1 st Extensor, Digitorum Longus Proximal tibia & radius metatarsal Distal toes 2-5 Dorsiflexes & inverts foot Extends toes & dorsiflexes foot Fibularis Fibula Metatarsals Plantar flex & evert foot Gastrocnemius Distal femur Calcaneus (heel) via cal. tendon (Achilles) Soleus Proximal tibia & fibula Calcaneus Plantar flexes foot & flexes knee Plantar flexes foot

Superficial Muscles: Anterior

Superficial Muscles: Posterior