Anatomy of the muscular system Ch. 10 Anatomy of the muscular system

The incredible human machine

Introduction Myology - Study of muscles Energy for Muscular contraction - ATP Three types of muscle - skeletal, cardiac, smooth Number of skeletal muscles - more than 600 Weight of muscles - 40-50%

Full muscular system

Connective Tissue coverings Fascia - surrounds and separates muscles Tendons - connects muscle to bone Aponeurosis - broad sheet of connective tissue Epimysium - covers whole muscle Perimysium - covers fascicles Endomysium - covers myofibrils

Structure Size - range from small to large Shape -broad, narrow, short, long Arrangement Parallel, converging, oblique, pennate, bi- pennate, sphincter

Attachment of muscles Origin - attachment to immovable bone Insertion - attachment to movable bone

Muscle actions Prime movers (agonists) - main action Antagonists - opposite action Synergists - helper muscle

The power of muscle

Lever systems Bones serve as levers and joints serve as fulcrums Contracting muscles applies pulling force on bone lever Four components of lever system Rigid bar - bone Fulcrum - joint Load - what is moved Pull - muscle contraction

How muscles are named Latin based or English Naming - supply hints as to muscle action Location, function, shape Direction of fibers Number of heads Points of attachment Relative size

Muscles of facial expression Epicranius - raises eyebrows Orbicularis oculi - closes eye Orbicularis oris - draws lips together Buccinator - smiling Zygomaticus - laughing

Muscles of mastication - chewing *Masseter - closes jaw Temporalis - closes jaw

Muscles that move the head *Sternocleidomastoid - flexes head *Splenius capitis - extends head Semispinalis capitis - extends head

Muscles of the thorax *Intercostals - lift ribs *Diaphragm - enlarges thorax

Muscles that move the shoulder girdle *Trapezius - raises shoulders Rhomboideus major - rotates/retracts scapula Levator scapulae - elevates/retracts scapula Serratus anterior - pulls shoulder down and forward *Pectoralis minor - pulls shoulder down

Muscles that move the upper arm Flexors Coracobrachialis - adduction *Pectoralis major - flex upper arm Extensors Teres major - extension, medial rotation *Latissimus dorsi - extends upper arm Abductors Supraspinatus *Deltoid Rotators - *rotator cuff Subscapularis- medial rotation Infraspinatus - outward rotation Teres minor - outward rotation

Muscles that move the forearm Flexors *Biceps brachii Brachialis Brachioradialis Extensor *Triceps brachii

Muscles that move the hand Flexors Flexor carpi radialis and ulnaris Palmaris longus *Flexor digitorum profundus Extensors Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris *Extensor digitorum

Muscles of the abdominal wall *external and internal obliques - compresses abdoment - allows for side to side motion *Rectus abdominis Flexes waist Transverse abdominus synergist Compresses abdomen

Muscles of the back *Trapezius *Rhomboideus Infrapinatus Extends head/neck *Rhomboideus Retracts scapula Infrapinatus Extends/rotate arm Teres major and minor Extends, adduts arm *Latissimus dorsi - extends arm

Muscles of the pelvic floor Levator ani Superficial transversus perinei Bulbospongiosus Ischiocavernoses

Muscles that move the thigh Anterior group *Psoas major Iliacus Posterior group *Gluteus maximus, medius, minimus Tensor fasciae latae Adductors Adductor longus Adductor magnus Gracilis

Muscles that move the leg Flexors *Biceps femoris Semitendinosus Sartorius Extensor *Quadriceps femoris group Rectus femoris Vastus lateralis/medialis/intermedius

Muscles that move the ankle foot and toes Dorsal flexors *Tibialis anterior Peroneus tertius Exensor digitorum longus Plantar flexors *Gastrocnemius Soleus (synergist) Flexor digitorum longus

Ch. 11 The physiology of the muscular system

Introduction Purpose - move framework of body, produce heat, facilitate posture Characteristics Excitability - ability to be stimulated Contractibility - ability to shorten producing movement Extensibility - ability to stretch and return to resting length.

Structure of muscle fibers Description - each fiber - muscle cell (spans a joint) Sarcolemma - cell membrane Sarcoplasm - cytoplasm of muscle cell Contains mitochondria, nuclei, myofibrils Myofibrils - filaments Myosin - thick Actin - thin Sarcomere - unit within myofibril Extends from z line to z line. Z lines produce striations Sarcoplasmic reticulum (endoplasmic reticulum) Contains transverse tubules (nerve impulse)

Neuromuscular Junction Where neuron and muscle fiber meet. Abundant mitochondria present for ATP production Neurotransmitters - chemical communicators located at the end of neuron in the Cytoplasm Motor Unit Mucle fibers contract at once when triggered by neurotransmitters Recruitment - increase in number of motor units activated.

Skeletal Muscle Contraction Shortening of sarcomeres results in muscle pulling against attachments Myosin - two twisted strands with crossbridges Actin contains myosin binding sites Sliding filament theory Myosin cross-bridge attaches to binding site on actin filament and bends Pulls actin filament, releases and attaches to next binding site, pulling again. Energy from atp used to prepare the cross-bridges.

Stimulus for contraction Neurotransmitter - Acetylcholine released from synaptic vesicles at end of axon of neuron. Note - botulinus toxin prevents acetylcholine release. Receptors detect neurotransmitter Impulse spreads over sarcolemma then travels through transverse to sarcoplasmic reticulum Calcium released by sarcoplasmic reticulum High calcium moves Troponin and tropomyosin aside, exposing binding site Myosin Crossbridge attaches to binding site Crossbridge shortens pulling filaments across each other Sarcomere shortens Acetylcholinesterase decomposes acetylcholine Calcium returns to sarcoplasmic reticulum Link between actin and myosin is broken. Note - rigor mortis - lack of ATP - prevents muscle relaxation.

Muscle contraction

Oxygen supply and cellular respiration During rest - enough oxygen to support aerobic cellular respiration. Oxygen deficiency during exercise Lactic acid end product of anaerobic respiration. - lactic acid diffuses out of muscle cells and is carried to liver. Oxygen debt - amount of oxygen that liver cells require to convert lactic acid into glucose plus amt. muscle cells need to make atp to original concentration. Muscle fatigue-muscle loses ability to contract during strenuous exercise. Result of lactic acid accumulation (lower ph) Muscle cramp - lack of ATP required to return calcium ions back to sarcoplasmic reticulum so muscle fibers can relax. Heat production - energy produced by cellular respiration is lost as heat.

Muscular responses One method of studying muscle function - remove single fiber and connect to device that records response to electrical stimuli. Muscle fibers remain unresponsive till they reach Threshold stimulus (stimulus of a certain strength) All or none response Summation - series of stimuli of increasing frequency Recruitment of motor units-increase in number of activated motor units Sustained contractions - muscle tone - achieved by continuous state of sustained contraction. Treppe-staircase phenomenon - twitch contractions 1 second apart Tetanus-multiple wave summation/no relaxation

Recording a muscular contraction Myogram - recording of electrically stimulated muscle contraction Myograph - machine that records the contraction Twitch-single short contraction Latent period - time delay followed by period of contraction and relaxation.

Muscle tone Tonic contraction-continual partial contraction of a muscle Flaccid - less tone than normal Spastic-more tone than normal Negative feedback mechanism controls tone Graded strength - affected by: Metabolic condition of fibers Number of fibers contracting Number of motor units recruited

Physical training Strength training- results in hypertrophy - enlargement of fibers Endurance training - increases ability to sustain moderate contractions for longer time. Increase of mitochondria. Atrophy - result of disuse Decreased capillary networks, decreased mitochondria, decreased filaments.

Smooth muscle Fibers - elongated with tapered ends Lack striations Undeveloped sarcoplasmic reticulum Located in iris of eye and walls of hollow organs Display rhythmicity - allow for peristalsis Contraction uses acetylcholine and norepinephrine Slower to contract and relax but can contract longer

Cardiac muscle Mechanism - same as smooth and skeletal Difference: transverse tubules supply extra calcium allowing for contraction for longer periods. Structure Intercalated discs - join cells and cause cells to contract as a unit. Rythmic Self-exciting