Muscular System (Part 1) PDF

Muscular System Sci13 Topic 4  General Functions of Muscular System 1. Movement - Voluntary - skeletal muscles - Consists of about 700 muscle organs that are typically attached to the bones across a joint to produce voluntary movements  Gene...

Muscular System Sci13 Topic 4  General Functions of Muscular System 1. Movement - Voluntary - skeletal muscles - Consists of about 700 muscle organs that are typically attached to the bones across a joint to produce voluntary movements  General Functions of Muscular System 2. Control of Body Openings and Passages - Ring-like sphincter muscles around eyelids, pupils, mouth, urethra, anus Closes eyelid & pumps tears Orbicularis oculi muscle Deep/ Orbital Lagrimal part part Palpebral part  General Functions of Muscular System 2. Control of Body Openings and Passages - Ring-like sphincter muscles around eyelids, pupils, mouth, urethra, anus Iris sphincter muscle/pupillary sphincter/ sphincter pupillae sphincter muscle iris dilator muscle Bright light Low light  General Functions of Muscular System 2. Control of Body Openings and Passages - Ring-like sphincter muscles around eyelids, pupils, mouth, urethra, anus Orbicularis oris muscle / Musculus orbicularis oris - Kissing muscle - Orofacial function - swallowing, sucking, whistling, chewing, vowel pronunciation, kissing  General Functions of Muscular System 2. Control of Body Openings and Passages - Ring-like sphincter muscles around eyelids, pupils, mouth, urethra, anus Internal and External urethral sphincter IUS - controls involuntary urine flow from the bladder to the urethra EUS - controls voluntary urine flow from the bladder to the urethra Any damage to these muscles can lead to urinary incontinence.  General Functions of Muscular System 2. Control of Body Openings and Passages - Ring-like sphincter muscles around eyelids, pupils, mouth, urethra, anus Internal and External anal sphincter IAS - is an involuntary smooth muscle EAS - is a thick, red voluntary muscle Defecation reflex- stool moving through the digestive tract triggers the internal anal sphincter to relax, which in turn makes the external anal sphincter contract.  General Functions of Muscular System 3. Posture and Stability - Sustained partial contractions - Resists gravity, prevents unwanted movement Optimal postural alignment is vital in counteracting the constant gravitational forces opposing the body. When the two are in balance, muscles are able to function with the least amount of work. Less strain is placed on the muscles, ligaments, and bones thereby enhancing their efficiency and increasing bone density and muscle mass.  General Functions of Muscular System 3. Posture and Stability - Sustained partial contractions - Resists gravity, prevents unwanted movement antigravity muscles help maintain an upright, balanced posture  General Functions of Muscular System 4. Communication - facial expression, hand gestures, body language, writing, speech 5. Control of body temperature - muscles comprises 40-50% of body mass - Metabolism requires lots of energy (ATP) for movement ~25% = energy of movement ~ 75% = heat energy - skeletal muscles generate up to 85% of our body heat Muscle Organs: - almost 700 muscle organs in body - each limb is operated by over 50 muscles not including many stabilizer muscle - Range from extremely small (Stapedius muscle) to broad (Latissimus dorsi) Muscle Organs: muscle organs each consists of several kinds of tissue: 1. Fibrous Connective Tissue - forms continuous sheath from muscle to bone - arranged in overlapping layers: individual cells = endomysium fascicles = perimysium whole organ = epimysium (deep fascia) Muscle Organs: muscle organs each consists of several kinds of tissue: 1. Fibrous Connective Tissue - very tough and strong yet flexible, very elastic (collagen fibers mostly) - very strong, rarely separated from bone or muscle - extends beyond muscle and attaches muscle to bone or to other muscles tough strap = tendon (=sinews) broad sheet = aponeurosis - tendons are continuous with periosteum of bones Muscle Organs: muscle organs each consists of several kinds of tissue: 1. Fibrous Connective Tissue - very tough and strong yet flexible, very Extensor Tendons elastic (collagen fibers mostly) - very strong, rarely separated from bone or muscle extend and straighten your - extends beyond muscle and attaches fingers muscle to bone or to other muscles lift your toes up tough strap = tendon (=sinews) and lift the front of broad sheet = aponeurosis your foot off the ground Muscle Organs: muscle organs each consists of several kinds of tissue: 1. Fibrous Connective Tissue - very tough and strong yet flexible, very elastic (collagen fibers mostly) - very strong, rarely separated from bone or muscle - extends beyond muscle and attaches muscle to bone or to other muscles tough strap = tendon (=sinews) broad sheet = aponeurosis Muscle Organs: muscle organs each consists of several kinds of tissue: 1. Fibrous Connective Tissue - Tendons are continuous with periosteum of bones Tough and thin membrane covering bones Muscle Organs: muscle organs each consists of several kinds of tissue: 2. Nervous Tissue - muscles are under direct control of the CNS - skeletal muscles are innervated by motor neurons - skeletal muscles will not contract without stimulation - each motor neuron branches into 200 or so synaptic knobs (within a motor end plate) - each muscle cell in innervated by only one motor neuron - each neuron typically innervates ~200 muscle cells  Muscle Organs: muscle organs each consists of several kinds of tissue: 2. Nervous Tissue connection between neuron and muscle cell = neuromuscular junction - at motor end plate - not a direct connection, synapse or gap - neurotransmitter, Acetylcholine, is released - NT crosses synapse to trigger contraction - (30-40 M ACh receptors/motor end plate) - binding opens channels! creates action potential  Muscle Organs: muscle organs each consists of several kinds of tissue: 3. Muscle Tissue - close to half of body consists of striated (voluntary) muscle tissue - elongated cells, spindle shaped, up to 1 ft long = muscle fibers - very little matrix, instead embedded in framework of fibrous connective tissue - highly contractile and elastic - muscle cells generally stop dividing at birth - but each cell can expand greatly in volume - development is affected by sex hormones - males’ muscles respond better than females’ to exercise Blood Supply to Muscle our voluntary muscles have a rich blood supply to bring needed oxygen and energy molecules to the cells endomysium is full of capillaries that reach every muscle fiber all skeletal muscles receive ~1.25 liter of blood/min at rest (~1/4th total blood supply) during heavy exercise they can use up to 11.6 liters/min (>3/4th ‘s of all blood) Muscle Compartments - muscles of the limbs are arranged into tightly packed “compartments” - fascia surround and enclose the muscles, nerves and blood vessels within each compartment Muscle compartments of the leg Muscle Compartments if the blood vessels within a compartment are damaged blood and tissue fluid accumulate - fascia prevent swelling and relief of pressure - blood vessels and nerves are compressed and obstructed - if pressure persists for >2-4 hrs nerves begin to die Some Basic Principles of Voluntary Muscle Function 1. Bones act as levers and pivots (fulcrums) - most skeletal muscles are arranged in bundles with ends attached to two different bones - muscles pull across joints to produce movement - Each muscle must attach to at least two different bones on opposite sides of an articulation: - origin (proximal; less mobile point of attachment) - body (most muscle fibers are grouped) Intramuscular Injections: muscles with thick - insertion (distal; more mobile point of bellies commonly used when drug must be attachment absorbed more slowly or is given in large doses (eg. deltoid) Some Basic Principles of Voluntary Muscle Function 2. Muscles can only pull not push - Any movement requires coordination of several muscles - Opposing pairs - Functional groups - Prime mover (agonist) - Synergist (including fixators) - antagonists Some Basic Principles of Voluntary Muscle Function 3. Kinds of body movements the synovial joints of the body each allow specific kinds of voluntary movements, such as: flexion/extension - decrease vs increase angle - inc. hyperextension (beyond anatomical position) Some Basic Principles of Voluntary Muscle Function 3. Kinds of body movements the synovial joints of the body each allow specific kinds of voluntary movements, such as: supination/pronation - rotate outward vs inward Some Basic Principles of Voluntary Muscle Function 3. Kinds of body movements the synovial joints of the body each allow specific kinds of voluntary movements, such as: adduction/abduction - toward vs away from median levator/depressor - produces upward vs downward movement Some Basic Principles of Voluntary Muscle Function 3. Kinds of body movements the synovial joints of the body each allow specific kinds of voluntary movements, such as: rotation/circumduction - Rotation only occurs in the hip and shoulder (medial/lateral) - Circumduction - moving body part in circular part (comb. of flexion/extension & abduction/adduction eversion/inversion - turns sole outward vs inward dorsiflexion/plantarflexion Some Basic Principles of Voluntary Muscle Function 3. Kinds of body movements the synovial joints of the body each allow specific kinds of voluntary movements, such as: dorsiflexion/plantarflexion - Toes up vs toes down other muscle movements - tensor (makes body part more rigid) - sphincter (decrease size opening) Some Basic Principles of Voluntary Muscle Function 4. Skeletal muscle can be named according to: - direction of muscle fibers (rectus, transverse, oblique) - location (temporalis, orbicularis oris) - size (maximus, minimus) - origin and insertion (stenocleidomastoid) - number of origins (biceps, triceps) - shape (deltoid, trapezius) - action (flexor, extensor) Human Muscle Groups: Muscles of the Appendages Human Muscle Groups Human Muscle Groups Human Muscle Groups Human Muscle Groups: Head and Trunk Muscles Human Muscle Groups: Head and Trunk Muscles Hernia - occurs because of weakness in body wall may cause rupture - visceral organs protrude through opening - wall is weak because of spaces between bundles of muscle fibers Hernia - undue pressure on abdominal viscera may force a portion of parietal peritoneum and intestine through these weak spots - eg. heavy lifting can create up to 1,500 lbs pressure/sq “ in abdominal cavity (~100x’s normal pressure) - most common at inguinal area, also diaphragm & naval - women rarely get inguinal hernias Muscle Cell Anatomy & Function T tubules - tube or tunnel-like infoldings of sarcolemma - open to cell surface - extend into muscle - cell surround SR - conversion of the action potentials into muscle contractions Myofibrils - most of muscle cell is filled with myofibrils - regularly overlapping filaments (in striated mm) - surrounded by SR - SR in turn surrounded by T-Tubules Myofibrils consists packets of: a. Thick filaments (myosin) - each filament consist of several 100 molecules of myosin - each myosin molecule is shaped like a golf club with heads directed outward Myofibrils consists packets of: b. Thin filaments (actin, troponin, tropomyosin) - one type of actin (G-actin) contains active sites - each tropomyosin has a calcium binding troponin molecule to attached to it a) In the absence of Ca2+, tropomyosin prevents the binding of myosin heads to actin. (b) When the [Ca2+] rises, Ca2+ binds to a subunit of troponin, which causes the tropomyosin to shift slightly into the groove of the actin filament. Muscle cell contraction Relaxation Kinds of Muscle Contraction 3. Tetanus Muscular System (Part 2) Sci13 Topic 3 Most body activities involve both isotonic and isometric contractions.  Tension Curve Muscle tension be measured as a function of sarcomere length. Twitch: A single isotonic response as a result of a single threshold (liminal) stimulus  3 Types of Skeletal Muscle Fibers In humans, we see 3 types of skeletal muscle fibers classified based on: 1. How fast a muscle will twitch (due to how fast it splits ATP) 2. Metabolic pathway used to generate ATP (anaerobic glycolysis / glycolysis) We will concentrate on only 2 fiber types a. slow twitch= slow oxidative fiber b. fast twitch= fast glycolytic fiber  3 Types of Skeletal Muscle Fibers In humans, we see 3 types of skeletal muscle fibers classified based on: 1. How fast a muscle will twitch (due to how fast it splits ATP) 2. Metabolic pathway used to generate ATP (anaerobic glycolysis / glycolysis) fast glycolytic fiber - muscle fiber that primarily uses anaerobic glycolysis fast oxidative fiber - intermediate muscle fiber that is between slow oxidative and fast glycolytic fibers slow oxidative fiber - muscle fiber that primarily uses aerobic respiration Implications for Sports Number of red (slow twitch) vs. white (fast twitch) muscle fibers is hereditary - Conditioning and training can do nothing to change the ratio (New research may show otherwise) - E.g. Alberto Salizaar – New York marathon winner had 92% red vs. 8% white. - Other runners tend to have fewer red and more white in comparison. - Sprinters contain about 60% fast oxidative. - Weight lifters have about equal amounts fast glycolytic and slow oxidative - Determination of muscle fiber ratios can be done by muscle biopsy.  Other animals of muscle cell types Concentrations of fast and slow twitch muscles can be observed in other animals as well as humans The light and dark meat of a chicken has to do with concentrations of different types of muscle fibers. ○ A chicken uses it’s breast muscle (white meat) for short flight if at all = fast twitch ○ The legs (dark meat) of a chicken serve for endurance = slow twitch What type of meat would you expect to find in the breast of a migratory duck?  Anabolic Steroid Abuse Testosterone (found in men) and human growth hormone influence muscle growth Anabolic steroid drugs are testosterone-like and are abused by athletes to increase muscle size & strength and endurance ○ Moderate doses – no better than optimal training ○ Large doses.....damage to body  Anabolic Steroid Abuse Problems in Males: testes atrophy, less sperm production, baldness.  Anabolic Steroid Abuse Problems in Females: sterility, facial hair, deep voice, atrophy of breasts and uterus, menstrual irregularities  Incomplete Tetanus Complete Tetanus Tetanus is the sustained contraction resulting from high frequency stimulation Complete = no hint of reduce tension/ force bet. stimuli (80-100 stim/sec) smooth mov Incomplete = stim is reduced slightly (20-30 stim/sec) eg. trembling Wave summation occurs when a given set of cells is repeatedly stimulated without complete relaxation Treppe – increased strength of contraction as muscle “warms up”due to identical stimuli too far apart for wave summation to occur Treppe can be explained as follows: Ca++in the sarcoplasm probably accumulates because the stimuli release Ca++faster than the Ca++pump can move them back in to the SR. - The troponin becomes saturated for maximum binding to myosin heads. - Eventually the inflow and outflow of calcium ions equalize and the strength of contraction level off Treppe can be explained as follows: In your warming muscles, the sarcoplasm becomes less viscous. - With more heat and the internal resistance of the muscle lessened it allows more energy to be directed to muscle shortening and less to overcome resistance - With heat from ATP splitting and other chemical reactions, the enzyme systems become more efficient.– This is the basis for the wa Muscle Tone - Tone is a sustained partial state of contraction in the muscle. - Tone is maintained in the body without fatigue by the alternation of different motor units - It serves to keep the body in a state of readiness for activity at all times - It is believed that the contractions are some type of involuntary spinal reflexes responding to activation of stretch receptors in muscles and tendons Muscle Tone Hypotonia– Refers to decreased or lost muscle tone, resulting in flaccid (flattened) shape instead of round Muscle Tone Atrophy – Wasting of muscle tissue where muscle fibers decrease in size as myofibrils are lost It can be caused by disuse of your muscles or neurogenic conditions. Symptoms include a decrease in muscle mass, one limb being smaller than the other, and numbness, weakness, and tingling in your limbs. Muscle Tone Hypertrophy – Opposite of atrophy. - Refers to an increase in diameter of muscle fibers where myofibrils, 768 × 768 mitochondria, and SR are increased - No increase in # of cells. - Capillaries servicing muscle fibers are increased too Muscle Tone Muscle tone can be lost quickly: - If muscle usage is prevented by a cast (disuse atrophy), or by a severing of the nerves (denervation atrophy), the muscle fibers begin to atrophy in just a few days. - Prolonged inactivity can lead to degeneration of the muscle fibers and potential replacement by scar tissue (C.T., including fat), which cannot be reversed when complete. Smooth Muscle - involuntary muscle (under ANS control) - nonstriated muscle (lacks organized sarcomeres) - Actin and myosin myofilaments are present but are not regularly arranged  Characteristics of Smooth Muscle vs Skeletal Muscle - 7x less actin & myosin in smooth muscle than skeletal muscle - Lower levels of ATP & creatine phosphate - Fewer number of mitochondria with slow contractions - Smooth muscle cells lack T-tubules (Slower onset of contraction) - Have poorly developed sarcoplasmic reticulum. Takes Ca++ longer to diffuse. Also delays in transport of Ca ++for longer contraction. - Contraction stimulated by a. neurotransmitters (ACh, NE by ANS), b. hormones c. local chemical changes (pH, O2, CO2), d. stretching. smooth muscle is designed for slow reacting, but prolonged contractions. Effects of Aging on Muscular System - strength and muscle mass peak in 20’s - by age 80 most have only half as much strength and endurance - eg. a large percentage of 70 yr olds cannot lift 10 lb weights - major factor in falls, fractures, etc - as we age lean body mass is replaced with fat - eg. young well conditioned male, muscle accounts for 90% of cs area of mid thigh; - in 90 yr old woman only 30% muscle fiber have fewer myofibrils; sarcomeres less organized, less ATP, glycogen, myoglobin, etc (fatigue more quickly) - reduced circulation means muscles heal more slowly - motor units have fewer muscle fibers per neuron - less ACh is produced Abnormal Contractions Of Muscle Tissue Spasm - A sudden involuntary muscle twitch (contraction of short duration), usually due to a chemical imbalance Cramp - A sustained, painful, spasmodic (tetanic) contraction of a muscle – Can last minutes to hours – Severe cramps usually occur when the muscle is shortened(when there is little pull on the tendons) – Usually occurs at night or after exercise (straining/overuse). – It is not known what actually happens at the level of a sarcomere during a cramp. However, the pull on the tendons of muscles are constantly monitored by sense organs called golgi tendon organs Abnormal Contractions Of Muscle Tissue Golgi tendon organs - act to inhibit or “apply the brakes” to muscular contraction to prevent the development of too great of tensile force that could result in injury to the muscle or tendon. - Learning how to disinhibit may be an important part of strength training - Maximal vigorous contractions in a shortened position seems to increase the probability of cramping as you have maximal innervation with minimal inhibition Abnormal Contractions Of Muscle Tissue How can you relieve cramps in light of this information? - Simply forcing the muscle into its longest position (stretching) will create tension on the golgi tendon organ - The inhibition caused by the golgi tendon organ will then stop the cramp Abnormal Contractions Of Muscle Tissue Convulsions - Violent, involuntary contractions of whole groups of muscles - occur when motor neurons are stimulated by factors such as fever, poisons, hysteria, and changes in body chemistry due to drug withdrawals - The stimulated neurons send seemingly senseless impulses to the muscle fibers - This is a nervous disorder, not a muscular disorder  Abnormal Contractions Of Muscle Tissue Fibrillation - Uncoordinated contraction of individual muscle fibers so that the muscle fails to contract smoothly - Cardiac muscle is most prone to this type of activity and is recorded by electromyography Myasthenia Gravis (Heavy Weakness) - weakness in the skeletal muscles - esp. In the face and neck (eg. drooping eyelids) - immune attacks ACh receptors prevents fibers from contracting - mostly woman (20-50 yrs old) - damage leads to easy fatigue and weakness on exertion often eyes are affected w/ drooping eyelids and double vision, difficulty swallowing or speaking End