Microscopic Anatomy, Organization, and Classification of The Three Types of Muscles :Microscopic Anatomy, Organization, and Classification of The Three Types of Muscles Anatomy and Physiology Mr. Alexander and Mr. Mullins


Warm-up :Warm-up JOURNAL RESPONSE: in your journal write a half page paragraph in response to the following question. WHY DO WE NEED TO KNOW THINGS ABOUT MUSCLES? Phrase of the Day “I MAY BE COOL BUT THAT DOES NOT MEAN THAT I MUST ACT, OR AM, DUMB” FROM A FELLOW STUDENT AT BURBANK HIGH SCHOOL


Objectives :Objectives To describe the structure of skeletal muscle from gross to microscopic levels Define and explain key vocabulary words: Describe contraction and relaxation of muscles Describe the structure of a neuromuscular junction and to explain its role I muscle function To cite criteria used in naming skeletal muscles Function of skeletal muscle tissue; skeletal muscle organs; and cardiac and smooth muscle tissue. Big picture? Why do we need to know this


IntroductionFigure 10-1/10-2 :IntroductionFigure 10-1/10-2 The bulk of the body’s muscle is called skeletal muscle composed of more than 600 muscles 40%-50% of our body weight is skeletal muscle. Muscles, along with the skeleton, determine the form and contour of our body. Each of the three muscle types has a structure and function uniquely suited to its task in the body Skeletal muscles are also known as voluntary muscle and is striated muscle (because it appears to be striped)


The Cells of Skeletal Muscle :The Cells of Skeletal Muscle


Function Of Muscle Tissue :Function Of Muscle Tissue Characteristics of skeletal muscle cells: Excitability (irritability)—ability to be stimulated Contractility—ability to contract, or shorten, and produce body movement


Vocabulary words :Vocabulary words Overview of the muscle cell (fig 11-1 through 11-3) Fibers--Muscles cells (threadlike shape) Sarcolemma—is the plasma membrane of muscle fibers Sarcoplasmic reticulum Is a network of tubules and sacs found within muscle fibers Membrane of the sarcoplasmic reticulum continually pumps calcium ions from the sarcoplasm and stores the ions within its sacs Muscle fibers contain many mitochondria and several nuclei Myofibrils—numerous fine fibers packed close together in the sarcoplasm


Vocabulary Words :Vocabulary Words Sarcomere Segment of myofibril between two successive Z lines Each myofibril consists of many sarcomeres Contractile unit of muscle fiber Striated muscle Dark stripes called A BAND; light H ZONES runs across midsection of each dark A BAND Light stripes called I BANDS; dark Z LINES extends across center of each light I BAND T tubules TRANSVERSE TUBULES EXTEND ACROSS THE SARCOPLASM AT RIGHT ANGLES TO THE LONG AXIS OF THE MUSCLE FIBER FORMED BY INWARD EXTENSIONS OF THE SARCOLEMMA MEMBRANE HAS ION PUMPS THAT CONTINUALLY TRANSPORT Ca++ ions inward from the sarcoplasm Allow electrical impulses traveling along the Sarcolemma to move deeper into the cell TRIAD Triplet of tubules; a T tubule sandwiched between two sacs of sarcoplasmic reticulum. Allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the sarcoplasmic reticulum


Myofilaments Breakdown :Myofilaments Breakdown Electron microscope show that myofibrils are made up of even smaller threadlike structures called myofilaments The myofilaments are composed largely of four varieties of contractile proteins: Actin Globular protein that form the bulk of the thin filament Myosin Makes up almost all the thick filament Myosin “heads” are chemically attracted to actin molecules Myosin “heads” are known as “CROSS BRIDGES” when attached to actin Tropomyosin Protein that blocks the active sites on the actin molecules Troponin Protein that holds tropomyosin molecules in place Actin and Myosin slide past each other during muscle activity to bring about shortening or contraction of the muscle cells The actual contractile units of muscle termed sarcomeres, extend from the middle of on I band to the middle of the next I band, along the length of the myofibrils.


Mechanism of Contraction :Mechanism of Contraction Excitation and Contraction: Figures 11-5 through 11-7; Table 11-1 Muscles fiber remains at rest until stimulated by a motor neuron Neuromuscular junction—motor neurons connect to the sarcolemma at the motor endplate (fig 11-5) Neuromuscular junction is a synapse where neurotransmitter molecules transmit signals Acetylcholine—is the neurotransmitter that is released into the synaptic cleft that diffuses across the gap, stimulates the receptors, and initiates an impulse in the sarcolemma Nerve impulse travels over the sarcolemma and inward along the T tubules, which triggers the release of calcium ions Calcium binds to troponin, causing the tropomyosin to shift and expose active sites on the actin


Sliding Filament TheoryFigure 11-8 :Sliding Filament TheoryFigure 11-8 When active sites on the actin are exposed, myosin heads bind to them Myosin heads bend, pulling the thin filaments past them Each head releases, binds to the next active site, and pulls again The entire myofibril shortens


Relaxation :Relaxation Immediately after the calcium ion (Ca++) are released, the sarcoplasmic reticulum begins actively pumping them back into the sacs The Ca++ ions are removed from the troponin molecules, shutting down the contractions


Energy Source for Contraction :Energy Source for Contraction Hydrolysis of ATP yields the energy required for muscular contraction Adenosine triphosphate (ATP) binds to the myosin head and then transfers its energy to the myosin head to perform the work of pulling the thin filament during contraction Muscle fibers continually re-synthesize ATP from the breakdown of creatine phosphate Catabolism by muscle fibers requires glucose and oxygen At rest, excess oxygen (O2) in the sarcoplasm is bound to myoglobin Red fibers—muscle fibers with high levels of myoglobin White fibers—muscle fibers with little myoglobin


Types of respiration for muscles :Types of respiration for muscles Aerobic respiration occurs when adequate O2 is available Anaerobic respiration occurs when low levels of O2 are available and results in the formation of lactic acid Skeletal muscle contraction produces waste heat that can be used to help maintain the set point body temperature (chills, shivering)


Function of Skeletal Muscle Organs :Function of Skeletal Muscle Organs Motor units Motor neuron plus the muscle fibers to which it attaches Some consist of only a few muscle fibers, others have many Generally, the smaller the number of fibers in a motor unit, the more precise the movements available; the larger the number of fibers in a motor unit, the more powerful a contraction is available Myography is the study of muscles. Twitch contraction (figure 11-12) Quick jerk of a muscle that is produced as a result of a single, brief threshold stimulus (generally only seen in experimental situations The twitch contraction has three phases Latent phase—nerve impulse travels to the sarcoplasmic reticulum to trigger release of Ca++ Contraction phase—Ca++ binds to troponin and sliding a filaments occurs Relaxation phase—sliding of filaments ceases


TYPES OF CONTRATIONS :TYPES OF CONTRATIONS Tetanus Multiple wave summation—multiple twitch waves are added together to sustain muscle tension for a longer time Incomplete tetanus—the stimulation is such that twitch waves fuse into a single peak (FIGURE 11-13 D) Muscle tone Tonic contraction—continual partial contraction of a muscle At any one time, a small number of muscle fibers within a muscle contract, producing a tightness or muscle tone Muscles with less tone than normal are flaccid Muscles with more tone than normal are spastic Muscle tone is maintained by negative feedback mechanisms


TYPES OF CONTRATION :TYPES OF CONTRATION Graded Strength principle Is skeletal muscles contract with varying degrees of strength at different times Factors that contribute to the phenomenon of graded strength (figure 11-17) Metabolic condition of individual fibers Number of muscle fibers contracting simultaneously; the greater the number of fibers contracting, the stronger the contraction Number of motor units recruited Intensity and frequency of stimulation (figure 11-14)


TYPES OF CONTRATIONS :TYPES OF CONTRATIONS Length-tendon relationship (figure 11-15) Maximal strength that a muscle can develop bears a direct relationship to the initial length of its fibers A shortened muscle’s sarcomeres are compressed, therefore the muscle cannot develop much tension An overstretched muscle cannot develop much tension because the thick myofilaments are too far from the thin myofilaments Strongest maximal contraction is possible only when the skeletal muscle has been stretched to its optimal length


TYPES OF CONTRACTIONS :TYPES OF CONTRACTIONS Stretch reflex (figure 11-16) (seen when you carry something) The load imposed on a muscle influences the strength of a skeletal contraction Stretch reflex—the body tries to maintain a constancy of muscle length in response to increased load Maintains a relatively constant length as load is increased up to a maximum sustainable level


ISOTONIC AND ISOMETRIC :ISOTONIC AND ISOMETRIC MOST BODY MOVEMENTS OCCUR AS A RESULT OF BOTH TYPES OF CONTRACTIONS Isotonic contraction (best way to exercise) (use a stretch band for example) CONTRACTION IN WHICH THE TONE OR TENSION WITHIN A MUSCLE REMAINS THE SAME AS THE LENGTH OF THE MUSCLE CHANGES CONCENTRIC MUSCLE SHORTENS AS IT CONTRACTS ECCENTRIC MUSCLE LENGTHENS WHILE CONTRACTING ISOTONIC LITERALLY MEANS “SAME TENSION” ALL OF THE ENERGY OF CONTRACTION IS USED TO PULL ON THIN MYOFILAMENTS AND THEREBY CHANGE THE LENGTH OF A FIBER’S SARCOMERES Isometric contraction (like lifting common weights in the gym) CONTRACTION IN WHICH MUSCLE LENGTH REMAINS THE SAME WHILE THE MUSCLE TENSION INCREASES ISOMETRIC LITERALLY MEANS “SAME LENGTH


CARDIAC MUSCLE :CARDIAC MUSCLE


FUNCTION OF CARDIAC MUSCLE TISSUE :FUNCTION OF CARDIAC MUSCLE TISSUE Only in the heart Also termed “striated involuntary muscle” Contracts rhythmically and continuously Looks like skeletal muscle BUT has specialized features related to its role Contains parallel myofibrils (fig 11-19) Strong electrically coupled junctions Syncytium—continuous, electrically coupled mass Can be continuous, contractile band around the heart chambers that conducts a single impulse across a continuous sarcolemma T tubules are larger and form dyads Sustain each impulse longer therefore not producing tetanus (figure 11-20) Does not run low on ATP and does not experience fatigue Are self-stimulating


SMOOTH MUSCLES :SMOOTH MUSCLES


Function of Smooth Muscles :Function of Smooth Muscles Composed of small, tapered cells with single nuclei (figure 11-21) NO T tubules Ca++ comes from outside the cell and binds to calmodulin instead of troponin No striations, because thick and thin myofilaments are arranged differently Two types of smooth muscles: Visceral muscle (single unit) Gap junctions join smooth muscle fibers into large, continuous sheets Forms muscular layer in the walls of hollow structures such as the digestive, urinary, respiratory and reproductive Exhibits autorhythmicity, producing peristalsis Multiunit Does not act as a single unit but is composed of many independent cell units Each fiber responds only to nervous input specifically


Lab Activity: Examining Skeletal Muscle Cell Anatomy :Lab Activity: Examining Skeletal Muscle Cell Anatomy Look at the 3-D model of skeletal muscle cell, note the relative shape and size of the cells. Identify the nuclei, myofibrils, and light and dark bands. Obtain forceps, two dissecting needles, slide and cover slip, and a dropper bottle of saline solution. With forceps, remove a very small piece of muscle from the chicken breast (or thigh). Place the tissue on clean microscope slide, and add a drop of the saline solution Pull the muscle fibers apart with the dissecting needles (tease them) until you have a fluffy looking mass of tissue. Cover the teased tissue with a coverslip, and observe under the high-power lens of a microscope. Look for the banding pattern. Regulate the light carefully to obtain the highest possible contrast. Now compare you observations with figure 1 on the next power point and with what can be seen with professionally prepared muscle tissue. Obtain a slide of skeletal muscle and view it under high power. Form you observations draw a small section of a muscle fiber in you journal. Label the nuclei, sarcolemma, and A and I bands.


Organization of Skeletal Muscle Cells into Muscles :Organization of Skeletal Muscle Cells into Muscles Muscle fibers are soft and fragile. Thus thousands of muscle fibers are bundled together with connective tissue to form the organs we refer to as skeletal muscle. Each fiber is enclosed in a tissue sheath called endomysium (inner most sheath) Several muscle fibers are wrapped by a collagenic membrane called perimysium (middle sheath) to form a bundle of fibers called a fascicle. A large number of fascicle are bound together by a coarser “overcoat” of dense connective tissue called an epimysium (out side sheath) which sheathes the entire muscle. These epimysia blend into the deep fascia (coarser sheets of dense connective tissue that bind muscles into functional groups) or into tendons or sheetlike aponeuroses (which attach muscles to each other or indirectly to bone)


Determining “insertion” or “origin” :Determining “insertion” or “origin” A muscle’s more moveable attachment is termed its insertion A muscle’s fixed or immovable attachment is known as its origin


Tendons :Tendons Perform several functions, two of the most important being to provide durability and to conserve space They are tough collagenic connective tissue They can span rough bony prominennces that would destroy the more delicate muscle tissues In addition to muscle fibers supporting and binding the muscle they provide strength to the muscle as a whole and provide a route for the entry and exit of nerves and blood vessels that feed the muscle Have synovial fluid surrounding them


Aging and muscles :Aging and muscles As we age the mass of the muscle fibers decreases and the amount of connective tissue increases; thus the skeletal muscles gradually become more stringier


Lab Activity: Observing the Structure of Skeletal Muscle Tissue :Lab Activity: Observing the Structure of Skeletal Muscle Tissue Obtain a slide showing a cross section of skeletal muscle tissue. Identify the muscle fibers, endomysium, perimysium, and spimysium. Use the power point diagram as a reference Draw a picture in your journal


Classification of Skeletal Muscles :Classification of Skeletal Muscles


Naming Skeletal Muscles :Naming Skeletal Muscles Muscles are named on the basis of the following criteria: Direction of muscle fibers Some are named in reference to some imaginary line, usually the midline of the body or the longitudinal axis of a limb bone Muscles with fibers running parallel to the imaginary line will have the term rectus (straight) in its name Example: rectus abdominis is the straight muscle of the abdomen. Likewise the terms transverse and oblique indicate that the muscle fibers run at right angles and obliquely to the imaginary line.


Slide 45:2. Relative size of the muscle Terms such as maximus (largest) minimus (smallest) longus (long) and brevis (short) Example gluteus maximus and gluteus minimus 3. Location of the muscle Some muscles are named for the bone with which they are associated with. Example: frontalis muscle…overlies the frontal bone of the skull 4. Number of origins when the terms biceps, triceps or quadriceps forms part of the muscles name you can generally assume that the muscle has two, three, or four orgins 5. Location of the muscle’s origin and insertion For example sternocleidomastoid muscle has its origin on the sternum (sterno) and clavicle (cleido), and inserts on the mastoid process of the temporal bone 6. Shape of the muscle For example, the deltoid muscle is roughly triangular, and the trapezius muscle resembles a trapezoid 7. Action of the Muscle For example all the adductor muscles of the anterior thigh bring about its adduction, and all the extensor muscles of the wrist extend the wrist


Types of Muscles :Types of Muscles Most often body movements are not a result of the contraction of a single muscle but instead reflect the coordinated action of several muscles acting together. Muscles that are primarily responsible for producing movement are called prime movers or agonists Muscles that oppose or reverse a movement are termed antagonists


Major Muscular Disorders :Major Muscular Disorders


Muscle Injuries :Muscle Injuries Muscle Injury Contusions Bruise to the muscle Strains overexertion Myalgia Muscle pain Overstretching or tearing of muscle fibers Sprain Area of the joint and a ligament is damaged Myositis Muscle inflammation Fibromyositis Charley horse involves the tendon and muscle


Muscle Infections :Muscle Infections Muscle Infections Caused by several bacteria, viruses, and parasites Producing local or widespread myositis Most common is trichinosis (found in soil and water) (common name is roundworm which is a nematode) Muscles pain and stiffness that accompany influenza is another example Poliomyelitis (polio) Once very common Viral infection of the nerves that control skeletal muscle Virtually eliminated in the U.S. but still in other countries


Muscular Dystrophy :Muscular Dystrophy Muscular Dystrophy Is a group of genetic diseases characterized by atrophy of skeletal muscles tissues Some forms can be deadly Common forms Duchenne muscular dystrophy (DMD) Meaning pseudohypertrophy (false muscle growth) because the atrophy of muscle is masked by excessive replacement of muscle by fat and fibrous tissue Characterized by mild leg muscle weakness that progresses rapidly to include the shoulder muscles. Appears at 3 yrs of age and severely affected within 5-10 years. By 21 most die from respiratory/cardiovascular failure Caused by a mutation on the X chromosome. Occurs primarily in boys because girls have two X’s The X gene involved in DMD normally codes for the protein dystrophin which forms strands in the muscle fiber and helps to hold the cytoskeleton to the sarcolemma. But normal dystrophin is missing in DMD


Myasthenia Gravis :Myasthenia Gravis Myasthenia Gravis Is a chronic disease characterized by muscle weakness especially the face and throat Begin with mild weakness and chronic muscle fatigue in the face then progress to wider muscle involvement When severe muscle weakness causes immobility in all four limbs a myasthenic crisis occurs A person is in danger of dying form respiratory failure because of weakness in the respiratory muscle Patients are give vital capacity test every hours to measure the extent of the crisis and if needed are put onto ventilators Is an autoimmune disease in which the immune system attacks muscle cells at the neuromuscular junction


Hernias :Hernias Hernias (protrusion of an abdominal organ) Pain and vomiting are usually experienced and emergency surgical intervention is required Normally the protrusion entails the small intestines through an opening in the abdominal wall Hernia is referred to as “reducible” when the protruding organ is manipulated back into the abdominal cavity, either naturally by lying down or by manual reduction through a surgical opening in the abdomen A strangulated hernia occurs when the mass is not reducible and blood flow is affected or stopped. Obstruction and gangrene can occur Is a weakness in the abdominal muscles Most common type is Inguinal Hernia Occurs when the hernia extends down the inguinal canal, often into the scrotum or labia Males more often than females Occurs at any age Females may experience a femoral hernia below the groin because of changes during pregnancy


Location of MusclesOf the 600 muscles, you will learn the 21 most common :Location of MusclesOf the 600 muscles, you will learn the 21 most common


Types of Levers I, II, III :Types of Levers I, II, III


Levers Type I, II, III. :Levers Type I, II, III.


Muscular Levers I, II, III. :Muscular Levers I, II, III. First picture is example of a lever III. (F,E,L) Middle picture is example of a lever I. (E, F, L) Foot picture is an example of a lever II. (F, L, E)


Secrets to Remembering Levers :Secrets to Remembering Levers Level I E, F, L Acronym “Every Flea Leaps on a dog” Level II F, L, E Acronym “FLEa” (know my dog has a FLEa) Level III F,E,L Acronym “FEeL” (I treat my dog for fleas to FEeL better) CAN YOU MAKE UP SOME OF YOUR OWN?


Facial/Neck Muscles :Facial/Neck Muscles Facial/Neck Masseter (for chewing food) Closes the jaw Sternocleidomastoid (for turning head) Flexes head Commonly termed the “prayer muscles” One muscle along causes head to rotate toward the opposite side Orbicularis oculi (for controlling eyes such as in winking) Closes eye Orbicularis oris (for controlling mouth such as in kissing) Draws lips together


Trunk and Back Muscles :Trunk and Back Muscles Trunk Rectus abdominis Aid in straining, defecation, forced expiration, childbirth External abdominal oblique Rotates trunk laterally Important postural function With muscles is lost in tone, a protruding abdomen and lordosis can develop Inguinal ligament (inguinal hernia) (separates abdominal cavity from pelvic cavity) Linea alba (center line of stomach) External/internal intercostals (between the ribs) (like the meat you eat on spareribs) Depresses (internal) or elevate ribs (external) Diaphragm (controls breathing) (separates thoracic cavity from abdominal cavity) Enlarges thorax causing inspiration This can also herniated and cause intestinal organs up into the thoracic and/or visa versa Back Erector spinae Group of muscles that extend the vertebral column and also flex the back laterally and rotate it a little


Pelvic Muscles :Pelvic Muscles Male/Female Levator ani Forms most of the pelvic floor Supports pelvic organs Urogenital triangle Ischiocavernosus (compresses base of penis or clitoris) Bulbospongiosus Male (constricts urethra and erects penis) Female (erects clitoris) Anal triangle (allows passage of anal canal) Sphincter externus ani Regulates defecation by closing anal canal


Upper Limbs Muscles :Upper Limbs Muscles Upper limbs Perctoralis minor and major (chest muscle) (pulls shoulder down and forward) Trapezius (the muscle above your collar bone and covers the shoulder blade) (rises and lowers shoulder) Serratus anterior (located near your underarms) Assist in pulling shoulder down and forward Deltoid (common place for inoculations) Abducts upper arm Triceps brachii (lateral aspect of upper arm) Extends lower arm Biceps brachii (medial aspect of arm, like “making a muscle to show off for to the girls) Flexes supinated forearm Brachioradialis (Tennis elbow) Supinates forearm and hand Flexor digitorum superficialis Flexes fingers Flexor digitorum produndus (moves the fingers) Flexes distal interphalangeal joints Extensor pollicis longus and brevis move the thumb


Lower Limbs Muscles :Lower Limbs Muscles Lower limbs Rectus femoris (attach to patella) major portion of you quads Flexes thigh Gluteus maximus (your butt) Extends thigh Iliotibial track (the muscle on lateral aspect of upper leg, very prominent in runners, football players, and gymnastics) Flexes thigh Biceps femoris (Hamstring) (rear, common injury in sports) (muscles in the back of your upper leg) Flexes leg Tibialis anterior (sheen splints) Flexes foot Gastrocnemius (calf) Extends foot Gracilis (common injury is termed “pulled groin muscle”) Adducts thigh and flexes and adducts lug Flexor hallucis brevis (moves the toes)


Muscles for the test :Muscles for the test