Anatomy Chapter 9 - Muscular System

Structure of a Skeletal Muscle: Connective Tissue Coverings: ____ covers the entire muscle and separates it from other muscles. May form ____ which bind muscle to bone. May form _____ which may attach to the coverings of adjacent muscles. _____ - think connective tissue covering of muscles, under fascia _______ - extensions from epimysium to divide it into sections = _______ = bundle of muscle fibers _______ surrounds each muscle fiber of a fasicle.

Fascia; Tendons; Aponeuroses Epimysiumm; Perimysium; fascicle Endomysium

Organs composed of specialized cells that use chemical energy store in nutrients to exert a pulling force on structures to which they are attached.

Muscles

Muscular Responses: Types of CONtractions: 1. An _____ occurs when the muscle contracts and shortens in length. Because of shortening, it is called _____. A lengthening contraction is called _____ - the force a muscle generates is less than that required to move or lift an object - such as laying down a book on a table. 2. in _____, the tension within the muscles increases, but the muscle does not change in length. These occur continuously in postural muscles that stabilize skeletal parts and hold the body upright. Most _____ involve both of these contractions.

1. Isotonic contraction; concentric; eccentric; 2. Isometric contractions; body actions

Cardiac Muscle COntraction: 1. Cardiac muscle fibers contract ___ than skeletal muscles. 2. Impulses travel _____ from cell to cell because of the _____ of ions through intercalated disks. 3. The whole structure, ____ contracts as a unit - in all or non fashion. 4. It is ____ and rhythmic. 5. _____ period is longer than skeletal and lasts until the contraction ends - therefore sustained or tetanic contractions do not occur in cardiac muscle fibers.

1. longer 2. rapidly; rapid diffusion 3. syncytium 4. self-exciting 5. refractory period

Smooth Muscle Contraction: Resembles skeletal muscle: 1. reactions of _____. 2. Triggered by _____. 3. Releases _____. 4. Uses energy from _____. Differences from skeletal muscle: 1. Lack _____ - instead use a protein called ____, which binds to calcium ions, thus activated the actin-myosin contraction mechanism. 2. Much of calcium diffuses into the cell from ______. 3. _____ and _____ affect smooth muscle. Each stimulates contractions in some muscles and inhibits contractions in other muscles. 4. ____ can affect smooth muscle contractions. 5. ____ of smooth muscle can trigger contractions. 6. ______ to contraction and ____ to relax than skeletal muscle. 7. Can forcefully contract ____ with same amount of ATP> 8. Can change ______ without changing _____.

1. myosin and actin; 2. membrane impulses 3. calcium ions 4. ATP; 1. troponin; calmodulin; 2. extracellular fluid; 3. acetylcholin and norepinephrine; 4. Hormones; 5. Stretching 6. Slower; slower; 7. Longer; 8. length, tautness

Skeletal Muscle Contraction: Relaxation: When nerve impulses cease, two events relax the muscle fiber: 1. The ACh remaining in the synaptic cleft is _______ - this action prevents a single nerve impulse from _______. 2. The ______ quickly moves calcium ions back into the sarcoplasmic reticulum. Cross-bridge linkages ______, and tropomyosin rolls back into its groove, preventing any ______. Skeletal muscles partially contract a few hours after death in a condition called _____ which may last up to 72 hours. Results from an increase in ______ to calcium ions, which promotes cross-bridge formation. Without ATP to break the linkage, the muscle ______ until the proteins begin to decompose.

1. rapidly decomposed by an enzyme called acetylcholinesterase; continuously stimulating a muscle fiber; 2. calcium pump (requires ATP); break; preventing cross-bridge attachment; Rigor mortis; membrane permeability; stays contracted;

Skeletal Muscle Contraction: Energy Source for Contraction: _____ is the energy used to power the interaction between actin and myosin during a contraction. A muscle fiber only has enough ATP to contract briefly - so when a fiber is active, ATP ______. _____ supplies the initial source of energy to regenerate ATP. It contains a high energy _____ bond. It is 4-6 times more abundant in muscle fibers than ATP. It stores excess energy released from mitochondria - creating ______ promotes the synthesis of creatine phosphate in the mitochondria, whenever sufficient ATP is present. The energy from creatine phosphate is transferred very quickly to ____ molecules converting them back to _____ - but this action is usually not sufficient to support maximal muscle contraction for more than _______. The muscle fibers must then depend upon ______ as a source of energy for synthesizing ATP. A muscle stores glucose as ______.

ATP; must be regenerated; Creatine Phosphate; Phosphate; Phosphokinase; ADP; ATP; 10 seconds during an intense contraction; Cellular respiration of glucose; GLycogen

Muscular Response: A muscular response where a muscle fiber that is exposed to a stimulus of a threshold strength or above will respond with a complete twitch. Increasing the strength of stimulus does not affect the ______.

All-or-None Response; strength of contraction

Found only in the heart. Striated cells joined end to end, forming fibers that are interconnected in branching, three-dimensional networks. Single nucleus in each cell and actin and myosin are similar to skeletal muscle. Well-developed sarcoplamsmic reticulum, a system of transverse tubules, and many mitochondria. Cisternae are less developed and store less calcium than skeletal fibers. Transverse tubules are larger, and release calcium ions into the sarcoplasm in response to a single muscle impulse. Intercalated disks connect cells to each other - transmit the force of contraction from cell to cell - allow ions to diffuse between cells.

Cardiac Muscle Fibers

Structure of a Skeletal Muscle: Continuing Skeletal muscle fibers: Each myosin molecule consists of two protein strands with globular parts called _______. Actin filaments consists of ______ - they are globular, and have a binding site to which the cross-bridges of myosin can attach. 2 proteins ______ and ____ are associated with actin filaments. ______ - molecules are rod-shaped and occupy the longitudinal groove of the actin helix. Each tropomyosin molecules is held in place by a troponin molecule, forming a ______. _____ is a network of membranous channels surrounding each myofibril and running parallel to it. Corresponds to smooth ER of other cells. _____ are membranous channels extending into the sarcoplasm as invaginations continuous with the sarcolemma, thus contain extracellular fluid. Each one lies between 2 enlarged portions of the sarcoplasmic reticulum called _____ and these structures form a ______.

Cross-bridge; double strands of actin twisted into a helix; Troponin and tropomyosin; tropomyosin; tropomyosin-troponin complex: sarcoplasmic reticulum; transverse tubules; cisternae; triad

Skeletal Muscle Actions: Body Movement: Bones and muscles interact as simple mechanical devices called ____. It has 4 basic components: List the 4. Ex: a third class lever - sequence of resistance-force pivot Origin and INsertion: The immovable end of the muscle is the ____. The moveable end of the muscle is the _____. When a muscle contracts the ___ moves toward the _____. Interaction of Skeletal Muscles: Skeletal muscles almost always function in ______. The muscle primarily responsible for a movement is the ______. A muscle that contracts and assist the prime mover are _____. Muscles that can resists a prime mover's action and cause movement in the opposite direction are ______.

Levers; 1. Rigid bar/rod 2. A pivot or fulcrum on which the bar turns 3. An object that is moved against resistance 4. A force that supplies energy for the movement of the bar. Origin; insertion; insertion; origin; groups; prime mover; synergists; antagonists

Muscular Responses: Recording a Muscle Contraction: A muscle is removed from an animal and stimulated electrically - the pattern of the muscle's activities is called a _____. A single stimulus of threshold strength activates some of the motor units, the muscle will contract and relax in a _____. There is a ____ period between the time of stimulus and time of contraction (0.01 second in a frog, shorter in human). ____ - when the muscle pulls at its attachments. _____ - when the muscle relaxes to its former length. _______ is a brief moment after an initial stimulus when the muscle fibers are unresponsive to a second stimulus.

Myogram; twitch contraction; latent; period of contraction; period of relaxation; refractor period;

Major Skeletal Muscles: ______ - a muscle of large size (major) located in the chest region (pectoral) ____ - shaped like a delta or triangle _____ - extends the digits (fingers or toes) _____ - a muscle with 2 heads, located in the brachium ______ - attached to the sternum, clavicle and mastoid process _____ - located near the outside with fibers that run obliquely or in a slanting direction.

Pectoralis major; deltoid; extensor digitorum; biceps brachii; sternocleidomastoid; external oblique

Skeletal Muscle Contraction: Cross-bridge cycling: Sarcomeres ____ due to the cross-bridges pulling on the thin filaments. The _____ attaches to an actin binding site and bends slightly, doing what? The head releases the actin, combines with another binding site further down the actin filament and ______. Myosin cross-bridges contain the enzyme _____ which catalyses the breakdown of ATP to ADP and phosphate, thus releasing energy providing the force for muscle contraction. Breakdown of ATP puts the myosin cross bridge ________, which can then attach to actin, causing _______. When another ATP binds, the cross-bridge is _______, then the ATP breaks down to return to the _______. As long as ATP is present and nerve impulses cause ACh release, the cross bridge _______.

Shorten; myosin cross-bridge; pulling on the actin filament; pulls again; ATPase; ina cocked position; shortening of the sarcomere; is released from the actin binding site; returns to cocked position; cycle may repeat over and over.

Structure of a Skeletal Muscle: _____ - single cell of a muscle, thin elongated cylinder with rounded ends. _____ - is the muscle cell membrane. _____ - is the cytoplasm of the muscle celll; lots of mitochondria and nuclei. _____ - Abundant, parallel, threadlike fibers within the sarcoplasm. _____ - thick protein filaments. _____ - thin protein filaments. What do these filaments produce? Striations form a repeating pattern of units called _____ - the myofibrils may be though of as a sarcomeres joined end to end. The Striation pattern has two main parts: 1. _____ - are composed of thin actin filaments help by direct attachments to structures called Z lines (appear at center of the I bands) 2. _____ - are composed of thick myosin filaments overlapping the thin actin filaments. Within this band is a slightly lighter central region, _____, consisting only of thick filaments. The _____ consists of proteins that help hold the thick filaments in place. The myosin filaments are held to the Z line by a large protein called ______.

Skeletal muscle fibers; sarcolemma; sarcoplasm; Myofibrils; Myosin; Actin; Produce the alternating light and dark bands of skeletal muscles called striated muscles. sarcomeres; 1. The I band (light bands); 2. The A bands (dark bands); H zone; M line; Titin

What muscle is this? Fibers are shorter than skeletal muscle. Have a single, cnetrally located nucleus. Are elongated with tapering ends. Actin and myosin filaments extend the entire length of cells. The protein filaments are thinner and more randomly organized than skeletal muscle proteins. They lack striations, lack transverse tubules, and their sarcoplasmic reticula are not well developed. In ______, the muscle fibers are less well organized and function as separate units. Found in ________ and ______. In ______, the cells are composed into sheets of cells held in close contact by gap junctions. The fibers respond as a single unit. FOund in _____. Usually 2 thicknesses. When 1 fiber is stimulated, the impulse may excite adjacent fibers, that in turn excite others. Some cells display ____ - pattern of spontaneous repeated contractions. Transmission from cell to cell and rhythmicity are responsible for _____.

Smooth muscle fibers; Multiunit Smooth muscle; irises of eyes, walls of blood vessels; Visceral smooth muscle; in walls of hollow organs 0 uterus, stomach, intstines, urinary bladder rhythmicity; peristalsis;

Muscular Response: A muscular response when a muscle fiber is exposed to a series of stimuli of increasing frequency it reached a point when it can't completely relax before the next stimulus arrives - the individual twitches begin to combine and the muscle contraction becomes sustained. In this ______, the force of individual twitches combines by a process of summation. WHen the resulting forceful, sustained contraction lacks even partial relaxation, it is called a ______.

Summation; sustained contraction; tetanic contraction

Muscular Responses: When an isolated muscle fiber is exposed to a series of stimuli of increasing strength, the fiber remains unresponsive until a certain stimulation is applied. THis minimal strength required to cause contraction is the ______

Threshold Stimulus

Skeletal Muscle Contraction: Excitation Contraction Coupling: Because of calcium pumps in the sarcoplasmic reticulum membrane, there is ________. In response to a muscle impulse, the membranes of the cisternae ________. At rest, the tropmyosin-troponin complexes block ________. As the calcium ion concentration increases the calcium ions _______ - this movement exposes the binding sites of the actin filaments, allow _____ to form between myosin cross bridges and actin.

a high concentration of calcium in the SR; become more permeable to calcium ions and the calcium ions diffuse out of the cisternae into the cytosol of the muscle fiber; the binding sites of the actin molecules and prevent the formation of linkages with myosin cross-bridges; bind to troponin, changing its hape and altering the position of tropomyosin; linkages

Muscular Responses: Fast and Slow Muscle Fibers: Muscle Fibers vary in ____ and ______. 3 combinations: 1. ______ - always oxidative and are resistant to fatigue. Often called _____ because they contain the red, oxygen storing pigment myoglobin - long muscles of the back. Well supplied with blood, contain many mitochondria, high respiratory capacity - can generate ATP enough to keep up with ATP breakdown - contract for long periods without fatiguing. 2. _________ - contain less myoglobin. Often called _____ because contain less myoglobin. Poor blood supply, found in hand muscles, muscles that move eye. Fewer mitochondria - reduced respiratory capacity. More extensive sarcoplasmic reticulum to store and reabsorb calcium ions. ATPase is faster than red fibers. Can contract rapidly, tend to fatigue as lactic acid accumulates and as the ATP and biochemicals regenerate ATP are depleted. 3. _______ -Have fast-twitch speed with a substaintial oxidative capacity more like red fibers. Often called _____.

contraction speed and whether they produce ATP glycolytically or oxidatively; 1. Slow twitch (type 1) fibers; 2. Fast-twitch glycolytic fibers (type IIa) 3. Fast-twtich fatigue-resistant fibers (type IIb)

Skeletal Muscle Contraction: Oxygen Supply and Cellular Respiration: Glycolysis occurs in the _____, is anaerobic and only partially breaks down energy-supplying glucose releasing only 2 ATP molcules. Further breakdown occurs _____ in the mitochondria releasing _____ ATP. Blood carries oxygen within _____ loosely bound to hemoglobin to the body cells. including muscle cells. Hemoglobin is the pigment that gives blood a ____ color. ____ is a pigment synthesized in the muscle cells, giving muscles a reddish brown color. How does this compare to hemoglobin?

cytoplasm; aerobically; 32-34; RBC; Red; Myoglobin; It has a greater attraction for oxygen and can temporarily store oxygen in muscle tissue, which reduces a muscle's requirement for a continuous blood supply during contraction.

Skeletal Muscle Contraction: The Sliding Filament Theory of Muscle Contraction: When sacromeres shorten the thick and thin filaments _______ - they ______ one another, with the actin filaments moving _____ the center of the sarcomere from both ends.

do not change length; slide past; toward

Muscular Response: Recruitment of Motor Units: The number of muscle fibers in a motor unit varies considerably. The fewer muscle fibers in the motor unit, the ______. Motor units of the muscles that move the eyes may contain less than _____ fibers per motor unit and therefore can produce very slight movements. Motor units of the large back muscles may contain ______ muscle fibers, producing movements that are less gradual than those of the eye. All the muscle fibers in a motor unit are stimulated _____ - responding in an all or none manner. A whole muscle is composed of _____, controlled by different _____, some of which are more easily stimulated than others. As the intensity of stimulation increases, more motor units are activated, this is called _________.

more precise the movements that can be produced; 10; a hundred or more; at the same time; motor units; motor neurons; Multiple motor unit summation or recruitment

Skeletal Muscle Contraction: Neuromuscular Junction: Each skeletal muscle fiber is connected to a ____ - normally a skeletal muscle fiber contracts only when stimulated by this. The axon of the motor neuron and muscle fiber meet at a _______. A ____ is formed by the skeletal muscle fiber sarcolemma. Motor neuron axons are densely branched, therefore _______. A motor neuron and the muscle fibers it controls forms a _____. A _____ separates the membranes of the motor neuron and muscle fiber. The distal end of the motor neuron axon is rich in mitochondria and contains many synaptic cells that sore _______>

motor neuron; neuromuscular junction; motor end plate; therefore one motor neuron may connect to many muscle fibers; motor unit; Synaptic cleft; Neurotransmitters;

Muscular Responses: Sustained Contractions: Contractions of the whole muscle are ____, rather than irregular or jerky because of a mechanism within the spinal cord that ______ in different sets of motor units at different moments. Partial ____ occur frequently in skeletal muscles - in many cases, only a portion of the muscle. A certain amount of sustained contractions is occurring in the fibers of a muscle, even when it appears to be resting. This is called ______, it is responsible for ______.

smooth; stimulates contractions; tetanic contractions; muscle tone; maintaining posture;

Skeletal Muscle Contraction: Stimulus for Contraction: When a nerve impulse reached the end of a motor neuron, ______ in the axon terminal release a neurotransmitter, ______, into the _____. What does the ACh do after this? The response is a _____, an electrical impulse very much like a nerve impulse. The impulse travels ______, into the transverse tubules, into the sarcoplasm, and ultimately to the sarcoplasmic reticulum and cisternae.

synaptic vesicles; acetrlcholin (ACh); synaptic cleft; The ACh diffuses across the cleft and combines with ACh receptors on the motor endplate, and stimulates the muscle fiber. Muscle impulse; In all directions along and around the muscle cell.