Anatomy and Physiology I Ch 8

Which structure binds to the active site of the thin filament to cause muscle contraction? Quiz

The head of the myosin

Two types of contractile proteins are myosin and actin. The first contractile protein is made up of blank 1 filaments and the second is made up of blank 2 filaments, respectively. LO2

1. Thick 2. Thin

Label the figure by matching the terms below to their corresponding boxes. LO2

Box A - neuromuscular junction Box B - Somatic motor neuron Box C - Spinal cord Box D - skeletal muscle fibers

A discrete bundle of muscle cells.

Fascicle

Cordlike extension of connective tissue beyond the muscle, serving to attach it to the bone.

Tendon

Which band is narrowed as the thin filaments slide inward for contraction and which bands remain unchanged LO3

1. 2. 3. 4. 5. 6. 7. 8.

Thin connective tissue enclosing each muscle cell.

Endomysium

Actin- or myosin-containing structure.

Myofibril

Which protein covers the active sites of the thin filaments, and therefore prevents muscle contaction? Quiz

Tropomyosin

Two types of regulatory proteins are Tropomyosin and blank 3. LO2

Troponin

Titin is a type of blank 4 protein, that holds the thick filament to both the blank 4, which is located on the sides of the sarcomere, and the blank 5, which is located in the middle of the sarcomere. LO2

4. Z line 5. M line

For each statement below, classify them as belonging to contractile, regulatory or structure proteins. LO2

Generate force during contraction - Contractile proteins Help switch contraction process on and off - Regulatory proteins Myosin and actin - Contractile proteins Keep thick and thin filaments in proper alignment - Structural protein Tropomyosin and troponin - Regulatory proteins Titin and dystrophin - Structural proteins

Aponeurosis: Quiz

Consists of collagen fibers

Which of the following is a main characteristic of a skeletal muscle fiber? Quiz

Incredibly long

True or false. LO3

Myosin are known as thick filaments while tropomyosin as thin filaments - False The myosin tail of each myosin molecule points toward the Z line in the center of the sarcomere. - False A thin filament contains actin, troponin, and tropomyosin. - True In a relaxed muscle, myosin is blocked from binding to actin because the strands of troponin cover the myosin-binding sites on actin. - False Myosin functions as a motor protein in all three types of muscle tissue. - True Troponin is a protein that consists of three globular subunits—one that binds to tropomyosin, one that binds to myosin, and one that has binding sites for calcium ions (Ca2+). - False Each myosin head has two binding sites: (1) an actin-binding site and (2) an ATP-binding site. - True A flexible hinge is located where the myosin heads join the myosin tail. - True The main component of the thin filament is the protein actin. - True To initiate muscle contraction, Ca2+ binds to tropomyosin. - False

The epimysium is a layer of dense irregular connective tissue that: Quiz

surrounds the entire skeletal muscle, separating the muscle from surrounding tissues and organs.

Which statement defines elasticity? Quiz

The ability of a muscle to rebound toward its original length after a contraction

Define each type of contraction below. LO4

When the length of a muscle increases during a contraction. - Eccentric Isotonic Contraction The tension generated is not enough to exceed the load, and the muscle does not change its length. - Isometric Contraction The tension generated is great enough to exceed the load and the muscle shortens, pulling on another structure (such as a tendon) to produce movement. - Concentric Isotonic Contraction

In what order are the various types of skeletal muscle fibers recruited when you sprint to make it to the bus stop? LO5

First - Slow Oxidative fibers Second - Fast Oxidative Glycolytic fibers Third - Fast Glycolytic fibers

A long, filamentous organelle found within muscle cells that has a banded appearance.

Myofilament

The epimysium, endomysium and perimysium come together at the end of a skeletal muscle to form a: Quiz

Tendon

Which of the following is a main characteristic of a skeletal muscle fiber? Quiz

Multinucleated

Connective tissue surrounding a fascicle. Lab

Perimysium

Plasma membrane of the muscle cell.

Sarcolemma

Contractile unit of a muscle. Lab

Sarcomere

Which is the smallest functional unit of a skeletal muscle? Quiz

Sarcomere

Connective tissue covering the entire muscle.

Epimysium

G) Another molecule of ATP binds to the ATP binding site on myosin allowing for myosin to detach from actin H) The energized myosin head then attaches to the myosin binding site on actin and a phosphate is released. This is referred to as the "crossbridge" I) Action potential travels along T-tubules J) The calcium ions then bind to troponin, which moves tropomyosin away from myosin binding sites on actin K) The myosin head pivots changing its position from 90 degrees to 45, pulling the thin filament past the thick filament towards the center of the sarcomere. This is referred to as the power stroke LO3

Step 7. J Step 8. C Step 9. H Step 10. K Step 11. G

Creatine phosphate is a molecule that can store energy in its phosphate bonds. In a resting muscle, excess blank 1 transfers its energy to creatine, producing ADP and blank 2. This acts as an energy reserve that can be used to quickly create blank 3 (more/less) ATP. When the muscle starts to contract and needs energy, creatine phosphate transfers its phosphate back to ADP to form ATP and blank 4. The enzyme blank 5 catalyzes the transfer of one of the high-energy phosphate groups from ATP to creatine. Because the formation of ATP from creatine phosphate occurs blank 6, creatine phosphate is the blank 7 source of energy when muscle contraction begins. LO3

1. ATP 2. Creatine phosphate 3. More 4. Creatine 5. Creatine Kinase (CK) 6. Very Rapidly 7. First

If sufficient oxygen is present, the pyruvic acid formed by glycolysis enters the mitochondria, where it undergoes blank 1 respiration, a series of oxygen-requiring reactions that produce blank 2. Although aerobic respiration is blank 3 (slower/faster) than anaerobic glycolysis, it yields much blank 4 (less/more) ATP. Each molecule of glucose catabolized under aerobic conditions yields about 36 molecules of ATP. Muscle tissue has two sources of oxygen: (1) oxygen that diffuses into muscle fibers from the blank 5 and (2) oxygen released by blank 6 within muscle fibers. Both myoglobin (found only in blank 7) and hemoglobin (found only in blank 8) are oxygen-binding proteins. They bind oxygen when it is plentiful and release oxygen when it is scarce. LO3

1. Aerobic 2. ATP, carbon dioxide, water, and heat 3. Slower 4. More 5. Blood 6. Myoglobin 7. Muscle cells 8. Erythrocytes

When muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, blank 1 is catabolized to generate blank 2 . Glucose passes from the blank 3 into contracting muscle fibers and it is also produced by the breakdown of blank 4 within muscle fibers. Then a series of reactions known as glycolysis quickly breaks down each glucose molecule into two molecules of blank 5. Glycolysis occurs in the cytosol and produces a net blank 6 (gain/loss) of two molecules of ATP. Because glycolysis does not require blank 7, it can occur whether oxygen is present (blank 8 conditions) or absent (blank 9 conditions). LO3

1. Glucose 2. ATP 3. Blood 4. Glycogen 5. Pyruvic acid 6. Gain 7. Oxygen 8. Aerobic 9. Anaerobic

A blank 1 is the brief contraction of a group of muscle fibers within a muscle in response to a blank 2 action potential. The record of a muscle contraction is called a blank 3 . Twitches of skeletal muscle fibers last anywhere from blank 4 msec. The three sequential phases of a twitch are: blank 5 periods. LO4

1. Twitch 2. Single 3. Myogram 4. A few to 100 5. Latent, contraction, and relaxation

During heavy exercise not enough oxygen is available to skeletal muscle fibers hence the pyruvic acid generated from glycolysis is converted to blank 10. When produced at a rapid rate, this acid can accumulate in active skeletal muscle fibers and in the bloodstream. This acid buildup is thought to be responsible for muscle blank 11 that is felt during strenuous exercise. LO3

10. Lactic acid 11. Soreness

Why is tension maximal at a sarcomere length of 2.2 μm? LO4

A muscle fiber develops its greatest tension when: There is an optimal zone of overlap between thick and thin filaments.

Match the definition of each twitch phase below.

Ca2+ is actively transported back into the SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases. - Relaxation Period Brief delay that occurs between application of the stimulus and the beginning of contraction. During this time, the events of excitation-contraction coupling occur. In addition, Ca2+ ions are released from the endoplasmic reticulum. - Latent Period Ca2+ binds to troponin, myosin-binding sites on actin are exposed, and myosin cross bridges form. Peak tension also develops in the muscle fiber. - Contraction Period

Muscle has four special properties that enable it to function and contribute to homeostasis. Match their definitions below. LO1

Electrical Excitability - Ability to respond to stimuli (neurotransmitter or hormones) by producing action potentials that trigger movement. (definition 3) Contractibility - Ability of muscle fibers to contract forcefully when adequately stimulated. (definition 2) Elasticity - Ability of muscle to return to its original length and shape after contraction or extension. (definition 4) Extensibility - Ability of muscle to stretch without being damaged. (definition 1)

A muscle cell.

Fiber

Match the terms to their definition/function. 1) Formed by transverse tubules and two terminal cisternae. 2) Plasma membrane of a muscle fiber. 3) Contractile element of the skeletal muscle fiber; containing thick and thin filaments. 4) Red, oxygen binding protein that is only found in the muscle; stores oxygen until it is needed by mitochondria for ATP. 5) Surrounded by the sarcolemma; the cytoplasm of the muscle fiber. 6) Serves as storage form of glucose; can be broken down and used to synthesize ATP. 7) Storage center for calcium in relaxed muscle. 8) Invaginations of the sarcolemma; filled with extracellular fluid. 9) Repeating units of a myofibril.LO3

Number 1 - Triad Number 2 - Sarcolema Number 3 - Myofibril Number 4 - Myoglobin Number 5 - Sarcoplasm Number 6 - Glycogen Number 7 - Sarcoplasmic reticulum Number 8 - T tubules Number 9 - Sarcomere

Fill in the blank below for each type of fiber.

SO Fibers - Fiber Diameter: Smallest - Myoglobin content: Large amount - Mitochondria: Many - Capillaries: Many - Color: Red - Capacity for generating ATP and method used: High capacity, by aerobic respiration - Rate of ATP hydrolysis by myosin ATPase: Fast - Contraction velocity: Slow - Fatigue resistance: High - Order of recruitment: First - Location where fibers are abundant: Postural muscles such as those of the neck - Primary functions of fibers: maintaining posture and aerobic endurance activites FOG fibers - Fiber Diameter: Intermediate - Myoglobin content: Large Amount - Mitochondria: Many - Capillaries: Many - Color: Red-pink - Capacity for generating ATP and method used: Intermediate capacity, by both aerobic respiration and anaerobic respiration - Rate of ATP hydrolysis by myosin ATPase: Fast - Contraction velocity: Fast - Fatigue resistance: Intermediate - Order of recruitment: Second - Location where fibers are abundant: Lower limb muscles - Primary functions of fibers: Walking, sprinting FG Fibers - Fiber Diameter: Largest - Myoglobin content: Small amount - Mitochondria: Few - Capillaries: Few - Color: White (pale) - Capacity for generating ATP and method used: Low capacity, by anaerobic glycolysis - Rate of ATP hydrolysis by myosin ATPase: Fast - Contraction velocity: Fast - Fatigue resistance: Low - Order of recruitment: Third - Location where fibers are abundant: Upper limb muscles - Primary functions of Rapid, intense movements of short duration

Choose the best answer for each muscle type. LO1

Skeletal muscle - Multi nucleated - Primarily involved in voluntary movements and in some cases such as in the case of the diaphragm in involuntary movement. - Has striations with several nuclei on the surface Found attach to bones throughout the skeletal body Smooth muscle - Uni nucleated - Primary controls involuntary movements throughout the body - No striations - Found attached to hollow internal structures, such as blood vessels, airways, stomach, intestines, uterus, and glands Cardiac muscle - 1-2 nuclei - Responsible for the involuntary movement of the heart which enabled the pumping of blood through the circulatory system - Presence of striations and intercalated discs - Found in the heart

Classify as true or false each of the sentences below.

Slow oxidative fibers are smallest in diameter and are the least powerful type of muscle fibers. - True Fast oxidative- glycolytic fibers are fast-twitch fibers adapted for intense movements of short duration like weight lifting or throwing a ball. - True Skeletal muscle fibers that have a high myoglobin content are termed red muscle fibers. - True Slow oxidative fibers generate ATP mainly by aerobic respiration. - True Fast glycolytic fibers have low myoglobin content, few blood capillaries, few mitochondria, and appear white in color. - True Fast oxidative-glycolytic fibers have a high intracellular glycogen level, which allows them to generate ATP by aerobic respiration. - True A fiber is categorized as slow or fast depending on how rapidly the ATPase in its myosin heads hydrolyze ATP. - True Fast glycolytic fibers are intermediate in diameter and have a high resistance to fatigue. - False

A) ACH that is stored in the synaptic vesicle of the synaptic end bulb is released and diffused across the synaptic cleft B) Entry of Na+ ions causes depolarization of sarcolemma. C) Now that the binding sites are free, ATP is hydrolyzed into ADP and a phosphate. This energizes the myosin head which then assumes the "cocked" position D) Action potential occurs in the somatic motor neuron E) At the onset of muscle fiber contraction, the sarcoplasmic reticulum releases calcium ions into the sarcoplasm F) ACH binds to specific receptors on the motor end plate

Step 1. D Step 2. A Step 3. F Step 4. B Step 5. I Step 6. E

The endomysium is a layer of connective tissue that: Quiz

Surrounds each skeletal muscle fiber and therefore binds each muscle fiver to its neighbor, and supports capillaries that supply individual fibers.

Identify which of the four key muscle functions belong to each statement. LO1

Thermogenesis - Used to maintain body temperature. - Body shivers when you are cold. Production of body movement - Localized movements such as grasping a pencil, keyboarding, or raising your hand. - Total body movements such as walking and running. - Rely on the integrated functioning of skeletal muscles, bones, and joints. Stabilizing body positions - Postural muscles contract continuously when you are awake. - Help maintain body positions, such as standing or sitting. Storing and moving substance - Sustained contraction of a ring-like smooth muscle called sphincter. - Propelling food down the digestive tract.