BIO 254 Tested Questions with Correct Answers (Guaranteed A).

BIO 254 Tested Questions with Correct Answers (Guaranteed A). Skeletal muscle - Attached to bones of skeleton - Voluntary Cardiac muscle - Makes up most of the wall of the heart - Involuntary - Responsible for pumping action of the heart Smooth muscle - Found in walls of internal organs - Involuntary Skeletal muscle structure - Skeletal muscle tissue - Nervous tissue - Blood - Connective tissues Connective tissue coverings over skeletal muscles: fascia Thin covering of connective tissue around a muscle Connective tissue coverings over skeletal muscles: tendon Cord-like mass of connective tissue that connects muscle to a bone Connective tissue coverings over skeletal muscles: aponeurosis Sheet-like mass of connective tissue that connects a muscle to bone, skin, or another muscle Connective tissue in and closely surrounding a muscle: epimysium - Surrounds whole muscle - Lies beneath fascia Connective tissue in and closely surrounding a muscle: perimysium Surrounds fascicles within a muscle Connective tissue in and closely surrounding a muscle: endomysium Surrounds muscle fibers within a fascicle Sarcolemma Cell membrane Sarcoplasm Cytoplasm Skeletal muscle fiber - Cell - Multinucleated - Many myofibrils - Has SR & TT Myofibril - Long parallel structures that run down fiber - Consists of thin actin & thick myosin filaments - Made of sarcomeres Sarcomere Connect end-to-end to make up a myofibril Sarcoplasmic reticulum (SR) - Endoplasmic reticulum of muscle fiber - Stores Ca+ Transverse tubule (TT) Relays electrical impulses to SR Triad Unit consisting of 1 TT and 2 SR cisternae Skeletal muscle fiber structure - Myofibrils - Striation pattern made by arrangement of myofilaments in myofibrils Sarcomere structure - I band - A band - H zone - Z line (disc) - M line I band - Light - Thin actin filaments A band - Dark - Thick myosin filaments H zone - Center of A band - Thick myosin filaments Z line (disc) - Sarcomere boundary - Center of I band - Anchors filaments in place M line - Center of sarcomere and A band - Anchors thick filaments Thick filaments - Myosin - Heads form cross-bridges with thin filaments Thin filaments - Actin - Troponin and tropomyosin prevent cross-bridge formation when muscle is not contracting Skeletal muscle contraction - Results from movement in myofibrils in which actin and myosin filaments slide past each other shortening sarcomeres - Muscle fibers shortens and pulls on attachment points Neuromuscular junction (NMJ) - Type of synapse - Site where axon of motor neuron and skeletal muscle fiber interact - Skeletal muscle fibers contract only when stimulated by a motor neuron Part of NMJ: motor neuron Neuron that controls skeletal muscle fiber Part of NMJ: motor end plate Specialized folded portion of skeletal muscle fiber where fiber binds to neurotransmitter Part of NMJ: synaptic cleft Space between neuron and muscle fiber across which neurotransmitter travels Part of NMJ: synaptic vesicles Membrane-bound sacs containing neurotransmitters Part of NMJ: neurotransmitters Chemicals released by motor neuron to deliver message to muscle fiber Stimulus for contraction - Acetylcholine (ACh) is neurotransmitter - Nerve impulse causes release of ACh from synaptic vesicles - ACh binds to ACh receptors on motor end plate - ACh causes changes in membrane permeability to Na+ and K+ - Impulse causes release of Ca+ ions from SR Myasthenia Gravis (MG) - Autoimmune disorder - Antibodies attack ACh receptors on motor end plates - Person may have only 1/3 normal number of ACh receptors - Leads to widespread muscle weakness and muscle fatigue Tx of myasthenia gravis (MG) - Drugs that inhibit acetylcholinesterase - Immunosuppressant drugs - Administering antibodies that inactivate harmful antibodies - Plasma exchange Muscular dystrophy - Deficiency or abnormality/mutation in scarce muscle protein called dystrophin - Dystrophin binds to internal side of muscle cell membranes, and holds them together during contraction - In absence of normal dystrophin, cells lose normal structure and die Clostridium botulinum - Anaerobic bacteria that produces a toxin that causes food poisoning - Grows in food that is not properly preserved - Causes digestive, muscular, respiratory symptoms - Used in small does as Botox to smooth wrinkles, treat migraines Tx of clostridium botulinum Antitoxin Excitation-contraction coupling Connection between muscle fiber stimulation and muscle contraction Excitation-contraction coupling during relaxation - Ca+ stored in SR - Troponin-tropomyosin complexes cover binding sites on actin filaments Excitation-contraction coupling during stimulation - Impulses cause SR to release Ca+ into sarcoplasm - Ca+ binds to troponin to change its shape - Each tropomyosin is held in place by a troponin molecule; change in shape of troponin alters the position of tropomyosin - Binding sites on actin are now exposed - Myosin heads bind to actin forming cross-bridges Sliding filament model of contraction - When sarcomeres shorten, thick and thin filaments slide past each other - H zones and I bands narrow - Z lines move closer together - Thin and thick filaments do not change length - Overlap between filaments increases Cross-bridge cycling - Myosin head attaches to actin binding site forming cross-bridge - Myosin cross-bridge pulls thin filament toward center of sarcomere - ADP and P are released from myosin - New ATP binds to myosin - Linkage between actin and myosin cross-bridge breaks - ATP splits - Myosin cross-bridge goes back to original position ready to bind to another binding site on actin Muscle fiber relaxation - Acetylcholinesterase rapidly decomposes ACh remaining in the synapse - Muscle impulse stops when ACh is decomposed - Stimulus to sarcolemma and muscle fiber membrane ceases - Ca+ pump moves Ca+ back into the SR - Troponin-tropomyosin complex again covers binding sites on actin - Myosin and actin binding are now prevented - Muscle fiber relaxes Energy sources for contraction - ATP reserves - Creatine phosphate - Cellular respiration Energy source for contraction: ATP reserves - 1st source - Muscle cells store only a small amount Energy source for contraction: creatine phosphate Initial source of energy to regenerate ATP from ADP and P Energy source for contraction: cellular respiration - Must be used to fuel longer periods of muscle contraction - Breaks down glucose to produce ATP - Glucose stored as glycogen in muscle cells Phase of cellular respiration: anaerobic - Glycolysis - Occurs in cytoplasm - Produces little ATP Phase of cellular respiration: aerobic - Citric acid cycle and electron transport system - Occurs in mitochondria - Produces most ATP - Myoglobin stores extra O2 in muscles Systems that supply enough O2 to support aerobic respiration during rest or moderate exercise - Respiratory - CV Anaerobic (lactic acid) threshold - Shift in metabolism from aerobic to anaerobic during strenuous muscle activity - Lactic acid is produced O2 debt - Most of O2 in strenuous exercise is used to produce ATP for muscle contraction and not for converting lactic acid to glucose - Muscles may be left with O2 debt after strenuous exercise - This is amt of O2 needed by liver cells to convert accumulated lactic acid to glucose and to restore muscle ATP and creatine phosphate concentrations Muscle fatigue - Inability to contract muscle Common causes: - Decreased blood flow - Ion imbalances across the sarcolemma - Loss of desire to continue exercise - Accumulation of lactic acid (controversial) Muscle cramp - Sustained involuntary muscle contraction - May be caused by changes in electrolyte concentration in extracellular fluids in the area Heat production - By-product of cellular respiration in active cells - Muscle cells are a major source - More than half of the energy released in cellular respiration becomes this product and less than half is transferred to ATP - Blood transports throughout the body core Muscular responses - Contraction can be observed by removing a single skeletal muscle fiber and connecting it to a device that senses and records changes in the overall length of the muscle fiber - Electrical stimulator promotes the contractions Motor unit - Consists of motor neuron plus all of the muscle fibers it controls - Whole muscle consists of many - Coarse movements are produced with large numbers of muscle fibers - Precise movements are produced with fewer muscle fibers Recruitment - Increase in the number of motor units activated to produce more forceful contraction - Certain motor units are activated first and others are activated only when the intensity of stimulus increases - Continues until all motor units are activated as intensity of stimulation increases Sustained contractions - Sm motor units (sm diameter axons) recruited 1st - Lg motor units (lg diameter axons) recruited later - Summation and recruitment can produce ongoing contractions of increasing strength - Whole muscle contractions are smooth movements - Muscle tone Muscle tone - Tonus - Continuous state of partial contraction in resting muscles Isotonic contraction - Muscle contracts and changes length - Means "equal force" - Types: concentric and eccentric Concentric contraction Isotonic contraction where the muscle shortens Eccentric contraction Isotonic contraction where the muscle lengthens Isometric contraction - Muscle contracts but does not change length - Means "equal length" - Tension develops but parts attached to muscle do not move Lift dumbell Concentric Lowering dumbell Eccentric Holding an object in place with no movement Isometric Fast and slow twitch muscle fibers - Vary by contraction speed: slow and fast - Vary by method of ATP production: oxidatively and glycolytically - 3 types found in humans: slow, fast fatigue resistant, fast glycolytic - All muscles contain a combo of the 3 Slow-twitch fibers - Type I - Always oxidative - Resistant to fatigue - Red fibers - Abundant myoglobin - Good blood supply - Many mitochondria - Slow ATPase activity; slow to contract Fast-twitch fatigue-resistant fibers - Type IIa - Intermediate twitch fibers - Intermediate oxidative capacity - Intermediate amount of myoglobin - White fibers - Resistant to fatigue - Rapid ATPase activity Fast-twitch glycolytic fibers - Type IIb - Anaerobic respiration (glycolysis) - White fibers (less myoglobin) - Poorer blood supply than slow-twitch fibers - Fewer mitochondria than slow-twitch - More SR than slow-twitch - Susceptible to fatigue - Fast ATPase activity; contract rapidly Hypertrophy Enlargement of skeletal muscle that is exercised Atrophy Decrease in size and strength of the skeletal muscle that is unused Aerobic exercise stimulates slow-twitch fibers, in response: Fibers increase their capillaries and mitochondria Forceful exercise stimulates mainly fast-twitch fibers, in response: Fibers produce new actin and myosin filaments and the muscle enlarges Smooth muscle compared to skeletal muscle - Shorter - Single centrally located nucleus - Elongated with tapering ends - Myofilaments randomly organized - Lack striations - Lack TT - SR not well developed Cardiac muscle compared to skeletal muscle - Located only in heart - Striated - Joined together by intercalated discs - Fibers branch and contain a single nucleus - Network of fibers contract as a unit (syncytium) - Self-exciting and rhythmic - Longer refractory period - No sustained or tetanic contractions Skeletal muscle characteristics per chart Length: Up to 30 cm Diameter: 10 to 100 µm Location: skeletal muscles Function: movement of bones at joints; maintenance of posture Striations: present Nucleus: multiple Special feature: TT system well developed Control: Voluntary Characteristics: contracts and relaxes relatively rapidly Smooth muscle characteristics per chart Length: 30 to 200 µm Diameter: 3 to 6 µm Location: walls of hollow organs Function: movement of walls of hollow organs; peristalsis; vasoconstriction Striations: absent Nucleus: single Special feature: lacks TT Control: involuntary Characteristics: contracts and relaxes relatively slowly; some types self-exciting; rhythmic Cardiac muscle characteristic per chart Length: 50 to 100 µm Diameter: 14 µm Location: wall of the heart Function: pumping action of the heart Striations: present Nucleus: single Special feature: TT system well developed; intercalated discs connect cells Control: involuntary Characteristics: network of cells contracts as a unit; self-exciting; rhythmic; remains refractory until contraction ends Skeletal muscle actions - Generate many different types of body movements - Action depends on type of joint it is associated with - Action depends on the way the muscle is attached on both sides of the joint Origin and insertion - One end of a skeletal muscle is more fixed and the other end is more movable - Muscle can have more than one of either When a muscle contracts Insertion is pulled toward origin Origin Less movable end Insertion More movable end Most skeletal muscles function in Groups Agonist Muscle that causes an action Prime mover - Agonist primarily responsible for movement - Used interchangeably with agonist in some cases Synergist Muscles that assist agonist/prime mover Antagonist Muscles whose contraction causes movement in the opposite direction of the prime mover