Exam 3: Chapter 10 – Flashcards
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The unit of skeletal muscle structure that is composed of bundles of myofibrils, enclosed within a sarcolemma, and surrounded by a connective tissue covering called endomysium is a __________.
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Fasicle
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What is the physiological event that takes place at the plasma membrane of a skeletal muscle?
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Propagation of an action potential
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In a skeletal muscle fiber, Calcium is released from the ______
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Sarcoplasmic Reticulum
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Tendon
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A bundle of dense regular connective tissue that attaches skeletal MUSCLE TO BONE
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In excitation-contraction coupling, the transverse tubules function to ____________.
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conduct an action potential into the sarcoplasmic reticulum to cause release of calcium
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During muscle contraction, the I Band ____________
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Hides the H Zone
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What event causes a troponin-troposyosin complex to regain its original shape in muscle relaxation?
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Return of calcium to the sarcoplasmic reticulum
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In sustained, moderate exercise, skeletal muscle is predominantly using _____________ as its energy source.
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Fatty acids
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Skeletal muscle and cardiac muscle are similar in that both types of muscle _____
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are STRIATED
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The wall of the heart is composed of ____ muscle.
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Cardiac
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Oxygen Debt
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the amount of additional oxygen that must be inhaled in order to restore pre-exercise levels
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List the events in correct order of occurrence once ACh diffuses across the synaptic cleft of a NMJ
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1. ACh binds to receptors on the motor end plate
2. The resulting action potential moves down the sarcolemma
3. The action potential moves down the t-tubules
4. The action potential reaches the terminal cisternae of the SR (sarcoplasmic reticulum)
5. Calcium ions are released into the sarcoplasm
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Neuromuscular Junction
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The point where a motor neuron meets a skeletal muscle fiber
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The diameter of a muscle fiber will predict ______
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how much power it will produce
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Sarcomere
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repeating microscopic cylindrical units of myofilaments within myofibrils
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Thin Filament
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-approximately 1/2 the diameter of thick filaments
- composed of 2 strands of actin protein twisted around itself to form a helical structure
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Actin
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Contractile protein forming the major part of the thin filament in a sarcomere
-2 types
a) G-actin
b) F-actin
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G-actin
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Globular Actin
small, spherical molecules that are connected to form a fibrous strand (f-actin)
ex: the individual "beads" of a necklace
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F-actin
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Filamentous actin
The fibrous strand formed by individual G-actin molecules connecting
ex: 2 beaded necklaces twisted together
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Tropomyosin
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short, thin, twisted filament that is a "string-like" protein twisted over the thin filament
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Troponin
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A globular, "ball-like" protein attached to tropomyosin
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Titin
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Also called CONNECTIN
Cable-like protein that extends from the Z discs to the M line through the core of each thick filament
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Thick Filament
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assembled from bundles of myosin protein molecules
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Myosin
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Protein molecules that consist of 2 strands, each which contain 2 parts:
1. Globular head
2. Elongated Tail
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Myosin Head
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-contains a binding site to actin of the thin fibers
-contains a catalytic site where ATP attaches and is split into ADP and P (myosin ATPase)
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Myosin Tails
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the 2 tails are intertwined and oriented so that the tails point toward the center of the thick filaments, and the heads point toward the ends of the thick filaments
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On what protein of a thin myofilament do Calcium ions bind?
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Troponin
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Epimysium surrounds what connective tissue layer of the muscle?
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Muscle
(the outside layer- think EPI-dermis)
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Perimysium surrounds what connective tissue layer of muscle?
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Fascicles
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Endomysium surrounds what connective tissue layer of muscle?
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Muscle cells
(think ENDO-cytosis, to bring in; Endo= covers the inner-most layer)
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In which function of skeletal muscle do muscles contract and pull on the tendons that attach the muscles to the bones?
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Body Movement
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The contraction of specific skeletal muscles that stabilizes joints is called _____
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Posture
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Through what function of skeletal muscle is heat produced as a waste product of energy useage?
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Temperature regulation
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what is the function of Storage and Movement of materials in skeletal muscles?
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Voluntary sphincter muscles of the GI and Urinary tracts can be kept closed or opened
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After a contraction, muscle returns to its original relaxed position due to its natural ______.
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Elasticity
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Imbalances in Na+ or K+, Buildup of intracellular P, and insufficient Ca2+ can all lead to _____ ______.
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Muscle Fatigue
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The striated appearance in skeletal muscle cells is due to the size and density differences between ______ and ____ filaments.
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Thick and Thin
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Sliding Filament Theory
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explained how muscle fibers shorten during contractions
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Myosin head attachment and pivoting do not require energy, but ATP is needed for the myosin head crossbridge to ________ and re-cock.
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Release
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Tendon
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a cord-like structure that attaches muscle to bone
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The muscle that surrounds the opening to your esophagus and opens reflexively to allow you to swallow food is what type of muscle?
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Sphincter
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List the events at a Neuromuscular Junction in order
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1. Arrival of nerve signal to synaptic knob
2. Calcium entry into synaptic knob
3. Exocytosis of ACh into synaptic cleft
4. Binding of ACh to motor end plate
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How much muscle tension is generated during the Latent Period of a muscle twitch?
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There is no tension
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What is happening to tension during the Contraction Period of a muscle twitch?
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Tension is INCREASING
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What is happening to tension during the Relaxation Period of a muscle twitch?
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Tension is DECREASING
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List the events that occur at a NMJ in order:
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1. Nerve signal arrives at synaptic knob
2. Calcium enters and binds to synaptic vesicles
3. ACh is released via exocytosis into the synaptic cleft
4. ACh binds to receptors on the motor end plate
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Skeletal muscle fibers are considered _________ due to their multiple nuclei.
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Multinucleate
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A neuromuscular junction contains what 3 structures?
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Synaptic Cleft
Synaptic Knob
Motor End Plate
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Slow muscle fibers are about _____ the diameter of fast muscle fibers.
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1/2
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List the concentric layers of connective tissue in a muscle from DEEP to SUPERFICIAL
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Endomysium
Perimysium
Epimysium
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Thick myofilaments are composed of bundles of what protein molecule?
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Myosin
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Isometric Contraction
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When muscle tension is insufficient to overcome the resistance; the muscle contracts and tension is increased, but muscle length stays the same
-No movement, holds steady
ex: Holding a baby in one position, pushing on a wall to stretch your leg muscles
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Isotonic Contraction
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When muscle tension results in movement of the muscle
2 Types:
a) Concentric
b) Eccentric
ex: walking, lifting a baby, swinging a tennis racket
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Concentric Contraction
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Muscle tension is greater than resistance = Muscle shortens
ex: lifting a baby, bicep curl
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Eccentric Contraction
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Muscle exerts less force than needed to move the load = Muscle Lengthens
ex: laying baby down, bicep release
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White fibers, anaerobic respiration, and low concentration of myoglobin are characteristics of _______ fibers.
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Glycolytic Fibers
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List the events of the NMJ in order of occurrence after ACh has diffused across the synaptic cleft
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1. ACh binds to receptor sites on the motor end plate
2. The resulting action potential moves down teh sarcolemma
3. the action potential moves down the t-tubules
4. the action potential reaches the terminal cisternae of the SR
5. Calcium ions are released into the sarcoplasm
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In the neuromuscular junction _____ ions move into the axonal terminal
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Calcium (Ca2+)
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In the neuromuscular junction _____ ions move into the sarcoplasm
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Sodium (Na+)
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In the neuromuscular junction _____ moves across the synaptic gap
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Acetylcholine (ACh)
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In the neuromuscular junction _____ ions move out of the sarcoplasm
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Potassium (K+)
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Terminal Cisternae
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Part of the Sarcoplasmic Reticulum that appear as blind sacs perpendicular to the fiber's length.
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Skeletal muscles arranged in layers along teh walls of the abdominal cavity and the floor of the pelvic cavity perform what function(s)?
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Protection
Contraction
Support
Compression
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Intermediate fibers (Fast Oxidative Fibers) have a high resistance to ______.
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Fatigue
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In a motor unit, a single ______ neuron typically controls numerous muscle fibers in a muscle.
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Motor
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This enzyme resides in the synaptic cleft
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Acetylcholinesterase
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The motor end plate has folds and indentations to increase the membrane surface area adjacent to the ______.
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Synaptic knob
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Good for endurance, red fibers, high concentration of myoglobin, and aerobic respiration are characteristics of ________ fibers.
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Oxidative
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List the stages of Crossbridge cycling
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1. Calcium binds troponin; myosin binding site is uncovered
2. Cross-bridge formation
3. Power stroke
4. Release of myosin head by ATP
5. Reset of myosin head
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A sarcomere is defined as the distance from one Z _____ to the next
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disc
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Aerobic respiration requires what molecule to be present?
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Oxygen
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Within a myofibril, Z discs separate the functional units known as ______.
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Sarcomeres
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As a result of muscle fiber contraction, thick filaments in neighboring sarcomeres move ______.
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Closer together
