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50 Cards in this Set
- Front
- Back
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Myosin
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Motor protein with the ability to create movement.
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Describe the structure of Myosin
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Each myosin molecule is composed of protein chains that intertwine to form a long tail and a pair of tadpole like heads. The tail is stiff, but the protruding myosin head has a en elastic hinge region.
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What is the head chain?
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The motor domain that binds ATP and uses energy from ATP's high energy phosphate bond to create movement.
Also considered myosin ATPase. |
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Describe the thick filament.
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The thick filament consists of about 250 myosin molecules joining together.
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How is the thick filament arranged?
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The myosin heads are clustered at each end of the filament, and the central region of the filament is a bundle of myosin tails.
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What is Actin?
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A protein that makes up the think filaments of the muscle fiber.
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Describe the structure of actin.
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Globular protein (G-actin), represented by round ball.
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What connects the thick and thin filaments of the myofibril?
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Connected by myosin crossbridges that span the space between the filaments.
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One repeat of the alternating light and dark bands is called a what?
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sarcomere
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Describe and Define Z disks
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They are zig-zag like protein structures that serve as the attachment site for thin filaments. One sarcomere is composed of two z disks and the filaments in between.
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Describe and Define I bands
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Theres are the lightest color bands of the sarcomere.
Represent only think filaments. I comes from isotropic. |
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Describe and Define the A band.
Is this band uniform? |
The darkest of the sarcomere's bands and encompasses the entier length of a thick filament.
No, the outer edges overlap with the I bands. |
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Describe and Define the H zone
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The central region of the A band that is lighter than the outer edges of the A band because the H zone is occupied by the thick filaments only.
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Define and describe the M line
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This band represents proteins that form the attachment site for thick filaments. It is the equivalent of the Z disk for the think filaments.
Each M line divides an A band in half. |
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List all the elements within a sarcomere
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1.Z disks
2.I bands 3.A bands 4. H bands 5. M line |
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What proteins ensure proper alignment of filaments within a sarcomere?
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Titin and nebulin
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What is Titin? How many amino acids does titin comprise of?
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Protein structure that aligns from one Z disk to neighboring M line.
It is a huge elastic molecule and the largest known protein. Roughly more than 25,000 amino acids. |
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How many and what are the functions of titin?
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(1) It stabilizes the position of the contractile filaments and.
(2) Its elasticity returns stretched muscles to their resting length. |
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What is nebulin? Whats its purpose?
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It is an inelastic giant protein that lies alongside thin filaments and attaches to the Z disk.
Its main function is to help align the actin filaments of the sarcomere. |
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What is the force created by contracting muscle? What is this process called?
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Muscle Tension, contraction
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What is the load?
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The load is a weight or force that opposes contraction of a muscle.
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What energy source does contraction of the muscles use?
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ATP
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What is relaxation?
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The release of tension created by a contraction.
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How does the sarcomere shorten during contraction?
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As contraction takes place, actin and myosin do not change length but instead slide past one another.
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What are the events that lead up to skeletal muscle contraction?
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a) The events at NMJ
b) Excitation contraction coupling c) Calcium ion signal d) Contraction relaxation cycle e) Muscle twitch/Sliding filament theory |
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What is the relationship described in the Sliding Filament Theory?
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Tension generated in a muscle fiber is directly proportional to the number of high force crossbridges between the thick and think filaments.
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What is a power stroke?
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Myosin cross bridges swivel and push the actin filaments toward the center of the sarcomere.
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What controls the positioning of an elongated protein polymer, tropomysosin?
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Troponin
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What is the rigor state?
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Where the myosin heads are tightly bound to G-Actin molecules.
Occurs for a brief period. |
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What is a twitch?
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A single contraction-relaxation cycle in a skeletal muscle fiber is known as a twitch.
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What is the latent period? What happens during this period?
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The delay between the muscle action potential and the beginning of muscle development. This delay represents the time required for calcium release and binding to troponin.
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A single action potential in a muscle fiber evokes a ____ twitch.
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single
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Why do muscle contraction require steady source of ATP?
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Muscles require energy for contraction of crossbridge movement and release, relaxation to pump calcium ions back to sarcoplasmic reticulum, and after E-C coupling to restore Na and K ions to respective compartments.
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The amount of ATP in a muscle fiber at any one time is sufficient for only how many?
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The amount of ATP in a muscle fiber at any one time is sufficient for only about 8 twitches
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What is a backup energy source?
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Phosphocreatine, a molecule whose high energy phosphate bonds are created from creatine and ATP.
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What does Creatine Kinase do?
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It is an enzyme that transfers the phosphate group from phosphocreatine to ADP.
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What does high levels of creatine kinase would usually indicate?
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It indicates damage to skeletal or cardiac muscle.
-different isozymes can distinguish cardiac tissue damage during a heart attack from skeletal mescle damage. |
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What is fatigue? What influences it?
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A reversible condition in which a muscle is no longer able to generate or sustain the expected power output.
It is influenced by the intensity and duration of the contractile activity. |
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Which muscle fiber type has the slowest speed of development of maximum tension?
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Slow-Twitch Oxidative;Red Muscle
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Which muscle fiber type has the fastest speed of development of maximum tension?
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Fast-Twitch Glycolytic; White Muscle
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Which fiber type is the most resistant to fatigue?
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Fast-Twitch Oxidative Glycolytic; Red Muscle
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Which fiber type has a small diameter?
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Slow-Twitch Oxidative;Red
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What affects tension?
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Resting Fiber Length
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What is the state of maximal contraction
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tetanus
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The basic unit of contraction in an intact skeletal muscle is?
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a motor unit, contains a group of muscle fibers that function together and the somatic motor neuron.
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All muscle fibers in a single motor unit are of the same fiber type? (T/F)
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True
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What is Asynchronous recruitment?
Whats its significance? |
Nervous system modulates the firing rates of the motor neurons so that different motor units take turns maintaining muscle tension.
Alternation allows rest and but prevents fatigue in only sub maximal contractions. |
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Which is more plentiful in smooth muscles than striated? Actin or Mysoin
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Actin
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Sarcomeres are absent in which kind of muscle?
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Smooth Muscles
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Smooth muscles contain troponin (T/F)?
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F- They dont have troponin
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