Chr. 10 - Muscular Tissue Flashcards
[10.1] List the types of muscle tissue.
Skeletal, cardiac, smooth.
[10.1] List the functions of muscular tissue.
Producing body movement,
Stabilizing body position,
Storing and moving substances,
Generating heat.
[10.1] List and briefly describe the properties of muscular tissue.
Electrical excitability, the ability to respond to stimuli,
Contractility, the ability to contract forcefully when stimulated,
Extensibility, ability of the tissue to stretch within limits without being damaged,
Elasticity, the ability to return to original length and shape after contraction or extension.
[10.2] Describe the subcutaneous layer.
Loose connective tissue layer housing nerves, blood vessels, and lymphatic vessels entering and exiting muscle tissue, and providing energy from triglycerides and acting as insulation.
[10.2] Describe fascia.
A dense sheet of irregular connective tissue lining body walls and limbs supporting and surrounding muscles. Extends as epimysium, perimysium, and endomysium.
[10.2] Describe the epimysium.
Outer layer of dense irregular connective tissue encircling the entire muscle.
[10.2] Describe the perimysium.
Layer of dense irregular connective tissue surrounding 10-100 muscle fibers forming fascicles.
[10.2] Describe the endomysium.
Layer of reticular fibers penetrating fascicles and separating myocytes (muscle fibers).
[10.2] Describe a tendon.
A ropelike structure formed by all three layers of fascia as they extend from the muscle to periosteum of bone.
[10.2] What is an aponeurosis?
Connective tissue that forms a tendon-like structure in a broad, flat shape.
[10.2] What is the sarcolemma?
The plasma membrane of a muscle cell, distinguished by invaginations called transverse tubules tunneling to the center of the fiber.
[10.2] What are transverse tubules?
Tunnels in the sarcolemma leading to the center of a myocyte filled with interstitial fluid. Ensure quick spreading of action potential to activate the muscle fiber simultaneously.
[10.2] What is the sarcoplasm?
The cytoplasm of a muscle fiber, contains a large amount of glycogen for ATP synthesis and myoglobin.
[10.2] What is myoglobin?
Protein found in muscles that binds oxygen that have diffused into muscle fibers.
[10.2] Describe myofibrils.
Contractile organelles of skeletal muscle that extend lengthwise throughout the muscle fiber.
[10.2] Describe the sarcoplasmic reticulum.
Membranous structure within myofibrils connected to each other at “terminal cisterns” on either end as well as to transverse tubules.
[10.2] What is a triad?
A term referring to a unit composed of a transverse tubule and two terminal cisterns (one from either side of the transverse tubule.
[10.2] What are myofilaments?
Protein structures within myofibrils, classified as thin filaments or thick filaments and present in 2:1 thin:thick
[10.2] What are thin filaments?
Myofilaments 8nm in diameter composed of actin.
[10.2] What are thick filaments?
Myofilaments 16nm in diameter composed of myosin.
[10.2] What are sarcomeres?
Compartments of myofilaments that form basic units composing myofibrils.
[10.2] What are Z discs?
Plate-shaped regions of dense protein material separating sarcomeres.
[10.2] What is an A band?
Darker middle part of the sarcomere extending from one edge to the other of thick filaments.
[10.2] What is the I band?
Lighter, less dense area extending from one end of thin filaments to the other.
[10.2] What is the zone of overlap?
Regions where the A band and I band overlap where thick and thin filaments rest side by side.
[10.2] What is the H zone?
Region of the A band that contains no overlap with thin filaments.
[10.2] What is the M line?
A line distinguishing the middle of a sarcomere.
[10.2] List and describe the types of proteins composing myofibrils?
Contractile proteins, generate force during contraction
Regulatory proteins, switch contractions on and off
Structural proteins, maintaining structure and arrangement of myofibril and generating elasticity and extensibility while linking myofibrils to sarcolemma.
[10.2] List and describe the contractile proteins.
Myosin, main component of thick filaments and functions are the motor protein, pulling cellular structures using energy derived from ATP.
Actin, main component of thin filaments that features a binding site for myosin to anchor, moving when myosin contracts.
[10.2] List and describe the regulatory proteins.
Tropomyosin, covers myosin-binding site of actin preventing attachment and there force inhibiting contractions of myofibrils.
Troponin, holds tropomyosin in place until calcium ions bind to it, changing its shape and releasing tropomyosin from actin.
[10.2] Describe titin.
Structural protein connecting Z discs to M line in sarcomeres, stabilizing thick filaments. Responsible for elasticity and extensibility.
[10.3] Describe the sliding filament mechanism.
Myosin heads progressively pull thin filaments towards the M line. As the sarcomere shortens, the I band and H zone eventually disappear and the muscle reaches maximum contraction.
[10.3] List the steps of the contraction cycle.
ATP Hydrolysis,
Attachment of myosin to actin,
Power stroke,
Detachment of myosin from actin.
[10.3] Describe the ATP Hydrolysis step of the contraction cycle.
ATP binds to myosin and the binding site acts as ATPase, hydrolyzing ATP into ADP+Phosphate. This releases energy that is stored in the myosin for later use.
[10.3] Describe the Attachment of Myosin to Actin step of the contraction cycle.
The energized myosin attaches to actin and releases the phosphate group as it attaches. When myosin is bound to actin, its known as a cross-bridge.
[10.3] Describe the Power Stroke step of the contraction cycle.
Myosin changes its angle once the cross-bridge is formed, pulling the thin filament towards the M line and generating tension. ADP is released from myosin as the energy is used to generate the force.
[10.3] Describe the Detachment of Myosin from Actin step.
After the power stroke, ATP binds to myosin deforming the cross-bridge and starting the cycle over again as it remains bound to myosin for hydrolyzing.