Chr. 10 - Muscular Tissue Flashcards
(93 cards)
1
Q
[10.1] List the types of muscle tissue.
A
Skeletal, cardiac, smooth.
2
Q
[10.1] List the functions of muscular tissue.
A
Producing body movement,
Stabilizing body position,
Storing and moving substances,
Generating heat.
3
Q
[10.1] List and briefly describe the properties of muscular tissue.
A
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.
4
Q
[10.2] Describe the subcutaneous layer.
A
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.
5
Q
[10.2] Describe fascia.
A
A dense sheet of irregular connective tissue lining body walls and limbs supporting and surrounding muscles. Extends as epimysium, perimysium, and endomysium.
6
Q
[10.2] Describe the epimysium.
A
Outer layer of dense irregular connective tissue encircling the entire muscle.
7
Q
[10.2] Describe the perimysium.
A
Layer of dense irregular connective tissue surrounding 10-100 muscle fibers forming fascicles.
8
Q
[10.2] Describe the endomysium.
A
Layer of reticular fibers penetrating fascicles and separating myocytes (muscle fibers).
9
Q
[10.2] Describe a tendon.
A
A ropelike structure formed by all three layers of fascia as they extend from the muscle to periosteum of bone.
10
Q
[10.2] What is an aponeurosis?
A
Connective tissue that forms a tendon-like structure in a broad, flat shape.
11
Q
[10.2] What is the sarcolemma?
A
The plasma membrane of a muscle cell, distinguished by invaginations called transverse tubules tunneling to the center of the fiber.
12
Q
[10.2] What are transverse tubules?
A
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.
13
Q
[10.2] What is the sarcoplasm?
A
The cytoplasm of a muscle fiber, contains a large amount of glycogen for ATP synthesis and myoglobin.
14
Q
[10.2] What is myoglobin?
A
Protein found in muscles that binds oxygen that have diffused into muscle fibers.
15
Q
[10.2] Describe myofibrils.
A
Contractile organelles of skeletal muscle that extend lengthwise throughout the muscle fiber.
16
Q
[10.2] Describe the sarcoplasmic reticulum.
A
Membranous structure within myofibrils connected to each other at “terminal cisterns” on either end as well as to transverse tubules.
17
Q
[10.2] What is a triad?
A
A term referring to a unit composed of a transverse tubule and two terminal cisterns (one from either side of the transverse tubule.
18
Q
[10.2] What are myofilaments?
A
Protein structures within myofibrils, classified as thin filaments or thick filaments and present in 2:1 thin:thick
19
Q
[10.2] What are thin filaments?
A
Myofilaments 8nm in diameter composed of actin.
20
Q
[10.2] What are thick filaments?
A
Myofilaments 16nm in diameter composed of myosin.
21
Q
[10.2] What are sarcomeres?
A
Compartments of myofilaments that form basic units composing myofibrils.
22
Q
[10.2] What are Z discs?
A
Plate-shaped regions of dense protein material separating sarcomeres.
23
Q
[10.2] What is an A band?
A
Darker middle part of the sarcomere extending from one edge to the other of thick filaments.
24
Q
[10.2] What is the I band?
A
Lighter, less dense area extending from one end of thin filaments to the other.
25
[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.
26
[10.2] What is the H zone?
Region of the A band that contains no overlap with thin filaments.
27
[10.2] What is the M line?
A line distinguishing the middle of a sarcomere.
28
[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.
29
[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.
30
[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.
31
[10.2] Describe titin.
Structural protein connecting Z discs to M line in sarcomeres, stabilizing thick filaments. Responsible for elasticity and extensibility.
32
[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.
33
[10.3] List the steps of the contraction cycle.
ATP Hydrolysis,
Attachment of myosin to actin,
Power stroke,
Detachment of myosin from actin.
34
[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.
35
[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.
36
[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.
37
[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.
38
[10.3] Describe excitation-contraction coupling.
The sequence of events that links muscle action potential to sliding of filaments. Begins when an action potential triggers release of calcium from sarcoplasmic reticulum into the sarcoplasm and results in the contraction of the muscle.
39
[10.3] Describe the role of the two types calcium channels in muscle fibers.
Voltage-gated calcium channels are located in the transverse tubule membrane and are present in clusters known as tetrads. Responsible for sensing voltage changes to trigger opening of calcium release channels.
Calcium release channels are present in terminal cisternal membranes of sarcoplasmic reticulum, opening by voltage-gated calcium channels when an action potential travels down and releasing calcium into the sarcoplasm. Once in the sarcoplasm, calcium binds to troponin, releasing it from tropomyosin and allowing myosin to form cross-bridges with actin.
40
[10.3] What are calcium-ATPase pumps?
Transport proteins that use ATP to transport calcium from the sarcoplasm into the sarcoplasmic reticulum. Constantly returning calcium but at a slower rate than it is release during contractions, leading to a limit on the duration of contractions.
41
[10.3] What is a calsequestrin?
A protein present within the sarcoplasmic reticulum that binds to calcium and stores it within.
42
[10.3] Describe the length-tension relationship.
A relationship indicating the forcefulness of muscle contraction depending on length of sarcomeres before a contraction showing that optimal overlap occurs near resting length. Overextension reduces the overlap of myosin on actin as the filaments are pulled further away from each other, and partially contracted muscles have reduced overlap due to the structure of myosin crumpling rendering it unable to bind with actin.
43
[10.3] What are somatic motor neurons?
Neurons that innvervate skeletal muscle fibers.
44
[10.3] What is a neuromuscular junction?
The synapse between a somatic motor neuron and a skeletal muscle fiber. Usually occurs at the midpoint of a muscle fiber.
45
[10.3] What is a synapse?
A region where communication occurs between a neuron and another neuron or target cell.
46
[10.3] What is the motor end plate?
The receiving muscular side of the neuromuscular junction.
47
[10.3] What are junctional folds?
Deep grooves in the motor end plate increasing surface area for acetylcholine receptors.
48
[10.3] What are acetylcholine receptors?
Integral transmembrane proteins that bind acetylcholine as a ligand and trigger an action potential.
49
[10.3] List the sequence of a muscle action potential.
Release of acetylcholine,
Activation of ACh receptors,
Production of muscle action potential,
Termination of ACh activity.
50
[10.3] Describe the "release of acetylcholine" step of the muscle action potential.
Action potential travelling along neuron triggers synaptic bulb ends to release acetylcholine into synapse of neuromuscular joint.
51
[10.3] Describe the "activation of ACh receptors" step of the muscle action potential.
ACh binds to transmembrane proteins on the motor end plate, opening ion channels of receptor cell.
52
[10.3] Describe the "production of muscle action potential" step of the muscle action potential.
Inflow of ions increases the charge within the muscle fiber and generating a muscle action potential which travels along the sarcoplasmic reticulum and releases calcium ions into the sarcoplasm initiating a contraction.
53
[10.3] Describe the "termination of ACh activity" step of the muscle action potential.
Acetylcholine is quickly broken down by acetylcholinesterase (AChE), an enzyme on the motor end plate. This allows for another molecule of acetylcholine to bind and trigger another action potential.
54
[10.3] Describe a muscle contraction from the initiation of an action potential along the somatic motor neuron to relaxation.
A nerve action potential reaches the synaptic bulb ends and releases acetylcholine which binds to integral transmembrane proteins on the motor end plate. Once attached, acetylcholine triggers a muscle action potential and is quickly broken down by acetylcholinesterase. The muscle action potential travels along the sarcoplasm and activates voltage-gated calcium channels within transverse tubules that in turn open calcium release channels on the sarcoplasmic reticulum. Calcium flows into the sarcoplasm and bind to troponin, removing it from tropomyosin allowing tropomyosin to detach from myosin. Myosin forms cross-bridges with actin and uses energy from hydrolyzed ADP for the power stroke. Once completed, binding of an ATP to myosin releases the cross-bridge and calcium pumps in the sarcoplasmic reticulum have removed ions from the sarcoplasm, allowing for troponin to bind to tropomyosin reattaching it to myosin.
55
[10.4] List the different methods of ATP production in a muscle.
Creatinine phosphate,
Anaerobic glycolysis,
aerobic respiration.
56
[10.4] Describe the creatine phosphate method of ATP production.
Creatine is a small molecule similar to amino acids. Creatine kinase attaches phosphate groups to creatine to produce creatine phosphate storing large amounts of energy in the bond. When ADP levels rise, creatine kinase phosphorylates ADP with the phosphate from creatine to produce ready-to-use ATP.
57
[10.4] Describe the anaerobic glycolysis method of ATP production.
Catabolism of glucose without oxygen occurring in the cytosol to produce ATP and pyruvic acid when creatine phosphate stores have been depleted. Normal process of glycolysis, but without oxygen, pyruvic acid is converted to lactic acid and diffuses into the blood stream. Can build up in muscle if rate of production exceeds rate of diffusion
58
[10.4] Describe the aerobic glycolysis method of ATP production.
Catabolism of glucose with oxygen, involves glycolysis, Krebs cycle, and electron transport chain that uses pyruvic acid in conjunction with oxygen to produce addition ATP, carbon dioxide, water, and heat.
59
[10.4] What are the sources of oxygen for muscle fibers?
Oxygen diffusing from blood into muscle fibers,
Oxygen released from myoglobin within muscle fibers.
60
[10.4] What is muscle fatigue?
The inability of a muscle to maintain force of contraction after prolonged activity.
61
[10.4] What is recovery oxygen uptake?
A term used to refer to the additional oxygen above resting consumption taken in after exercise to restore metabolic conditions. Also referred to as oxygen debt.
62
[10.4] In which ways is the recovery oxygen used to restore metabolic conditions?
Convert lactic acid back to glycogen in the liver,
Resynthesize creatine phosphate and ATP in liver,
Replace oxygen consumed from myoglobin.
63
[10.5] What does the force of muscle tension depend on?
The rate of which nerve impulses arrive at a neuromuscular junction.
64
[10.5] What is a motor unit?
Consists of a somatic motor neuron and all the muscle fibers it innervates. Muscle fibers are typically dispersed throughout a muscle.
65
[10.5] What is a twitch contraction?
Brief contraction of all muscle fibers in a motor unit in response to a single action potential.
66
[10.5] What is the latent period?
A brief delay, about 2msec, between application of a stimulation and the beginning of a contraction.
67
[10.5] What is the contraction phase ?
The period in which contraction occurs, reaching peak tension.
68
[10.5] What is the relaxation phase of a twitch contraction?
Period where calcium in transported back inside the sarcoplasmic reticulum and the troponin-tropomyosin system re-engages.
69
[10.5] What is the refractory period?
Period in which muscle fiber has lost excitability due to response to a previous action potential.
70
[10.5] Describe wave summation.
When stimuli arrives at different times during contraction causing larger contractions.
71
[10.5] What is unfused tetanus.
A sustained, wavering contraction when a skeletal muscle partially relaxes between stimuli. Occurs at a rate of 20-30 stimulations per second.
72
[10.5] What is fused tetanus?
A sustained contraction where individual twitches cannot be detected and the muscle does not relax between stimulation. Occurs with rate of stimulation of 80-100 per second.
73
[10.5] Describe motor unit recruitment.
The process where the amount of active motor units increases as a task requires more force.
74
[10.5] Describe muscle tone.
The small amount of tension exhibited b weak, involuntary contractions of motor units at rest.
75
[10.5] What is a flaccid muscle?
A muscle in a state of limpness where muscle tone is loss. Occurs when a neuromuscular junction is interrupted.
76
[10.5] What is an isotonic contraction?
A constant development of tension while a muscle changes length.
77
[10.5] What is a concentric isotonic contraction?
A contraction producing tension that overcomes force and shortens the muscle.
78
[10.5] What is an eccentric isotonic contraction?
A contraction producing tension that resists a force, slowing lengthening of the muscle.
79
[10.5] What is an isometric contraction?
A contraction producing tension that does not overcome a force and prevents lengthening of muscle.
80
[10.6] What are red muscle fibers?
Skeletal muscle fibers with higher myoglobin and mitochondria content.
81
[10.6] What are white muscle fibers?
Skeletal muscle fibers with lower myoglobin and mitochondria content.
82
[10.6] Describe slow oxidative fibers.
Fibers with large amounts of myoglobin and blood capillaries. Slow oxidative fibers generate ATP mainly by aerobic respiration and have myosin that hydrolyze ATP, contract, and reach tension slower than other types of fibers. Considerable resistance to fatigue.
83
[10.6] Describe fast oxidative-glycolytic fibers.
Largest fibers containing large amounts of myoglobin and blood capillaries. Generate ATP by aerobic and anaerobic respiration, as they have high intracellular levels of glycogen. Moderate resistance to fatigue and able to reach peak tension quicker but maintain it for briefer durations.
84
[10.6] Describe fast glycolytic fibers.
Low amounts of myoglobin and few blood capillaries/mitochondria. Hydrolyze ATP and reach peak tension rapidly and intensely.
85
[10.9] List the types of smooth muscle tissue.
Visceral smooth muscle tissue,
Multi-unit smooth muscle tissue.
86
[10.9] Describe visceral smooth muscle tissue.
Forms walls of arteries, veins, and hollow organs in tubular arrangements. Autorhythmic fibers connected by gap junction allowing for muscle action potentials to spread and produce unison contractions.
87
[10.9] Describe multi-unit smooth muscle tissue.
Individual fibers featuring neuromuscular junctions and few gap junctions.
88
[10.9] Describe the anatomy of a smooth muscle fiber.
Spindle arrangement of thick and thin filaments, contain a sarcoplasmic reticulum without sarcomeres. "Dense bodies" functionally similar to Z discs providing structure to the cell, connected to each other by intermediate filaments. Contain pouchlike invaginations of the plasma membrane called caveolae that replace transverse tubules.
89
[10.9] What is calmodulin?
A regulatory protein found in smooth muscle that binds calcium. When bound, activates myosin light chain kinase, an enzyme allowing myosin to bind to actin in smooth muscle.
90
[10.9] How does smooth muscle tone occur?
Smooth muscle tone occurs due to the slow movement of calcium in and out of the muscle fiber, allowing for it to sustain the long-term tone important in the GI tract and cardiovascular system.
91
[10.9] What is the stress-relaxation response?
The quality of smooth muscle that triggers an initial contraction when stretched, before relaxing and allowing for greater change in length.
92
[10.10] What is hypertrophy?
Enlargement of existing cells, main way muscle fibers grow.
93
[10.10] What is hyperplasia?
An increase in the number of muscle fibers.
