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96 Cards in this Set
- Front
- Back
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What are the three types of muscle?
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Skeletal
Smooth Cardiac |
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What are the main characteristics of skeletal muscle?
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Cross-striations
Voluntary movement Attached by connective tissue to bone |
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What are the main characteristics of smooth muscle?
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They lack cross-striations and are involuntary movement
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What are the main characteristics of cardiac muscle?
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Striated
Involuntary movement |
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Which is the most abundant muscle in the body?
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Striated skeletal
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How are muscle cells attached to CT?
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Junctional complexes associated with the sarcolemma to the CT collagen
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What is epimysium?
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Dense CT, surrounds entire muscle
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What is perimysium?
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CT that surrounds each bundle of fibres
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What is a fasicle?
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Bundle of skeletal muscle fibers
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What is endomysium?
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Thin layer of CT surrounding each muscle fiber.
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What does endomysium consist of?
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BM and associated reticular and elastic fibers
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How long are skeletal muscle cells?
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1-40 mm in length
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What does the diameter of a skeletal muscle range?
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10-100um
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Characterize the skeletal muscle cell nucleus
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Multi-nucleated
Peripherally located |
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What are satelite cells?
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Stem cells that site between the BM and the sarcolemma. Can give extra nuclei to the muscle fiber
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What are red fibers?
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Slow-twitch motor units
Resistant to fatigure Postural muscles in the limbs and back More myoglobin and mitochondria |
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What are white fibers?
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Fast-twitch motor units
Fatigure rapidly Strong contractions Leg and arm muscles Bigger than red fibers Less myoglobin and mitochondria |
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What is the diameter of a myofibril?
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1-2 um
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How many thick filaments are in a myofibril?
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1500
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How many thin filaments are in a myofibril?
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3000
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What are thick filaments composed of?
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Myosin
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What are thin filaments composed of?
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F-actin
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How big is a sarcomere unit?
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2-3 um
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What are T tubules?
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Invaginations of the sarcolemma
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Where do T tubules occur in skeletal muscle?
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At regular intervals, at the level of the A and I junction
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What is the sarcoplasmic reticulum?
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The smooth ER of the skeletal muscle cells. It is a network of canals that end in terminal cisternae. It is NOT connected to the T-tubules
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What is the triad?
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A T-tubule with two adjoining terminal cisternae
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What is the A band?
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The arrangement of thick filaments in the middle of the sarcomere
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Why is the A band called that?
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It is anisotropic - appears dark when viewed with polarized light under the microscope
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What is the I band?
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It is composed of parallel thin filaments and is bisected by the Z line.
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What is the M line?
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Bi-sects the H zone?
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What is the H zone?
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It is the area within the A band that has only thick filaments and is NOT overlapped with thin filaments
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Which bands shorten during contraction?
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I and H
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How many myosin molecules are in thick filament?
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400
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How are myosin molecules arranged?
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As a dimer of intertwining heavy polypeptide chains
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What is L-meromyosin?
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The body/tail of the myosin heavy chain
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What is H-meromysin?
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The head and stalk of the myosin heavy chains
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What does H-meromysin consist of?
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S-1, which forms the globular head
S-2-forms the short neck |
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How are the light chains arranged with the heavy chains?
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Two light chains, L1 and L2 are associated with each of the two globular heads
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Which sites do the myosin heads contain?
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Actin binding site
ATP binding site A site capable of hydrolyzing ATP |
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What is titin?
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A cytoskeletal protein that anchors thick filaments to the Z lines
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How are thick filaments anchored to the M line?
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Structural proteins
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What is the ratio of actin to tropomyosin to troponin?
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7:1:1
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How are thin filaments arranged?
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Two strands of F-actin wound around each other
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What are F-actin strands composed of?
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300 globular or G-actin subunits
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How is tropomyosin arranged along the actin filaments?
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It is a double-stranded twisted molecule that runs along the groove formed by the F-actin
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What are the components of the troponin complex?
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TN-I
TN-T TN-C |
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What does TN-T bind?
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Tropomyosin
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What does TN-I bind?
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Actin
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What does TN-C bind?
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Simultaneously binds TN-T and TN-I, anchoring the tropomyosin to the actin
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What happens in the absence of calcium?
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Troponin complex plays an inhiitory role- keeping actin/tropomyosin in a complex that blocks myosin binding sites
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What is nebulin?
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Giant protein molecule, part of the muscle cell cytoskeleton, that regulates the assembly of actin filament, stabilizing its length and helping anchor it to the Z line
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What is the Z line composed of mostly?
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Alpha-actinin
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What are some characteristics of the axon terminal at the neuromuscular junction?
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Many synaptic vesicles
Mitochondria |
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What are some characteristics of the post-synaptic membrane?
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Many invaginations - increasing the surface area of the muscle fiber at the motor end-plate
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Which neurotransmitter stimulates skeletal muscle contraction by acting interacting with receptors of the sarcolemma at the post-synaptic membrane?
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Acetylcholine
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What is the acetylcholine receptor composed of?
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2 alpha
1 beta 1 gamma 1 delta |
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How big is the AchR?
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270,000
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What is acetyl cholinesterase?
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Degrades Ach in the synaptic cleft - to acetate and choline
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What is Myastenia Gravis?
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A neuromuscular disease leading to muscle weakness. It is an autoimmune disorder caused by Abs that recognize AchR
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What are the three layers of the wall of the heart?
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Epicardium
Myocardium Endocardium |
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What is the pericardium?
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Envelopes the heart
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What is the pericardium composed of?
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Fibrous pericardium - CT
Serous pericardium - Parietal Lamina and Visceral lamina |
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What is the epicardium?
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The same layer as the visceral lamina of the serous pericardium
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What is the endocardium?
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A smooth thin membrane consisting of endothelium, CT and SM, lines the inner aspect of the heart
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What is the myocardium?
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The thickest part of the heart wall and is made of CARDIAC MUSCLE
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Where else is cardiac muscle located?
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The base of the pulmonary veins
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Characterize the nucleus of the cardiac muscle cell
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It is single and located centrally
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What surrounds the sarcolemma of each cardiac muscle cell?
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BM + reticular fibers
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How are individual cardiac muscle cells joined?
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Intercalated disk
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How does the cardiac muscle cell compare to skeletal in terms of size/branching?
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It is smaller but more branched
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What are the two parts of the intercalated disk?
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Transverse
Lateral |
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What is in the transverse portion of the intercalated disk?
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Desmosomes and adherens junctions
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What is in the lateral part of the intercalated disk?
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Gap junctions
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WHat do gap junctions provide to the heart?
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A way to pass signals frm one cell to another to have a synchronus heart beat
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What are Purkinje fibers?
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Modified myocytes that regulate synchronization in the heart
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Where are T tubules found?
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At the level of the Z lines of the sarcomere
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What is a diad?
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The T tubule + larger terminal cisternae
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What do the secretory granules of the cardiac muscle fibers of the atria contain?
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Atrial natrieuretic factor
Brain natrieuretic factor |
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What do atrial natriueretic factor and brain natrieuretic factor do?
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Inhibit renin secretion in the kidney
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Where is smooth muscle found?
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Respiratory tract
Gastrointestinal tract Ciliary body of the eye Blood vessels |
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How is smooth muscle organized?
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In layers or sheets
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How does smooth muscle contract?
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In a spontaenous fashion under the control of the autonomic nervous system or hormones
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Characterize the nucleus of the smooth muscle cell
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Single
Centrally placed Elongated Corkscrew when cell is contracted |
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What is the BM of the smooth muscle cell?
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Reticular fibers and elastic fibrils
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Which cell synthesizes the components of the reticular and elastic fibers that surround the smooth muscle cell?
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Collagen types III and IV
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What are calveolae?
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Invaginations of the sarcolemma
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What are the calveolae believed to be equivalent to?
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T tubules of the striated and cardiac muscle
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What are myoepithelial cells?
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Epithelial cells that show smooth muscle characteristics
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Where are myoepithelial cells found?
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Sweat glands, mammary glands and salivary glands
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How are thin filaments arranged in smooth muscle cells?
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Originating from dense patches
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What are the dense patches composed of?
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Alpha-actinin
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Where is desmin located in smooth muscle cells?
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Intermediate filaments that attach to the dense patches in all smooth muscle
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Where is vimentin located in the smooth muscle cells?
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Intermediate filaments taht attach to desnse patches in smooht muscle of vessels only
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What are the thick filaments made of in smooth muscle cells?
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Myosin II
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How does contraction occur in smooth muscle?
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Calcium binds to calmodulin. A myosin light chain kinase phosphorylates one of the two light chains of myosin. Myosin can now interact with actin and contract the cell
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