Muscle Flashcards
(13 cards)
A muscle cell is called a _____, contains several contractile units called _____, and is enveloped by _____ (connective tissue). Bundles of muscle cells form a _____, enveloped in ____. Multiple bundles form a muscle, which is enveloped in ____, which ultimately connects to _____.
muscle fiber, myofibrils, endomysium; fasciculus/fascicle, perimysium; epimysium, tendon
Which muscle types are striated? Which are involuntary?
skeletal, cardiac
cardiac, smooth
Why are muscle fibers multinucleated?
They are formed by the fusion of multiple myoblasts, some of which can be seen as ‘satellite cells’ in mature muscle fibers.
Which protein anchors two myofibrils to each other? Which anchors actin to the Z disk? Myosin to the Z disk?
desmin, α-actinin/nebulin, titin
In muscle contraction, the release of Pi causes _____, then the release of ADP causes ____, and the binding of ATP causes ____.
binding of myosin head to actin; power stroke (ACTIN is dragged toward the CENTER of the sarcomere); release of myosin from actin (relaxation)
Actin filaments are wrapped with ____ fibers that are held in place with _____. This blocks myosin binding and inhibits contraction unless ____ is present.
tropomyosin, troponin, Ca2+ (calcium binds troponin which moves tropomyosin out of the way)
Deep invaginations of the sarcolemma that penetrate the muscle fiber are called _____. Membrane depolarization travels down these invaginations, opening ______ and stimulating contraction.
Transverse tubules (T-tubules), calcium channels
Type 1 muscle is \_\_\_\_\_\_ and Type 2B is \_\_\_\_\_\_. How do they differ in these qualities? Vascularization Fiber diameter Contraction speed Myoglobin Mitochondria Enzymes Sarcoplasmic reticulum Innervation
Red/slow twitch relative to white/fast twitch: Rich vasculature Small diameter fibers (weaker contraction) Slow (resistant to fatigue) High [myoglobin] (gives it red color) Many mitochondria Rich in oxidative enzymes SR not extensive Small diameter nerve fibers
What is the function of a muscle spindle? What types of fibers does it contain? What type of innervation?
Detects muscle stretching (propioception)
Nuclear bag fibers and nuclear chain fibers (“Intrafusal fibers”)
Group 1A afferent, Group 2 afferent (sensory), static gamma motor (efferent) neurons
How can cardiac muscle be easily identified?
intercalating disks that connect the branches of cardiac muscle fibers; one nucleus (sometimes two)
What types of cellular connections do intercalating disks use?
Gap junctions (important for electrochemical communication!), desmosomes
Atrial granules are released from atrial myocytes and contain _____, which lowers blood pressure by…
atrial natriuretic peptide; increasing Na+ export from circulatory system (taking water with it, reducing blood volume) and relaxing smooth muscle of blood vessels (vasodilation). This is the exact opposite of aldosterone.
In smooth muscle, networks of ___, ___, and ____ intersect at junctions called ____, distributing the contractile strain throughout the cell.
actin, desmin, vimentin; dense bodies
