Tissues 7: Muscle Flashcards
Name the two types of muscle contraction?
Isometric Contraction Isotonic Contraction
What is Isotonic Contraction
muscle changes length and tension remains the same Concentric: shortening Eccentric: lengthening add pic
What is isometric contraction
tension develops and muscle does NOT change length add pic
What is the ultrastructure of Skeletal muscles?
Skeletal muscle consists of bundles of muscle cells known as myofibres. add pic
Name some features of myofibres?
Large & Cylindrical Multinucleate Packed with myofibrils
What doe myofibrils appear as?
Light & dark bands giving them a ‘striated’ appearance Add pic
How is muscle contraction initiated?
Muscle contraction is initiated by an increase in the cytosolic calcium concentration
List the steps that causes contraction of a skeletal muscle?
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Name some microscopic features of Myofibres
long, multinucleate cells, T-tubules, extensive SR
What is the strucural and functional unit of skeletal muscle called
Sarcomere
Recall the process of excitation and contraction coupling
AP propagates along T-tubules®– change in conformation of DHPR®– RyR opening ®– Ca2+ efflux from SR into cytoplasm
What is a Z line in a Scarcomere
Defines lateral boundaries of sarcomere add pic
What effect does Calcium have on troponin and tropomyosin.
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List the steps for the sliding filament theory?
In the presence of Ca2+ movement of troponin from tropomyosin chain Movement exposes myosin binding site on surface of actin chain ‘Charged’ myosin heads bind to exposed site on actin filament This binding & discharge of ADP causes myosin head to pivot (the ‘power stroke’) pulling actin filament towards centre of sarcomere ATP binding releases myosin head from actin chain ATP hydrolysis provides energy to ‘recharge’ the myosin head add pic
What are purkinje fibres
large cells that rapidly conduct electrical impulses
What are cells of the heart known as
Cardiomyocytes
What are myocytes
Muscle cells
Where are pacemaker cells found
Atrial ventricular node and Sinotrial node add pic
What type of muscle are cardiomyocytes
striated muscle
What are intercelated discs and what features do they have to help action potentials spread rapidly around the heart?
Specialised regions connecting individual cardiomyocytes Contain numerous gap junctions: allow action potentials to spread rapidly from cell to cell. add pic
What is the difference between Excitation- Contraction cupling in skeletal and cardiac E-C coupling?
In Skeletal muscle, Ca comes from intracellular Ca stores (via changes in receptors), whereas in Cardiac muscle, Ca entrs through VGCaCs and Ca induced Ca release (from SR) occurs.
As with skeletal muscle, contraction is initiated by an increase in the cytosolic Calcium concentration. However there are subtle differences in the way the intracellular Calcium levels rise within these two cell types:
1) The action potential propagates along the cardiomyocyte membrane and T-Tubule (same as Skeletal Muscle)
2) Depolarisation opens voltage-gated Ca2+ channels (VGCCs) Ca2+ influx
3) This Ca2+ has three main effects: Ca2+ induced Ca2+ release
i) (CICR) by binding to RyR on SR
ii) Initiate contraction binding to troponin
iii) Further depolarisation
4) Thus depolarisation increase in intracellular Ca2+ muscle contraction ( Same as skeletal muscle)
What is different about the arrangement of actin and myosin in smooth muscle?
Do NOT contain regular arrangement of actin & myosin
List the steps for E-C coupling in Smooth muscle
Depolarisation activates VGCCs (voltage gated calcium channel) which allows the influx of calcium into the cells The calcium binds to the intracellular protein Calmodulin (CaM) This Calcium-CaM complex activates myosin light chain kinase (MLCK) MLCK phosphorylates the myosin ligh chains allowing them to form cross-bridges with the actin filaments resulting in contraction
