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Flashcards in Muscle tissue Deck (11)
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Overview of muscle form & function

•Muscle tissue responsible for body movement
•Produce heat (as much as 70% of body heat)
•Maintenance of posture
•Muscle cells consist of filaments containing proteins
•actin and myosin
•together enable muscle contraction
•Three types of muscle tissue in the vertebrate body
•skeletal muscle
•smooth muscle
•cardiac muscle


Skeletal muscle tissue

•Consists of bundles of long cells that are called muscle fibers
•Form by the fusion of many cells-resulting in multiple nuclei in each muscle fiber
•Arrangement of contractile units (sarcomeres) along thefibers give the cells a striped (striated) appearance


Skeletal muscle tissue function

•Attached to bones by tendons
•Skeletal muscle, or striated muscle, is responsible for voluntary movements
•Produce ~70% of body heat, through involuntary movement, i.e. shivering
•Maintenance of posture
•In adult mammals, building muscle increases the size but not the number of muscle fibers


Smooth muscle tissue

•Lacks striations
•Found in the walls of the digestive tract, urinary bladder, arteries, and other internal organs
•Spindle shaped


Smooth muscle tissue function

•Forms the supporting tissue of blood vessels, hollow internal organs, such as the stomach, intestine, and bladder
•Responsible for involuntary body activities
•churning of the stomach
•constriction of arteries


Cardiac muscle tissue

•Striated like skeletal
•Branched fibers that interconnect via intercalated disks


Cardiac muscle tissue function

•Cardiac muscle forms the contractile wall of the heart
•Has similar contractile properties as skeletal muscle
•Branched fibers relay signals from cell to cell and help synchronize heart contraction


The Role of Calcium and Regulatory Proteins

•The regulatory protein tropomyosin and the troponin complex, a set of additional proteins, bind to actin strands on thin filaments when a muscle fiber is at rest
•This prevents actin and myosin from interacting


what is required for a muscle fiber to contract?

•For a muscle fiber to contract, myosin-binding sites must be uncovered
•This occurs when calcium ions (Ca2+) bind to the troponin complex and expose the myosin-binding sites
•Contraction occurs when the concentration of Ca2+is high; muscle fiber contraction stops when the concentration of Ca2+is low


what is thee stimulus leading to the contraction of a muscle fiber?

•The stimulus leading to contraction of a muscle fiber is an action potential in a motor neuron that makes a synapse with the muscle fiber
•The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine
•Acetylcholine depolarizes the muscle, causing it to produce an action potential


what happens after acetylcholine depolarises the muscle, causing it to produce an action potential?

•Action potentials travel to the interior of the muscle fiber along transverse (T) tubules•The action potential along T tubules causes the sarcoplasmic reticulum (SR)to release Ca2+•The Ca2+binds to the troponin complex on the thin filaments•This binding exposes myosin-binding sites and allows the cross-bridge cycle to proceed