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cardiac muscle characteristics
T-tubules and mitochondria, SR is less developed than skeletal muscle and stores less Ca++,
functions of skeletal muscle tissue
produce movement, maintain body posture and body position, support soft tissues, guard entrances and exits, body temperature, store nutrient reserves
delicate, elastic connective tissue, surrounds individual skeletal muscle cells (fibers) contains capillary networks, satellite cells and nerve fibers
sarcoplasmic reticulum (SR)
network of smooth ER surrounding each myofibril, pairs of terminal cisternae form perpendicular cross channels, functions in the regulation of intracellular Ca2+ levels
intercalated disks in cardiac muscle tissue
provide very little resistance to the passage of action potential
cardiac muscle tissue
involuntary control, contracts rhythmically and does not tire easily, self exciting
skeletal muscle characteristics
voluntary control, contracts rapidly and vigorously but tires easily, may exert great force
high concentration of calcium ions compared to sarcoplasm, membrane becomes more permeable to calcium ions when stimulated, controls contractions
continuous with the sarcolemma, penetrate the cells interior at each A-band - I-band junction, associate with the paired terminal cisternae to form triads that encircle each sarcomere
muscle contraction occurs when
SR releases Ca++ into the sarcoplasm, signal rapidly distributed by t tubles
physically and functionally discrete parts of a muscle fiber, shorten to produce muscle contractions, composed of myofilaments
region of a myofibril between two successive Z discs, smallest contractile unit of a muscle fiber, composed of thick and thin myofilaments
holds the myosin in place, thus maintaining the organization of the A band, helps the muscle to resist excessive stretching and helps in muscular recoil, structural protein
cytoplasmic protein that links the cytoskeleton to the extracellular matrix, stabilizes the sarcolemma, structural protein
thick filament (myosin)
rod-like tail that ends in two globular heads (cross bridges), cross bridges (head) interacts with active sites on thin filaments
skeletal muscle contraction
pull on attached tendons which create tension and tension applied to object overcomes resistance and pulls object towards source of tension, this requires ATP
normal skeletal muscle is under neural control
1. activated by somatic motor neurons 2.neurons stimulate of sarcolemma
sliding filament theory
muscle contraction involves the sliding movement of the thin filaments past the thick filaments, Hugh Huxley 1954
steps in muscle contraction
1. signal from brain/spinal cord 2.excitation-contraction coupling 3.contraction cycle
Neuromuscular Junction (NMJ)
place where a neuron meets the sarcolemma of a muscle cell, usually found in the middle of a muscle cell
part if NMJ, neuron coming from the spinal cord and connecting with the sarcolemma, secretes the neurotransmitter Ach
post-synaptic membrane (motor end plate)
part of NMJ, region on sarcolemma that contains membrane receptors for ACh
events at the neuromuscular junction
1.nerve impulse arrives at axon terminal 2.ACh is released and binds with receptors on the sarcolemma 3.Electrical events lead to the generation of an action potential 4. Begins the excitation-contraction cycle
recruitment of motor units
not every fiber of a muscle HAS to contract simultaneously, increase intensity=increase in motor units
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