Muscle Review
Muscle Fascicle Muscle cell/fiber Myofibril Myofilament
Muscle: Consists of hundreds to thousands of muscle cells
Fasicle: Discrete bundle of muscle cells, segregated from the rest of the muscle by connective tissue sheath.
Muscle Fiber: Elongated multinucleate cell, has branded, striated appearance.
Myofibril: Contractile element, oupy most of muscle cell composed of sacromeres, appear banded.
Sarcomere: Contractile unit, composed of myofilaments made up of contractile proteins. Between 2 Z-discs
Myofilamentsliding of thin and thick filaments cause muscle shortening Thick: contain bundled myosin molecules Thin: contain actin molecules (and other proteins).
Endomysium: Connective tissue around muscle fiber. (Within Perimysium}
Perimysium: Connective tissue around fascicle.
Epimysium: Connective tissue surrounding the whole muscle.
Sarcolemma: Plasma membrane.(around muscle fiber)
Sarcoplasm: similar to cytoplasm- contains large number of glycosomes and myoglobinstores Oxygen.
Striationsrepeating series of A&I bands.
Thick filaments: A-bands. (H- Zone(Thick Filaments), I-Band(Thin Filaments), M-Line(Thick filaments connected by proteins)). Composed primarily of the protein myosin.
Thin Filaments: I-Bands. Extend across I-Bands. Z-Discs(connect Myofibrils). Composed primarily of the protein Actin.
Tropomyosin: spiral about Actin and stiffen it.
Troponin: Binds to actin and tropmyosin.
Regulation of Muscle Contractions: 1. Sarcoplasmic Reticulum: surround each myofibril and on terminal cisternae (end sacs). Regulate ionic calcium. Stores and releases it. 2. T tubules: At each A&I Band junction, the sarcolemma penetrates into the cell creating a tube. Forms triads terminal cisternae, T-tubule, Terminal cisternae. Condut impulses to deepest regions of muscle cell and every sarcomere.
Sliding Filament Theory of Contraction
Neuromuscular Junction: terminal position where neuron meets muscle
Motor Neuron: Causes skeletal muscles to contract.
Recruitment: Stimulation of additional motor units for increased strength of contractions. # of cells affect the degree and strength of movement.
Smaller motor units containing less cells precise movements
Large motor units provide constant level of tension and resistance to stretch (muscle tone).
Motor nerve cut causes a muscle to be flaccid (muscle tension lost).
Motor Unit: motor neuron and all the cells it stimulates.
Muscle Metabolism:
Hydrolisis: ATPADP
ADPATP: synthetic energy and dehydration synthesis.
When ATP supplies are low 1. Hydrolysis with Phosphate 2. Glycolysis 3. Kreb’s Cycle.
Muscle Fiber Types
White Muscle Fiber: Large in diameter, high glycogen, few mitochondria,