Skeletal Muscles Flashcards
What is the characteristics of skeletts muscle?
Long cylindrical cells Polynuclei Striated VOLUNTARY Rapid contractions
What is the special nomenclature for muscle organelles?
“sarco-“
What is the sarcolemma?
Plasma membrane
What is the sarcoplasm?
Cytoplasm
What is the sarcoplasmic resticulum (SR)?
Endoplasmic Reticulum
What is a sarcosome?
Mitochondria
What does the muscle cell (myocyte) contain of?
Myofibrils (muscle fibres) which contains myofilaments which is composed of thin filaments (actin) and thick filaments (myosin)
What is actin?
Thin filaments
What is myosin?
Thick filaments
What is a T-tubule?
Transverse tubule- deep invagination of the sarcolemma
What is the function of T-tubules?
Transmitting AP through cell
What is a triad?
T-tubule and two terminal cisternae
What is a cisternae?
Enlarged areas of the SR surrounding the transverse tubules
What is the function of SR?
Concentrate Ca++ via ion pumps
Releasing Ca++ into sarcomeres to begin muscle contraction
What are the thin filaments proteins?
F-actin= 2 twisted rows of globular G-actin. The active sites of G-actin strands bind to myosin Tropomyosin= a double strand, prevents actin-myosin interaction Troponin= globular protein, binds tropomyosin to G-actin, controlled by Ca++ Nebulin= holds F-actin strands together
What are the parts of thick filaments?
Myosin tails and myosin heads
Describe how muscle contraction is initiated
AP is propagated along the sarcolemma down the T-tubules releasing Ca++ from the terminal cisternae of SR.
Calcium ions binds to troponin that changes shape and remove the blocking action of tropomyosin exposing actin active sites.
Myosin heads crossbridning and attach to actin pulling the filaments towards center of sarcomere= muscle contraction
How does muscle contraction end? (Relaxation)
Ca++ is recaptured by SR actin active sites is blocked by tropomyosin= no crossbridge formation and relaxation occures= passive return to resting length
What is the all or non principle?
Muscle fibers are either contracted or relaxed
What is a motor unit?
The number of fibers affected of one motor neuron
What is summation?
Rapid sequence of stimuli, muscle twitches fuse into each other each subsequent one being stronger than the one before
What is tetanus?
Very rapid sequence of stimuli without relaxation
