mammalian muscles- animal responses Flashcards
3 types of muscle found within mammals
-skeletal, cardiac, smooth
muscle fibres
-makes up striated muscle
-each fibre contains an organised arrangement of contractile proteins in the cytoplasm
-each fibre surrounded by cell surface membrane
-each contains many nuclei
muscle equivalent of csm, cytoplasm, and endoplasmic reticulum
-csm=sarcolemma
-cytoplasm=sarcoplasm
-endoplasmic r=sarcoplasmic reticulum
sarcolemma overview
-contains many deep tube-like projections (similar to crystae) called T tubules which run close to sarcoplasmic reticulum
-contain many protein pumps taht transport calcium ions into the lumen of the SR
myofibrils
-in sarcoplasm
-bundles of actin and myosin filaments which slide past each other during muscle contraction
6 main parts of a myofibril + DESCRIPTION
-H band, only thick myosin present
-I band, only thin actin present
-A band, areas where only myosin is present and areas where actin and myosin overlap
-M line, attachment for myosin filaments
-Z line, attachment for actin filaments
-sarcomere, section of myofibril between 2 z lines
Fast muscle fibres
-myosin heads bind and unbind from the actin-binding sites five times faster than slow muscle fibres
-Their rapid contraction-relaxation cycle means they need large amounts of calcium ions present to stimulate contraction
-fewer capillaries
-lower amounts of myoglobin
sliding model theory (full steps)
-AP arrives at neuromuscular junction=Ca ions released from SR
-CA bind to troponin, causing to change shape=changes position on actin
-mysoin binding sites now exposed on actin
-globular heads on myosin molecules bind to sites on actin forming cross bridges
-myosin heads move and pull actin filaments towards sarcomere causing muscle to contract small distance
-ATP hydrolysis occurs at myosin heads, providing the energy needed to detach from actin
-process repeats, shortening the sarcomere until the muscle has fully contracted
