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CH9
9.2-3 Skeletal Muscle Fibers
| Question | Answer |
|---|---|
| What's the difference between sarcolemma, sarcoplasm, and sarcomeres? | Sarcolemma acts as the plasma membrane, it acts as a barrier between extra/intracellular compartments. Sarcoplasm is the striated muscle fiber's cytoplasm. Sarcomeres are the smallest functional unit of muscle fibers. |
| What is the makeup of a sarcomere? How does that relate to a myofibril? | Sarcomere is an A band with half an I band on each end. They line the myofibril like boxcar trains. |
| What does the sarcoplasm contain? | Glycosomes for glycogen storage and myoglobin for O2 storage. |
| What ARE myofibrils? | They're densely packed, rodlike units of cells that take up 80% of muscle cell volume. |
| What are 4 features of myofibrils? | Striations, sarcomeres, myofilaments, and molecular composition of myofilaments. |
| What is myocytes/myogenesis? | Myocytes develop from myoblasts to form muscles, the process is called myogenesis. Myogenesis is the formation of muscle tissue during embryonic development. |
| Striations (feature of myofibrils) | Stripes repeating from repeating dark/light colored bands. A bands=dark, I bands=light. |
| What are some traits of the A band & I band? | The A band contains a medial H zone, which is a "lighter" region between the two dark ones. In that H zone, is the vertically bisecting protein M line. The I band contains a Z disc/line, which is a sheet of proteins in the middle of I band. |
| Myofilaments (feature of myofibrils) | Actin/myosin filaments within sarcomeres. ACTIN: thin filament, through I band & partly into A band. Its anchored to Z disc-line MYOSIN: thick filament, extended thru A band & connected @ M line. |
| What are thick myofilaments composed of? | Myosin, obviously! |
| What are thin myofilaments composed of? | Actin, obviously! |
| Molecular composition of myosin | 2 heavy + 4 light polypeptide chains. Heavy chains form the tail of myosin, light chains form globular head. |
| Molecular composition of actin | Composed of G-actin subunits, which bear attachment sites for the myosin heads during contraction. G-actin link=F-actin. |
| What do 2 f-actin strands twist together to become? | A thin filament, actin :) |
| How is actin different than other proteins? | It can transition between two states: G actin & F actin. |
| What is an important function of actin protein? | It's an important contributor to contractile property of muscles and other cells. |
| What is the most abundant protein found in muscle? | Myosin |
| What is skeletal muscle? | Organ made of different tissues |
| 3 Features of Skeletal Muscle | Nerve & blood supply, C.T. sheaths, & attachments |
| Why does each muscle fiber get nerves, artery, and veins? | Nerves supply fibers to control activity, w/o nerves we wouldn't be able to control our skeletal muscles. |
| What is the function of C.T. in skeletal muscles/fibers? | It supports cells and reinforces the muscle. |
| What are the 3 sheaths of C.T. from external to internet? | Epimysium, perimysium, and endomysium |
| Epimysium | Dense irregular C.T. surrounding ENTIRE muscle |
| Perimysium | Fibrous C.T. surrounding the fascicles as a whole and individually |
| Endomysium | Fine areolar C.T. that surrounds each muscle fiber |
| Fascicle | Group of muscle fibers |
| How are the two attachment sites (Insertion/Origin) different/similar? | Insertion is the attachment to movable bone and origin is the attachment to immovable or less movable bone. |
| What is indirect attachment? | C.T. extends BEYOND the muscle, exm: roselike tendon or sheetlike Sponeurosis. |
| How do muscles attach to bone? | By the fusion of their fibrous C.T. to the periosteum of the bone. |
| Which end of the muscle is where the action takes place? | The movable, insertion, end |
Created by:
taylorstenger