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CH 48
Musculoskeletal system
| Question | Answer |
|---|---|
| What are microfilaments? | Proteins that generate contractile forces by changing conformation. They reach their highest level of organization in muscle cells |
| What is myosin and actin? | The proteins responsible for the contraction and relaxation of muscle |
| What are the three types of vertebrate muscle? | Smooth, Cardiac, and Skeletal |
| What does smooth muscle do? | Provides contraction for internal organs, moves food through digestive tract, controls blood flow, and empties bladder. Structurally simple - single nuclus & long spindle shaped |
| What is the structure of cardiac muscle? | They are branched & appear striated b/c of the regular arrangement of their actin and myosin filaments. Branching creates a meshwork that resists tearing & allows the heart to withstand the high pressures of blood pumping w/o leaking |
| What are intercalated disks? | Disks that provide strong mechanical adhesions between adjacent cells |
| How are cardiac muscle cells in electrical contact with one another? | Depolarization begun at one point in the heart rapidly spread through muscle mass |
| What are all voluntary movements controlled by? | Skeletal muscle, or striated muscle (called this b/c of its striped appearance) |
| What are muscle fibers and what is their structure? | Skeletal muscle cells. They are large and have many nuclei because they're a fusion of many individual cells |
| What are myofibrils? | Thin actin units surrounded by thick myosin units. Each muscle fiber is packed with bundles of myofibrils. |
| Myofibrils consist of repeating units called: | Sarcomeres |
| What are sarcomeres bounded by? | Each sarcomere is bounded by Z-lines, which anchor the thin actin filaments |
| Where is the A-band? | At the center, housing all the myosin filaments |
| What is the H-zone and the I-band? | Areas where actin and myosin do not overlap and appear light. |
| What contains proteins that support the myosin filaments? | M-band |
| What happens when a muscle contracts? | The sarcomere shortens. H-zone becomes narrower, Z-lines move toward A-band and actin & myosin slide past each other as the muscle contracts. |
| What does each myosin molecule consist of? | Two long polypeptide chains coiled together, each ending in a large globular head |
| What are myosin filaments composed of? | Many myosin molecules arranged in parallel |
| What does an actin filament consist of? | Two chains of actin molecules twisted together |
| What occurs when a myosin head binds to actin? | Its orientation changes & a force is exerted that causes actin to slide. The myosin head then binds ATP & releases the actin |
| What does contraction of the sarcomere involve? | Many cycles of interaction between many myosin heads and actin |
| Can backsliding of actin occur? Why or why not? | No because the many surrounding filaments create a system of interacting cycles |
| What purpose does ATP serve in muscle contractions? | ATP is needed to break actin-myosin bonds. The energy is used to stop muscles from contracting |
| What is rigor mortis and what is the cause? | Rigor mortis is the stiffening of muscles after death. With no ATP being made after death, the actin-myosin bonds can't be broken |
| What two proteins block the myosin binding sites on the actin filament when the muscle is at rest? | Tropoyosin and troponin |
| What happens when Ca2+ is released to the sarcoplasm? | Ca2+ binds to troponin. Troponin and tropomyosin change shape, exposing actin-myosin binding sites. W/ the binding sites out, actin-myosin bonds are made & filaments are pulled past each other, resulting in muscle fiber contractions |
| What structure spreads action potentials into the fiber? | T-tubules |
| Describe slow-twitch fibers (red muscle) | Red muscle is well supplied with blood vessels & fuel reserves. It has many mitochondria & a lot of oxygen-binding molecule myoglobin to provide steady, prolonged ATP production. Long term aerobic work depends on this type of fiber |
| Describe fast-twitch fibers (white muscle) | Have fewer mitochondria & very little myoglobin. They develop maximum tension more rapidly and with greater tension, but they fatigue rapidly too |
| What does the vertebrate skeleton do? | Provides support and protection for the body & is capable of movement with the help of joints. Bones are connected by joints that allow a range of movements |
| How many bones & muscles does the human body have? | 206 bones which work together with more than 600 muscles to provide movement for the body |
| What is the appendicular skeleton? | One of the two main anatomical categories of bones, consisting of the bones of the shoulder and pelvic girdles and bones of the upper & lower extremities |
| What is the axial skeleton? | The other main categories of bones that form the bodies upright axis - skull, vertebral column, ribs and sternum |
| What is cartilage? | Connective tissue with an extracellular matrix of a rubbery mix of collagen & polysaccharide which give strength and reiliency. Found in joints & in stiff, flexible structures, such as the nose and ears |
| What is bone? | Mostly extracellular matrix material of collagen fibers & crystals of calcium phosphate, which makes bone hard and rigid |
| Describe the embryonic skeleton of vertebrates | Primarily cartilage, which is gradually replaced by bone during development |
| What is a joint? | Where two bones meet. The human body has several types of joints. Movement is accomplished by antagonistic muscle pairs - one contracting, the other relaxing |
| What is the difference between the flexor and extensor? | The flexor bends the joint and the extensor straigtens the joint |
| What are bones at a joint held together by? | Ligaments, flexible bands of tough, fibrous tissue that connects and supports bones |
| What are tendons? | Straps of connective tissue that attach the muscles to bone |
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cassidylm34
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