Lecture 17

What is deep fascia?

-Deep fascia is a layer of fibrous connective tissue covers skeletal muscles, and binds muscle together -Really inelastic (lots of collagen, not a lot of elastic fibers) -Can divide groups of muscles into fascial compartment -Inflammation will compress vessels and nerves -Puts pressure on nerves and vessels

Why are skeletal muscles always found connecting two different structures? Where will a muscle create movement if it crosses multiple joints?

-If a muscle was attached at both ends to the same bone, no movement would occur -It will create movement at both joints, instead of just one.

What are the myofilaments? What are the proteins of interest in those myofilaments?

-Myofibrils are made up of bundles of myofilaments -Myofilaments are responsible for muscle contraction -There are thick and thin filaments -The thin filaments are made of several proteins including actin, troponin, tropomyosin, and structural proteins -One thin filament=two strands of actin proteins; tropomyosin is the strand that covers active sites/block myosin; Troponin moves tropomyosin out of the way -The thick filament is made mostly of myosin (twisted myosin subunits), it also contains Titin (A structural protein) strands that recoil after stretching -Titin keeps myosin where it needs to be, gives an elastic element to muscles -Actin and Myosin are the contractile components -Troponin and Tropomyosin are Regulatory components -Titin is structural -Titin is anchored at the M-Line, runs the length of myosin, and extends to the Z disc

Describe the internal anatomy of a skeletal muscle fiber (you should know all the structures with pointers in the following figure). What organelles are present? What is the function of those organelles? What are the myofilaments? What are the proteins of interest in those myofilaments?

-Skeletal muscle fibers are very long, large, and multi nucleated -many nuclei allows for production of the large amounts of proteins and enzymes needed for maintaining normal function of these large protein dense cells. -Muscle fibers develop through the fusion of mesodermal/embryonic muscle cells called Myoblasts -Each myoblast contributes a nucleus to the mature muscle fiber -Myofibers contain a cell membrane (Sarcolemma) and their own muscle cell cytoplasm (Sarcoplasm) -The internal Organelles of a myofiber are myofibrils (cytoskeletal proteins arranged in bundles) -Sarcoplasmic Reticulum- surrounds myofibrils, chambers full of Ca2+; stores, releases, and retrieves calcium ions (Ca++). -Transverse tubules- special inward extensions of cell membrane; transmit signals into and through the cell; Extracellular fluid (ECF) is found in T-tubules -Mitochondrion -Free Ribosomes -Sacromeres are the subunit of myofibrils (contractile units of muscle); distance or space between Z discs (zig zag lines); a highly organized arrangement of contractile, regulatory, and structural proteins.

In some individuals, they do not produce the proteins that connect the myofibrils to the sarcolemma. What is the consequence? Can they move their bodies to pick up the telephone?

-Tension would not be transferred to the tendon -No, if tension wasnt transferred to the tendon then the tendon would not be able to pull on the bone to create movement

What are the functions of the skeletal muscle system? What are skeletal muscles capable of doing?

-The functions of the skeletal muscle system are to attach to bones and produce movement Functions of Skeletal Muscle Organs: 1. Produce skeletal movement 2. Maintain body position 3. Support soft tissues 4. Guard body openings 5. Maintain body temperature -Abdominal support -Burns ATP- must be made on demand -Only 60% efficient, rest given off as heat -Skeletal muscles contribute to the maintenance of homeostasis in the body by generating heat. Muscle contraction requires energy, and when ATP is broken down, heat is produced. This heat is very noticeable during exercise, when sustained muscle movement causes body temperature to rise, and in cases of extreme cold, when shivering produces random skeletal muscle contractions to generate heat.

What is significant about the fact that all the connective tissues in a whole muscle are connected to one another and connected to bone?

-Work together to pull on bones and produce movement -the collagen in the three connective tissue layers intertwines with the collagen of a tendon. At the other end of the tendon, it fuses with the periosteum coating the bone. The tension created by contraction of the muscle fibers is then transferred though the connective tissue layers, to the tendon, and then to the periosteum to pull on the bone for movement of the skeleton. -Strong connections, unlikely to tear -Fiber orientation gives muscle "grain" -Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) -Sarcolemma, endomysium, perimysium, and epimysium connected and join to tendon (bundle) or aponeurosis (sheet)

What is the structure of a skeletal muscle cell?

1. Each skeletal muscle is wrapped by a dense, irregular connective tissue called the Epimysium (allows muscle to contract and move while maintaining stability, also separates muscle from other tissues and organs in the area 2. Skeletal muscles are made up of many fascicles which are wrapped in perimysium and are made up of bundles of muscle fibers -This fascicular organization is common in muscles of the limbs; it allows the nervous system to trigger a specific movement of a muscle by activating a subset of muscle fibers within a fascicle of the muscle. 3. Between the individual muscle fibers of a fascicle, there is the endomysium (thin connective tissue layer consisting of collagen and reticular fibers) -The endomysium surrounds the extracellular matrix of the cells and plays a role in transferring force produced by the muscle fibers to the tendons.

In compartment syndrome inflammation within a deep fascial compartment presses on the nerves and blood supply, causing pain. How might this be treated?

Cut an incision in the fascial compartment to relieve pressure and allow blood to flow

Can Skeletal Muscles push?

No, they only pull

Are skeletal muscle tissue and skeletal muscle organs the same? How are they different?

Skeletal muscles organs contain skeletal muscle tissue/fibers, blood vessels, nerves and connective tissues. Skeletal muscle tissue makes up skeletal muscle organs, therefore it is at a lower level of organization.