Lecture 8 Flashcards
What are the three muscle types and their function? What are they made of?
Cardiac muscle is an involuntary muscle used to pump blood around the body, and is only found in the heart. Smooth muscle is involuntary muscle found lining hollow organs e.g intestines. Skeletal muscle is voluntary muscle that applies force to bones to control posture and body movements. All three muscles are made of muscle fibres.
What are the roles of skeletal muscle?
Develops force by contracting/shortening. It is important for movement and posture. It is also used for support and protection of internal organs, and voluntary control over major openings for the passage of substances (e.g feces). It is mostly voluntary, but sometimes moves involuntarily (e.g shivering, coughing)
What is skeletal muscle structure?
Each muscle is made of of individual muscle cells called fibres, which are arranged parallel. These fibres bundle up into fasicles. These fasicles then bundle into muscles. These are highly vascular and nerves, and are sheathed in connective tissue. This connective tissue forms tendons, which connect muscle to bone.
Why must muscle fibres run parallel?
So that they can generate adequate amounts of force.
Why is skeletal muscle highly vascular?
This is because they need more energy and have more waste to take away.
Why does skeletal muscle have lots of nerves?
Because it is a muscle that is voluntary, so it needs lots of nerves to send signals to make the muscle move/contract.
Why is there connective tissue around the fasicles and muscles?
So that they do not rub against each other, causing friction which would gradually wear the muscles away. Also there to connect to the bone.
What is the structure of an individual muscle fibre?
Made of bundles of myofibrils, which are made of repeating sarcomeres. Sarcomeres are made of contractile proteins/myofilaments, which are made of myosin and actin. A sarcomere is what contracts. Actin is the thin filament, and myosin is the thick filament. Outside of the muscle fibre is a plasma membrane called the sarcolemma, which signals travel across. There are also transverse tubules which go into the muscles, allowing signals to travel quickly. There’s also the sarcoplasmic reticulum on the inside of the sarcolemma, which stores Ca2+ for muscle contractions.
What is excitation-contraction coupling? (Brief idea)
This is how muscles work, and pairs a signal event with a mechanical event.
How does muscle excitation in EC coupling work?
3 proteins are key to muscle excitation. The DHPR is located on the T-tubule, and will receive the signal, activating it. The active DHPR will then interact with the RyR protein, which opens. It is a passive channel, allowing the passive diffusion of Ca2+ from the sarcoplasmic reticulum, activating the myofilaments and causing contraction. SERCA will then use active transport to pump the Ca2+ back into the sarcoplasmic reticulum, stopping the contraction and getting ready for the next one.
