Lecture 11 Flashcards
What are the levels of organisation of the human body?
Body > system (functionally related groups of organs) > organs (collection of tissues) > Tissue (similar cells specialised by function) > Cell > organelle (tiny organ that aids functioning of a cell) > Molecular/atomic.
What is the structure and function of muscle tissue?
Long fibre like cells capable of pulling loads which produce movement and heat, examples of this are our muscles, skeletal, smooth and cardiac.
What functions does skeletal muscle serve?
Movement, heat production, posture and communication.
Is muscle an organ? Why or why not?
Muscle can be an organ as it is constructed from many tissues.
What is the connective tissue arrangement of skeletal muscle?
Muscle fibres wrapped in endomysium and bundled into fascicles, fascicles wrapped in perimysium, these are bundled together along with blood vessels in epimysium and is then coated in fascia, before being joined to a tendon which connects it to bone.
What are the main components of muscle fiber?
T tubules, sarcoplasmic reticulum and myofibrils.
Describe a muscle fiber and its arrangement relative to the other muscle fibers? Why is it striated? What are the myofibrils made of?
Muscle fibers are up to roughly 40 cm, arranged parallel with a cylindrical shape and multi-nuclear. They are striated due to sarcomeres (a protein arrangement). The myofibril is made from long chains of sarcomeres, these sarcomeres are made up of the myofilaments myosin (thick filament) and actin (thin filament).
What are the sarcolemma and sarcoplasmic reticulum?
The sarcolemma is the cytoplasm of muscle cells, the sarcoplasmic reticulum is the muscle cells endoplasmic reticulum.
What are Z lines? What is the typical length of a sarcomere and how does contraction work?
Z lines are the boundaries of sarcomeres, they link the actin filaments. A typical sarcomere length is 2 micrometers and contraction works by pulling the actin filaments together by the myosin filaments, note that neither one shrinks, they just interdigitate.
What two things are necessary for contraction?
Energy and calcium ions.
What does the function of a muscle depend on? Why?
The length of the muscle fibres, the number of muscle fibres and the arrangement of muscle fibres.
Length: fibres can shorten up to 50% of the resting length, hence to give a large range of movement requires long muscle fibres
Number of muscle fibres: more muscle fibres means a greater cross sectional area and tension is directly proportional to cross sectional area. Hence more muscle fibres means more tension can be produced.
Muscle fibre arrangement: muscle fibres which are pennate to the tendon allows more fibres to fit in the same space but decreases length.
What does a pennate muscle mean? What arrangements can there be?
Oblique (diagonal) to the line of pull.
Unipennate: all from one angle
Bipennate: approaches from two angles
Multipennate: approaches from multiple angles.
What is muscle tone? How is it maintained?
Muscle tone refers to how even relaxed muscles are slightly active, this helps keep muscles firm and healthy and maintains posture but does not produce movement.
It is maintained by nerve impulses activating the muscle fibres.
