This is a summary of every learning objective (7.1-7.15) for Topic 7, RFL on the Edexcel Biology A (Salters-Nuffield) specification. I have arranged my notes answering each objective, and have given definitions, core practical information, and equations, based from the textbook.
These notes inc...
BIOLOGY SPECIFICATION NOTES
Edexcel Biology Salters-Nuffield A AS/A-Level
Key:
Definitions are in turquoise
Core practicals are in orange
Equations are in green
Topic 7: Run for Your ife (RFL)
7.1 Know the way in which muscles, tendons, the skeleton and ligaments interact to enable
movement, including antagonistic muscle pairs, extensors and flexors.
Muscles contract and relax to bend (flex) and straighten (extend). Muscles bring about
movement at a joint. A joint is a connection made between bones of the body.
Muscles work in antagonistic pairs. A muscle that contracts to cause extension of a joint is
an extensor, and the corresponding muscle is called a flexor as it contracts to reverse the
movement.
An example of this could be flexing your arm upwards. The bicep acts as a flexor, as it
contracts. The tricep acts as an extender, as it extends.
The hip, knee and ankle joints are called synovial joints. The bones have a cavity between
them filled with synovial fluid so they can move freely. Ligaments, strong and flexible, join
bone to bone. Tendons, inflexible, hold muscle to bone. Cartilage protects bones within
joints by acting as a shock absorber and absorbing synovial fluid.
, 7.10 i) Know the structure of a muscle fibre. p.135
A muscle is made out of fascicles.
A fascicle is made from muscle fibre. They are bound by connective tissue.
Muscle fibre is made from myofibrils.
Myofibrils are made from sarcomeres.
The muscle fibre is actually just a single muscle cell, and they can be several centimetres
in length. Muscle cells are also striped, and are multinucleate. This is because a single
nucleus can not control the metabolism of a long cell effectively.
The myofibrils are made up of repeating contractile units called sarcomeres. These are
made from two proteins. They contain the thin protein actin, and the thick protein myosin.
Contractions are brought about by coordinated sliding of these protein filaments with the
sarcomeres.
When actin is on its own, it forms a light band. When myosin is on its own, it forms a dark
band. When both occur, there is an intermediate coloured band.
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