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Muscles p1
AQA A-level biology nervous systems year 13
| Term | Definition |
|---|---|
| Cardiac muscle | Specialised muscle tissue found only in the heart, responsible for involuntary contraction and controlled by the autonomic nervous system, is striated and never fatigues |
| Smooth muscle | Non-striated muscle found in the walls of blood vessels and the intestines, under involuntary autonomic control, has slow sustained contractions |
| Skeletal muscle | Striated muscle under conscious control of the somatic nervous system, attached to the bones by tendons, can contract rapidly and powerfully, is able to adapt and undergo hypertrophy |
| Skeletal muscle pairs | Skeletal muscles often come in antagonistic pairs of flex ion and extension. The agonist (biceps) is the primary mover & creates force for the movement. The antagonist (triceps) don’t get longer when they relax but can be extended by the agonist |
| Actin filament | Thin thread-like protein structures composed of globular actin proteins that can polymerise to form long, flexible filaments |
| Tropomyosin | Long fibrous protein that controls the interaction between actin and myosin by covering binding sites on actin filaments and preventing the myosin from binding |
| Troponin | Protein complex which binds to calcium ions and undergoes a conformational shape change to shift the tropomyosin off the actin binding sites |
| Actin binding site | A specific region on the myosin that allows it to bind to the actin and slide along it, generating the tension needed for muscle movement |
| Process of muscle contraction: 1 | Myosin heads with ADP and Pi bound to them are ready to bind to the actin, however troponin is blocking it so the muscle is relaxed |
| Process of muscle contraction: 2 | Calcium ions from the sarcoplasmic reticulum bind to the troponin and change its shape to shift the tropomyosin and allow the myosin heads to bind to the actin and create tension |
| Process of muscle contraction: 3 | The myosin heads change shape due to binding with the actin and the two fibres pull each other along causing the ADP and Pi to be removed |
| Process of muscle contraction: 4 | ATP binds to the myosin head causing the myosin to release the actin |
| Process of muscle contraction: 5 | ATP breaks down to ADP and Pi and the myosin head is cocked to bind again. The process can now be repeated for as long as there is calcium and ATP |
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