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1. A neurone is separated from the skeletal muscle by the neuromuscular junction. This is a chemical synapse and so information is transferred via neurotransmitters. What name is given to areas of neurotransmitter release?
2. The neurotransmitters released from the neurone terminus (the post-synaptic bulb) are usually transported in a structure whose formation is encouraged by the action of the protein, clathrin. Examples of this structure include endosomes and lysosomes. What structure is this?
3. Once the neurotransmitters reach the sarcolemma (the membrane of the skeletal muscle), they bind to proteins which open as a response, allowing sodium ions to rush into the muscle fibre. What name is given to these proteins?
4. The entry of sodium ions (Na+) into the cell causes a small depolarization, which causes more sodium ions to enter, eventually leading to a full action potential at the sarcolemma. What is this an example of?
5. The action potential which is generated on the sarcolemma (muscle membrane) travels down a structure known as a T-tubule, eventually activating the Ca++ (calcium ion) release channel. On which intracellular component is the Ca++ release channel found?
6. The Ca++ release channel greatly increases the concentration of calcium ions within muscle fibres. The role of the Ca++ ions is to cause a conformational change, allowing muscle contraction to occur. What name is given to the tropomyosin associated protein which binds calcium ions in skeletal muscles?
7. The binding of calcium leads to a conformational change of the protein, tropomyosin. This change allows an actin-myosin cross-bridge to form. Which of the following best describes this cross-bridge?
8. The loss of a molecule of ADP (adenosine diphosphate) from the actin-myosin cross-bridge gives the first major step in muscle contraction, as the two actin and myosin filaments slide over one another, shortening the muscle fibre. What is this action called?
9. In order for further contraction or relaxation of the muscle to occur, the actin-myosin cross-bridge must be broken. Which molecule is directly responsible for this, its absence in death usually leading to rigor mortis?
10. As long as calcium levels within muscle fibres are high (and there is sufficent energy), a muscle will keep contracting until the fibres exist in their shortest possible form. How are calcium ions removed from the cytoplasm (sarcoplasm), allowing muscles to relax?
Source: Author
doublemm
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WesleyCrusher before going online.
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