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ANSWER: Nitrogen, oxygen or gas, dust particles
When an external stimulus crosses the threshold, a muscle fibre will respond.
<h3>The level of the threshold</h3>
- For the identification of the electrical activity carried out by the active muscles, the threshold level is a crucial consideration.
- A portion of the electrical activity carried out by the target muscles may be excluded if the chosen threshold level is higher than the overall activity.
<h3>What is the stimulus threshold for muscle contraction?</h3>
- A certain stimulus magnitude is necessary for muscle contraction.
- The threshold stimulus is the smallest amount of force needed for a stimulus to cause a muscle to contract in response.
- If the stimulus intensity is less than this threshold value, there is no response.
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Air moves into the lungs when the air pressure in the lungs is lower than the air pressure outside of the lungs. This occurs when the muscels of the diaphragm contract.
You can see this by breathing in and out deeply. When you breath in you can feel your chest being pushed up and out by your diaphragm. The reason the pressure in the chest is lower is that when you breathe in you are increasing the volume of your chest. As there is the same amount of air in your chest the pressure decreases.
Answer:
a or b
Explanation:
sorry cant really classify it brainlest on the effort tho?