In a model of labour, the oxytocin level starts at 1 unit…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In a model of labour, the oxytocin level starts at 1 unit. It is multiplied by the same number in each cycle of contraction. The birth needs a level of at least the units named below. Find the number of cycles in which the level first reaches or passes the need.
- The level rises by in each cycle, and the need is 10 units.
- The level rises by in each cycle, and the need is 40 units.
- The level rises by in each cycle, and the need is 10 units.
Need a reminder? The key ideaShow
Negative feedback keeps a level near a set point. Positive feedback drives a process to its end, as oxytocin does in childbirth. Insulin and glucagon, and PTH and thyrocalcitonin, work in opposite ways. The hypothalamus joins the nervous system to the endocrine system.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Start: unit. Factors: , and .
Plan. Find the smallest so that the factor to the power is at least the need.
Step 1. (a) , which is below . , which is above . So cycles.
Step 2. (b) , which is below . , which is above . So cycles.
Step 3. (c) , which is below . , which is above . So cycles.
Answer: cycles; cycles; cycles.
Check. A larger rise needs fewer cycles. Case (c) has the smallest rise and needs the most.
Watch out. The level is multiplied each time. It does not grow by the same number of units in every cycle.
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