it is considered feedback mechanisms because the menstrual cycle only happens when the hormone is released, it causes the target tissues to react, that reaction is the feedback.
Answer:
Cancer is basically a disease of uncontrolled cell division. Its development and progression are usually linked to a series of changes in the activity of cell cycle regulators. For example, inhibitors of the cell cycle keep cells from dividing when conditions aren’t right, so too little activity of these inhibitors can promote cancer. Similarly, positive regulators of cell division can lead to cancer if they are too active. In most cases, these changes in activity are due to mutations in the genes that encode cell cycle regulator proteins.
Explanation:
Receptors detect changes in the environment. For a stimulus to elicit a response, certain cells must have an appropriate receptor. Stimulation of the receptor initiates a specific signal pathway.
He is WRONG
Explanation:
Any atom at the ground state has its orbital levels fill from the bottom (close to the nucleus) – up. The inner orbitals are of lower energy state and fill first because the atoms ‘likes’ to exist in the low energy and more stable state. Only when the atom is in an excited state do some of the electrons in the lower orbital levels shift to higher unfilled orbitals.
