For each scenario in the attached handout write down whether the scenario is positive or negative feedback.
1. ________________________________ If blood temperature rises too high,
specialized neurons in the hypothalamus of the brain sense the change. These
neurons signal other nerve centers, which in turn send signals to the blood
vessels of the skin. As these blood vessels dilate, more blood flows close to the
body surface and excess heat radiates from the body.
2. ________________________________ If the blood temperature falls too low,
specialized neurons in the hypothalamus of the brain sense the change and
signals are sent to the cutaneous arteries (those supplying the skin) to constrict
them. Warm blood is then retained deeper in the body and less heat is lost from
the surface.
3. ________________________________ Part of the complex biochemical
pathway of blood clotting is the production of an enzyme that forms the matrix of
the blood clot. This has a self- catalytic, or self-accelerating effect, so that once
the clotting process begins, it runs faster and faster until, ideally, bleeding stops.
4. ________________________________ During childbirth stretching of the uterus
triggers the secretion of the hormone oxytocin, which stimulates uterine
contractions and speeds up labor.
5. ________________________________ The walls of arteries stretch in the
presence of high blood pressure. Baroreceptors located in these walls also
stretch and as a result, asignal is sent to the brain which in turn slows down the
body’s heart rate. This slows the flow of blood through the arteries causing less
pressure. As BP drops the baroreceptors become flaccid and a signal is sent to
speed up the heart rate.