Homeostasis is the capacity of the organism to keep internal systems at equilibrium. 1) Negative feedback. 2) Negative feedback to counter the blood pressure increase. 3) Possitive feedback.
When talking about homeostasis, we are referring to the organism's capacity to keep the body in constant internal equilibrium, even when the external environment is oscillating.
Homeostasis is critical to keep the correct internal functioning of the body.
Functions like blood pressure, body temperature, respiratory rate, and blood glucose levels, among others, are kept in a restricted range around a reference point, even though external conditions may be changing.
1. Negative feedback
- Body systems homeostatically controlled are kept constant by negative feedback.
- Any change that might occur in the internal functioning will be countered by negative feedback.
- Negative feedback needs receptors, central control, and effectors.
In the exposed example,
- Receptors are in vessels and they detect a decrease -or increase- in blood pressure.
- The central control is the SNC, the medulla oblongata. When it receives information about the blood pressure decrease, it sends signals to produce changes that correct that deviation and bring the internal conditions back to the normal range.
- Effectors are muscles, organs, and other structures that modify their function to correct the deviation. The heart muscle increases the heart rate, and the vessels muscles decrease the diameter.
2. Increases in blood pressure higher than the set point
- The receptors in the blood vessel walls detect the increase in blood pressure,
- The receptors send a message to the medulla oblongata,
- The medulla oblongata sends messages to effectors ⇒ the heart and blood vessels.
- The heart rate decreases and the blood vessels increase in diameter.
- The blood pressure drops to a value within the range around the reference value.
This is a negative feedback opposite to the first one.
3. Possitive feedback
- Positive feedback is opposite to negative feedback
- It is a process by which the body detects a change, and activates mechanisms that accelerate that change, instead of countering it.
- Depending on the scenario, positive feedback can also help homeostasis. However, in many cases it produces the opposite effects and can turn into life-threatening.
When an individual is suffering from a hemorrhage, a cascade of events occurs. There is constant blood loss and blood pressure decrease, which carries the consequent negative effects, such as the decrease in the capacity of ventricle contraction, and the decrease in the cardiac output.
A severe hemorrhage might lead to a quick death.
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