9.2

Question 1

Negative feedback

Answer 1

The primary mechanism of homeostasis is negative feedback.
-The response of a system that acts to maintain equilibrium by compensating for any changes made to the system.
—Homeostatic mechanisms include three elements:
-A sensor
-A integrator
-An effector

Question 2

Negative feedback mechanisms

Answer 2

The sensor consists of tissues or organs that detect any change in external or internal factors. The integrator accepts the information gathered by the sensor and acts as a processing centre. The effector is a system that is activated if the environmental conditions do not match set points.

Question 3

Negative feedback mechanisms in animals

Answer 3

Mammals and birds must maintain body temperature within a relatively narrow range around a set point.
The integrator in this mechanism is located in the hypothalamus.
Portions of the hypothalamus act like a thermostat for the body.
-Groups of neurons in the preoptic region of the hypothalamus receive information from thermoreceptors in various locations.
-This information is compared to the set point (37°C).
-The effectors that are activated depend on whether our body temperature is above or below the set point
-If temperature is too low, vasoconstriction is enacted and shivering commences.
-If temperature is too high, vasodilation is enacted and sweating commences.

Question 4

Sensor

Answer 4

The sensor or receptor is the sensing unit of homeostasis, where it monitors and responds to the changes in the body. The changes in the system are realized by the sensor, which then sends the information to the control unit.

Question 5

Integrator

Answer 5

The brain processes information about blood calcium levels being too high and determines that calcium levels need to be lowered.

Question 6

Set point

Answer 6

The set point for human body temperature, for example, is about 37 degrees C (98.6 degrees F). As the body works to maintain homeostasis for temperature or any other internal variable, the value typically fluctuates around the set point.

Question 7

Effector

Answer 7

Muscles and glands are the effectors as they respond to the signals from the brain to produce heat by shivering, or in the case of increased body temperature, to sweat as a way of cooling the body.

Question 8

Positive Feedback

Answer 8

Actually increase the change in the environmental condition.
-Usually do not result in homeostasis.
–Cause the system to become unstable.
–Almost always operate when a continuous increase in some internal variable is required.