7th Grade Science Student ebook

16.3 Other Organ Systems.

CHAPTER 16: HUMAN BODY SYSTEMS

Feedback control systems

What are

feedback control

systems?

Sophia was hot so she turned on the

air conditioner. The thermostat was

set to 70°F. After awhile, the air

conditioner turned off automatically

when the room temperature reached

the thermostat setting. A thermostat

is a feedback control that sends a

message to the air conditioner to turn

off when a pre-set temperature is

reached. Similarly, your body has

feedback control systems that turn your endocrine glands on or

off. These systems control the levels of hormones in your blood.

An example of a

feedback control

system

Recall that your cells need glucose for cellular respiration. A

feedback control system maintains your blood glucose levels. The

system involves your pancreas, which produces insulin, and your

liver, which stores glucose. When you eat something, glucose from

the food is absorbed by your small intestine and enters your blood.

When blood glucose rises above normal levels, your pancreas

releases insulin into your blood. Insulin tells your liver to take

glucose from the blood and store it for future use. When glucose

levels return to normal your pancreas stops producing insulin

(Figure 16.14).

Diabetes mellitus Sometimes, a feedback control system does not work properly. This

may cause problems for other body systems. A person whose

pancreas cannot make enough insulin has a condition called

diabetes mellitus. That person must monitor blood glucose levels

and may need injections of insulin to keep blood glucose levels

normal. Chronic high blood glucose levels may cause damage to the

eyes, kidneys, nerves, heart and blood vessels.

Figure 16.14: A feedback control

system for blood glucose.

feedback control systems -

systems that control the levels of

endocrine hormones in the blood.