Unit 1: Homeostasis and Feedback Loops

how living organism maintain steady/tolerable physical and chemical conditions

what is homeostasis?

breathing faster, secreting insulin, and pH levels in the digestive system

examples of homeostasis

stimulus

sensor

control

effector

response

negative feedback loop

deviation from a set point in the body

stimulus

the physiological value where the normal range fluctuates

set point

values considered healthy and stable

normal range

monitors physiological value and reports to control

sensor

compares value to normal range

control center

causes change to reverse situation and return value to the normal range

effector

mechanism that reverses a deviation to set point

negative feedback

When our bodies temperature exceed the normal range, our blood vessels begin to dilate, bringing them closer to the surface of our skin. This activates our sweat glands, and as our sweat evaporates, the heat from our bodies escapes with it, bringing us back to the set point.

explain how increase in body temperature goes through a negative feedback loop

intensifies change in body’s physiological condition rather than reversing it

positive feedback loop

childbirth, response to blood loss

examples of positive feedback

body temperature, glucose levels

examples of negative feedback loop

Contractions push the baby toward the cervix. Nerve cells in the cervix monitor the degree of stretching and send messages to the brain. Then, part of the brain releases oxytocin into the bloodstream. Oxytocin causes stronger contractions of smooth muscles, pushing the baby further down the birth canal. This repeats until the baby is born.

explain how normal vaginal childbirth goes through a positive feedback loop

As body heat rises, sensory nerves in your skin detect this change and send signals to the hypothalamus. The hypothalamus triggers blood vessels to dilate, nearing the surface of the body. This activates sweat glands, and as sweat evaporates off the body, body heat is released with it, bringing the body back to set point.

It's summer time and you are walking back to your car. It's close to 100 degrees outside and very humid. Explain how your body uses a negative feedback loop to maintain homeostasis.