Homeostasis, Feedback Loops, and Hormones

what is homeostasis

maintaining the constancy of the internalenviroment within a certain normal range

give examples of things the body maintains within a normal range

temperature, oxygen, pH, blood sugar

what is negative feedback

a feedback mechanism that reverses a change to maintain balance

in negative feedback, does the response move in the same or opposite direction as the original change

the opposite direction

what is an example of negative feedback involving insulin?

insulin decreases plasma glucose

what is positive feedback

a feedback mechanism in which the effectors amplify the original change

in positive feedback, does the response move in the same or opposite direction as the original change

the same direction

what are examples of positive feedback

oxytocin during labor, voltage-gated Na+ channels during nerve impulse, depolarization, and lactation

how does oxytocin demonstrate positive feedback

it increases uterine contractions during labor, which promotes oxytocin release.

how does lactation demonstrate positive feedback

more demand→more milk production

negates

reverses the change

positive

pushes/amplifies the change

What are 2 general ways hormones can affect a target cell?

they can increase/promote enzyme production or activate a gene, OR they can decrease/inhibit enzyme or gene activity

what determines whether a hormone increases/decreases activity

the specific repsonse of the target tissue to that hormone

what primarily controls blood levels of hormones

negative feedback systems

how much do hormone levels typically vary

they generally very within a narrow range

what can trigger hormone release

hypothalamus, endocrine gland stimuli, and nervous system modulation

what are theree stimuli that cause endocrine glands to release hormones

humoral, neural, and hormonal stimuli