AP Biology 018- Positive and Negative Feedback Loops Video Review Sheet

Feedback loops

(see notes for better chart) homeostasis-> feedback (used to maintian homeostasis- stable internal environment)-> 1) target set point-> 1) negative -> stabilization (tries to stay as stabilized and close to the target set point as possible)-> ex: temperature regulation 2) positive (away from set point)-> amplification-> ex: fruit ripening 2) alteration (when mistakes->can lead to tragedies)-> ex: diabetes mellitus (problem with insulin- feedback loop)

What are the two cells found in the pancreas and what does each do?

- beta +alpha cells - sensing the blood glucose level (see notes for better chart)

What pattern do you see with diabetes worldwide and why is that?

- high fat diet + sugar - huge diabetic increases - about 30% of world has diabetes + about 90-95% is typeII -whole thing tied to a mistake in a feedback loop

What is type II diabetes a result of usually?

- too much glucose throughout life. tied to lack of excessive, desity etc. - cells stop recognizing insulin and quit taking it in

Besides being in your blood, where else could glucose go? (2x)

-could be taken in by the cells-> cellular respiration-> ATP -could store in glycogen (mostly found in liver)

Positive Feedback loop: amplifying and moving...

away fromn the target set point

Why does the blood glucose levels usually rise three times per day?

breakfast, lunch, + dinner

What is the example of positive feedback in humans?

childbirth: pressure of head on cervix causes contractions causing more and more contractions

Negative Feedback loop: dance around that point, brings you...

closer to the target set point

Alpha

creates glucagon + adds glucagon and increases blood glucose level -frees up glucose from glycogen in liver

What plant hormone does ripe fruit give off?

ethylene (C2H4)

How does a hairless cat maintain homeostasis? Through...

feedback loops

How is fruit ripening an example of positive feedback?

first apple becomes ripe and gives off ethylene creating more and more causing all fruit on the tree to ripen

Positive feedback: Why can one "bad apple" spoil a barrel?

gives off ethylene as a gas and is picked up by apples next to it and causes them to ripen

What is wrong when you have type I diabetes?

have beta cells that don't work an autoimmune disease + genetic where destroy beta cells - glucose keeps going up +up can lead to coma/ deaths

Beta

if a lot of blood glucose outside cell in pancreas beta cells trigger influx of calcium + increase amount of insulin -make pancreas secrete insulin and tells cells to take in blood glucose and tells liver to store as glycogen

What two hormones help with blood glucose regulation:

insulin and glucagon

What else was rising at the same time?

insulin level causing blood glucose level to drop + causing blood glucose levels to maintain a fairly static position

Ectotherms defined:

internal temp= external

Endotherms defined:

keeps a constant internal temp (metabolism at same rate but eats more to maintain body temp)

What types of feedback loop do we use to maintain our temperature?

negative

If too cold we (again, explain why that behavior):

negative feedback loop goosebumps: would stand up hair and pulls skin in conserving heat vasoconstrict: shut off capillary shunts and hold blood towards inside of body so have less convection

If too hot we (also explain why we would do that):

negative feedback loop sweat: water molecules evaporate creating evaporative cooling- carry heat with them vasodilate: blood carried toward surface of skin and through convection (heat rises so released) loose some heat to environment fur: would lay really flat so more heat can be lost through convection

Homeostasis defined:

our internal environment internal stable environment

What organ regulates blood glucose level and what other job does it have?

pancreas major job= empty digestive enzymes into small intestine when food there

Positive feedback is not used for a long time, it is used when you want to do something....

really really quickly

What can alterations in our feedback loops lead to?

tragedies