Positive and Negative Feedback Loops

homeostasis definition

body’s ability to maintain a relatively stable internal environment despite environmental changes

negative feedback loops

process that reverses a change to maintain homeostasis

bringing it back to the target setpoint

positive feedback loops

process where the response increases the original stimulus, making the change stronger

moving away from the target setpoint

how does hairless cats maintain homeostasis

same internal systems as other mammals

but instead of fur, they eat more food to produce extra energy and heat

what can disruptions in our feedback loops lead to

diseases/disorders

hormonal imbalances

different conditions

ectotherms

Animals that rely on external heat sources to regulate body temperature

internal temp is same as external temp

endotherms

Animals that produce their own heat internally to maintain a constant body temperature

requires more energy to stay warm

what do we do to maintain homeostasis when we get too hot

as your sweat glands releases water onto your skin, the molecules will evaporate and carry some heat with it too (ex. sweating)

blood vessel near the surface of the skin widen to allow warm blood to flow close to the surface, heat can escape into the air (ex. red cheeks)

what do we do to maintain homeostasis when we get too cold

shivering causes muscle activity to contract, the movement generates heat

goosebumps

Blood vessels near the skin tighten, reducing blood flow to the surface to avoid heat escaping

what plant hormone does ripe fruit produce

ethylene gas

triggers ripening and spreads to nearby fruits

how is fruit ripening an example of positive feedback

once ripening starts, more ethylene is released

speeds up ripening even more

when should positive feedback be used

when you want to do something quickly

where does glucose go in the body

blood

liver

muscle cells

two hormones that help with blood glucose regulation

insulin and glucagon

two cells found in the pancreases

alpha and beta cells

alpha cells

secrete glucagon hormone when blood sugar is too low

raises blood glucose levels by stimulating the liver to convert glycogen into glucose

beta cells

secrete insulin hormone when blood sugar is too low

insulin lowers blood glucose levels by helping cells absorb glucose from the bloodstream

why does the blood glucose level usually rise three times per day

because of meals (breakfast, lunch and dinner)

Each meal causes a temporary rise in blood sugar

taking food increase glucose levels after its broken down into energy, insulin hormones will react this change and bring it back down

what happens when you have type I diabetes

immune system mistakenly attacks and destroys the beta cells in your pancreas

cannot make insulin, glucose starts to build up and blood sugar levels become too high

what is type ii diabetes usually a result of

unhealthy lifestyle

lack of exercise or healthy eating

feedback system includes 3 components

sensor, control center, effector

sensor

detects a change in the internal environment and sends a signal to a control centre

control center

sets the range of values within which a variable should be maintained

receives information from the sensor

sends signals to effectors when needed

effector

which receives signals from a control centre and responds

results in a change to an internal variable

2 types of feedback systems

regulates its internal environment

negative and positive

negative feedback system

process where the body detects a change in a variable and reverses that change to bring the variable back to a normal or balanced state

positive feedback system

process in which a change in a variable triggers responses that amplify or reinforce that change, moving the system further away from its normal state until a specific outcome is achieved

how does the pancreas respond when your blood sugar rises

pancreas responds through a negative feedback loop to bring it back to normal

when happens when glucagon is released by the pancreas

it helps raise blood sugar levels through a negative feedback loop

normal level of glucose in blood

around 5 mmol/L most of the time

where does glucose that is released into the blood ultimately end up

body cells and liver

relationship between the pancreas and homeostasis

pancreas maintains homeostasis by releasing insulin or glucagon to keep blood glucose within a narrow, healthy range