Negative and positive feedback loops Flashcards
What is a cell
Basic structural and functional unit of a living organism
What is a tissue
A group of cells with similar structures working together to perform a shared function
What is an organ
A group of tissues adapted to perform a specific function
What is an organ system
A collection of organs with related functions working together to perform bodily functions
What is an organism
Living thing performing all seven life processes
What is homeostasis
Keeping a variable relatively constant e.g. body temperature, pH, blood sugar level
What is a negative feedback loop
Promotes stability, reduces fluctuations. Our body will oppose a certain change e.g. if we get too hot
What is a positive feedback loop
A change or growth, a small change is amplified resulting in a greater change. It is a signal cascade
Example of negative feedback
Thermoregulation
1) If our body temp decreases (we get too cold), the sensor/ control centre in the hypothalamus will detect this
2) It will then produce changes to counteract this
3) E.g. blood vessels will vasoconstriction so we direct blood back into the core of our body
4) We will also shiver and get goosebumps
5) This will therefore then bring our temperature back to normal
Works the same way if our body temp was increased
Second example of negative feedback
Blood sugar regulation
TOO HIGH
1) When our blood sugar is too high, beta cells in the pancreas are stimulated to release insulin into the blood
2) The liver will then remove glucose from the blood and store it as glycogen
3) The blood glucose level will then decline to a set point and the stimulus for insulin release diminishes
TOO LOW
1) When our blood sugar is too low, alpha cells in the pancreas are stimulated to release glucagon into the blood
2) The liver will then break down glycogen and release glucose into the blood
3) The blood glucose level will then rise to a set point and the stimulus for glucagon release diminshes
Example of positive feedback
Childbirth
Homeostasis = The baby being inside
Change = Baby being born
Therefore homeostasis is not maintained and the baby is born
1) Nerve impulses from cervix transmitted to brain
2) Brain stimulated pituitary gland to secrete oxytocin
3) Oxytocin is carried in bloodstream to uterus
4) Oxytocin stimulates uterine contractions and pushes baby towards cervix
5) Head of baby pushes against cervix
This will continue and keep amplifying until the baby is born
Second example of positive feedback
Blood clotting
Change = Clot - as it wasn’t there before
1) Events occur to amplify a signal and activate clotting factors in a signalling cascade
2) Each level of the cascade, there is amplification. Therefore a very strong signal to cause blood clotting
3) Clot is formed and we stop bleeding
