Homeostasis Flashcards
What is Homeostasis?
(Steady state) The maintenance of the of the composition, temperature and
volume of the internal environments at relatively constant levels.
Why do cells need stability and what is kept stable?
For optimal function and pH, temperature, nutrient levels, hormone levels, blood gases and Bp e.g.
What are the elements of a control system?
1)Control Centre
2)Receptor
3)Effector
What is the function of each element?
1)Control centre= Receives and processes the information and sends out commands.
2)Receptor= Responds to a particular environmental change or stimulus.
3)Effector= Produces a response by carrying out commands.
What is a positive feedback loop?
A change in a variable initiates further disruption which
amplifies the initial change
What is a negative feedback loop?
A change in a variable initiates responses which serve to
cancel the change
Positive feedback loop examples:
1)Baby birth- there is a dilation of the walls of the uterus that causes a contraction that encourages further stretching.
2)Blood clotting after an injury to stop the bleeding.
3)Fruit ripening in a tree by the release of ethylene gas which stimulates ripening in the other fruits nearby as well.
What is feedforward?
Limits change. Anticipatory behaviour that acts to minimise
disruption to set points
Negative feedback examples:
1)Control of body temperature- hypothalamus in your brain. If your body gets too hot, your body begins to sweat to try and reduce it. If the body gets too cold, it begins to shiver to try and raise the temperature.
2)Control of blood glucose. change detected : Increase in glucose
.a response (insulin secretion)
is generated to correct the change back to the ‘set point’.
Failure of homeostasis causes
many disorders such as:
1)Diabetes (insulin failure)
2)Neuroendocrine disorders
3)Hypertension (high blood pressure)
4)Obesity
5)Heat stroke
