homeostasis & communication Flashcards
(12 cards)
Why is the ability to respond to changes in the environment important for organisms? (3)
Helps organisms survive by allowing them to respond to changes in
External environment: e.g., animals avoiding harmful environments that are too hot or cold
Internal environment: ensures optimal conditions for metabolic reactions
How do plants respond to changes in their environment? (2)
Plants grow towards light
To maximise the amount of light available for photosynthesis
What is cell signalling? (2)
Communication between cells that produces a response
Receptors need to communicate with effectors
How can cell signalling occur? (4)
Adjacent cells
E.g., cells in the nervous system communicate by secreting neurotransmitters that send signals to nearby nerve or muscle cells
Distant cells
E.g., hormones released by the hormonal system travel in the blood to act on distant cells
What role do cell surface receptors play in cell signalling? (1)
Cell surface receptors enable cells to recognise
The chemicals involved in cell signalling
What is homeostasis? (2)
The maintenance of a constant internal environment despite changes in the external environment
Essential for normal cell function and preventing damage
What factors must be maintained within certain limits in homeostasis? (4)
Temperature;
Water potential;
pH;
Blood glucose levels
What components are involved in homeostatic systems? (3)
Receptors: Detect stimuli (specific to one type of stimulus);
Communication system: Nervous or hormonal system;
Effectors: Cells that bring about a response to counteract the change
What is negative feedback in homeostasis? (2)
A mechanism that restores levels to normal when they are too high or too low;
Information is communicated via the nervous or hormonal system to effectors, which counteract the change
Why does negative feedback only work within certain limits? (2)
If the change is too big;
Effectors may not be able to counteract it
What is positive feedback, and why is it not involved in homeostasis? (2)
Positive feedback amplifies changes rather than keeping the internal environment constant;
It is used in situations where rapid activation is needed, e.g., blood clotting or dilation of the cervix during childbirth.
What is an example of positive feedback in the body? (2)
Blood clotting:
Activated platelets release chemicals that trigger more platelets to be activated, forming a blood clot;
Childbirth: Dilation of the cervix during labor is driven by positive feedback
