6C - Homeostasis basics Flashcards
What is homeostasis?
The maintenance of a constant (stable) internal environment within a living organism.
What can changes in your external environment affect?
Your internal environment - the blood and tissue fluid that surrounds your cells.
What does homeostasis involve?
Control systems that keep your internal environment roughly constant (within certain limits).
What is keeping your internal environment stable, vital for?
Cells to function normally and to stop them being damaged.
What is controlled in homeostasis?
Core body temperature.
Blood pH.
Blood glucose levels.
Why does body temperature need to be controlled by homeostasis?
- If it is too high, enzymes may become denatured.
- If it is too low, enzyme activity is reduced, slowing the rate if metabolic reactions.
- The highest rate of enzyme activity happens at their optimum temperature.
Explain how an enzyme becomes denatured if body temperature is too high
The enzyme’s molecules vibrate too much, which breaks the hydrogen bonds that hold them in their 3D shape. The shape of the enzyme’s active site is changed and it no longer works as a catalyst. This means metabolic reactions are less efficient.
Why does pH need to be controlled by homeostasis?
If blood pH is too high or too low (highly alkaline or acidic) enzymes become denatured. This means metabolic reactions are less efficient.
Explain how an enzyme becomes denatured if pH is too high/low
The hydrogen bonds that hold them in their 3D shape are broken, so the shape of the enzyme’s active site is changed and it no longer works as a catalyst.
At what pH does the highest rate of enzyme activity happen?
At their optimum pH - usually around pH 7 (neutral), but some enzymes work best at other pHs, e.g. enzymes found in the stomach work best at a low pH.
Why is important to maintain the right concentration of glucose in the blood?
- Because cells need glucose for energy.
- Blood glucose concentration also affects the water potential of blood.
What is water potential?
The potential (likelihood) of water molecules to diffuse out of or into a solution.
Why does glucose need to be controlled by homeostasis?
- If blood glucose concentration is too high the water potential of blood is reduced to a point where water molecules diffuse out of cells into the blood by osmosis. This can cause the cells to shrivel up and die.
- If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for respiration to provide energy.
What can homeostasis be controlled by?
Nervous system
Endocrine system
A combination of the two
How do homeostatic systems detect a change and respond?
By negative feedback.
What do homeostatic systems involve?
Receptors, a communication system and effectors.
What do receptors do in a homeostatic system?
Detect when a level is too high or too low.
Where is the information from a receptor communicated in a homeostatic system?
To the effectors.
How is the information from a receptor communicated to the effectors in a homeostatic system?
Via the nervous or the hormonal system.
What do the effectors in a homeostatic system do?
Respond to counteract the change - bringing the level back to normal.
What is the mechanism that restores the level back to normal in a homeostatic system called?
A negative feedback mechanism.
What is the negative feedback mechanism?
The mechanism that restores the level back to normal in a homeostatic system.
What does negative feedback do?
Keeps things around the normal level.
Negative feedback only works…
Within certain limits.
When does negative feedback not work?
If the change is too big then the effectors may not be able to counteract it.
Why does homeostasis involve multiple negative feedback mechanisms for each thing being controlled?
Because having more than one mechanism gives more control over changes in your internal environment than just having one negative feedback mechanism.
What does having multiple negative feedback mechanisms means you can do?
Actively increase or decrease a level so it returns to normal.
Only have one negative feedback mechanism would mean what?
A slower response and less control.
What does a positive feedback mechanism do?
Amplifies the change.
What do effectors do in a positive feedback mechanism?
Respond to further increase the level away from the normal level.
Why is positive feedback useful?
To rapidly activate something, e.g. a blood clot after injury.
Or in the labour point of pregnancy.
When can positive feedback happen?
When a homeostatic system breaks down, e.g. if you’re too cold for too long.
Why isn’t positive feedback involved in homeostasis?
Because it doesn’t keep your internal environment stable.
How do endotherms maintain body temp?
Maintain body temp at a set point.
Generate heat energy through respiration.
Change cellular and physiological processes.
How do ectotherms maintain body temp?
Mostly rely on external heat energy.
Warm or cool their body by changing their behaviour in response to changing conditions.
Expose themselves to the sun (basking).
Take shelter.
Gaining warmth from the ground.
How do endotherms gain heat?
Vasoconstriction Shivering Raising of hair Increased metabolic rate Decrease in sweating Behaviour
How do endotherms lose heat?
Vasodilation
Increase sweating
Lowering of body hair
Behavioural mechanisms
