| Homeostatis meaning | - Changes in ur external enviro. can affect your internal enviro. - blood + tissue that surrounds cells
- Hom. involves control systems that keep ur internal enviro. constant (within certain limits)
- Keeping ur internal envio. stable is vital for cells to function normally + to stop them being damaged |
| The importance of homeostasis | - Temperature
- pH
- Glucose |
| Temperature | - If bod temp to high enzymes may denature
- Breaks H bonds that no longer hold 3d shape
- Site of AS changed, no longer works as catalyst
- Makes metabolic reactions less efficient
- If bod temp too low enzyme activity happens at their op temp |
| pH | - If blood pH too high or low enzymes become denatured
- Breaks H bonds that no longer hold 3d shape
- Site AS changed, no longer works as catalyst
- Makes metabolic reactions less efficient
- Highest rate of enzyme activity happens at their op temp (pH 7)
- But some enzymes work best at other pHs |
| Glucose | - If blood glucose conc. is too high water potential of blood is reduced to a point where water mols diffuse out of cells into blood by osmosis
- This cause cells to shrivel up + die
- If blood glucose conc. is to low, cells unable to carry out normal activities coz there inst enough glucose for respiration to provide energy |
| Control mechanisms | - The optimum point
- Receptor
- Coordinator
- Effector
- Feedback mechanism |
| The optimum point | - The point at which the system operates best
- This is monitored by receptors |
| Receptor | - Detects any deviation for the optimum point (like a stimulus)
- Informs the coordinator |
| Coordinator | - Which coordinators info fro rectors and sends instructions to an appropriate effector |
| Effector | - Often a muscle or gland
- Brings abut changes needed to return the system to the optimum point
- This return normality creates a feedback mechanism |
| Feedback mechanism | - Where a receptor responds to a stimulus created by the change to the system brought about by the effector |
| Control mechanism | - Negative feedback
- Positive feedback |
| Negative feedback | - System that returns a factor to the norm after a deviation from the norm |
| Positive feedback | - Occurs when a deviation from an optimum causes changes that result in an even greater deviation from the normal |
| Coordination of control mechanism | - Control systems normally have many receptor + effectors
- This allows them to have separate mechanisms that each produce a + movement towards the optimum
- This allows a greater degree of control of the particular factor being regulated
- Having separated mechanism that controls departures in different directions form the original state is a general feature of homeostasis
- It is important to ensure that info provided by receptors is analysed by the coordinator before action is taken |
