5.1.1 - COMMUNICATION + HOMEOSTASIS Flashcards
Why do animals respond to changes in their environment?
- Animals increase chances of survival by responding to changes in external environment (e.g. by avoiding harmful environments such as places too hot or cold
- Respond to changes in internal environment to make sure that the conditions are always optimal for their metabolism (all chemical reactions inside)
Why do plants respond to changes in their environment?
- Increase changes of survival by responding to changes in environment
What is a stimulus?
Any change in the internal or external environment
Explain the detection of stimuli in receptors
- Reecptors detect stimuli
- Receptors are specific, detecting one particular stimulus (e.g. light or pressure)
- Some receptors are cells (e.g. photoreceptors connecting to nervous system) | Some receptors are proteins on cell surface membranes (e.g. glucose receptors)
What is a cell signalling?
Cells communicating with each other
^— e.g. may be with neurotransmitters in the nervous system
Explain how receptors communicate with effectors through distant and adjacent cells
- Cell signalling can occurs between adjacent or distant cells
^— e.g. cells in nervous system communicate by secreting neurotransmitters, which send signals to adjacent cells (nerve or muscle cells)
^— hormonal system works by cells releasing chemicals (hormones) that travel in the blood to distant cells - Cell-surface receptors allow cells to recognise the chemicals involved with cell signalling
What is homeostasis?
The maintenance of a constant internal environment via physiological control systems
^— involves negative feedback loops
What does homeostasis regulate?
- Body temp
- Blood pH
- Blood glucose
- Blood water potential
What is negative feedback?
- When a deviation from the optimum is detected in the body by a receptor
- Mechanisms are put in place to restore the conditions to the optimum
INVOLVES NERVOUS SYSTEM + HORMONES
What is positive feedback?
- When a deviation from the optimum triggers a response to increase teh deviation further
- RARE
Give an example of positive feedback?
- During childbirth, baby’s head presses on cervix, causing hormone oxytocin to be released
^— causes contractions, causing release of even more oxytocin
What is thermoregulation?
- Type of homeostasis
- If body temp drops too low, there would be insufficient kinetic energy for enzyme-controlled reactions
^— so temperature must be regulated to stop denaturation or cell death
What are ectotherms?
- Control internal temperature less well than endothermic
^— do so by changing behaviour
What are the behaviour responses of ectotherms to regulate temperature?
- Warm up through conduction against hotter surfaces (Basking behaviour on warm ground)
- Cool down by moving to chase, water or digging underground
What are endotherms?
- Regulate own body temperature through a nervous response
^— peripheral temp receptors in the skin detect changes in external temperature, sending impulse along a sensory neurone to the brain, where hypothalamus coordinates impulse (TRIGGERS response by glands + muscles)
