5.1 - Communication and Homeostasis Flashcards
- The need for communication systems - Cell Signalling - Homeostasis - Ecotherms and endotherms (22 cards)
Why do organisms need to maintain a limited set of conditions?
Cellular activities rely on enzymes which require a specific set of conditions to work effectively
Why do organisms need to coordinate activity?
To maintain optimal internal conditions that support survival
Briefly describe how cell signalling works.
One cell releases a chemical, the chemical is detected by another cell and the second cell responds to this signal
What are the 2 major systems of communication?
- Neuronal system
- Hormonal system
3 brief features of neuronal systems
- Network of neurons
- Quick signals
- Rapid responses
3 brief features of hormonal systems
- Uses blood to transport signals
- Only recognised by specific target cells
- Enables long-term responses to be coordinated
Definition of homeostasis
The maintenance of a constant internal environment despite external changes
6 examples of internal environments
- Temperature
- Blood glucose concentration
- Blood salt concentration
- Water content
- Blood pressure
- Blood carbon dioxide partial pressure (blood pH)
Definition of negative feedback
Reversal of a change in the environment to return to the optimum position
Describe the brief general pathway of negative feedback
- Receptors detect changes
- Communication system inform the effectors
- Effector reacts to REVERSE change
Where are changes in temperature detected in the body?
In the thermoregulatory centre in the hypothalamus
Definition of positive feedback
Responses causes the change to increase/enhance
NOTE: Positive feedback does NOT lead to homeostasis
Famous useful example of positive feedback
Uterine contraction during childbirth (release of oxytocin)
What is a stimulus?
Any change in the environment that causes a response
What is a response?
A change in behaviour or physiology as a result of a change in the environment
What are endotherms?
Organisms that can maintain body temperature within strict limits, independent of external temperatures.
How is body temperature maintained in endotherms?
Internal sources of heat, e.g. increasing respiration rate
Advantages of endotherms (3)
- Constant body temperature regardless of external environment
- Activity possible in cooler temperatures
- Able to inhabit cooler parts of the world
Disadvantages of endotherms (3)
- Significant part of energy intake used to maintain body temperature
- More food required
- Less energy from food can be used for growth
3 physiological adaptations of endotherms
- Sweat glands on skin
- Hairs on skin
- Capillaries near skin surface
If an endotherm is in a hot environment, how do sweat glands respond?
What about in a cold environment?
Hot environment - Secrete sweat: water has a high specific heat capacity so heat escapes body and converted into evaporation of sweat
Cold environment - Sweat glands inactive
If an endotherm is in a hot environment, how do blood capillaries under the skin surface respond?
What about in a cold environment?
Hot environment: - Capillaries dilate to increase surface area (vasodilation)
-Heat from blood transferred out of the body and through the skin more efficiently
Cold environment: Capillaries close to reduce heat lost through the skin (vasoconstriction)
