Communication and Homeostasis, 5.1 Flashcards
What conditions do living organisms need to maintain inside their cells? Why?
Suitable pH, suitable temperature, aqueous environment and freedom from toxins and excess inhibitors. As they affect enzyme acitivity.
Examples of a changing external enviroment
Changes externally put a stress on the living organism such as the temperature changing
Examples of a changing internal enviroment
Metabolic activities of cells, they use resources and produce waste which could be toxic, eg if CO2 is allowed to build up it will alter the pH
Cell Signalling
The way in which cells communicate with each other
What is the neuronal system?
Network of neurons, signal across synapse junctions, conduct signals quickly
What is a hormonal system?
Use the blood to transport signals, endocrine organs secrete hormones, hormones are detected by target cells with specific receptors
What makes a good communication system?
Covers whole body, enable communication between cells, communication is specific, rapid response, short and long term responses
Homeostasis
Maintaining a constant internal environment despite changes in internal and external factors. Within narrow limits.
Negative Feedback
Conditions in the body are brought back to the optimum, it reverses the change
What occurs during negative feedback?
Receptor detects the change (stimulus) and sends an input to the coordination center, the coordination center sends an output to the effectors which respond
Positive Feedback
Mechanism that increases the change taking the system further away from the optimum
Why is positive feedback more dangerous?
It destabilizes the system and is harmful
An example of positive feedback
During pregnancy, oxytocin is release to stretch the cervix more and more until to baby is born
Stimulus
Change in environment causing a response
Response
Change in behavior or physiology
Ectotherm
Organism that relies on external sources of heat to maintain body temperature
Ectotherm response to being too cold
Move into a sunny area, lie on a warm surface, expose a larger SA to the sun
Ectotherm response to being too hot
Move out of the sun, move underground, reduced body surface exposed to the sun
Ectotherm advantages
Less food used in respiration, more energy used in growth, need to find less food, won’t overheat as easily
Ectotherm disadvantages
Less active in cool temperatures, at risk from predators in the cold
Endotherm
Organism that uses heat from metabolic reactions to maintain body temperature as chemical reactions can be exergonic
Endotherm response to being too cold
Sweat glands release less sweat, hairs stand up, vasoconstriction, increased respiration in the liver, skeletal muscles contract (shivering)
Endotherm response to being too hot
Sweat glands secrete more sweat, hairs lie flat, increased panting, less respiration in the liver,
vasodilation
Endotherm advantages
Maintain a constant body temperature, remain active at cold temperatures, inhabit colder parts of the planet
Endotherm disadvantages
Most energy used to maintain body temperature, need more food, lower proportion of energy used for growth
What happens if the temperature rises?
Molecules gain kinetic energy, move faster, are more likely to collide and more likely to collide with sufficient energy, rate of reaction increases, however, structure of proteins and enzymes can be affected
Where are temperature receptors?
In the hypothalamus, detect core body temperature
What is the sensory cell that detects changes in external temperatures?
Thermoreceptor
