5.1 Flashcards
Why do animals and plants need to respond to changing environments
-In order for the organism to remain active and survive, the changes in the environment must be monitored and the organism must change its behaviour or physiology to reduce the stress
How does cell signalling work?
Cells communicate with each other through the process of cell signalling. This is a process in which on cell will release a chemical that is detected by another cell. The 2nd cell will respond to the signal released by the 1st cell.
How does signalling between adjacent cells work?
Neuronal system: an interconnected network of neurones that signal to each other across synapse junctions. The neurones can conduct a signal very quickly and enable rapid responses to stimuli that may be changing quickly.
How does signalling between distant cells work?
Hormonal system: a system that uses the blood to transport its signals. Cells in an endocrine organ release the signal (a hormone) directly into the blood. The hormone is transported throughout the body, but is only recognised by specific target cells. enables longer-term responses to be coordinated
what is the mechanism of homeostasis
stimulus ➡️ receptor ➡️ communication pathway (cell signalling) ➡️effector ➡️ response
difference between receptors and effectors
receptors- sensory receptors (monitor changes in the external environment, other receptors monitor internal environment) - detects change
effectors- effector cells such as liver/muscle cells- brings about a response
differences between negative and positive feedback
negative feedback - reverses any change from optimum conditions
positive feedback - increases original change
- destablilises system
- usually harmful
what are endotherms
control their body temperature within very strict limits
what are ectotherms
not able to control body temp as effectively as endotherms (except some in extreme temps) rely on external sources of heat
behavioural responses of endo/ectotherms controlling body temp
- move to/away from sun
- lie on warm surface/move underground
- increase/decrease surface area in sun
physiological mechanisms of endotherms to maintain body temp
- skin (sweat, hair, vasodilation/constriction)
- gaseous exchange system (panting)
- liver (less respiration takes place, less heat released)
- skeletal muscles (contractions - shivering)
- blood vessels (dilation etc)
what is the hypothalamus
the part of the brain that coordinates homeostatic responses
role of peripheral temperature receptors in endotherms
-in skin monitor temperature in the extremities
