Module 5.1 - Communication And Homeostasis Flashcards
(19 cards)
Define cell signalling
The way in which cells communicate with each other
Why is it important to respond to internal changes?
Some products of metabolic activities (e.g. CO2) are harmful, build up can be toxic
This acts as a stimulus for their own removal
Why is it important to respond to external changes?
To be able to adjust the internal environment in response to external environment (e.g. temperature)
To adapt to the changes in environment (e.g. wether/scenery, camouflage)
To find resources (e.g. tropisms)
What are the two systems of cell signalling?
Neuronal system
Endocrine system
Points about the neuronal system
Neurones signal to each other across synapses
Quicker (short-term)
Very specific effect
Electrical impulses carried by neurones, neurotransmitters carry message across synapse
Point about the endocrine system
Hormones transported in blood to specific target cells
Slower (long-term)
Specific to target cells, more general overall effect
Hormones carried in blood
Define homeostasis
The maintenance of the internal environment in a constant state despite external and internal changes
Define effector
A cell, tissue or organ that brings about a response
Define negative feedback
A process that brings about a reversal of any change in conditions in order to return to an optimum set point
Essential for homeostasis
Define positive feedback
A process that increases any change detected by the receptors, taking the conditions further from the optimum set point
Tends to be harmful and does not lead to homeostasis
Process of negative feedback
Optimum conditions
Change from optimum
Sensory receptor detects change
Cell signalling communicates change (CNS coordinates response)
Effector cells bring about change to reverse the response
Return to optimum
Process of positive feedback
Optimum conditions Change from optimum Sensory receptor detects change Cell signalling communicates change (CNS coordinates response) Effector cells increase change further
Define ectotherm
An organism that relies on external sources of heat to regulate body temperature
Define endotherm
An organism that can control the generation or loss of heat to maintain its body temperature using physiological or behavioural responses
Ectotherm advantages and disadvantages
Advantages: less food used in respiration as less energy needed; less food needed; more energy used for growth
Disadvantages: less active in cold; can’t adapt to change in external temperature
Endotherm advantages and disadvantages
Advantages: can maintain a constant body temperature despite external conditions; can be active in colder conditions
Disadvantages: large portion of energy intake needed to maintain body temperature; more food required; less energy from food used for growth
Examples of behavioural mechanisms in thermoregulation
Too cold - move into sun, decrease surface area, move to warm surface
Too hot - move out of sun, increase surface area, move to cooler surface
Examples of physiological mechanisms in thermoregulation
Too cold - no sweat, no panting, vasoconstriction in arterioles, more respiration in liver cells, repaid contraction and relaxation of skeletal muscles (shivering), hairs/feathers stand up
Too hot - sweat evaporates, panting evaporates, vasodilation of arterioles, less respiration in liver cells, no shivering, hairs/feathers lie flat
Explain thermoregulation
Example of negative feedback
Peripheral thermoreceptors in the skin sense temperature changes in the external environment
If too much change is detected this information is sent to the hypothalamus which brings about the relevant responses
