Communication and Homeostasis Flashcards
Communication
Communication is essential for the survival of organism as all living organisms must be able to detect and respond to changes in their internal and external environments.
Homeostasis
Homeostasis serves to ensure that a constant internal environment consisting of factors such as temperature, water potential, pH and blood glucose level is maintained, despite changes in the external environment of the organism.
Stimulus (external environment)
Cooler environment = greater heat loss = organism has to change behaviour/physiology to reduce stress = survives = RESPONSE
Stimulus (internal environment) +example
Cells and tissues aren’t exposed to the external environment = protected by skin or bark but they are bathed in tissue fluid = environment of cells
- Example is CO2 accumulation : toxic waste product = build up alters pH of blood/enzymatic activity = STIMULUS = RESPONSE = greater breathing activity to expel CO2 from the body
Factors contributing to a good communication system
- covers the whole body
- enables cells to communicate with each other
- enables specific and rapid communication
- enables long and short term responses
Cell signalling
Involves the communication between cells, in the form of electrical signals which are carried by neurones, or with the help of hormones
Neuronal signalling
- Interconnected network of neurones that signal via synapse junctions
- Quick but short term response to a stimuli that changes quickly
Hormonal signalling
- Uses hormones in the blood to transport its signals
- Cells in an endocrine organ release the signal directly into the blood and transported throughout the body, but only recognised by specific target cells
- Slower but long term response
Types of hormonal signalling
- Endocrine
- Paracrine
- Autocrine
Endocrine signalling
Signalling molecules (hormones), target cells at distant body sites
e.g oestrogen
Paracrine signalling
Act on neighbouring target cells
e.g neurotransmitters
Autocrine signalling
Respond to self-signalling molecules
e.g T lymphocytes: proliferation in response to cytokines produced by same cell
Types of regulation
Positive and negative regulation
Positive regulation/feedback
- Increases the original change in the conditions
- e.g: end of pregnancy causes dilation of the cervix- as cervix begins to stretch= posterior pituitary gland secretes oxytocin= increases uterine contractions= stretches cervix more= continuation of positive feedback
Negative regulation/feedback
- Counteracts any change in internal conditions
- e.g: a rise in core temp= thermoregulatory centre in hypothalamus detects change= nervous and hormonal systems carry signals to skin, liver, and muscles= less heat generated and more heat lost= fall in core temp
Ectotherms
- An organism which regulates its body temp with the help of external source- peripheral receptors
- Unable to increase their respiration rate to increase the internal production of heat
- Cannot rely on internal energy source
- Control their body temp by exchanging heat with their surroundings
- They have behavioural responses/adaptations
-e.g: snakes- bask in the sun to absorb heat directly from the sun
Endotherms
- Organism able to maintain a constant body temperature, independent of the external temperature
- Contain thermo-receptors which monitor core body temperature changes and communicate them to the hypothalamus, which in turn coordinates appropriate responses to restore the optimum temperature
- e.g: shivering- contractions of skeletal muscles stimulated by nerve impulses sent out by the hypothalamus, leads to increase in temperature due to increase in kinetic energy, generating heat
Key exam phrases to use
- Insects are smaller= smaller SA:V= greater heat loss
- Lower temperature= reduced kinetic energy of molecules= slowed enzyme activity= less metabolic heat generated= temperature then drops
- Idea of maintaining stable internal environment, within narrow range, even though the environment is changing
