Thermoregulation and Osmoregulation Flashcards
pp 1025 - pp 1030
What is homeostasis?
The maintenance of a “steady state” or internal balance, despite changes in the external environment
Dynamic equilibrium.
How is homeostasis achieved?
By the process of NEGATIVE FEEDBACK, mechanisms that get us back to our preferred set points/normal range by acting as an on/off switch = Reducing disturbance.
Fluctuations in the variable above/below a set point serve as the STIMULUS detected by a SENSOR (receptor). A control center generates output, triggering a RESPONSE (physiological activity to return to set point).
How is thermoregulation controlled in mammals?
It is controlled by the HYPOTHALAMUS, a gland at the base of the brain that regulates many physiological processes
What happens when you have a fever?
A fever, being a response to some infections, is the result of a CHANGE TO THE SETPOINT for the biological thermostat
What controls the internal environment of an organism?
Signals, generated by…
CHEMICALS (Hormones): Endocrine system
Biochemical triggering responses
ELECTRICAL MEANS (Neurons): Nervous system Impulses carrying messages
What hormones and neurons have in common?
Their signal to the internal environment involve a STIMULUS and a RESPONSE
True or False: Hormones and neurons are independent
False! They are used in concert, signalling to/triggering each other
What is the role of the endocrine system?
It transmits chemical signals called HORMONES to receptive cells throughout the body.
What is the endocrine system consisted of?
A network of glands, communicating via hormones
How are hormones transmitted throughout the body?
They are carried through the bloodstream
Are hormones region-specific?
No! They may affect one or more regions.
Hormones are relatively ________ acting, but can have _______ lasting effects.
Slow acting; Long-lasting
What is the role of the nervous system?
It transmits information, via interconnected neurons
What are the differences between hormones and neurons?
Neurons give off signals that are more specific in location.
Nerve signal transmission is very fast and short-lived.
What are regulators?
Organisms that use INTERNAL control mechanisms to moderate internal change, in the face of external, environmental fluctuation.
In other words, it accommodates the external environment.
**Use internal metabolic processes as a major heat source
= ENDOTHERMS
What are conformers?
Organisms that allow for their internal conditions to vary with certain external changes.
In other words, they do not adjust; they are internally insensitive!
= ECTOTHERMS
True or False: If an animal is a regulator, it is not a conformer.
False! An animal may regulate some environmental variables, conform to others.
How do animals tolerate extreme cold?
Freezing is lethal to most animal cells! The reason? When the cell ‘thaws’, it then ruptures.
What adaptation do tardigrades make to withstand extreme temperatures?
Tardigrades are able to change the composition of their cells to prevent freezing and overheating.
Why is extreme heat dangerous?
At high temperatures, cells stop functioning.
What are the four physical processes by which organisms exchange heat?
- Radiation: Heat exchange, without any contact
- Evaporation: Typically involves a loss of heat
- Convection: Flow of warm/cold air
- Conduction: Typically involves absorbing heat, via direct contact with a substrate
What is thermoregulation?
The process by which animals maintain an internal temperature within a tolerable range
How do ectothermic animals thermoregulate?
They gain heat from EXTERNAL sources
Which organisms are typically ectothermic?
Invertebrates, fishes, amphibian, nonavian reptiles
How do endothermic animals thermoregulate?
They generate heat by metabolism, consuming energy.
Their heat is internally-generated, they are warm-blooded.
Which organisms are typically endothermic?
Birds and mammals.
What five adaptions help endotherms thermoregulate?
- Behavioural responses: Movement
- Insulation: Morphological adaptation, by creating fat, fur, skin
- Cooling, by evaporative heat loss
- Adjusting metabolic heat production
- Circulatory adaptations, to extremities: Control of blood flow
What is osmoregulation?
The process of balancing the uptake and loss of water and solutes, to regulate the chemical composition of body fluids.
What type of movement is involved in osmoregulation?
CONTROLLED movement of solutes between the internal fluids and the external environment.
How does water enter and leave the cell?
Osmosis
What is osmolarity and why is it important?
Osmolarity is the solute concentration of a solution.
It determines the direction of movement of water across a selectively permeable membrane
= Flows towards the side with MORE concentrated solute (From the hypoosmotic to hyperosmotic)
What is isoosmolarity?
When osmolarity is equal on both sides;
Water molecules continually cross the membrane at equal rates in both directions –> No NET movement of water by osmosis
What are osmoconformers?
Organisms that are isoosmotic with their surroundings and do not regulate their osmolarity
What are osmoregulators?
Organisms that expend energy to control water uptake and loss in a hyper/hypo-osmotic environment.
What characteristic defines most animals’ comfort with osmolarity?
Most animals are STENOHALINE, meaning they have a narrow range of tolerance to changes in osmolarity.
Few are EURYHALINE, with a wide range of tolerance to osmolarity.
How does osmoregulation differ in saltwater and freshwater conditions?
Marine fish must balance their water loss by drinking seawater and excreting the salts within. They don’t have access to pure water.
They have excess salt ions, from drinking seawater and eating food, which they must get rid of.
They lose water by osmosis and gain salt by diffusion and from food.
They must resist LOSS of water from their tissues.
Freshwater fish need to obtain salt, as they lose salts by diffusion.
-Salts lost by diffusion are replaced in foods and by the uptake across the gills.
They must cope with INFLOW of water from the environment
What is diadromy?
The different lifestyles of marine and freshwater habitats that animals develop within depending on their stage of life (typically linked to reproduction)
Why did the evolution of terrestrial habits necessitate profound morphological and physiological adaptations?
There is a danger of dehydration and desiccation!
What is anhydrosis?
Surviving in the near absence of water
How do tardigrades tolerate dehydration?
They can be totally dehydrated then rehydrated!
What is excretion?
The removal of waste solutes, typically those that are nitrogen-based and can become toxic to cells at high concentrations
What are the functions of kidneys?
Nephrons, the fundamental units of chordate kidneys, maintain osmoregulating.
Blood is pressure-filtered; water & solutes are moved through the membrane(s), and eventually excreted.
What is needed to selectively move solutes in the kidneys?
Active transport!
What is positive feedback?
A control mechanism that amplifies, rather than reduces, the stimulus. This does not play a major role in homeostasis.
What is thermoregulation?
The process by which animals maintain an internal temperature within a tolerable range.
Why is thermoregulation so critical?
Most biochemical and physiological processes are very sensitive to changes in body temperature.
In which ways do ectotherms adjust body temperature?
By behavioural means, such as seeking out shade, basking in the sun.
What does thermoregulation depend upon?
The animal’s ability to control the exchange of heat with its environment.
Heat is always transferred from an object of ______- temperature to one of ______ temperature.
Higher; lower
What is the major thermoregulatory adaptation in mammals and bird?
Insulation - reduces the flow of heat between an animal and its environment = less heat exchange.
How are circulatory adaptions ways to thermoregulate?
Circulatory systems = Major route for heat flow between the body’s interior and exterior, by means of the amount of blood flow
What is vasodilation?
A widening of superficial blood vessels, warming the skin and increases transfer of body heat.
This is thanks to nerve signals that relax the muscles of vessel walls.
What is countercurrent exchange?
The transfer of heat between fluids that are flowing in opposite directions, to reduce heat loss from the body.
Traps heat in the body core, reducing heat loss from the extremities.
How do animals cool themselves?
Through evaporation, losing water from their skin and respiratory surfaces.
What is a common thermoregulatory response in both ectotherms and endotherms?
Behavioural responses!
What is thermogenesis?
Matching the heat production to the changing rates of heat loss, by increasing muscle activity such as moving or shivering.
What is non-shivering thermogenesis?
A process by which some animals produce heat by their abundant mitochondria as opposed to ATP.
This is thanks to brown adipose tissue, which is specialized to produce heat.
What is the hypothalamus?
A brain region comprising a group of nerve cells that function as a thermostat, responding to non-normal range body temperatures by activating mechanisms that promote heat loss/gain.
What do we call the two solutions when they differ in osmolarity?
Hyperosmotic: A greater concentration of solutes
Hypoosmotic: More dilute solution
Water flows from the hypoosmotic –> hyperosmotic
