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Communication & Homeostasis 5.1.1 (thermoregulation) - Coggle Diagram
Communication & Homeostasis 5.1.1 (thermoregulation)
Homeostasis - the maintenance of a constant internal environment
It’s advantageous for organisms to be at the optimum internal conditions
endotherms
= ‘warm blooded, include mammals & birds, maintain their core temp at close to 37’C wherever they are, & their temp is largely independent of their surroundings.
Can colonise most parts of the world, can remains active in cold night & winters, can hunt & escape predators efficiently as their core temps are maintained at close to optimum at all times.
Maintaining at close to 37’C has a cost. They need lost of quality high energy food, e.g. a shrew must eat 125% of its body weight every day to survive, its losing heat to its environment at a high rate cause of its high SA:volume ratio.
More energy goes into maintaining temp & less is therefore available for growth.
their peripheral temp can fluctuate but their core temp mustn't drop or increase too much or it could affect their survival
Exergonic reactions
Endotherms use internal source of heat to maintain body temp, this is a metabolic method of temp control. Respiration releases heat & they can adjust the metabolic rate to increase or decrease heat generation
Behavioural mechanisms
E.g. moving into shaded & slowing down body movements/physical activity
Physiological methods
sweat glands
Hot - sweat is secreted which evaporates, latent heat energy is removed from the body which cools it down.
Cold - less sweat, less loss of latent heat
lungs, mouth, nose
Hot - panting in some animals leading to evaporation & loss of latent heat
Cold - no panting, less evaporation, less loss of latent heat
Hairs on skin
Hot - hairs lay flat, little insulation, increases heat loss by convection & radiation
Cold - hairs raised by erector pili muscles to trap insulating air, less loss of heat via convection or radiation
Arterioles leading to capillaries in skin
Hot - vasodilation allowing more blood into capillary beds near skin surface, more heat is radiated away
Cold - vasoconstriction of arterioles stopping blood flow to capillary beds near skin surface, less heat radiated away
Shivering
Hot - no spontaneous muscle contraction when warm, no extra generated by muscles
Cold - spontaneous muscle contractions, extra heat generated by muscles
Metabolic/biochemical methods of endotherms
liver cells;
Hot - metabolic rate decreased, less heat released from exergonic reactions, e.g. respiration
Cold - higher rate of metabolism by the liver cells, more heat generated & more heat released into the blood.
Vasodilation & vasoconstriction in more detail;
https://docs.google.com/document/d/1q1MIwswee7leNKZs45L7YjvxpDj-5rZiOOfsiN8C2EU/edit
hot
Precapillary sphincters open & bloods is diverted to capillary beds near the surface of the skin.
arterioles leading to the capillary beds in the skin vasodilate
More heat is radiated away from rather body
cold
Precapillary sphincters close & blood is diverted away from the capillary beds near the surface of the skin
Less heat is radiated from the body
Arterioles leading to the capillary Beds in the skin vasoconstrict
Control of temp regulation in endotherms
The hypothalamus also monitors blood temp but peripheral receptors in the skin give it an early warning when environmental temp changes, long before core temp is affected
https://docs.google.com/document/d/1q1MIwswee7leNKZs45L7YjvxpDj-5rZiOOfsiN8C2EU/edit
Hormonal & nervous signals are involved
Your core temp is important - If it changes then your hypothalamus must instruct the body to reverse this change
ectotherms
= an organism that relies on external sources of heat to maintain its body temperature ‘cold-blooded’
They don’t need to eat so much because they don’t waste energy trying to thermoregulate as much as endotherms, their thermoregulation is minimal & let their body temp generally fluctuate with the environment.
They can regulate their body temp through behavioural responses, e.g. to warm up they may lay in sunlit areas, & if too hot they move out of the sun into shade. This is to either absorb or avoid gaining more heat from the environment respectively.
They are limited to here they can live, in cold places they would have a big disadvantage, enzymes wouldn’t be at optimum temp & biochemical reactions would be very slow. They can slow have problems at night and cold days as they will be more vulnerable.
Locusts can regulate their temperature by;
behavioural mechanisms - Locusts orientate themselves to be side on giving them a large SA for heat absorption. When too hot they climb high to get away from the hot ground & face the sun head on, exposing a small SA to the sun.
Physiological mechanisms - when hot they increase abdominal movements, this helps to take air in & out of their spiracles more quickly & helps to evaporate water vapour, cooling them down.
Using behavioural & physiological mechanisms only to help regulate temp to a lesser degree, they can’t use biochemical/metabolic methods. Their core temp tends to fluctuate with the environment.
Horned lizards - physiological mechanisms - can expand or contract its rib cage to increase or decrease its SA, it changes it body shape to alter SA:Volume ratio. It also uses its frill to absorb heat from the sun.
Behavioural temperature control
= regulating boy temperature by behavioural action, e.g. moving into the sun or moving underground
Physiological temperature control
= regulating body temp by changing their body, e.g. expanding or contracting the rib cage to increase or decrease surface area exposed to the sun
Biochemical temperature control
= regulating body temp by metabolic reactions, e.g.heat generated from increased respiration when muscles contract to move (ectotherms can’t do this)
feedback
The response from the effectors change the internal conditions & cause the input from the receptors to change - this is called feedback
https://docs.google.com/document/d/1422csrOOq_F1CdBgYQFVUyVQVY42YCDPtGSqAfXxlt8/edit
negative feedback :
The effectors bring about a change that reverses the initial change in the internal environment, moving the system close to the optimum
The coordination centre sends an output to the effectors
Receptors detect a change away from the optimum
Temperature control - an e.g. of negative feedback
If the internal temp rises too high the response brings it back down towards its optimum temp
Negative feedback must have…
The change must be signalled to other cells
There must be an effective response that reverses the change
A change that is detected
https://docs.google.com/document/d/1422csrOOq_F1CdBgYQFVUyVQVY42YCDPtGSqAfXxlt8/edit
positive feedback :
This destabilises the system & is usually harmful
E.g. is extreme hypothermia when the core body temp falls so low that enzymes become less active. The exergonic (heat releasing) reactions become slower & less heat released. This slows the enzyme activity even more. Body temp quickly spirals downwards
here the response results in an increase of the original change
its sometimes useful ...
The stretching causes oxytocin to be released which causes contractions to occur
The contractions cause greater stretching of the cervix which causes the release of even more oxytocin
During the latter stags of pregnancy, the cervix will stretch as the foetus grows
This continues until the cervix if fully dilated & birth can the occur
https://docs.google.com/document/d/1422csrOOq_F1CdBgYQFVUyVQVY42YCDPtGSqAfXxlt8/edit
Less common in biological systems
the endocrine system
= the hormone system
Hormones are released into the blood by endocrine glands
Target cells with complementary receptors will enable the hormone to bind. It is the glycocalyx on the cell surface membrane which has specificity for a particular hormone
cell signalling
One cell release a chemical that is detected by another.
E.g. beta cell in the pancreas release insulin & this is detected by the liver cells which then convert glucose into glycogen
Synapses use chemicals also to communicate from one cell to another
Monitoring changes
Stimulus —> response
For homeostasis to work a good communication system different parts of the body are need. A good communication system…
Allows specific communication
E.g. target cells
Allows rapid communication
Allows cells to communicate with each other
Allows both short & long term responses
Covers the whole body
These changes need to be monitored
The organism must then respond to counter these changes
Changes in the environment bring about physiological stress
Changes aren’t always rapid
The Arctic fox grows a thicker coat in the winter - to act as an insulator to prevent heat loss to the environment
The coat also change from grey in the summer to white in the winter - to aid in camouflage
Communication stations
Our body needs to know what is going in, inside & outside - the conditions always change
What changes;
Temperature
Water levels
Blood pH
Oxygen & carbon dioxide levels
Blood glucose
Blood urea
Blood pressure
Why they need too adjust
Enzymes for example in a narrow pH & temp ranges - if exceeds optimum them they may either work too slow or become denatured
