Homeostasis Flashcards
What is homeostasis?
Body maintains a dynamic equilibrium, with small fluctuations over a narrow range of conditions
What do sensory receptors do?
Detect changes in internal and external environments of organism
What are some examples of what homeostasis monitors?
Detecting changes e.g.
PH of blood, Core body temp, Conc of urea and sodium ions in blood
What do negative feedback loops involve?
-Receptor to detect stimulus
-Coordination system to transfer information through body
-Effector to carry out response
What are the outcomes of negative feedback loops?
-Stimulus continuously monitored
If there is an increase in the factor, the body responds to make the factor decrease
If there is a decrease in the factor, the body responds to make the factor increase
How do negative feedback loops work?
A small change is detected by sensory receptors, and effectors work to reverse the change and restore conditions to base level
What happens in positive feedback systems?
A change in the internal environment of the body is detected by sensory receptors, effectors reinforce that change and increase response.
Whats an example of a positive feedback loop
Blood clotting cascade
What is cell signalling and why do we need it?
Process where cells communicate with each other, allows multicellular organisms to control and coordinate bodies to respond to environment
What are the basic stages of cell signalling?
Stimulus received by receptor
Stimulus converted to a signal- transduction
Signal transmitted to effector
Response made
What is thermoregulation?
Maintenance of a relatively constant core body temp to maintain an optimum enzyme activity
What physical processes does thermoregulation depend on?
-Exothermic chemical reactions
-Latent heat of vaporisation
-Radiation
-Convection
-Conduction
What are ectotherms?
Use their surroundings to warm their bodies, dependant on environment
Include inveribrate animals, fish, amphibians and reptiles
Why do ectotherms living in water not need to regulate often?
High heat capacity of water, temperature of water doesn’t change much
What are endotherms?
Rely on their metabolic processes to warm up and maintain a stable core temperature despite the external temperature.
Metabolic rate is higher so needs to consume more food to meet needs
What behavioural responses have ectotherms developed?
Sometimes need to warm up to speed up metabolic reactions for them to be active e.g. orientate bodies for a large SA
Increase body temp by conduction through pressing body against warm ground
Cool down by preventing core temperature reaching point where enzymes begin to denature- shelter from sun etc
What are physiological responses to warming
Dark colours absorb more- lizards in cold climates are darker
Alter heart rate to maintain metabolic processes
How do endotherms detect temperature changes?
Peripheral temperature receptors detect changes in surface temp
Temp receptors in hypothalamus detect temp in blood
What is vasodilation?
Arterioles close to surface of the skin dilate when the temp rises
Vessels that provide a connection between arterioles and venues constrict
Forces blood between capillary networks
Skin flushes and cools as a result of increased radiation
If skin pressed against cold surfaces, cooling results from conduction
What causes increased sweating in endotherms?
As core temp increases- sweat increases- across surface of skin
As sweat evaporates from the skin, heat is lost, cooling blood below the surface.
How do endotherms cool down from reducing insulating effect of hair/feathers
As body temp increase, erector pili muscles in skin relax- hair flattens to skin which avoids trapping of insulating layer of skin
Large SA:V ratios- maximum cooling, pale fur to reflect radiation
How do endotherms warm up through vasoconstriction
Arterioles near surface of skin constrict. Arteriovenous shunt vessels dilate- so little blood flows through capillary networks near the skin.
Skin is pale and little radiation and warm blood kept below surface
How does decreased sweating keep the body warm?
As core temp falls, rate of sweating decreases. Reduces cooling by evaporation of water from skin surface-
How does raising body hair increase heating
As body temp falls, erector pili muscles in skin contract- pulling hairs erect
Traps an insulating layer of air and reduces calling
