Y2 ocr homeostasis. Flashcards
what is homeostasis?
The maintenance of dynamic equilibrium over a narrow range of conditions.
what kind of systems does the body use to monitor and respond to the changes from the steady state of the body?
electrical and chemical
give some examples of some conditions in the body that need to be maintained w/in narrow range?
- blood glucose concentration
- sodium ions in the blood (ie solute conc)
- pH and water balance of the bodu fluids
- the core temp of the body.
why is it impossible to maintain a living mammal in a completely stable state?
bc everything causes minute changes.
instead the body manages a “dynamic equilibrium”
what is the function of sensory receptors?
Sensory receptors detect changes in the internal and external environment of an organ isms.
give some examples of receptors and what they detect?
photoreceptors detect changes in light
chemoreceptors detect changes in chemicals (ie pH)
thermoreceptors in the SKIN detect changes in external temperature
mechanoreceptor detects changes in pressure
where is the information from the sensory receptor transmitted to?
the brain and impulses are then sent along motor neurones to the EFFECTORS (which bring about change)
what is the function of the effectors?
Effectors are muscles and glands that work to react to the motor stimulus and bring about a RESPONSE
what are the 2 main effectors ?
Muscles and glands.
How do the effectors, Muscles,bring about a response to stimuli?
muscles
- squeeze the gut
- squeeze chemicals from glands
- contract
How do the effectors, glands bring about a response to a stimuli?
glands secrete enzymes and hormones into the blood stream.
why are both receptors and effectors important in homeostasis?
- the body needs sensory receptors to monitor changes in the internal environment
- effectors respond to the changes , restoring them back to normal levels
what are the 2 main feedback systems?
negative and positive feedback
what is meant by the term negative feedback system?
A negative feedback system is one that works to reverse the changes brought on by a stimulus. It Aims to reverse the system back to normal level and to nullify and INHIBIT the effect of the change.
What is meant by a positive feedback system?
A system that works to increase (amplify ) the effect of the change brought on by a stimulus. It brings the system further away from normal base level.
what happens in a positive feedback system?
A change in the internal environment is detected , effecters are stimulated to REINFORCE THE CHANGE and thus increase the response
give an example of the -ve feedback system?
- regulation of blood glucose
- regulation of ADH
- regulation of temperature
give an example of the + feedback system
childbirth
explain the positive feedback seen in childbirth.
DUring labour, the head of the child pushes against the cervix stimulating the productio of the hormone OXYTOCIN
oxytocin stimulates the uterus to contract, pushing the head of the baby even harder agaisnt the cervix
as the baby pushes head against the cervix, it triggers the release of MORE oxytocin.
this continues until the baby is born.
EXAM Q : 6m : suggest why effective homeostasis depends on negative than positive feedback systems.
Negative feedbacks aim to inhibit change (1)to a system and they act to reverse the change brought on by a stimulus bringing the system closer to base level ;ie to normal(1).
Positive feedback systems bring the system away from the normal base level, amplifying the effects of the change brought on by a stimulus. The response works to reinforce the change(1)
In homeostasis the body seeks to maintain a dynamic equilibrium.(1)
If there is a change , the need is to inhibit and return the system to the original state(1)
This is only possible with -ve FBS not +BFS(1)
why is it important to maintain and control temperature in a mammal?
The enzymes controlled reactions take place in optimum temperatures.
If the temperature is TOO high, the the enzymes may become denatured.
what is thermoregulation?
Thermoregulation is the maintenance of a core constant body temperature that will be high enough to maintain the optimum enzyme activity
list the physical processes that cause the organisms to be constantly heating up and cooling down.
- exothermic chemical reactions
- latent heat of evaporation
- radiation
- convection
- conduction.
how do organisms lose heat by latent heat of evaporation?
objects cool down as water evaporates from a source, taking heate energy from the system.
