homeostasis Flashcards
what is an effector
cell tissue or organ bringing a response to reverse a change or contribute to a change internally
what is homeostasis
maintaining a constant internal environment, withing a narrow range despite changes in the external or internal factors
what is negative feedback
mechanism which reverses a change, bringing the system back to optimum
what is positive feedback
mechanism which increases a change bringing system farther away from optimum, usually harmful
what is more common- negative or positive feedback
negative
what are sensory receptors
cell nerve endings that respond to a stimulus in internal/ external environment and create action potentials
name factors that homeostasis controls
body temperature
blood glucose concentration
blood pressure
co2 conc
water potential of blood
what is the standard response pathway
stimulus
receptors
communication pathway/ cell signalling
effector
response
give an example of a sensory receptor
temperature receptors/ thermoreceptors on skin surface which monitor the conditions externally
give an example of an interal sensory receptors
temperature receptors in the brain- when it detects a stimulus, it sends an output messenger to the effector
what is an input
messages sent from receptor to the coordination centre
what organ is the coordination centre
brain
what are the two communication system
neuronal
hormonal
what does a communication system enable
a form of cell signalling
allows transmission of messages from receptors to effectors
what is an output
messages sent to effectors from coordination centre
describe negative feed back
-what happens
- reduction in further activity
stimulus- change in conditions
receptors detect stimulus and sends an input to the coordination centre.
coordination centre recieves input and sends output to the effectors
effectors bring change to reverse initial change
system is closer to optimum
stimulus then reduces, input and out put reduces, effectors reduce activity
what are the processes that take place to make negative feedback successful
stimulus must be detected
stimulus must be signalled to cells
there must be an effective response which reverses conditions
are conditions always perfect?
no they are constantly fluctuating
give an example of positive positive feedback
during birth
when cervix dilates, the pituitary gland produces oxytocin (hormone to dilate cervix more)
the more the cervix dilates, the more oxytocin produced.
increasing the change
birth ends production of oxytocin
name two types of effector
muscle cell or cells in glands
what is an ectotherm and endotherm
ectotherm- cold blooded animal
endotherm- warm blooded animal
how do ectotherm control body temp
expose there bodies to the sun
take shelter to prevent overheating
burrow to prevent overheating
press bodies against ground to gain warmth
Generate metabolic heat- respiration provides small amount of heat.
when endotherms are too hot, what are their physiological abilities to cool themselves down
vasodilation- arteriole diameter largens therefore more blood passes skin surface and heat is lost by radiation
panting- air evaporates water in mouth and cools them
sweating- heat from skin provides energy for evaporation
when endotherms are too cold, what are their physiological abilities.
vasoconstriction- arteriole diameter near skin is reduced so more blood is insulated inside body, no heat lost by radiation
shivering- involuntary muscle contractions to generate metabolic heat caused by production of adrenaline or thyroxine
piloerection- hairs stand to trap layer of air near skin and insulate it
what area of the brain control body temperature
Hypothalamus- by monitoring the temperature of blood passing through it
name four structures on the skin involved in mammal thermoregulation
Fat tissue
hair erector muscles
arterioles
sweat gland
can ectotherms thermoregulate
No
what are the advantages of ectotherms
respire less, therefore the food they eat is used for growth not energy- therefore they need less food.
what are the disadvantages of ectotherms
less active in cool temp and not capable of activity in winter as they hibernate
what are the advantages of endotherms-
they can maintain a constant temperature
active in cold temperature
what are the disadvantages of endotherms-
more food is needed and energy goes to metabolism and not growth.
will need more food
may overheat in hot weather
what actions does the liver do if it is too hot or cold
less respiration so less heat is released, if too hot
more respiration in hepatocytes so more energy from food is converted to heat.
name sensory cell in skin that detects change in environmental temperature change
thermoreceptor
if blood glucose concentration is low- what does the effector produce
glucagon
if blood glucose concentration is high, what does the effector produce
insulin.
why does shivering not conserve heat
shivering doesnt conserve heat it generates it.
