5.1 communication and homeostasis Flashcards
The first page is just an introduction so review it
What are the two major systems of communication that work by cell signaling?
neuronal system - neurons
hormonal system - blood system
What are the aspects maintained by homeostasis?
body temperature
blood glucose concentration
blood salt concentration
water potential of the blood
blood pressure
carbon dioxide concentration
What is the standard pathway for homeostasis?
stimulus > receptor > communication pathway > effector > response
What are the names for the receptors that detect the stimulus?
sensory receptors
What is the input?
The message from the receptor to the coordination centre
What is the output?
The messages sent to the effector.
What are some examples of effector cells?
liver or muscle cells
What is the negative feedback response to a raise in body temperature?
thermo-regulatory centre in hypothalamus detects change
nervous and hormonal system carry signals to skin, liver and muscles
less heat generated and more heat lost
back to optimum
What is the negative feedback response to a raise in body temperature?
thermo-regulatory centre in hypothalamus detects change
nervous and hormonal system carry signals to the skin, liver and muscles
more heat generated and less heat lost
back to optimum
What is a positive feedback system?
The response is to increaser the initial change, destabilizing the system and can sometimes be harmful.
What is the positive feedback system when the body’s core temperature is too low?
the exergonic reactions that heat up the body slow even more and allow the body to cool further
What is the positive feedback response during pregnancy?
cervix expands > posterior pituitary gland releases oxytocin > oxytocin increases uterine contractions and cervix expands further > more oxytocin > birth stops oxytocin
Are humans endotherms or ectotherms?
Endotherms
What is the difference between ectotherms and endotherms?
Endotherms control their internal body temperature
Ectotherms rely on external factors to maintain body temperature
What will ectotherms do if it is too hot?
move out of the sun
move underground
reduce body surface exposed to the sun
What will endotherms do if it is too cold?
move into a sunny area
lie on a warm surface
expose larger body area to the sun
Examples of how ectotherms maintain body temperature?
snakes - bask in the sun
locust - face the sun in the morning with whole body, only head at midday, move away from soil that radiates heat
lizards - use burrows and cervices
horned lizard - can expand ribcage to increase surface area
What are the advantages of ectothermy?
less food is used in respiration
more of the energy and nutrients can be used for growth
they need to find less food
can survive with no food for long times
What are the disadvantages of ectothermy?
At risk from predators when it is cooler as they try and conserve heat and less food is available
What is the skin’s response when it is too hot?
sweat glands secrete fluid to be evaporated
hairs and feathers lie flat to reduce insulation
vasodilation allows capillaries closer to the skin to radiate heat out
What is the skin’s response when it is too cold?
less sweat is secreted
hairs and feathers stand erect to maintain heat
vasoconstriction means capillaries are not near skin
What does the gaseous exchange system do when it is too hot?
Some animals pant, increasing evaporation in the lungs
What does the gaseous exchange system do when it is too cold?
Reduction in panting
What does the liver do when it is too hot vs too cold?
too hot - lowered respiration levels in cells
too cold - increased respiration levels due to exergonic reactions
What do the skeletal muscles do when it is too hot vs too cold?
too hot - fewer contractions
too cold - spontaneous muscle contractions (shivering)
What are the advantages to being an ectotherm?
maintain a constant body temperature
remain active even when there are low temperatures which stops predators and can take advantage of food
inhabit colder parts of the planet
What are the disadvantages of being an endotherm?
uses a lot of energy to maintain body temperature
need more food
less energy is used for growth
may overheat in hot weather
Where are temperature receptors found?
In the hypothalamus
What monitors the external temperature in ectotherms?
peripheral temperature receptors in the skin
