Communication and Homeostasis Flashcards
(39 cards)
What set of conditions does an organism need to maintain within their cells to survive?
- Suitable temperature
- Suitable pH
- Aqueous environment that keeps substrates and products in solution
- Freedom from toxins and excess inhibitors
Why are most cells not exposed to the external environment?
They are protected by epithelial tissue and organs such as skin or bark
What is a tissue?
A group of specialised cells working together to carry out a specific function
What is an organ?
A group of specialised tissues working together to carry out a specific function
What are the two main systems of communication that communicate by cell signalling?
- Neuronal system
- Hormonal system
What conditions does homeostasis maintain?
- Body temperature
- Blood glucose concentration
- Blood salt concentration
- Water potential of the blood
- Blood pressure
- CO2 concentration in the blood
What is the standard response pathway to a change in stimulus?
Stimulus → receptor → communication pathway/output → effector → response
Give an example of a change in stimulus
Change in body temperature
Give an example of a sensory receptor
Thermoreceptor, this detects a change in temperaure and sends a signal to an effector
Give an example of an effector
Muscle cells, these cells will bring about a response if they have received a signal from receptor cells
Describe the body’s response to a fall in core body temperature
- Thermoreceptors in hypothalamus detect that core body temperature has fallen below the optimum temperature
- Nervous and hormonal systems carry signals to skin, liver and muscles
- Vasoconstriction, piloerection, shivering and increased respiration of the liver all occur
- This causes more heat to be generated and less heat to be lost, therefore returning temperature back to its optimum
What are the 4 responses to a decrease in body temperature?
- Vasoconstriction
- Piloerection
- Shivering
- Increased metabolism in liver
What are the 4 responses to an increase in body temperature?
- Vasodilation
- Pilorelaxation
- Sweating
- Decrease in metabolism in the liver
What is positive feedback?
A change occurs to take conditions away from the optimum temperature, receptors detect the change and the communication system informs the effectors, the effector reacts to take the conditions further away from the optimum
How would an ectotherm respond to a decrease in body temperature?
- Move into a sunny area
- Lie on a warm surface
- Expose a larger surface to the sun
How do ectotherms respond to an increase in body temperature?
- Move out of the sun
- Move underground
- Reduce the surface are they’re exposing to the sun
What would a snake do to increase its body temperature?
Bask in the sun, this enables them to absorb heat directly from the sun
What would a locust do to regulate its body temperature?
- In the morning sit side on to the sun to expose a larger surface area to the sun while the sun is cooler, midday sit face on to the sun to reduce surface area exposed when the sun is at its hottest. They may also climb to the top of a plant at midday to get away from the soil surface which is hot as it radiates heat
- Locusts may also increase breathing rate and the depth of breathing movements when it’s hot so that more water evaporates from the tracheal system, this cools the Locust’s body due to energy being used from the locust’s body due to water’s high specific latent heat
How do Lizards regulate their body temperature?
Lizards tend to hide in burrows or crevices at the hottest and coolest parts of the day, this is because the burrow has a more stable temperature than the air meaning that in the hottest part of the day the lizards keep cool when it’s hot and keep warm when it’s cold
What do horned lizards do to regulate their body temperature?
Horned lizards can expand their ribcage, this increases the surface area of their body that is exposed to the sun and therefore they can absorb more heat
What are the responses of the skin of an endotherm to an increase in body temperature?
- Sweat glands secrete fluid onto skin surface, as this evaporates it uses heat from the blood due to the high specific latent heat of water
- Hairs and feathers lie flat to reduce insulation and allow greater heat loss
- Vasodilation of arterioles and precapillary sphincters directs blood to the skins surface, increasing heat loss by radiation
What is the gaseous exchange system of an endotherm’s response to an increase in body temperature?
Some animals pant to increase evaporation of water from the surface of the lungs and airways, evaporation uses heat from the blood due to the high specific latent heat of water
What are the advantages of being an ectotherm?
- Less of their food is used in respiration as they don’t use up energy to keep warm
- More of the energy and nutrients gained from food is used for growth
- They need to find less food
- They can survive for longer periods without food
What are the disadvantages of being an ectotherm?
- Ectotherms don’t generate heat
- They are less active in cooler temperatures to conserve heat energy, this means they are at risk from predators when they are cold
- They also can’t take advantage of food that is available when it’s cold as they need to conserve heat energy
