Communication and Homeostasis Flashcards
what conditions need to be maintained within cells?
temperature, pH, an aqueous environment and freedom from toxins and excess inhibitors
what does a good communication system do?
cover the whole body, enable cells to communicate with eachother, enable specific and rapid communication, and enable short and long term responses
what is cell signalling?
the process in which one cell will release a chemical that is detected by another cell, the second cell will then respond to this signal
what is the neuronal system?
an interconnected network of neurons that signal to each other across synapse junctions. The neurons can conduct a signal very quickly and enable rapid responses to stimuli that may be changing very quickly
what is the hormonal system?
a system that uses blood to transport its signals. Cells in an endocrine organ release the signal (a hormone) directly into the blood. The hormone is transported throughout the body, but is only recognised by a specific target cell. The hormonal system enables longer-term responses to be coordinated
what is homeostasis?
maintaining a constant internal environment despite changes in external and internal factors
what aspects can be maintained by homeostasis?
body temp, blood glucose, blood salt concentration, water potential of the blood, blood pressure and carbon dioxide cocentration
what is negative feedback?
the mechanism that reverses a change, bringing the system back towards the optimum
what processes must occur for negative feedback to work?
a change to the internal environment must be detected, the change must be signalled to other cells and there must be an effective response that reverses the change
what is positive feedback?
increasing the original change away from the optimum
what is an example of positive feedback?
During the dilation of the cervix. As the cervix begins to stretch it causes the posterior pituitary gland to secrete the hormone oxytocin. The birth ends the production of oxytocin
what is an ectotherm?
an organism that is not able to control body temperature as effectively as they rely on external sources of heat. Using various behavioural mechanisms some can control temperature in extreme conditions
what do ectotherms do if they are not warm enough?
Moving into a sunny area
Lie on a warm surface
Expose a larger surface area to the sun
what do ectotherms do if they are too warm?
Moving out of the sun
Move underground
Reduce the surface area exposed to the sun
what are advantages of ectotherms?
They do not use up energy to keep warm so:
Less of their food is used in respiration
More energy and nutrients gained from food can be used for growth
They need to find less food
Can survive for long periods without food
What are disadvantages of ectotherms?
Less active in cooler temperatures
At risk from predators while they are unable to escape
Can’t take advantage of available food when they are cold
what is an endotherm?
organisms that control their body temperature within very strict limits, they use a variety of mechanisms to control body temperature and are largely independent of external temperatures
what are responses of the skin if an endotherm is too hot?
Sweat glands secrete fluid, as it evaporates it uses heat from the blood as the latent heat of vaporisation
Hairs and feathers lie flat to reduce insulation and allow greater heat loss
Vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away
what are responses of the skin if an endotherm is too cold?
Less sweat is secreted, so less evaporation means less heat lost
Hairs and feathers stand erect to trap air that insulates the body
Vasoconstriction of arterioles and precapillary sphincters leading to the skin’s surface, blood is diverted away from the surface of the skin and less heat is lost
what is the response of the gaseous exchange system if an endotherm is too hot?
Panting can increase evaporation of water from the surface of the lungs and airways. Evaporation uses heat from the blood as the latent heat for vaporisation
what is the response of the gaseous exchange system if an endotherm is too cold?
Less panting, so less heat lost
what is the response of the liver if an endotherm is too hot?
Less respiration takes place so less heat is released
what is the response of the liver if an endotherm is too cold?
Increased respiration in the liver cells mean that more energy from food is converted to heat
what is the response of the skeletal muscles if an endotherm is too hot?
Fewer contraction mean less heat is released
what is the response of the skeletal muscles if an endotherm is too cold?
Spontaneous muscle contractions (shivering) releases heat
what is the response of the blood vessels if an endotherm is too hot?
Dilation to direct blood to the extremities so that more heat can be lost
what is the response of the blood vessels if an endotherm is too cold?
Constriction to limit blood flow to the extremities so that the blood isn’t cooled - can lead to frostbite
what are advantages of being an endotherm?
Maintain a fairly constant body temperature
Remain active even when external temperatures are low (can escape predators or catch prey)
Inhabit colder parts of the planet
what are the disadvantages of being an endotherm?
Use a significant part of their energy intake to maintain body temperature
Need more food
May overheat in hot weather
how is temperature regulated?
Temperature receptors in the hypothalamus detect change and then send an impulse to reverse the change
what happens if the core temperature is too low?
the hypothalamus will bring about:
Changes in the skin to reduce heat loss
Release of heat through extra muscular contraction
Increased metabolism in order to release more heat from exergonic reaction
what is the role of peripheral temperature receptors?
they monitor the temperature in the extremities as this can help initiate a faster response in the thermoregulatory centre in the hypothalamus
