5.1 Communication and Homeostasis Flashcards
what do all living things need to maintain
-a suitable temperature
-a suitable PH
-an aqueous environment that keeps the substrates and products in solution
-freedom from toxins and excess inhibitors
what is the environment of cells
they are protected by epithelial tissues and organs such as skin or bark. Internal cells and tissues are bathed in tissue fluid
how do activities of the cells alter their own environment
as cells undergo their various metabolic activities, they use up substrates and create new products. Some of these compounds may be unwanted or toxic. They move out of cells into the tissue fluid.
why is it Important that concentrations of waste products and other substances in the blood are monitored closely
it ensures that the body does not excrete too much of any useful substance but removes enough of the waste products to maintain good health. It ensures that the cells in the body are supplied with the substrates they need
why is a multicellular organism more efficient than a single celled organism
its cells are differentiated- they are specialised to perform particular functions. groups of these cells form tissues and organs. A good communication system is required to ensure that different parts of the body work together effectively
what will a good communication system do
-cover the whole body
-enable cells to communicate with eachother
-enable specific communication
-enable rapid communication
-enable both short term and long term responses
how does cell signalling work
one cell will release a chemical that is detected by another cell and the second cell will respond to the signal released by the first cell
define neuronal system
and interconnected network of neurones that signal to eachother across synapse junctions. It conducts signals very quickly and enables rapid responses to stimuli
define hormonal system
a system that used the blood to transport its signals. Cells in an endocrine organ release the signal directly into the blood and the hormone is transported to a specific target cell. It enables longer term responses to be coordinated
define aspects maintained by homeostasis
-body temp
-blood glucose conc
-blood salt conc
-water potential of the blood
-blood pressure
-CO2 conc
what is the standard response pathway
stimulus
receptor
communication pathway(cell signalling)
effector
response
define sensory receptor
cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potential
define communication system
system which signals between cells. is is used to transmit a message from receptor cells to effector cells via a coordination centre
define effector
a cell, tissue or organ that brings about a response
define homeostasis
maintaining a constant internal environment despite changes in external and internal factors
define negative feedback
the mechanism that reverses a change, bringing the system back to the optimum
what processes must occur for negative feedback to work?
- a change to the internal environment must be detected
2.the change must be signalled to other cells - there must be an effective response that reverses the change in conditions
define postitive feedback
the mechanism that increases a change, taking the system further away from the optimum
why must body temperature be controlled
Cell activities depend upon enzyme activity. All enzymes have an optimum temperature. Too low and they work too slowly, too high and they become denatured.
define ectotherm
an organism that relies on external sources of heat to maintain body temp
define endotherm
an organism that uses heat from metabolic reactions to maintain body temp
when ectotherms are not warm enough, they try to absorb more heat from the environment. What may they do to do this?
-move into a sunny area
-lie on a warm surface
-expose a larger surface area to the sun
what may ectotherms do if they re too hot
-move out of the sun
-move underground
-reduce the body surface exposed to the sun
what behavioural adaptations do snakes have
they bask in the sun and can often be found lying on an exposed path beside vegetation. this absorbs heat directly from the sun
what behavioural adaptations do lizards have
many lizards use burrows or crevices between rocks. they hide in them during the hottest part of the day and coolest part of the night. They tend to have a more stable temp than the air. In the hottest part of the day, it will be cooler in the burrow and at the coolest time, it will be warmer in it
what behavioural adaptations do horned lizards have
it can change its shape by expanding or contracting its ribcage. They can increase the surface area exposed to the sun so more heat can be absorbed
advantages of ectothermy
-less of their food is used in respiration
-more of the energy and nutrients gained from food can be converted to growth
-they need to find less food
-they can survive for long periods without food
disadvantages of ectothermy
-less active in cooler temp
-at risk from predators when they are cold and unable to escape
-cannot take advantage of food that is available while they are cold
define the hypothalamus
the part of the brain that coordinates homeostatic responses
many chemical reactions in the body are exergonic. what does this mean
they release energy in the form of heat
what is the behaviour or endothermic organisms when they are too hot
-hide away from sun in shade or burrows
-orientate body to reduce surface area exposed to sun
-remain inaction and spread limbs out to enable greater heat loss
-wet skin to use evaporation to help cool the body
what is the behaviour or endothermic organisms when they are too cold
-lie in the sun
-orientate body towards sun to increase surface area exposed
-move about to generate heat in the muscles
-roll into a ball shape to reduce surface area and heat loss
-remain dry
how does the skin respond if the body is too hot
-sweat glands secrete fluid onto the skin surface
-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 from the body
how does the skin respond if the body is too cold
-less sweat is secreted so less evaporation so less heat is lost
-hairs and feathers stand erect to trap air which insulates the body
-vasoconstriction of arterioles and precapillary sphincters leading to skin surface. blood is diverted away from the surface of the skin and less heat is lost
how does the gaseous exchange system respond if the body is too hot
some animals pant, increasing evaporation of water from the surface of the lungs and airways. Evaporation uses heat from the blood as the latent heat of vaporisation
how does the gaseous exchange system respond if the body is too cold
less panting so less heat is lost
how does the liver respond if the body is too hot
less respiration takes place so less heat is released
how does the liver respond if the body is too cold
increased respiration in the liver cells means that more energy from food is converted to heat
how does the skeletal muscles respond if the body is too hot
fewer contractions mean that less heat is released
how does the skeletal muscles respond if the body is too cold
spontaneous muscle contractions release heat (shivering)
how do the blood vessels respond if the body is too hot
dilation to direct blood to the extremities so that more heat can be lost
how do the blood vessels respond if the body is too cold
constriction to limit blood flow to the extremities so that blood is not cooled too much- this can lead to frostbite in extreme conditions
advantages of endothermy
-can maintain a fairly constant body temp whatever the temp is externally
-they can remain active even when external temperatures are low, which means they can take advantage of prey that may be available or escape from potential predators
-inhabit colder parts of the planet
disadvantages of endothermy
-use a significant part of their energy intake to maintain body temp in the cold
-need more food
-use for growth a lower proportion of the energy and nutrients gained from food
-may overheat in hot weather
what is the importance of maintaining a core body temperature
core temp changes alter the temp of the blood. this is detected by temp receptors in the hypothalamus. It then sends out imposes to cause different responses that will reverse the change.
what will the hypothalamus bring about if the core temp is too low
-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 reactions
what’s the role of a thermoregulatory centre
monitor blood temperatures and detect changes in the core body temp
when will the brain initiate behavioural mechanisms
if the thermoregulatory centre signals to the brain that the external environment is very cold or very hot
what is the role of peripheral temperature receptors
monitor the temperature of the extremities
