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Biology Module 5 > Commnication and Homeostasis > Flashcards

Flashcards in Commnication and Homeostasis Deck (49):

What is cell signalling

this is the way that cells communicate with each other


what are the set of conditions that all living things need to maintain

- a suitable temperature
- a suitable pH
- an aqeous environment that keeps the substrates and products in solution
- freedom from toxins and excess inhibitors


What happens when cell conditions are not maintained

- the cells become inactive and die, in multicellular organisms cells are specialised and rely upon each other therefore they must be able to communicate in order to coordinate their activities without this they may die


what threat can the external environment cause

- if the external environment changes it may put pressure on the organism, for example cooler environment will cause greater heat loss
- if the organism wants to survive then it has to monitor the changing environment and change its behaviour and physiology to reduce stress
- environmental is a stimulus and the way which the organism changes its behaviour or physiology is a response
- may adapt slowly as the environment changes throughout the year


How do organism change there internal environment

- range of tissues that are protected by epithelial tissues and organs
- internal cells and tissues are bathed in tissue fluid and this is the environment of the cells
- cells undergo metabolic activities and use up their unwanted substrates and create new products these move into and out of the tissue fluid therefore the cells create their own environment
- for example a waste product is co2 this goes into the tissue fluid and alters the ph of the cells which can stop enzymes from functioning, this change in environment is a stimulus and causes a response


How does the body maintain its internal environment

- composition of tissue fluid is maintained by the blood - blood is a transport so gets rid of unwanted substances and brings wanted substances to the cells
- wastes are removed by excretion
- concentrations are monitored closely to make sure that they do not excrete to much useful substances and too little waste


What does a good communication system have

- covers the whole body
- enables cells to communicate with each other
- enable specific communication
- enable rapid communication
- enables both short term and long term responses


Why is a multicellular organism more effective than a single celled organism

Because cells are differentiated
- cells perform specific jobs and work together in tissues
- cells monitor blood can remove waste substances


What are the two major systems of communication

Neuronal system
Hormonal system


Describe the neuronal system

- interconnected network of neurones that signal to each other across synapse junctions
- very quick and get rapid responses to stimuli that may be quickly changing


Describe the hormonal system

- uses blood to transport signals
- cells in endocrine organ release signal directly into the blood this is then transported throughout the whole body but is recognised by specific target cells
- long term responses


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


describe the standard response pathway

stimulus - receptor - communication pathway - effector - response


what is needed for the response pathway to work

- sensory receptors
- communication system
- effector


describe sensory receptors

- for example temperature receptors
- receptors may be on the surface of the skin, monitor changes in the external environment
- other monitor internal conditions in the body
- when it detects a change it will be stimulate to send a message to an effector


describe an effector

- cells such as liver or muscle cells
- bring about a response


What is homeostasis

- maintaining a constant internal environment despite changes in external and internal factors


what is negative feedback

the mechanism that reverses change bringing the system back to the optimum


what is positive feedback

the mechanism that increases a change taking the system further away from the optimum


Describe how negative feedback works

- condition changes
- receptors detect
- coordination centre sends an output to the effectors
- effector responds to output
- reverses the initial change in conditions and stimulus is reduced as it returns to its optimum
- receptors detect reduction
- reduce the input to the coordination centre and therefore the output is reduced as the system gets closer to the optimum


what has to happen for negative feedback to work

- a change to the internal environment must be detected
- the change must be signalled to other cells
- must be an effective response that reverses the change in conditions


Describe the negative feedback loop for temperature

Rise in temperature
- thermoregulatory centre in hypothalamus detects change
- nervous and hormonal system carry signals to skin, liver, and muscles
- less heat generated and more heat lost
- temperature falls
decrease in temperature
- thermoregulatory centre in hypothalamus detects change
- nervous and hormonal systems carry signals to skin, liver, and muscles
- more heat generated and less heat lost


is it possible to maintain a constant environment

- slight range in when the optimum internal environment can happen
- when stimulus occurs it may take time to response this can cause a slight overshot


what is positive feedback used for

- to increase the original response


describe how positive feedback works

- optimum condition
- optimum condition changes away
- receptor detects change
- input
- communication system informs effector
- output
- effector reacts to increase change
change away from optimum....


give examples of positive feedback

- below a certain core temperature enzymes become less active and exergonic reactions that release heat are slower and release less heat this allows the body to cool further and slows enzyme controlled reactions even more
- end of pregnancy to bring about the dilation of the cervix, as the cervix stretches this causes the pituitary gland to secrete the hormone oxytocin this increases uterine contractions which stretch the cervix even more which causes the secretion of more oxytocin
- activity of neurons


what is ectotherm

an organism that relies on external sources of heat to maintain body temperature


what is endotherm

an organism that uses heat from metabolic reactions to maintain body temperature


What are the 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


what are the disadvantages of ectothermy

- they are less active in cooler temperatures, therefore they are at risk from predators while they are cold and unable to escape
- cannot take advatage of food that is available while they are cooled


what happens when body temperature changes

- they have a dramatic effect upon the activity of cell processes
- temperature rises therefore molecules have more kinetic energy this means that they move more quickly and collide more frequently
- chemical reaction happen more quickly
- protein structure is affected, enzymes loose their shape slow their rate of reaction down


describe endotherms

- control body temperature in strict limits
- use a variety of mechanisms to control body temperature
- largely independent of external temperatures


describe ectotherms

- not able to control body temperatures as effectively as endotherms
- rely on external sources of heat ad their body temperatures
- temperature fluctuates with external temperature
- can control their body temperatures in all but most extreme conditions


How do ectotherms control temperatures

if they are not warm enough they try to absorb more heat from the environment
- move into a sunny area
- lie on a warm surface
- expose a larger surface area to the sun
if they are too hot
- move out of the sun
- they move underground
- reduce the body surface exposed to the sun


describe how a snake is behaviorally adapted and how it benefits for controlling temperature

- basks in the sun
- this means that is absorbs heat directly from the sun


describe how a locust is behaviorally adapted and how it benefits for controlling temperature

- in early morning locusts sit side on to the sun and expose a large surface area, climb to the top of a plant at midday, increases both the rate of breathing and the depth of breathing movements when it is hot
- in cool orig they can absorb more heat, midday when the sun is hot they absorb less heat, the soil gets hot and radiates heat, locusts moves away from the soil it gains less heat from the soil


describe how a lizard is behaviorally adapted and how it benefits for controlling temperature

- many lizards use burrows or crevices between rocks, they will hide in a burrow during the hottest art of the day and coolest part of the night
- an underground burrow has more stable temperature than air, hottest part of the day it is cooler and in the night it is warmer than the outside


describe how a horned lizard is behaviorally adapted and how it benefits for controlling temperature

- can change its shape by expanding or contracting its ribcage
- expanding ribcage increases the surface area exposed to the sun so more heat can be absorbed


What are the advantages of endothermy

- can maintain a fairly constant body temperature whatever the temperature externally
- remain active even when external temperatures are low which means they can take advantage of prey that may be available or escape potential predator
- inhabit cooler parts of the plant


what are the disadvantages of endothermy

- use a significant part of their energy intake to maintain body temperature 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


How do endotherms regulate temperature

- they rely on effectors in the skin and muscles
- skin is in contact with external environments
- many chemical reactions in the body are exergonic this means that release energy in the form of heat
- increase respiration in the muscles and liver simply to release heat
- direct blood towards or away from the skin to alter the amount of heat lost to the environment


describe the response of the skin if its too hot and too cold

Too hot
- sweat glands secrete fluid onto the skin and this evapourates cooling the body
- hairs and feathers lie flat to reduce insulation and allow greater heat loss
- vascodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away from the body
Too cold
- less sweat secreted, so less evaporation therefore less heat is loss
- hairs and feathers stand erect to trap air which insulates the body
- vasoconstriction of arterioles and precapillary sphincters leading to the skin therefore blood is diverted away from the surface of the skin and less heat is lost


describe the response of the gaseous exchange system if its too hot and too cold

Too hot
- increase evaporation of water from the surface of the lungs and airways, uses heat from the blood as the latent heat of vaporization
Too cold
- less panting so less heat lost


describe the response of the liver if its too hot and too cold

Too hot
- less respiration takes place so less heat is released
Too cold
- increased respiration in the liver cells means that more energy from food is converted to heat


describe the response of the skeletal muscles if its too hot and too cold

Too hot
- fewer contractions mean that less heat is released
Too cold
- spontaneous muscle contractions release heat - shivering


describe the response of the blood vessels if its too hot and too cold

Too hot
- dilation to direct blood to the extremities so that more heat can be lost
Too cold
- constriction to limit blood flow to the extremities, so that blood is not cooled too much - can lead to frostbite in extreme conditions


Behaviour of endotherms if too hot

- hide away from the sun in the shade or in a burrow
- orientate body to reduce surface area exposed to sun
- remain inactive and spread limbs out to enable greater heat loss
- wet skin to use evaporation to help cool the body


Behaviour of endotherms if too cold

- lie in the sun
- remains dry
- orientate body towards sun to increase surface area exposed
- move about to generate heat in the muscles or roll into a ball shape to reduce surface area and heat loss


what is the role of the peripheral temperature receptors

-early warning that temperature may change
- the peripheral temperature receptors in the skin monitor the temperature in the extremities this info is fed to the thermoregulatory centre in the hypothalamus
- if sends signals to the brain that external environment is very cool or hot the brain can initiate behavioral mechanisms for maintaining body temperature