communication

Question 1

outline he need for communication within multicellular organisms, with reference to the need to respond to changes in the internal and external environment and to co-ordinate the activities of different organs

Answer 1

in multicellular organisms, diffrent parts perform different fucntions. it;s therefore essential that internal communication systems control the activities of these different parts. a communication system between receptors and effectors, which may be far apart from one another allows the organism to:

1. monitor changes in the internal and external env
2. respond adaptively to such changes
3. coordinate the activities of different organs

Question 2

cell signalling

Answer 2

cells need to communicate to each other

Question 3

examples of cell signalling

Answer 3

neuronal and hormal systems
the signals may be:
electrical- by means of nerve cells or neurones
chemical- by means of messengers called hormones

Question 4

define negative feedback

Answer 4

a mechanism by which a change in a parameter is detected and which brings a response that loves the parameter back towards the norm

Question 5

define positive feedback

Answer 5

a mechanism by which a change in a parameter is detected and which brings about an action that takes the parameter even further away from the norm

Question 6

define homeostasis

Answer 6

maintenance of a constant internal environment regardless of changes to the ourside environment

Question 7

explain the principles of homeostasis in terms of receptors, effectors and negative feedback

Answer 7

homeostasis requires:

• a receptor (sensor or detector) that receives info (input
• a control mechanism that responds to information and stimulates an effector
• an effector to perform the appropriate action

Question 8

describe the physiological and behavioural responses that maintain a constant core body temp in ecto and endotherms (with ref to peripheral temp receptors, hypothalamus and effectors in skin and muscles)

Answer 8

most animals are ectotherms- the heat energy that warms them comes from outside their body. ectotherms may use behavioural means to adjust their temp- a lizard move into sunshine to raise temp or shade to lower it.

mammals and birds are endotherms- releasing enough heat within their body to maintain them above temp of their surrounding when necessary.
they also maintain body temp through negative feedback loops- which balance heat loss against heat gain.
also use behavioural means like ectotherms