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Module 1: Communication
(a) Outline the need for communication systems within multicellular organisms
Multicellular organisms have many layers of cells that need to communicate with each other. The vast
number of cells results in the great amount of distance that messages need to travel, hence the need
for a communication system. Changes in the internal and external environment known as a stimulus
can be addressed by a series of actions that are brought about by a series of messages that can be
or hormonal and or neuronal nature.
(b) State that cells need to communicate with each other by a process called cell signalling;
Cell signalling is the process in which in an organism communicate with each other through means of
hormonal, neuronal or both on an occasion.
(c) State that neuronal and hormonal systems are examples of cell signalling;
Neuronal and hormonal systems are examples of cell signalling. Receptors communicate with the
effectors through these means of communication.
(d) Define the terms negative feedback, positive feedback and homeostasis;
o The counteract action to restore the level back to normal.
o This is when an action occurs that amplifies the change applied to the level.
o It is the process in which the internal environment is kept at a constant level
despite changes to the external environment.
(e) Explain the principles of homeostasis in terms of receptors, effectors and negative feedback
(f) Describe the physiological and behavioural responses that maintain a constant core body
Vasodilation and vasoconstriction Shivering