f214 communication

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F214 Module 1-Communication and Homeostasis

Chapter 1 - Communication

a. Outline the need for communication systems within multicellular organisms

·         External environmental changes are the changes in the external environment can cause stress. It may change slowly so there will be a gradual response. It may be a quick change so a rapid response is needed.


·         Internal environmental changes are the environment of internal cells is that they are protected by epithelial cells and they are bathed in tissue fluid. The activities of cells alter their environment e.g. releasing toxic products that need to be removed.


·         Coordination of activities of organs is that the groups of specialised cells form tissues and organs. Cells monitor the blood and can release a substance into the blood to remove certain substances.

b. State that cells need to communicate with each other by a process known as cell signalling

·         Cells need to communicate to ensure that the different parts of the body work together effectively.

·         Cell signalling is the process where one cell releases a chemical that is detected by another cell which will react and respond to the signal.

c. State that neuronal and hormone systems are examples of cell signalling

·         Neuronal systems are the interconnected network of neurones that signal to each other across synapse junctions.

·         Hormonal systems are the blood is used to transport signals. Cells in an endocrine organ release a hormone which is the signal into the blood which is then carried around the body and recognised by specific target cells.

d. Define the terms negative feedback, positive feedback and homeostasis

·         Negative feedback is the process that brings about a reversal of any change in conditions. It maintains and optimum steady state due to the return of the internal environment to its original set of conditions.

·         Positive feedback is the process that increases the change detected by the receptors. It destabilises the system meaning that it tends to be harmful.

·         Homeostasis is when the internal environment is kept constant even though there are external changes. It can include conditions such as body temperature, blood glucose concentration, blood pressure and carbon dioxide concentration.

e. Explain the principles of homeostasis in terms of receptors, effectors and negative feedback

From optimum conditions, it changes away from optimum, the receptor detects change, the communication system informs effector, the effector reacts to change and it returns to optimum conditions.

1.     Sensory receptor

·         Internal receptor to monitor conditions inside the body.

·         If a change is detected they will be stimulated to send a message.

2.    Communication system

·         E.g. nervous system, hormonal system.

·         Acts via cell signalling to transmit a message from the receptor cells to the effector cells.

3.    Effector cells

·         E.g. Liver cells, muscle cells.

·         They bring about a response to reverse the change detected.

f. Describe the


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