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PinkMonkey Online Study Guide-Biology

23.3 Receptors And Effectors

Sense organs make an animal aware of conditions or events in its own body and in the world around it. Information collected by sense organs is passed to the nervous system, which determines and initiates an appropriate response. The stimuli or the sensations are received by the nerves which are associated with special sensory cells called receptors (Figure 23.7). Impulses from the receptors reach the brain (Central Nervous System), where they are interpreted or analyzed, following which a proper command is given to the effector organs. The effector organs are usually muscles or glands which contract or secrete chemicals producing suitable responses.

In higher animals, different types of cells (receptor cells) receive a variety of stimuli. These receptor cells are grouped together to form a sensitive structure known as sense organs. Generally, five senses are known in higher animals. These are, sense of touch, smell, taste, hearing and sight. A particular sense receptor or a sense organ is specialized and responds to only one kind of stimulus. The main types of receptors, functions and locations are given in following table:

S.No. Type Function Location
1 Mechanoreceptors Sensitive to tactile stimuli : vibrations or pressure change and sound Skin and ears
2 Thermoceptors Sensitive to thermal or pressure changes and sound. Skin
3 Chemoreceptors Sensitive to concentrations of chemicals intensity and wave-length of light. Tongue, olfactory chambers
4 Photoreceptors Sensitive to change in in the internal and external environment Eyes

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Figure 23.7 Various receptors

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Table of Contents

23.0 Introduction
23.1 Central nervous system
23.2 The automatic nervous system
23.3 Receptors and effects
23.4 Reflex action - mechanism of nervous action

Chapter 24


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