Sensory Receptors
Sensory Receptors and their Stimuli
Sensory receptors are specialised cells that detect specific stimuli from the environment and convert them into electrical signals, which are then transmitted to the brain for interpretation. These receptors allow the body to respond appropriately to changes in its internal and external environment, playing a role in maintaining homeostasis.
There are several types of sensory receptors, each tuned to a specific type of stimulus:
Chemoreceptors: Chemoreceptors detect chemical stimuli, such as changes in the composition of body fluids or the presence of specific molecules in the air. They are found in structures like the taste buds on the tongue and the olfactory receptors in the nasal cavity, where they respond to chemicals in food and odours. Chemoreceptors also play a vital role in monitoring the levels of carbon dioxide, oxygen and pH in the blood, helping to regulate breathing rates.
Thermoreceptors: Thermoreceptors are sensitive to changes in temperature. These receptors are located in the skin, where they detect external temperature variations, and in the hypothalamus, which monitors the body’s core temperature. Thermoreceptors help maintain thermal homeostasis by triggering responses such as sweating, shivering or adjusting blood flow to the skin.
Mechanoreceptors: Mechanoreceptors respond to mechanical stimuli, such as pressure, touch, vibration and stretch. They are found in various locations, including the skin, where they detect touch and pressure and in the inner ear, where they play a role in hearing and balance. Mechanoreceptors also include baroreceptors, which monitor blood pressure within the cardiovascular system.
Photoreceptors: Photoreceptors are specialised receptors located in the retina of the eye, sensitive to light. There are two main types: rods, which detect light intensity and are essential for vision in low-light conditions, and cones, which detect colour and are responsible for sharp, detailed vision in bright light. Photoreceptors enable the brain to process visual information, allowing us to perceive the world around us.
Nociceptors: Nociceptors are pain receptors that detect potentially harmful stimuli, such as extreme temperatures, mechanical damage or chemical irritants. They are widely distributed throughout the body, including the skin, joints and internal organs. Activation of nociceptors triggers pain responses, serving as a protective mechanism by alerting the body to potential injury.