Receptors: Function and Types (Internal and Cell Surface)

Ans. A receptor is a type of organ or cell that responds to heat, light, or other environmental stimuli by sending a signal to the sensory nerve. They gather data from both the external and interior worlds. They can form a sense organ when gathered, or they can be dispersed throughout the body to fulfil diverse roles. For various goals, several types of signalling are utilized. As a result, different types of receptors serve distinct purposes. Receptors are biological transducers that turn energy into electrical impulses that are then transmitted to the brain. Changes in the environment can also be detected by receptors. Our skin, for example, can react to pain, touch, and temperature. When we are exposed to too much light, our eyes become irritated.

Ans. In a feedback loop, positive feedback is a way in which the end products of action cause more of the same action to occur. The one-of-a-kind activity gets amplified as a result. Negative feedback, on the other hand, occurs when the outcomes of action prevent that action from continuing. In many biological systems, these mechanisms are activated. The process of labour and delivery is an excellent example of positive feedback.

Ans. The extracellular fluid outside the plasma membrane of a nerve fibre is positively charged in comparison to the cell contents inside the plasma membrane. A potential difference between the interior and outside of this plasma membrane can be seen in a resting nerve fibre. The ‘resting potential' is the differential in electrical charges across the plasma membrane. Electrically polarized membranes have a resting potential across them.

Ans. Nociceptors aid in the detection of pain caused by changes in temperature, pressure, or chemicals. To communicate all experiences to the brain, most sense receptors have low sensitivity. Nociceptors, on the other hand, only signal pain when the body has reached a point of tissue damage. During tissue damage, inflammatory markers proliferate, bind to receptors, and initiate pain signals either outwardly or in the viscera. TRP (transient receptor potential) ion channels are one of the ion channel families found on nociceptive neurons. Extreme temperatures, high pressures, and chemicals that cause tissue damage are all examples of signals that activate nociceptive receptors.

Ans. The smell is produced when odorant molecules attach to receptors on the cilia's membrane, resulting in an action potential that delivers the information to the brain. G-protein receptors and adenylate cyclase are used in these systems. When a drug binds to its receptor, the substrate permits electrons to travel along their gradient, causing a flow of chemical changes and subsequent signalling to the brain through their distinct vibrational energies.

Ans. In the retina, the retinal is the most important molecule for vision. It can absorb a variety of light frequencies. Its isomer (Cis-retinal) is found in rhodopsin, a photosensitive transmembrane G-protein found in rods and cones that includes both cis-retinal and opsin. The stimulus is light, and the receptor is the retina. The conversion of cis-retinal to trans-retinal occurs when energy is absorbed. Rhodopsin turns into an active version known as meta-rhodopsin because of this conformational shift.

Ans. Sensory systems are found all over the body, including those that detect the outside world (exteroceptors), those that detect information from internal organs and processes (interoceptors), and those that detect the sensation of position and load (proprioception). Sensory receptors can be found in both external and internal organs, including the eyes, ears, nose, and mouth. Each receptor type transmits a separate sensory modality that eventually combines into a single perceptual frame. Specialized mechanisms convert energy into an electrical signal to obtain this information.

Ans. Balance is sensed by the inner ear. The endolymph vibrates in response to head motion or sound pressure impulses, providing stimulation for the vestibular system's utricle and saccule receptors. Maculae have hair cells with a membranous coating of microscopic otoconia that sense endolymph movements inside the utricle and saccule. Vertical accelerations are sensed by those in the saccule, while horizontal accelerations are sensed by those in the utricle. The shifting of these hair cells induces the opening of receptor channels, which leads to action potentials propagating from the hair cells to the auditory nerve, because of changes in location and hence changes in fluid motion. The pace of fluid motion, together with the fluid's quality, provides additional information about the motion.

Ans. The placement of a sense neuron among its surrounding neuronal population is critical in determining where its neural communication, whether tactile, visual, auditory, or other, will be delivered. The receptive field is the area of the body where a stimulus can activate a sensory receptor. This feature, which takes the shape of a physical dimension, is essential for encoding the precise position of a stimulus. The fovea of the retina, as well as regions of the skin such as fingertips and lips, can attain improved spatial resolution by having a higher number of tiny receptor fields.

Ans. Sensory systems work by responding exclusively to specific stimuli and then transducing that information into a neuronal message that travels along a predetermined path to the brain. This is the labelled line principle, which restricts a receptor class's specificity in encoding a sensory modality to a certain brain location. This holds for somatosensory systems as well as other specialized systems like vision and hearing.