In humans the three different types of cones correspond with a primary response to short wavelength (blue), medium wavelength (green), and long wavelength (yellow/red). There are three primary types of photoreceptors: Cones are photoreceptors that respond significantly to color. This pathway is the most direct way for transmitting visual information to the brain. The first action potential occurs in the retinal ganglion cell. The basic circuitry of the retina incorporates a three-neuron chain consisting of the photoreceptor (either a rod or cone), bipolar cell, and the ganglion cell. The five basic classes of neurons within the retina are photoreceptor cells, bipolar cells, ganglion cells, horizontal cells, and amacrine cells. These signals are refined and controlled by the interactions with other types of neurons in the retina. Photoreceptor cells are capable of phototransduction, a process which converts light ( electromagnetic radiation) into electrical signals. Similar to olfactory receptors, taste receptors (gustatory receptors) in taste buds interact with chemicals in food to produce an action potential. This can lead to depolarization of the cell membrane, creating an electrical signal. In response to tastant binding, ion channels on the taste receptor cell membrane can open or close. When taste receptor cells are stimulated by the binding of these chemical compounds (tastants), it can lead to changes in the flow of ions, such as sodium (Na+), calcium (Ca2+), and potassium (K+), across the cell membrane. The brain then processes these signals and interprets them as specific taste sensations, allowing you to perceive and enjoy the flavors of the foods you consume. When you eat or drink something, chemicals in the food or liquid interact with receptors on these sensory neurons, triggering signals that are sent to the brain. These sensory neurons are responsible for detecting different taste qualities, such as sweet, sour, salty, bitter, and savory. Taste sensation is facilitated by specialized sensory neurons located in the taste buds of the tongue and other parts of the mouth and throat. The neurons in the olfactory bulb that receive direct sensory nerve input, have connections to other parts of the olfactory system and many parts of the limbic system. They do not use the same route as other sensory systems, bypassing the brain stem and the thalamus. Their axons form the olfactory nerve, and they synapse directly onto neurons in the cerebral cortex ( olfactory bulb). These sensory neurons produce action potentials. The molecules in the air are detected by enlarged cilia and microvilli. These neurons contain receptors, called olfactory receptors, that are activated by odor molecules in the air. The sensory neurons involved in smell are called olfactory sensory neurons. Exteroreceptors include olfactory receptors (smell), taste receptors, photoreceptors (vision), hair cells (hearing), thermoreceptors (temperature), and a number of different mechanoreceptors (stretch, distortion). See also: Perception § Types of perceptionĮxternal receptors that respond to stimuli from outside the body are called exteroreceptors. There are at least six external and two internal sensory receptors: The stimulus can come from exteroreceptors outside the body, for example those that detect light and sound, or from interoreceptors inside the body, for example those that are responsive to blood pressure or the sense of body position.ĭifferent types of sensory neurons have different sensory receptors that respond to different kinds of stimuli. Spinal nerves transmit external sensations via sensory nerves to the brain through the spinal cord. The sensory information travels on the afferent nerve fibers in a sensory nerve, to the brain via the spinal cord. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord. This process is called sensory transduction. Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. JSTOR ( September 2017) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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