Sensory Systems BIOL 172 31 2024 PDF

Sensory Systems https://birdfact.com/articles/owl-legs  Nerve Pain endings Epidermis Dermis Free nerve endings transmit pain signals in response to thermal and mechanical stimuli or molecules r...

Sensory Systems https://birdfact.com/articles/owl-legs  Nerve Pain endings Epidermis Dermis Free nerve endings transmit pain signals in response to thermal and mechanical stimuli or molecules released by injured cells. Nerve  Hearing and Equilibrium Hearing and perception of body equilibrium are related in most animals. For both senses, settling particles or moving fluid is detected by mechanoreceptors.  Hearing and Equilibrium The receptors of equilibrium hearing, and electroreceptive organs are all of a similar structure called hair cells.  Hearing and Equilibrium Hair cells are receptors with mechanically-gated ion channels that open in response to displacement. Channels are actually pulled open by movement of the hair-like projections from the cell.  Middle Outer ear ear Inner ear Skull Stapes Semicircular bone Incus canals Malleus Auditory nerve to brain Cochlea Eustachian Pinna Auditory tube canal Tympanic membrane The vertebrate ear functions in sound reception and in balance. Vibrations from sound are transmitted from the tympanic membrane through the three middle ear bones to the cochlea.  Hair cells Tectorial membrane 500 Hz (low pitch) 1 kHz auditory nerve Basilar Volume is membrane detected by the number of hair cells stimulated, pitch by the 4 kHz position of the stimulated cells 8 kHz 16 kHz along the (high pitch) cochlea.  Movement and position relative to Cilated gravity is detected with statolith- receptor containing organs in invertebrates and by the inner ear of vertebrates Statolith Semicircular canals Flow of fluid Vestibular nerve Cupula Hairs Hair cells Vestibule Axons Vertebrate Body movement inner ear  Lateral Line Lateral line The lateral line system of aquatic vertebrates is used to detect vibrations and currents in water. Cross section SURROUNDING WATER Opening of Scale Lateral line canal lateral line Epidermis canal Cupula Sensory hairs Hair cell Supporting Segmental muscle cell Lateral nerve FISH BODY WALL Nerve fiber  Chemoreceptors Chemoreception, detection of specific molecules, is the oldest and most universal sense. Chemoreception is important in identifying: Food Mates, predators Noxious chemicals CO2 H2O  Olfaction Olfactory cells are chemoreceptors providing a sense of smell. These receptors detect signals that: are distant from their source are at low threshold originate from volatile/soluble substances  Bombyx – silk moth Pheromones are Some insect chemicals used for antennae function communication as nets to collect among members of chemical signals the same species. from the air.  Mammals have the most well-developed olfactory sense with over 1000 different molecule receptors. Brain Action potentials Olfactory bulb Odorants Nasal cavity Bone Epithelial cell Odorant receptors Chemo- receptor Plasma Cilia membrane Odorants Mucus Some vertebrates have a vomeronasal organ in the roof of the mouth for chemoreception, primarily in response to pheromones. The flehmen response increases its effectiveness. This pulling back of the lips draws molecules towards the organ.  Gustation Gustatory cells are the receptors of taste. These receptors detect signals that: come from contact with the chemical, especially contact with mouth parts are food-related are water-soluble are high concentration  Tongue Papilla In humans, receptor cells for taste are organized as Papillae taste buds. Taste buds Key Taste bud An individual taste cell Sweet Salty expresses one receptor Taste Sour pore type and detects one of Bitter the five tastes. Umami Sensory neuron Sensory Food receptor cells molecules  Taste receptors are not always only in the mouth. Catfish, for example, have concentrations of taste receptors on barbels around the mouth and scattered across the body. Electroreception Electroreceptors detect the electric field produced by the muscle activity of living organisms. These are well- developed in sharks and important in prey detection. Electroreception is widely distributed among aquatic chordates. It is an ancestral trait that has been lost in terrestrial species. Platypuses have electroreceptors in their bills.  Photoreception Receptors that respond to light are called photoreceptors. Electromagnetic radiation All electromagnetic radiation is energy-carrying waves. Photoreceptors contain molecules whose form is altered by electromagnetic radiation within a specific range of wavelengths.  Cornea Crystalline Lens cone Photoreceptor Axons The compound eyes of arthropods are comprised of many adjacent photoreceptors each with their own protective cornea and focusing lens. Each contributes a “pixel” to the image perceived by the animal across its field of view.  ocellus compound eye Individual arthropods can have diverse sets of visual sensors. Compound eyes convey images, singe-lens ocelli give single light readings and are useful in orientation and detection of movement.  Compound eyes are good for motion tracking, but are not well-adapted to conveying high resolution images. For a compound eye to have the visual performance of a human eye it would have to be a meter across. Kirschfeld 1976 https://www.ted.com/talks/diy_neuroscience_the_terrifying_accuracy_of_dragonfly_strikes  Retina Cornea Optic nerve Lens The single-lens eye of vertebrates focuses light on photoreceptors in the retina lining the interior rear surface.  Dark Responses Light Responses Pigments called rhodopsins change Rhodopsin inactive Rhodopsin active configuration in response to light and Na+ channels open Na+ channels closed trigger a reaction that stimulates nerves. Rod photoreceptors are sensitive to low Rod depolarized Rod hyperpolarized light and cone photoreceptors, Glutamate No glutamate sensitive to specific released released frequencies of light, Bipolar cell either are used in color Bipolar cell either depolarized or hyperpolarized or vision. hyperpolarized depolarized  Retina Choroid Photoreceptors Neurons Retina Cone Rod Light To brain Optic nerve Light Optic nerve axons Bipolar cell Amacrine cell Horizontal cell Interaction among neurons of the retina results in lateral inhibition that increases contrast in the image. Some vipers have pit organs that detect infrared radiation and function in thermal imaging, the detection of fine-scaled temperature differences in the habitat. Free nerve endings in membrane https://commons.wikimedia.org/wiki/File:Emerald_Tree_Boa_Facing_Forward_2646px.jpg