Sensory Systems

Playtpus

"Bill" has both electroreceptors and mechanoreceptors 100,000 individually innervated receptors! -receptive field are really tiny -reminant of montremes w/ echinda

Fish Neuromasts for Balance!

Hair cells detect body position and movement Neuromast -Hair cells and cupula: Stereocilia embedded in gelatinous cap - Detect movement of water - depenind on position will lean one way or the other to stay upright Neuromasts are found in the skin, either scattered over the body surface or grouped in particular areas (often at the anterior end of the animal). Most fish species (and some aquatic amphibians) have a conspicuous array of neuromasts arranged in a line along both sides of the body. This lateral line system Lateral line system -Array of neuromasts within pits or tubes running along the side of the body -allow them to stay upright in the water -allows fish to detect changes in water pressure, such as those caused by the movements of other fish.

Isomerization of Retinal

In the unactivated state, the chromophore is present in the *cis* conformation. When the chromophore absorbs the energy of incoming light, it undergoes a conformational change, rotating the molecule to an *all-trans* conformation cis: two H, removal of phospate to switch bakc to cis trans: one H detects light once swtich

Taste in Invertebrates: insects

Located on sensilla -Inside and outside the mouth -Along the wing margin -Ends of the legs: on foot to taste -vaginal receptors Gustatory sensilla are found on many parts of the insect body, including the outside of the proboscis or mouth, in the internal mouthparts (pharynx), along the wing margin, at the ends of the legs, and in the female vaginal plates. Receptors -Bipolar sensory neurons -G-protein coupled -Express only a single receptor protein

Cristae Detect Angular Acceleration

capulla nd hair cell flow depending on the head tilt The vestibular sacs play an important role in maintaining the orientation of the body with respect to gravity. If your head and body start to tilt, the vestibular sacs send a signal to the brain, which automatically compensates by altering posture in order to maintain your position.

otter family video

otters chanse fish towards the net, fish in rover is rapidly decreasing due to climate change otters endangers in bangladesh, otter fishing is key to their conservation

know linear vs angular , how work in the fish, how diff parts work

(a) The hair cells of the utricles are overlain with a gelatinous layer topped with bony otoliths. (b) At rest or during constant motion, the hair cells are partially depolarized. (c) During forward acceleration, the hair cells pivot toward the longest stereocilium (recall that mammalian hair cells lack a kinocilium). This bending activates mechanogated channels on the stereocilia, which depolarizes the cell, increasing its release of neurotransmitter and thus increasing the frequency of action potentials in the primary afferent neurons. (d) During backward acceleration (e) forward tilt of the head, the stereocilia pivot away from the longest stereocilium, reducing the frequency of action potentials. Fish: In fish, incoming sound waves cause the otoliths in the vestibular sacs to move, causing the stereocilia of the hair cells to pivot, and stimulating the auditory neurons. Some fish use their swim bladder to help amplify the sounds coming to the inner ear. The clupeids (fish in the herring family) have a gas duct that connects the swim bladder to the hearing system. Sounds cause the swim bladder to vibrate, and this vibration is passed through the gas duct to the ear. Clupeid fish such as shad use their excellent hearing to detect the echolocation sounds produced by whales and dolphins (their main predators). In carp, the swim bladder is connected to the inner ear via a system of bones called the Weberian ossicles.

Convex Eye

(annelids, molluscs, arthropods) -Photoreceptors radiate outward Convex retina. -Forming a convex, rather than a concave, light-gathering surface

Vesicular Eyes

(present in most vertebrates) -Lens in the aperture improves clarity and intensity -Lens refracts light and focuses it onto a single point on the retina -Image formation -Good resolution: photons hit rentina EX: -Found in some mollusks, but only the cephalopod mollusks have the capacity to alter the shape or position of the lens to focus the image.

The Vertebrate Retina

-Arranged into several layers -Rods and cones are are in the retina and their outer segments face backwards -Other cells are in front of rods and cones -Bipolar cells, ganglion cells, horizontal cells, amacrine cells -Axons of ganglion cells join together to form the optic nerve -Optic nerve exits the retina at the optic disk ("blind spot")

Cup-shaped eyes (e.g., Nautilus)

-Retinal sheet is folded to form a narrow aperture -Much better discrimination of light direction and intensity -Improved light-dark contrast -Image formation -Poor resolution, dim image -increase vision EX: Nautilus, a cephalopod -Have extremely small, pinhole-sized openings. The pinhole blocks most of the light from entering the eye so that an incoming point light source illuminates a single point on the retina, forming an image.

Flat sheet eyes (Planaria)

-contain a layer of photoreceptor cells that form a primitive retina lined with a pigmented epithelium. -Some sense of light direction and intensity -Often in larval forms or as accessory eyes in adults pigment layer: rentina: sheet of photoreceptor cells

Mechanoreceptors

-detecting psychial change Transform mechanical stimuli into electrical signals All organisms (and most cells) sense and respond to mechanical stimuli Mechanoreception is important for cell volume control, and the senses of touch, hearing, and balance, and it plays a critical role in regulating blood pressure in vertebrates. Channels are linked to extracellular matrix -Mechanical stimuli alter channel permeability Parts: Anchors get knocked: exoskeleton link These ion channels are unique in that they are mechanically gated - not chemical or voltage. intrcelluar link cytoskeleton:

More on lateral line:

-more than 3 on line -more towards lone = more AP

Detecting Sound Location

Brain uses time lags and differences in sound intensity to detect location of sound Sound in right ear first -Sound located to the right Sound louder in right ear -Sound located to the right Rotation of head helps localize sound ex: foxes locate prey under snow If a sound does not come from the sides, but rather from above, below, or immediately in front of the face, there is no time lag or discrepancy in intensity between the ears, and it is more difficult to determine the location of a sound. In mammals, the outer ears also help in localizing sounds

platypus video

6th sense: ekectroreception: can sense electromagnetic waves: uses ectrolocation

Photoreception

Ability to detect *visible light* -A small proportion of the electromagnetic spectrum from ultraviolet to near infrared -Ability to detect this range of wavelengths supports idea that animals evolved in water -Visible light travels well in water; other wavelengths do not Animals lack the ability to detect other wavelengths of electromagnetic radiation: - ex: radio waves. -supports the idea that animals evolved in water. -The wavelengths that represent visible light travel relatively well through water, whereas water blocks most other wavelengths. tarcer: bottom of primate tree -highly phareniverous: whole animals eaters, hunt at night -huge eye sockets: lost ability to move their eyes, must move their head. detect light in dark envir humans: dinural creatures, can detect colors how bright light is what wavelength how much light there is

Magnetoreception

Ability to detect magnetic fields -For example, migratory birds, homing salmon -magnetic clusters that respond to magnetic field which respond to neurons -Neurons in the olfactory epithelium of rainbow trout contain particles that resemble magnetite -Responds to magnetic field

Accommodation

Accommodation -Light rays must converge on the retina to produce a clear image Focal point -Point at which light waves converge Focal distance -Distance from a lens to its focal point A sharp image can be formed only at the focal point of a lens. Thus, incoming light rays must converge at the retina, not behind it or in front of it, in order to produce a clear image. Distant objects -Light rays are parallel when entering the lens -Ciliary muscles contract -Lens is pulled and becomes thinner >Little refraction of light by lens Close objects -Light rays are not parallel when entering the lens -Ciliary muscles relax -Lens becomes thicker >More refraction of light by lens Because the location and shape of the cornea are fixed, the cornea does not participate in accommodation. Instead, the lens must either change position relative to the retina, or change shape.

The Fovea

Also called the visual streak. The fovea is a circular region in center of retina -Overlying bipolar and ganglion cells are pushed to the side - allowing light to strike the photoreceptors without passing through several layers of neurons -Contains only cones >Color vision -Provides the sharpest images -Image is focused on the fovea

Vertebrate Mammal Photoreceptors

Both cillary photoreceptors Rod: -is there light, what direction is it coming from, how much light is there -more photopigment -slower response time -integrate signals over a longer period -high sensitivity to dim light: can response to one photon > many noctural animals have more rods -saturate at low light levels -proteins, opsiens, retniols Cone: -see color, what types of obsense, what key of color they can recognize - sensitive to brighter light at bottom of both: vesciles that transport Both: -Outer segment composed of a series of membranous disks that contain the photopigments. -A connecting cilium joins the outer segment to the inner segment that contains the nucleus. -The other end of this cell forms synaptic connections with other cells of the vertebrate eye. For example, frogs have several types of rod-shaped photoreceptors in their eyes that they use to see colors. Thus, the shape of the photoreceptor cell is not the important characteristic that determines whether it is involved in color vision or dim-light vision. Instead, the properties of a photoreceptor cell depend on the properties of the photopigment that it contains.

Compound Eyes of Arthropods

Composed of many ommatidia arranged radially to form the convex light-gathering surface. indiv eyes, bunch of tiny eyes together: compound eye ex: fly better at detecting motion that we are Structure of ommatidia: -Consists of a modified region of the cuticle called the cornea overlying a crystalline cone that forms a lens. -Immediately below this lens is a group of photoreceptive cells, called retinular cells, in a tubular arrangement. -The retinular cells are rhabdomeric photoreceptor cells, as is typical for invertebrates. -The microvilli of these photoreceptors project toward a central area called the rhabdom. -Thus, in cross section, the ommatidium resembles a slice through an orange.

Terms to know (general):

Dynamic range: the lowest vs the higher level to be able to sense -reaches highest lvl if all receptors are saturated - Or if the membrane potential reaches the equilibrium potential for the particular ion involved in the receptor or generator potential ex: like taste with sugar in water Threshold of detection: point at bottom of lowest level, The weakest stimulus that produces a response in a receptor 50 percent of the time Receptive field: the area of where you can sense something happening ex: touch finger tips vs back adequate stimulus: a preferred stimulus modality, detects one type of stimulus Stimulus: -modality: what your trying to detect -location: where is it coming from, -intensity: how much the signal is -duration: how long the signal lasts Polymodal receptors: respond to many things. - ex: nociceptors sense pain

Odorant Receptors: g protein receptors signal transduction, deploration happens because of thershold, send AP

Each olfactory neuron expresses only one odorant receptor protein There are 1000s of different receptor proteins Each receptor can recognize more than one odorant Each odorant can stimulate more than one receptor Odorant receptor is linked to G-protein Odorant binding causes formation of cAMP Opening of ion channels Depolarization

The Olfactory System

Evolved independently in vertebrates and insects Vertebrate olfactory system: -Can distinguish thousands of odorants: signals detected by olfactory sys -Located in the roof of the nasal cavity -Mucus layer to moisten olfactory epithelium, odorant molecule comes into contact with and starts process -Odorant binding proteins: Allow lipophilic odorants to dissolve in mucus -Receptor cells are bipolar neurons with cilia: one end in the olfactory epithelium and another end that passes through holes in the bony cribriform plate and forms synapses with neurons in the olfactory bulb of the brain -Odorant receptor proteins are located in the cilia: are the receptor proteins involved in detecting incoming chemical signals.

Eyes

Eyespots -Cells or regions of a cell that contain photosensitive pigment and a shading pigment that helps provide directional information by shading light coming from some directions. -For example, protist Euglena: uses this eyespot to orient itself toward the light. Eyes are complex organs -Detect direction of light -Light-dark contrast -Some can form an image

The Gustatory System

Five classes of tastants: -Salty: find sodium ex: elephants in africa go into caves and find natural salt lick and fall and die -ion (iontropic) -Sweet: find sugar (metabtropic): -Sweet substances such as sugars bind to G protein-coupled receptors at the apical cell surface, and activate the G protein gustducin, which signals through an adenylate cyclase signal transduction pathway. -The receptors for "sweetness" have recently been identified in mice. -Bitter (toxic?): posinous (metbatrpoic) -Humans have at least 25 genes coding for bitter-taste receptors, and each taste cell that is sensitive to "bitterness" expresses many of these genes. -The way in which this complex pattern of expression is translated into the perception of bitterness is still unknown, although the signal transduction mechanisms within the bitter-taste receptor cells have been worked out -Sour (vinegar): something has expired, proton (iontropic) -These taste receptor cells sense sourness via an apically localized K+ channel that is blocked directly by protons. -Blocking these K+ channels leads to depolarization of the taste cells, by decreasing K+ permeability and altering the resting membrane potential, as described by the Goldman equation. -This depolarization ultimately causes neurotransmitter release. -In contrast, in frogs, taste cells contain H+-gated Ca2+ channels and H+ transporters that are believed to be involved in detecting sourness, although the specific proteins involved have not yet been sequenced. -In mammals have suggested that acid-sensing ion channels (ASICs) may be important for detection of sourness. These channels appear to be Na+ channels that open in response to changes in pH. -Umami (savory or meaty): protein -Fat??? Yes, new research suggests we have receptors for it: very important for energy -When glutamate binds to this modified glutamate receptor, the receptor undergoes a conformational change, activating an associated G protein. -The G protein then activates a phosphodiesterase that degrades cAMP into AMP. -The decreases in cAMP are thought to trigger neurotransmitter release, although the precise pathways involved have not yet been identified. Sweet, umami, and salty indicate carbohydrates, proteins, and ions Bitter and sour indicate potentially toxic substances

Types of Eyes

Flat-shape Cup-shape Vesicular Convex

Vertebrate Ears MC

Function in both equilibrium and hearing Aye-Aye: big pina for pinpointing prey, bit through wood and pull out grub with long creepy fingers. Outer ear -Not in all vertebrates -Pinna: means outer ear, forms the distinctive shapes of mammalian ears, and the auditory canal -Auditory canal Middle ear -Not in all vertebrates -Interconnected bones in *air-filled cavity* - transfer sound waves to the inner ear Inner ear -*Present in all vertebrates* -Series of fluid-filled membranous sacs and canals -Contains mechanoreceptors: hair cells: play important part in hearing and equilibrium.

Tapetum lucidum

Iridescent layer found in nocturnal animals for maximizing vision under low intensity light. reflecting light photons

The amazing star nosed mole

Later we will look at the somatosensory map of this creature - most of it is devoted to the star and its front feet! -star nose: for hunts, used to look for prey in the soil -feat: equpiied with mechnosensors

Taste Receptor Transduction Pathways

Ligand activated ion channels. - sodium channel: calcium is the second messanger tell cells to fuse and dump contents - acidic: channel gets block, then message gets sent Bitter: dectect bitter Gprotein guesgotin: sugar: lactose, gluactose G protein

Invertebrate olfactory systems employ sensilla:

Located in many parts of the body Most near the head Primarily on antennae in Arthropods Sensilla -Hair-like projections of cuticle -Sensilla contain odorant receptor neurons -Odorant receptor is linked to G-protein -Odorant binding causes formation of cAMP -Opening of ion channels =Depolarization Some predatory spiders emit a chemical that mimics the pheromones used by specific moth species; the male moths are lured to the spider and trapped in the web. Some species of orchids have evolved to produce chemicals that mimic insect pheromones to attract them as pollinators. Humans also lack an accessory olfactory bulb, the part of the brain responsible for interpreting pheromone signals in other animals. In addition, the majority of the genes encoding vomeronasal receptors contain deletions or other changes that would likely make them nonfunctional, and humans do not have a copy of the TRP2 ion channel. Together, these data suggest that pheromone signaling via the vomeronasal organ is unlikely in humans.

The happy hair cell!

Mechanoreceptor for hearing and balance -Modified epithelial cells (not neurons) -Cilia on apical surface Kinocilium (a true cilium): actin rod - tall/long rod - 9 + 2 arrangement of microtubules Stereocilia (microvilli) -microvilli that contain polymerized actin molecules. -Tips of stereocilia are connected by proteins: tip links Tip Link: -connects the top of each shorter stereocilium to the side of the adjacent taller one. - thought to play a critical role in sound transduction. -The hair cells in the ears of adult mammals lack the kinocilium, suggesting that the kinocilium is not necessary for mechanoreception. Instead, the stereocilia play a critical role in mechanosensory transduction. Mechanosensitive ion channels in stereocilia -Movement of stereocilia change in permeability -near the tips of the stereocilia are involved in sound transduction -Under these conditions, a modest number of voltage-gated Ca2+ channels are open on the hair cell, causing some release of neurotransmitter onto the primary afferent neuron, and a modest frequency of action potentials in the afferent sensory neuron. Change in membrane potential Change in release of neurotransmitter from hair cell

Vestibular Apparatus

Mechanoreceptors of the inner ear -detects movements or changes in body position with respect to gravity and is thus responsible for the sense of equilibrium or balance Macula -Present in utricle and saccule -Mineralized otoliths suspended in a gelatinous matrix -Stereocilia of hair cells embedded in matrix ->100,000 hair cells -*Detect linear acceleration and tilting of head, looking down* -detect when train stop bc of macula -in linear acceeration: otolith crystals move in response to how to tilt your head. Cristae -Present in ampullae of semicircular canals -Gelatinous matrix (cupula) lacks otoliths -Stereocilia of hair cells embedded in matrix -*Detect angular acceleration (turning) of head*' -in the tubes a) The mechanoreceptors of the utricle and saccule are found in structures called maculae. The hair cells of each macula are embedded in a gelatinous matrix that is overlain with a series of otoliths. b) The mechanoreceptors of the semicircular canals are located in the ampullae in structures called cristae. Cristae are similar in structure to the neuromasts shown in Figure 7.21, consisting of hair cells embedded in a cup-shaped gelatinous mass called the cupula.

Vertebrate Proprioceptors

Monitor the position of the body Three major groups: Muscle spindles: how long is the muscle -Located in skeletal muscles -Monitor muscle length - on the surface of skeletal muscles monitor the length of the muscle. -Each muscle spindle consists of modified muscle fibers called intrafusal fibers enclosed in a connective tissue capsule. Golgi tendon organs -Located in tendons -Monitor tendon tension -located at the junction between a skeletal muscle and a tendon. -These receptors are stimulated by changes in the tension in the tendon Joint capsule receptors -Located in capsules that enclose joints -Monitor pressure, tension, and movement in the joint -Several types of receptors are in this category, including receptors similar to free nerve endings, Pacinian corpuscles, and Golgi tendon organs.

Chemoreception

Most cells can sense chemical stimuli Animals have many types of chemoreceptors: Olfaction (smell) -Detection of chemicals in air Gustation (taste) -Detection of chemicals emitted from food In aquatic vertebrates: -Gustation always involves detecting sensations involving food -Olfaction involves detecting a wide variety of environmental chemicals, including those associated with food, predators, potential mates, and particular locations. Olfaction and gustation are distinguished by structural criteria -Performed by different sense organs -Different signal transduction mechanisms -Processed in different integrating centers

Statocysts

Octopus: suspended in water when sleep, more complex because can go in all different directions, structure allows you get a lot more info depending where it is in space. -looks like part of human ears that detect equlibrium. -two one on each sideof head lobster:when on it's back, uses statocyts: hollow balls, with neurons on the ooutside like ball, has cilla lined in it. statoysts balls roll around depending on what position the lobster is in. Organ of equilibrium in invertebrates -Hollow, fluid filled cavities lined with mechanosensory neurons -Statocysts contain statoliths Dense particles of calcium carbonate -Movement of statoliths stimulate mechanoreceptors

Role of graded potentials, distinguish between receptor and generator potentials

Once the message is received, it needs to be converted into a message. Two main ways this happens (and both generate graded potentials): Generator potential: sensory neuron -Sensory receptor is also the primary afferent neuron -Change in membrane potential spreads along membrane -often bi-polar or uni-polar -An incoming stimulus activates a receptor protein in the sensory neuron, causing a depolarization called a generator potential. -The generator potential triggers action potentials in the axon of the neuron. Receptor potential: epthieal sensroy receptor cell -Sensory receptor is separate from the afferent neuron -Change in membrane potential triggers release of neurotransmitter -Important point - the receptor is not a neuron - An incoming stimulus activates a receptor protein on the surface of the receptor cell, causing a receptor potential. -The receptor potential opens voltage-gated Ca2+ channels, causing the release of neurotransmitter onto the primary afferent neuron. -The stimulated afferent neuron generates action potentials that are conducted to integrating centers.

Photopigments: Chromophores Allow Photoreceptors to Absorb Light

Photopigments have two covalently bonded parts: consist of a vitamin A-derived chromophore bound to a G protein in the opsin gene family. Chromophore -Derivative of vitamin A >Ex: retinal -Contains carbon-carbon double bonds -Absorption of light converts bond from cis to trans Opsin -G-protein-coupled receptor protein -covalently linked to chromophore -Opsin structure determines photopigment characteristics >Ex: wavelength of light absorbed Examples: rhodopsin, iodopsin, melanopsin

Cephalopod Eye and Retina

Photoreceptors are on the surface of the retina -Project forward -Supporting cells are located between photoreceptor cells -No other layers of cells associated with photoreceptors -Axons of photoreceptors form optic nerve positions forward photreceptor cells neurons behind them''do it backwards of humans

Mammalian Middle and Inner Ear

Plays the most important role in improving detection of sounds in air. The air-filled middle ear is separated from the outer ear by the tympanic membrane and from the fluid-filled inner ear by the oval window. eardrum: tympanic membrane - has a surface area about 20 times that of the oval window. Thus the energy from the vibration of the tympanic membrane is concentrated into a smaller area in the oval window, amplifying the sound. Bones: (small and delicate) Malleus:hit hammer incus: anvil stapes: stirrup, wacks on oval window How sound gets in our ears: -Sound waves traveling through the auditory canal cause the thin tympanic membrane to vibrate. -Vibration of the tympanic membrane causes the first of the bones (the malleus in mammals) to vibrate. -The vibration is transferred through the bones (from the malleus to the incus to the stapes in mammals) to the oval window. -Vibrations of the oval window transfer the sound stimulus to the fluid-filled inner ear. -The malleus, incus, and stapes of mammals are connected to each other with the biological equivalent of hinges, which allows these bones to act as levers that amplify the vibrations cholea: fluid filled space, - consists of a bent tube leading from the oval window to the round window. -The top portion of the tube is called the vestibular duct and is lined with the vestibular membrane. -The bottom of the tube is called the tympanic duct and is lined with the organ of Corti, which contains hair cells embedded in the basilar membrane. -filled with paralymph outside -endolymph on inside with hair cells -movment of hair cells and fluid waves, dictates whether they are open or closed.

Photoreceptors

Range from single light-sensitive cells to complex, image-forming eyes Two major types of photoreceptor cells: Ciliary photoreceptors: -Have a single, highly folded cilium - forms lamellae or disks that contain photopigments -Folds form disks that contain photopigments: molecules specialized for absorbing the energy coming from incoming photons Rhabdomeric photoreceptors: - microvillus photoreceptors -Apical surface covered with multiple outfoldings called microvillar projections -Microvillar projections contain photopigments - use distinct signal transduction mechanisms for converting the energy carried by incoming photons to a change in the membrane potential of the receptor cell. Both use: Photopigments -Molecules that absorb energy from photons -also in plants in chloraphil The majority of invertebrate groups have rhabdomeric photoreceptors in their eye Some invertebrate groups: mollusks and platyhelminths, also have some ciliary photoreceptors, but these are generally present only as small, isolated photoreceptors, or in very simple photoreceptive organs that are located outside the main eyes A few species of mollusk, such as the bay scallop Pecten irradians and the file clam Lima scabra, in which the adults have eyes that contain both rhabdomeric and ciliary photoreceptors Most deuterostomes: sea urchines, have rhabdomeric eyes, similar to those of the protostome invertebrates vertebrates: have only ciliary photoreceptors in their eyes. The cnidarians: jellyfish, also have only ciliary photoreceptors.

The receptive field and location of stimulus

Receptive field - the region of the sensory surface that causes a response when stimulated Smaller receptive field allows more precise location of the stimulus (i.e., greater acuity) Improved ability to localize stimuli by: -Using more than one sensory receptor cell -Population coding: information about the stimulus is encoded in the pattern of firing of multiple neurons. Lateral inhibition - Signals from neurons at the center of the receptive field and inhibit neurons on the periphery allows for precise localization of input. If a single neuron covers a large receptive field, location information cannot be as precise b/c it can only send a message that the stimulus occurred somewhere, much less precise than multiple neurons with smaller fields.

Image Formation

Refraction - bending of light rays Cornea and lens focus light on the retina bc of convex shape Converging lenses work by bending light rays toward each other, a process called refraction. Light refracts as it passes through objects of differing optical densities. In terrestrial vertebrates, most of the refraction occurs between air and cornea -cornea plays greatest role in focusing the image -Lens does fine focusing Lens changes shape to focus on near or far objects -Accommodation fovea: blind spot

non mammalian ears

Right at tympanic membreane no pinnai owl: ears at different levels so they can get pinpoint of where sound comoing from Bird: uses feather as pianni

Structure of The Vertebrate Eye

Sclera a tough layer of connective tissue that makes up the "white" of the eye Cornea Transparent layer on anterior, allows light to enter the eye Retina Layer of photoreceptor cells -assists in stabilizing the eye and provides support for the retina Retinal pigment epithelium -Contains the cells that regenerate all-trans retinal back into the 11-cis conformation following light absorption Choroid Pigmented layer behind retina -Contains blood vessels, providing nourishment to the eye. -In most diurnal animals, such as humans, the choroid also absorbs light that reaches the back of the eye so that it is not reflected, which might cause distortion of the visual image. Tapetum Layer in the choroid of nocturnal animals that reflects light -Amplifies the light and allows noctural animals to see better than diurnal animals in dim light. -Light reflected off the tapetum can make a cat's eyes appear to glow in the dark. Iris Two layers of pigmented smooth muscle -constrict or dilate, controlling the amount of light that enters the eye -dialte in dim light, constructs in bright light limits amount of light Pupil Opening in iris allows light into eye Lens Focuses image on retina -Held in place behind the pupil by suspensory ligaments that are attached to the ciliary body, which contains the ciliary muscles - suspended in the posterior chamber, which contains a gelatinous mass called the vitreous humor Ciliary body Muscles that change lens shape Aqueous humor Fluid in the anterior chamber -Secreted by the ciliary body and circulates into the anterior chamber via the pupil Vitreous humor Gelatinous mass in the posterior chamber -assists in stabilizing the eye and provides support for the retina

Sensory Receptors

Sensory receptors range from single cells to complex sense organs - we will discuss single neurons to the complex components of the vertebrate eye. Types of receptors: Chemoreceptors,: chemical change, presynaptic to postsynaptic mechanoreceptors,: respond to physical changes, pull channel open, balance, hearing, touch, detect internal body changes: blood pressure photoreceptors,: light stimulus, basis of for the sense of the vision electroreceptors,: electrical changes magnetoreceptors,: magentic changes thermoreceptors: changes in temp All receptors transduce incoming stimuli into changes in membrane potential. -Receptor protein detects stimulus -Opening or closing of ion channel -Change in membrane potential- ma inly depolarizing stimuli -Signal sent to integrating center (central nervous system)

Electroreception

Sharks possess Ampullae of Lorenzini. : detect muscle movements and heart beats of prey -detect electromagnectic field -glycoproetin semi conductor, elec sigs travel through cell, go through jelly to neruon cell -feel their prey: lateral line, pick up cell vibrations and pressure in water

Mammalian Inner Ear

Specialized for sound detection Perilymph Fills vestibular and tympanic ducts Similar to extracellular fluids (high Na+ and low K+) Endolymph -Fills cochlear duct -Different from extracellular fluid -High K+: rush in and low Na+ Organ of Corti -Hair cells on basilar membrane Inner and outer rows of hair cells -Stereocilia embedded in tectorial membrane in cochlear duct (filled with endolymph) -Sound waves vibrate tympanic membrane -Middle ear bones transmit vibration to oval window > Oval window vibrates -Pressure waves in perilymph of vestibular duct -Basilar membrane vibrates -Stereocilia on the inner hair cells bend -Hair cells depolarize: the tip links connecting the stereocilia pull open the mechanosensitive ion channels in the membrane of the inner hair cells -Inner hair cells release neurotransmitter: glutamate -Glutamate excites sensory neuron, causes them to generate AP Round window serves as a pressure valve: In this way, the cochlea transduces the pressure waves in the perilymph into electrical signals. The round window of the cochlea serves as a pressure valve, bulging outward as fluid pressure rises in the inner ear, which prevents the waves from doubling back through the fluid, thus improving sound clarity Frequency Detection -Basilar membrane is stiff and narrow at the proximal end and flexible and wide at distal end >High frequency sound: vibrates stiff end >Low frequency sound: vibrates flexible end Specific regions of brain respond to specific frequencies >Place coding: - Thus, different areas of the basilar membrane vibrate in response to sounds of different frequency, transforming a frequency signal carried by the sound waves into a spatial signal coded by location on the basilar membrane. - Neurons from each part of the basilar membrane form synaptic connections with neurons in particular areas in the auditory cortex of the brain; therefore, specific areas of the auditory cortex respond to particular frequencies.

Specialized Thermoreception

Specialized organs for detecting heat radiating objects at a distance Pit organs -Pit found between the eye and the nostril of pit vipers -Can detect 0.003°C changes (humans can detect only 0.5°C changes) -Detect heat for hunting for prey

Phototransduction

Steps in photoreception -Chromophore absorbs energy from photon -Chromophore changes shape -Double bond isomerizes from cis to trans -Activated chromophore dissociates from opsin >"Bleaching" -Opsin activates G-protein -Formation of second messenger -Ion channels open or close -Change in membrane potential The chromophore is then reconverted to the cis isomer by isomerase enzymes in an ATP-requiring process that takes several minutes.

Insects use sensilla and chordotonal organs to sense sound vibrations MC how often are sensilla are employed by insects

Strong vibrations sensed by trichoid sensilla (what a surprise!) Weak vibrations and sounds are detected by chordotonal organs -Clusters of scolopidia -Located on leg -Mechanosensitive ion channels Tympanal organs -Thin layer of cuticle (tympanum) overlays chordotonal organ -Hollow cavity detect vibrations -A chordotonal organ in this air space detects these vibrations, and sends signals in the form of action potentials to the nervous system. -Tympanal organs are found on many locations on the insect body, including the legs, abdomen, thorax, and wing base. Subgenual organ: -Cockroaches, honeybees, and water striders, use to detect vibrations carried through the ground (or the surface of the water, in the case of a water strider), and in at least some species, these subgenual organs may also be able to detect sound waves. -Subgenual organs are located inside the insect leg. -Vibrations of the leg cause the subgenual organ to vibrate, opening a mechanosensitive ion channel on the sensory neuron within the chordotonal organ, initiating action potentials that send a signal to the integrating centers of the nervous system. Johnston's organ: - Located at the base of the antennae of many insects, including moths, fruit flies, honeybees, and mosquitoes. - Sound waves bend fine hairs on the antennae, stretching the membrane of the cells within the underlying chordotonal organ, opening mechanosensitive ion channels, and initiating action potentials in the mechanosensory neuron. - These insects use Johnston's organ to detect sounds such as mating calls.

Taste Buds in Vertebrates

Taste receptors are epithelial cells that release neurotransmitter -Vertebrate taste receptors are not neurons Each taste receptor expresses more than one kind of taste receptor protein Taste buds are onion-shaped structures that contain multiple taste receptor cells (in humans each bud contains between 50 and 100 taste receptor cells), with a pore that opens out to the surface of the body. Dissolved chemicals from food, termed tastants, enter through this pore and contact the taste receptor cell. Taste receptor cells clustered in groups in terrestrial verts: -On tongue, soft palate, larynx, and esophagus -On external surface of the body in some fish: taste buds on the barbells (whiskerlike projections from the lower jaw).

types of reception

Telereceptor: detect stimuli coming from locations at some distance from the body. ex: hearing, seeing Exoteroceptors: detect stimuli occurring on the outside of the body. ex: temperature, pressure Interoreceptors: detect stimuli occurring inside the body ex: body pressure and oxygen. Magnetoreception: sense magnetic changes electroreception: sense eletric changes thermoreception:sense temperature changes Chemoreception - olfactory, gustation Mechanoreception - balance, sound, touch Photoreception - vision

Sound Detection by Inner Ear

Terrestrial Vertebrates -Hearing involves the inner, middle, and outer ear Sound transfers poorly between air and the fluid-filled inner ear Amplification of sound waves -Pinna acts as a funnel to collect more sound -birds create funnel with their feather to catch sound -Middle ear bones increase the amplitude of vibrations from the tympanic membrane to the oval window Pinna: -Ears with a larger pinna capture more of the sound wave for a given sound intensity and hence receive more sound energy, so animals with large external ears typically have excellent hearing. -While passing the pinna, sound also goes through a filtering process. -For example, in humans sounds are enhanced in the frequency range where human speech is normally found. -The filtering process also adds directional information.

Touch and Pressure

Three classes of receptors Baroreceptors Interoceptors detect pressure changes(inside) -detect pressure changes in the walls of blood vessels, parts of the heart, and in the digestive, reproductive, and urinary tracts of vertebrates. Tactile receptors Exteroceptors detect touch, pressure, and vibration(outisde) -detect touch, pressure, and vibration on the body surface. -Both vertebrates and invertebrates have tactile receptors, although their structure and function vary substantially between these groups. Proprioceptors Monitor the position of the body Pacinian corpuscle! -layers like onion, have to get through layers to activate the nueron, for deep touch

Proprioception is mediated by several mechanisms.

True

Tonic and Phasic Receptors

Two classes of receptors encode stimulus duration: Phasic -information about the stimulus only when it first happens or ends -Produce APs at the beginning or end of the stimulus -Encode change in stimulus, but not stimulus duration Phasic receptors adapt very rapidly, and thus depolarize only at the beginning of a stimulus. Tonic - information about stimulus the entire time it's happening -Produce APs as long as the stimulus continues -Encode duration of stimulus -Receptor adaptation - AP frequency decreases if stimulus intensity is maintained at the same level ex: get used to temps like in hot water Tonic receptors remain depolarized throughout the duration of a stimulus. Many tonic receptors show the phenomenon of adaptation, in which the response declines with time.

Insect Tactile Receptors

Two common types of sensilla Trichoid -Hairlike projection of cuticle -Bipolar sensory neuron -When the hair bends in the socket of a trichoid sensillum (as a result of a touch or vibration), accessory structures transfer the movement to the tip of the bipolar sensory neuron located beneath the hairlike projection. TRP channel -Campaniform -Dome-shaped bulge of cuticle -Bipolar sensory neuron -They are usually found in clusters, particularly on or near the joints of the limbs, and detect the deformation of the cuticle as an insect moves. Thus, campaniform sensilla are critical in allowing an insect to make coordinated movements. -The movement opens stretch-sensitive TRP ion channels in the membrane of the mechanoreceptor neuron, changing the membrane potential, and sending a signal in the form of action potentials to the insect's nervous system. Scolopidia: -proprioceptor that can detect bending of the cuticle. These proprioceptors are organized into functional units -consist of a specialized bipolar sensory neuron and a complex accessory cell (the scolopale) that surrounds the ciliated sensory dendrite at one end. -This structure is attached to the cuticle via a ligament or attachment cell. -These mechanoreceptors can exist as isolated cells or may be grouped to form complex organs called chordotonal organs, which form the basis for the sense of hearing in some insects.

Equilibrium and Hearing

Utilize mechanoreceptors Equilibrium ("balance") -Detect position of the body relative to gravity Hearing -Detect and interpret sound waves Vertebrates -Ear is responsible for *equilibrium and hearing* Invertebrates -Organs for equilibrium are different from organs of hearing -depends on exoskeleton

Mammalian Ear

Vestibular apparatus detects movements -Three semi-circular canals with enlarged region at one end (ampulla) -Two sacklike swellings: (utricle and saccule) inner ear: hearing an balance Lagena -Extension of saccule -Extended in birds and mammals into a cochlear duct or cochlea for hearing -Hair cells present in vestibular apparatus and lagena (cochlea)

Pheromones and the vomeronasal organ horses and mammals

Vomeronasal organ -Detects pheromones, chemical signals between animals -Structurally and molecularly distinct from the olfactory epithelium -Located in base of nasal cavity in mammals and located in palate in reptiles Pheromones play an important role in maintaining social hierarchies and stimulating reproduction in many animals Receptor is linked to G-protein -Activates phospholipase C transduction system -Opening of ion channels, alter membrane potential -Depolarization felming: horses and cats lift lip to sense sex pheromones usually in urine The importance of the TRP2 gene in pheromone reception has been clearly demonstrated using mice in which the TRP2 gene is knocked out. Normal male mice do not attack intruder females, and they ignore castrated males. However, if urine from an intact male mouse is applied to a castrated mouse, the resident male mouse will attack the castrated male intruder, just as it would an intact male. If a TRP2 knockout male establishes a territory, it ignores introduced castrated male mice swabbed with the urine of an intact male. It also mates indiscriminately with both females and males. These data demonstrate that TRP2 signal transduction is an essential part of the communication of sexual signals in mice.

Vertebrate Tactile Receptors

Widely dispersed in skin -haair has muscle around it to sense touch Receptor structure -Free nerves endings -Nerve endings enclosed in accessory structures (e.g., Pacinian corpuscle) ex: Merkel's disks are free nerve endings that are associated with an enlarged epidermal cell called the Merkel cell. These receptors have a very small receptive field, and are used for fine tactile discrimination.

Vertebrate Inner Ears

cohcela for hearing better, more advanced: mammal balance structures are similar for ivert and mammal -Consists of three semicircular canals with an enlarged region at one end (called the ampulla), and two saclike swellings called the utricle and the saccule (Figure 7.23). In most vertebrate the saccule contains the legena: -In birds and mammals, the lagena is greatly extended and is called the cochlear duct (in birds), or the cochlea(mammals) The utricle, saccule, and the ampullae of the semicircular canals contain mechanoreceptive hair cells that are involved in the sense of equilibrium The cochlea also contains hair cells, but it is involved in hearing and is not a part of the vestibular apparatus. The inner ear in most vertebrates consists of three semicircular canals arranged in planes at right angles joined at their base by a swelling called the ampulla, and a series of sacs including the utricle and the saccule. In many vertebrates, the floor of the saccule contains a small pocket called the lagena. In birds and mammals, the lagena is greatly extended to form the cochlear duct or cochlea.

octopus

coloration change: on mantle, change when they sleep change their physical shape: typohgraphy

The Olfactory System in Mammals

dogs have more sensory devoted to smell cribfriform plate has holes so neurons can go through the bone to the sinuses associate particular chemical associated with food has reaction Mammals: The olfactory epithelium of mammals, located in the nasal cavity, contains supporting cells and olfactory receptor neurons. These bipolar sensory neurons have one end that forms synapses within the olfactory bulb of the brain. These neurons then pass through holes in the bony cribriform plate so that the ciliated end of the neuron is located in the olfactory epithelium. The cilia of the bipolar neurons contain the odorant receptor proteins that detect incoming chemical stimuli. These cilia project into a mucus layer containing odorant-binding proteins that coats the olfactory epithelium.

inner ear better at detecting

faint sounds

Tongues!

fish: louse eats the fishes real tounge and the nebcomes the tounge cats: hydrogen bonds with water moleculers chamelon: stick for prey griaffe: prehesal get around thorns.

Maculae: Utricle Detect Linear Acceleration and Tilting

go backward, otoliths cyrtals move away from the tall one, get fewer AP When you tilt your head, gravity pulls on the gelatinous mass of the sacs, which stimulates particular subsets of the hair cells, depending on the direction of the tilt. Because different hair cells are stimulated by a forward and a backward tilt, the brain can determine the direction of the tilt. The intensity of the hair cell response is related to the angle of tilt, so the brain can also determine the degree of tilt.

cell that allows you to know your position in space and help with balance

hair cell

Signal Transduction in Hair Cells

high extrenal postassium extermal concentraction, *will come in* towards the long rod: channel open: calcium comes in: go to nuero transmitter: relase calium across synapse more gates open no gates open when other rods are away from the tall rod (a) At rest the hair cell is slightly depolarized and releases moderate amounts of neurotransmitter onto the primary afferent neuron, causing an intermediate frequency of action potentials. (b) When a pressure signal causes the stereocilia to pivot toward the kinocilium, mechanically gated channels on the stereocilia open, allowing additional K+ to enter the cell from the extracellular fluid, which has a high concentration of K+. The resulting depolarization opens voltage-gated Ca2+ channels, allowing Ca2+ to enter the cell. The influx of Ca2+ causes increased release of neurotransmitter onto the primary afferent neuron, increasing the frequency of action potentials. (c) When a pressure signal causes the stereocilia to pivot away from the kinocilium, the mechanically gated channels on the stereocilia close, hyperpolarizing the cell and closing voltage-gated Ca2+ channels. The resulting reduction in intracellular Ca2+ decreases the release of neurotransmitter onto the primary afferent neuron, reducing the frequency of action potentials.

how many hair cells in a region open, and how much potassium rushes in dictates how ___ a sounds is The protein responsible for this change in shape of the outer hair cells has been identified, and if the gene that codes for this protein called _____

how loud Inner hair cells code for sound loudness. Loud noises cause greater movement of the basilar membrane, and greater depolarization of the hair cell, which in turn generates a higher frequency of action potentials in the afferent sensory neurons. The outer hair cells also play an important role in the loudness of sounds. Outer hair cells amplify sounds by increasing the movement of the basilar membrane for a sound of a given loudness, thus causing a larger stimulus to the inner hair cells. Outer hair cells change shape in response to sound waves, rather than releasing neurotransmitter. When the stereocilia of an outer hair cell pivot in response to a sound wave, the mechanosensory channels on the stereocilia open, allowing K+ to enter the cell. The resulting depolarization acts as a signal to a voltage-sensitive motor protein, which causes the cell to change shape and pull on the basilar membrane, increasing the amount the basilar membrane moves in response to a particular sound. -------------------- Prestin, If knocked out in mice, the animals are born profoundly deaf. Certain types of deafness in humans are also caused by mutations in the prestin gene.

fig 7.37

light comes in through len, vitrus gou, hit the retina inagration for retina, set up backwards pigmental epithelium involved in recycling rentol

Sensilla (silkmoth) detect the hormone bombykol

live about a week, pick up pheromones from two miles away

Whales and echolocation:

melon struct: minulate sounds that send out, direct where the sounds go phonic lips: emits sounds control the intensitity of the sound lower jaw bone: recieve sound wave and ampulify sound, to auditory bullea

Vertebrate Taste Bud

microvilli: actin and taste receptor embedded in tounge afferent neurons that send info to brain The apical surface of the taste cell is folded into numerous microvilli, which contain the receptors and ion channels that mediate the transduction of the taste signal.

banana is going extinct

no replacement for dying out crop -rust fungus killing them

nearsight farsight

photons fall short of retina: nearby obj clear photons over shot the retina: far away things are clear

mantis shrimp eyes

radio lab ep

Minke Whale skull

smallest of balene whale

The Brain Processes the Visual Signal

visual field, which consists of the entire area that can be seen without moving the eyes. Action potentials from retina travel to brain -Optic nerves optic chiasm optic tract lateral geniculate nucleus visual cortex Binocular vision -Eyes have overlapping visual fields -Binocular zone -Removes the "blind spot" -Combine and compare information from each eye to form a three-dimensional image -Depth perception granuk: prey eyes on side monocular vision barn owl: forward facing eye

pitch varies on

wave big slow wave: low -membrane that responds to the sounds wave with hair cells -changes pyshically in section - one section: high sounds at beginning of cochlea, another for low sounds at end

effecting whales

whales are trying to make sounds that go over the sounds that human make in effort to be hear by their families

how well can hear relates to

what the org needs to hear in order to survive