Unit 3 Part 2

Equilibrium: Vestibular Apparatus What is the vestibular system?

- balance and spatial orientation otolith organs in vestibular apparatus detect changes in linear acceleration and head movement - Semicircular canals are sensitive to rotational acceleration/movement of the head

What is taste transduction?

-each taste cell senses only one type of ligand - receptor cells with GPCR bind either bitter or sweet or umami ligands and release ATP as a signal molecule (green) -presynaptic cells sense sour taste (H+) but it is not clear whether H+ acts on a receptor or enters the cell ATP doesnt need to be put in a channel here, has calcium influx with signal at end

What is the cellular organization of the Retina?

-light comes through pupil or lens, "inverted retina" backwards retina Are there animals with inverted retinas? Some have "verted" retinas Light has to find its way to the back , the black lines are the axons, so we have to relay it back out Level of ganglion cell is most useful is receiving from 4 photoreceptors working to put signal together, ganglion cells decide action potential or no action potentials

What is the structure and distribution of taste buds

-pores in tongue -ends have increased SA, where protein is expressed -100 taste receptor cells are there -pap need to be stimulated to threshold thalamic relay fungiform at front of tongue foliate at side of tongue circumvallate at back of tongue - number of taste buds per papillae depends on type (1-2 to thousands) - each taste bud contains 50-150 taste receptor cells - supporting epithelial cells secrete fluid into lumen of taste pore

What are the 3 main steps of the vision process?

1) light enters eye, lens focuses light on retina 2) photoreceptors of the retina transduce light energy into an electrical signal 3) neural pathways from the retina to the brain process electrical signals into visual images

What are the 3 fluid filled channels of the cochlea?

1) vestibular duct 2) central cochlear duct 3) tympanic duct (drum) vestibular and tympanic are continous and connect at tip of cochlea through small opening called helicotrema

What are the steps/pathway for the pupillary light reflex

1)detector: photoreceptors in retina 2)afferent: afferent neurons travelling in optic nerve (II) 3) integrating centre: thalamus / brainstem (midbrain) 4) efferent: motor neurons travelling in oculomotor nerve (III) 5) effectors: smooth muscles regulating pupil diameter i) circular (sphincter) - constriction (parasympathetic) ii) radial - dilation (sympathetic) my explaination Response of pupils to light - non vision response Autonomic pathways - Open pupils - sympathic efferent pathways Constricting - parasympathetic - zoned out after a dinner for example Say you wanted max constriction - tighten circular sphicntor parasympthatic and inhibit dialotor Sensors - photoreceptor in retina (not rod or cone) integreating centre is NOT the visual cortex NOT NOT NOT (star) Cool reflex - info coming into the efferent back to eye

Review of steps for sound transmission of ear

1. Vibrating tympanic membrane (ear drum) middle ear fluid amplifies it and vibrates cochlea is fluid filled not compressible so it moves, push on fluid in closed chamber - sensory hair cells along bottom of blue zone pressure wave is caused hits blue of cochlear duct and then there's bending of hair cells in particular regions

what range is visible light?

400 - 700 nm

What are the neural pathways for equilibrium?

Bundle of axons, primary afferent neurons, bundled info from cochlea going to brain project primarily to the cerebellum -Vestibular hair cells = tonically active (like cochlea) -release neurotransmitter onto primary sensory neurons of the vestibular nerve -They synapse in the vestibular nuclei of the medulla or run without synapsing to the cerebellum

Anatomy of ear

Compressed air - vibration to ear drum - this is all outer ear Ear drum vibrates and attached to 3 tiny bones maleus incus stapes - boney osicles (these are middle ears between tempanic membrane and cochlea are) these transmit vibration to oval window to cochlea

Explain the retina in detail

Fine vision - aiming at particular spot in retina (macula) - refer to stain or heavily pigmented area on retina Fig 10.25 - pale spot where optic nerve fibres are exiting - they are ends of those cells, each sends an axon out, that's a blind spot bc no photoreceptors, least useful for vision The macula in fig 10.25 - high intensity vision spot called the fovea -neural retina all those layers with supportive epithelium, and cell types are retina neurons, exit out optic nerve, goes to optic disk (no photoreceptors, all axons exiting)

What is the cellular organization at the fovea?

Fixed at fovea - spot in macula say for reading The dent in the retina - forest of photoreceptor cells allow for better access to those cells at fovea Purple are cones Yellow for rod Fovea is rich in cones Good spot for high res vision - fovea: Push aside layers, high density of cones Previous slide: notice convergence from layers of cell - ganglion cells whose axons make the optic nerves Lots of convergance This pic: Each ganglion cell are connected to very few photoreceoptor cells - so we cant detect low intensity signal here, minimal convergence, it can mostly see black and white cant see in dark and use rods of non-colour vision

Explain the process of signal transduction in photoreceptor cells (rods)

Rods contain rhodopsin, the visual pigment. When activated by light, rhodopsin separates into opsin and retinal Signal transduction is backwards here CNG channels are held open Psoitive ions are flowing in at rest when theres no light, whenvur sleeping etc, When positives are coming in youre depolarized, -40,mV it is receving neurotransmitter In light (2) : Lght comes, retinal changes, falls so far out, epithelial cells Dissociation off opsin GPCR changes shape, signal transduction happens, and the enzyme turns on phosphodiesterase - off swtich - bringd down cyclic gmp, neurotransmitter shit goes down so its kinda backwards "dark current"

Photoreceptor cells: Rods and Cones

Take chunk out - have disk - take one slice of membrane - magic molecules called opsin - g protein coupled receptors Rhodopsin - first GPCR, opsin = general family Subfamily - slight sequence differences that change wavelength of light Retinal - light coming in that changes shape of retinal that is basis of photo/light construction in all species The dark pigment epithelium absorbs extra light and prevents that light from reflecting back and distortig vision

Convergence of the Retina:: Rods and Visual Fields - Where does the AP take place?

The circle is where AP occurs, at ganglion cell

Response to chromophore to light: Absorption of a photon by 11-cis Retinal How do these bonds relate to signal transduction?

Top: shape of retinal with no light - bent bc - arrangement of the one double bond Light comes in - double bond shifts from cis to trans, no longer fits on GPCR, GPCR changes shape and signal transduction happens, This tiny molecule is the basis, first domino

Describe the steps for sound transmission through the ear

Tympanic membrane is hit and vibrate - boney osicles - they amplify vibrationg Vibrates In oval window Cochlea - pink and blue - theyre diff department Blue - liquid - endolymph Hair cells are housed in cochlea duct surrounded by blue fluid Pink - vestibular duct top Tympanic lymph - pink bottom Perilymph in pink Vibrate #3 air in external air in middle and internal then goes into fluid If you feel window you push on fluid and indicate and press on cochloear duct - bends the hair cells!!! Closed fluid filled system

What is the vestibular apparatus connected to?

Vestibular apparatus connected to cochlea (picture) blue is endolymph filled chambers When youre spinning theres stimulation of all 3 semi circular canal Bulge - ampulla (bulge in tube) Housed in ampulla - what is?

Picture example of Pupillary Light Reflex? Why do both pupils constrict when light is flashed in only one eye?

You could follow fibres that cross or don't cross Midbrain - another opportunity to cross - no info needs to go back to visual cortex Cover one eye and shine bright light some will cross at chiasm some wont (because of crossing points, both pupils will constrict So they'll shine a light and look at other eye for consensual response of both eyes constricting Why is it useful? - low tech indicator of brain stem activity

What are sound waves and what do amplitude and fequencies have represent about sound waves

amplitude - volume intensity frequency - pitch the shorter the wavelength the higher the ptich

What is the effect of fluid waves travelling through the cochlea?

as waves travel through cochlea, displace basilar and tectorial membranes, creating up-and down oscillations that bend hair cells

What are the zonules?

attach lens to ciliary muscle

What type of reflex is the puillary light reflex?

autonomic reflex

How does central hearing loss happen?

central damage to neural pathway between ear and cerebral cortex or damage to cortex itself (e.g. stroke) uncommon cant fix much

where does most integration for equlibrium occur?

cerebellum

what is the scelera?

connective tissue

What is the ciliary muscle?

contraction alters curvature of the lens

What is the pupillary light reflex?

control of pupil diameter according to intensity of light

What is phototransduction?

conversion of light into changes in membrane potential by photoreceptor cells in retina

How does sensorineural hearing loss occur?

damage to structures of inner ear e.g. death of hair cells due to loud noises common in both young and elderly hair cells can be replaced in other vertebrate groups but not mammals (yet?) sensory hair cells are delicate and break at stereocilia base through loud sounds -other vertebrate groups can replace sensory hair cells but mammals cant

What expresses odorant receptor proteins?

dendrites ending in non-motile cilia

Where are taste buds located?

dorsal surface of the tongue

What is the canal of Schlemm?

drains aqueous humor collects fluid produced in front chamber of aqueous humor which is produced frequently so it drains into that, its like a endothelial lined sinus. Dumped into venus drainage

What are the two components of the vestibular apparatus?

dynamic component movement of body through space somersaulting, spinning on skates static component position of head

How does the Coding of Olfactory 'Quality' happen?

each ORN expresses only 1 type of odorant receptor protein BUT -each receptor can recognize more than one odorant -each odorant can stimulate more than one receptor -subsequent processing en route to olfactory cortex input from 100s of olfactory neurons in combination is then interpreted as a particular odour animation: http://www.leffingwell.com/combi.htm -need lots of mixed population of these things -super specificity and neuron expresses one but receptors detect multiple processing on way to olfactory cortex

What is the olfactory bulb?

extension of the forebrain that recieves input from primary olfactory neurons

What is the cochlea filled with?

fluid

Neural code for pitching: What is the temporal code hypothesis?

frequency of sound wave determines frequency of action potentials travelling along auditory nerve, perceived as pitch e.g. low freq slow waves along basilar membrane low firing rate of primary afferent neurons perceived as low pitch sound problem: we can hear sounds up to 20,000Hz but no neuron can transmit at that rate High freq sound wave - high action potentials also a hypothesis Cant account for high pitches at all, we cannot hear it, so we cant use action potential freq to be covered with sound freq

What is the marge simpson runnig reference?

hair bends when she runs and then bends back when she slows down, theres change in velocity that makes movement that you feel (like moving elevator, only notice the beginning)

What is the organ of corti?

in cochlear duct composed of hair cell receptors and support cells sits on basilar membrane and is partially covered by tectorial membrane Organ of corti refers to bottom Fluid wave has shear in the that depicts hair cells Bend is ensured by tectorial membrane Tips of hair cells are embedded in tectorial membrane Hair cells synapse with primary afferent neuron which carries information to cns

Whst type of info is the vestibular apparatus integrated with?

info from other sensory systems muscle and joint proprioceptors visual information

what is the retina?

layer that contains photoreceptors

Photoreceptor cells: Rods and Cones- What does the outer segment do?

light transduction takes place using visual pigments and membrane disks

What is the detection in the vestibular apparatus similar to?

like hearing, detected by hair cells lining fluid-filled chambers otolith organs - utricle, saccule linear acceleration and head position semicircular canals rotational acceleration sends info to cerebellum ex motion sickness disconnect of what youre seeing and what youre feeling

Photoreceptor cells: Rods and Cones - What inner segment?

location of major organelles and metabolic operations such as ATP stuff synaptic terminal -synapses with bipolar cells

What are sterocilia of hair cells?

mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance actin in microvilli non-neural receptors apical surface modified into 50-100 stiffened cilia embedded in overlying tectoial membrane

What is the current hypothesis of coding for pitch

multiple neurons with staggered firing rates carry the temporal code pooled neural response interpreted as pitch place coding (which region / hair cells along basilar membrane are stimulated) also plays a role relative important of place and temporal coding depends on pitch (low pitches temporal coding, high pitches place coding) Team of neurons out of sync so its integrated further away from the hair cells Both things play a role, place coding (where hair cells are) and temporal coding - low frequency) and high pitches would be where along the membrane http://www.cns.nyu.edu/~david/courses/perception/lecturenotes/pitch/pitch.html

How does conductive hearing loss occur?

no transmission through either external or middle ear issues with earwax or fluid in middle ear can usually be repaired easy to diagnose and fix

What type of cells are taste receptor cells and who do they come in contact with often? how often are they replaced?

non-neural epithelial cells contact with noxious chemicals ~10 days

What does the human olfactory system consist of?

olfactory sensory neurons whose axons form the olfactory nerve (cranial nerve I) olfactory bulb olfactory tract olfactory cortex olfactory nerve synapses with seconday sensory neurons in the olfactory bulb, which then processes the incoming information

What is differnt about this sensory modality?

only sensory modality that doesnt cross midline and doesnt go to thalamus first -the only special sense for which sensory cell itself is the neuron that carries the info to the CNS

What are the neural pathways for vision? (dorsal)

optic nerve exits eye, goes to optic tract (bundles of fibre) and fibres in optic tract go through thalamic relay and goes to occipital lobe -this is where it needs to end up for actual vision

What is the neural pathway for vision - lateral?

optic nerve exits eye, goes to optic tract (bundles of fibre) and fibres in optic tract go through thalamic relay and goes to occipital lobe -this is where it needs to end up for actual vision

What is rhodopsin?

photopigment in rods a purplish-red light-sensitive pigment present in the retinas of humans and many other animal groups.

what do taste receptor cells synapse with?

primary neurons

What are the olfactory receptor neurons (ORNs)

receptor cells are neurons for olfactory goes from 1st order neuron to 2nd order neuron 1) bipolar neurons - olfactory receptor neurons are replaced every 60 days 2) dendrites end in non-motile cilia which express odorant receptor proteins 3) axons go through gaps in cribiform plate, synapse on second order neurons 4) odorant receptor proteins are GPCR's, form one of the largest gene families in vertebrates (3-5% of the genome)

What is the fovea?

region of sharpest vision

What is the optic disk (bind spot)

region where optic nerve and blood vessels leave the eye

what are the photoreceptors in phototransduction

rods cones modified ganglion cells mediate pupillary light reflex, circadian/ seasonal rhythms (non-visual responses to light)

What is gustation?

sense of taste

What are maculae?

sensory receptors for linear acceleration and head position hair cells grouped in maculae within utricles/saccules utricle - forward/bacward acceleration. head tilt saccule - vertical acceleration consists of hair cells, gelatinous mass known as otolith membrane and calcium carbonate and protein particles called otoliths (ear + stone)

What are cristae?

sensory receptors for rotational acceleration (detect spin) hair cells grouped in cristae, within ampulla of canals explanation: Hair Tips are embedded in cupula which is gelatinous Sits at base of semi circular canal, if you move your head, fluid shits, cupula bends, hair cells bend and you get info about the spin Chynocelium - look??

What is olfaction?

smell

What are the neural pathways for auditory information?

sound waves -> R/L cochlea -> cochlear nuclei -> cerebellum -> R/L thalamus -> R/L auditory cortex my ******* explanation: Bundle of axons leave cochlea and joins Lower brain has synapse, leaves thalamus and goes to temporal cortex

Neural Coding for Pitch: What is the place code hypothesis

sound waves trigger activity at different places along the cochlea's basilar membrane are perceived as different pitches 'tonotopic map' wave travels along cochlea, hair cells in areas that bend the most at a given frequency encode that pitch 'labelled line' based on which hair cells are stimulated this explanation based on anatomy of ear dominated field for ~100 years based on research done with human ears (postmortem) Depending on frequency of cell, it hit different bits of choclear duct High pitch activated hair cell bends near the front of cochlea and low frequency near the floppy end of coclear duct is activated higher pitch = closer lower pitch = farther

What are the semicircular canals?

superior - front to back - yes posterior - head tilt left right horizontal - head turning left - right (saying no)

What are the combination of 5 tastes in gustation?

sweet (carbs energy) sour (H+) salty (Na+) bitter (many compounds warning of possible toxicity) umami (glutamate, some nucleotides protein) discovered by asians as meatiness umami - receptors binded and activated bitter - evolutionary dangerous mushroom - loaded with things that trigger glutamate receptors which is why it taste like steak

What are papillae what is it composed of?

taste buds composed of taste cells joined near the apical surface with tight junctions

What is the taste pathway?

taste info travels via various cranial nerves (VII - front of tongue, palate; IX - back of tongue, pharynx; X - esophagus) to medulla thalamus gustatory cortex ...

What is olfaction closely linked to?

taste/emotion/memory smell goes into your nose, ends are in nasal cavity the boney plate, crosses through those gaps and synapse goes through blue thick blulb then to everything emotions and memory also goes to this sensor

Explain diagram for the taste bud and taste recepting cells

the blue are primary afferent neurons the holes are taste pores -sweet bitter umami hang together with receptor proteins they express sodium and sour are most mysterious all are modified epithelial cells - connected to primary afferent neurons

Hearing: What are the steps of signal transduction in Hair Cells

the stereocilia of haircells have "trap doors" that closs off ion channels -these openings are controlled by protein-bridge tip links connecting to adjacent cilia a) at rest: 10% ion channels open, tonic signal is sent by the sensory neuron b) excitation: hair cells bend in 1 direction, the cell depolarizes, which increases AP frequency in associated sensory neuron c) inhibition: if hair cells bend in the opposite direction ion channels close, the cell hyperpolarizes, sensory neuron signalling decreaes

How is an odour produced? what is the structure and preception of odour?

to be odourant, need to be a volatile molecule that travels in air since you cant inhale proteins duh -so its simple organic molecules in air octanoic acid (sweaty, goaty) vs octanol (floral, fruity) ps do we need to know slide 7?

The olfactory tract bypasses the thalamus true or false

true - the olfactory neurons synapse with secondary sensory neurons in the olfactory bulb the olfactory neurons in the olfactory epithelium live only about 2 months replaced by new neurons whose axons must find their way to olfactory bulb membrane proteins expressed at bottom and smell non-motile cicilia - gives more surface area for smell insert rat brain - two bulbs sticking out are olfactory bulbs

Are visual pigments of cones excited by light of different wavelengths?

yes Rods express GPCR called rhodopsin, cones will have different variant of opsins, 3 diff cone types that have 3 diff opson molecules responding to wave lentgths There are overlaps and its processing in visual cortex like whats cherry red or ruby woo Any genes in there could effect colour vision In men - red-green colour blindness is possible The eye contains cones for red, green, and blue light. Each cone type is stimulated by a range of light wavelengths but is most sensitive to a particular wavelength ( Fig. 10.31). there are 3 typoes of cone pigment, each with a characteristic light absorption spectrum rods are for black an white vision in low light most mammals are dichromats humans are tri