Nroc64 sensory motor system Introduction to sensory and motor ...
Nroc64 sensory motor system Introduction to sensory and motor system We have good understanding of the sensory side and some motor (like the coastlines of a continent) but have missing and limited understanding of the middle parts. (Integration) Ramon y Cajal- brought the concept of the neuron Simple minds – Studying simple brains allows more easier learning about system since our brain is more complex. Studying sensorimotor systems – memory – learning - e.g. you don't get burned on the same thing twice to learn not to touch it again The chemical senses – the oldest senses - gustation – olfactory – smell helps on most identify things e.g. danger (survival) – chemoreceptors Taste – salt, sour, sweet, bitter, umami – molecules activate special receptors – bitter – should be avoided – poison – survival – we learn to enjoy but primitive is survival – taste in combination (not only sweet) – but also use other senses e.g. taste and smell The organ of taste – Tongue, pallet, pharynx – all have taste receptors – Tongue Is the organ of taste specifically papillae – the tip of the tongue is sweetness – papillae are used to increase the surface area of the taste on tongue – tastebuds on the top or side of papillae
– hundreds of taste buds per papillae – microvilli allow to sense taste using receptor potential Taste receptor cells – Tuning – typically tastes cells are not only for one taste (sweet or salty) but have different levels of tuning to all tastes. Taste – mechanism for taste transduction sensory transduction – 3 mechanisms for 5 types of taste 1. through ion channels 2. block ion channels 3. bind to G protein coupled receptors Saltiness – mostly sense NaCl – special sodium channels (insensitive to voltage) cause depolarization – then open voltage gated sodium channels – and calcium vesicles fusion – cation and anion– anion have inhibitory effects to the point that you don't perceive sodium saccharine at salty but as sweet. Sourness – low pH Bitterness – poison detection – to G protein coupled receptors – Perceive different poisoning – T1R, T2R – different receptors but we don't really care what type of poison just that it is poison Sweetness – pair of receptors T1R2, T1R3 same 2nd messenger systems as bitterness Umami – pair of receptors T1R1, T1R3
- detect amino acid Taste Central Pathways -Three cranial nerves (VII, IX, X) – Information about taste travels on three cranial nerves - goes to gustaory nucleus – then to the thalamus, ventromedial nucleus, primary gustaory cortex Lesions – Ageusia – the loss of taste Labeled line hypothesis – selective Population coding – information is actually not encoded in only one cell but an entire set of neurons Pheromones – smell – ID information, food, survival, aggression, territory etc. – basal cells – future or olfactory cells – mucous layer – molecules of smell called odorants enter mucous layer to activate sensory receptors – cilia in mucus are the dendrites of the cell – axons are thin but also slow because they enter through the skull - very susceptible to damage Within the cilia – olfactory transduction Humans 300-400 smell receptor genes Adaptation – smell after effect – decreases response, less sensitive to odors after smelling for a while Rats have a very large snout to have a large nasal olfactory receptive area Glomeruli – there are inhibition between Glomerulus to enhance some things for over another
Smell and memory have a projection between them – you remember the smell you recognize Thalamus – not controlling smell – when you sleep, the thalamus shut down but since smell is not controlled by thalamus, it does not shut down when sleeping What is flavor? Not same as taste – retronasal olfaction – based on olfaction but it isn't smell, the brain make sense of it in a different way – involves touched (to the mouth), smell and taste Ventriloquism – audio-visual illusion – the system that is more reliable will dominate so vision dominates which is why the puppet moving his mouth we see and perceive it as it talking. Multisensory – flavor of food seems to come from mouth actually from the nose by retronasal olfaction taste – only sweet or sour flavor – if it tastes like apples or bananas Food appears to come from mouth because you sense that there is something in your mouth Multiplication - more salt or sugar is added so your brain believes more food is in your mouth so stronger flavor Flavor is ONLY when you sense that there is food in your mouth
Lecture 2 - vision
– Contrast than relative Optics – Light is waves – wavelength, frequency (brightness) and amplitude (color) – Polarity of light – Birds use, humans cannot – Three concepts: 1. reflection 2. absorption 3. refraction (transparent surfaces) - depends on which of the two mediums denser Anatomy of the eye – Pupil, sclera, Iris, cornea, optic nerve – cornea is important for the focus of light – only the cornea cannot change shape (like the lens) which is also important for focus – Optic disk = blind spot – macula – acute (good) vision – fovea – best vision here – helpfullness of iris – you can tell if the person is looking at you or what they are looking at (difference between Iris and Sclera) – contraction of the ciliary fibers stretches the lens flat – pressure of vitreous humor gives the eye round shape Eye disorders – Strabism: one eye becomes weak and affects oculomotor so you have double vision so you pick one eye causing oculardominance and eventually that becomes blind (the week eye) (cross eyes) – Cataracts - clouding of the lens – needs to replace the lens (artificial lens) – Glaucoma – the vitreus pressure if there is too much then you get glacoma and this is usually in the blind spot so usually don't even notice – Detached retina - the retina detaches from the back of the eye- this can be lasered back to the eye
– Retinitis pigmentosa - hereditary autoimmune disease where the body attacks the area right around the retina so you lose your sight starting with night vision. Spatial vision -Light that comes from a single source comes and collects at the cornea and then refracts the light – The cornea cannot change shape but the lens can – When the cilliary fibres relax, the lens stretches and thinner for far images – When the ciliary fibers contract, the lens relaxes (back to regular form) and thicker for images closer. Vision correction – Emmetropia – normal – Hyperopia – myopia – astigmatism – Cornia not being completely properly structured - not spherical The pupillary light reflex – the smaller the pupil, the more focused the vision is – the pupil controls the level of light going into the eye – consensual – both pupils should construct/relax at the same time – If the pupils are not consensual, it is a find that something is not right in the brainstem The visual field Visual acuity: the minimum distance between two dots that you can still see both dots. Anatomy of the retina Vertical pathway – photoreceptors– bipolar cells – ganglion cells Horizontal pathway Light enters from the ganglion cell layer and ends at the photoreceptor layer photoreceptors are special types of neurons
Graph – 0= the fovea – the blue curve equals count of cones – red is count of rods – so in the fovea there are only cones and no rods – in the peripheral retina, the further you go, the less light there is so you see less (almost blind) – there are more rods in the retina than cones 1 photoreceptor is attached to 2 bipolar cells is attached to it 1 ganglion cell – with the more photoreceptors/ bipolar/ ganglion cells, the more you can see (sensitive) but the less acuity so sensitivity and acuity are opposite. Pit shape of fovea – more visual acuity (find out why it is pit shaped) Phototransduction of rods – Rods are in the dark – don't send out action potentials, they send out graded potentials – since it is graded potential, it is more detailed and more sensitive to how much light is there and not just the presence or absence of light. – In dark, the sodium channels are open and let sodium flow in the depolarize the cell – Photodiesterase (PE) – know what happens in rods and cones when in the light and dark situations – Cones have different colors for different wavelengths so all three cones (for red, green, and blue) are all needed to perceive all the colors - Depending on how much each is activated or inhibited – Blue cones = 430 – green cones = 530 – red cones = 560 – rods (only see grey, black, and white) in the dark Light and dark adaptations – the light difference is 16
– regeneration of unbleached opsin – when photoreceptor is more bleached, it is more sensitive to light – you have maximum sensitivity after 20 to 30 minutes because it takes some time for the rods and cones to adjust – in daylight, the rods completely bleached because there's so much light – it takes the rods some time to adjust from being completely bleached to go back to being sensitive when going from light to dark (see graph) – nocturnal animals – only have rods – animals who cannot stay in the night (e.g. salamanders) only have cones – There is some plasticity in the retina – the retina is mostly designed to pick up differences or contrast in light calcium regulates photoreceptors – affects sensitivity to changes in light – in the dark calcium increases to a certain level so that cGMP levels decrease (mechanism goes against itself) because it slows down the depolarization – in light calcium release slows down hyperpolarization because less calcium increases cGMP production which then opens sodium channels again Retinal computations – a system with very many photoreceptors – 125 million – perception begins at a very early stage – photoreceptors are what are actually sensitive to light – the other cells are also sensitive but because they get a signal from the photoreceptors and not because they are receptive to light – depolarization in darkness - releases glutamine – in light, the horizontal cell is activated and the bipolar cell is inactivated (inhibited) – activate the light bipolar cell – each photoreceptor is attached to 1 ON and 1 OFF bipolar cell – on center ganglion cells and off center ganglion cells
– visual illusions Ganglion cells – M type and P type (parvo) Article on bipolar cells: introduction – 10 types of bipolar cells in vertebrate – 20 types of ganglion cells – piece of salamander retina and put an electrode to stimulate bipolar cells – 1 bipolar cell stimulated cause 2 different effects on 2 ganglion cells – this is due to the amacrine cells – so they block the amacrine cells – they found the greater action potential and now both ganglion cells are almost the same – so amacrine cells are found to be inhibitory
– Different types of lesions causing blindness Akinetopsia– in MT and lesions – regions in both affect motion perception Optic agnosia – difficulty with recognizing shapes – rare and might be memory or attention problems so these need to be ruled out before hand – They can have some shape awareness however, they cannot recognize the object but can use the object correctly (action can do but not name) Prosopagnosia – cannot recognize faces – but you know it is a face Capgras delusion – like opposite of prospoagnosia – no emotional response to looking at a face – delusion that person looks like the person but are actually imposters – only to someone close to them and not just anyone they know
Lecture 4– auditory and vestibular system Describe 3 pathways of visual system that are differently specialized for motion, colour, and shape – Magnocellular, Parvocellular, Conocellular Hearing and Balance – based evolutionary (still in fish) called lateral lines system – helpful to sense acceleration – response to differentenents Sound – air molecules that bunch together in regions of lower and higher air pressure – Amplitude – air pressure – Max - Min = intensity – pitch – perception of frequency – amount of physical energy (sound level on graph) – The one ( dot blue) that are at the same horizontal dimension but since the second is on a higher level, it will be perceived as louder – Outer ear – pinna and auditory canal – Tympanic membrane – sound pressure waves – three bones – smallest bone in body – ossicles – oval window – cochlea – Auditory vestibular nerve Function of bones – Since the surface area of the needle is smaller than the surface area of the other end of needle then it goes into the arm of the boy and not into hand of physician even though the pressure is the same The attenuation reflex – we listened to louder, higher sound and ignore lower sounds – High potassium in endolymph is important! Usually potassium goes out and not in
– basal membrane images stretched out – the cochlea is wide at the beginning and small at the end but the basal membrane (blue) is narrow at beginning and large at the end and floppy (floppy = lower frequency detection end and higher frequency at beginning) – Stapes causes pressure waves – Frequencies move the basilar membrane – different neurons respond to different frequencies along basilar membrane – Organ of Corti – inner hair cells – touch techtorial membrane – as basilar membrane moves, the organ of corti touches the techtoral membrane TRPAI channels – if brushing towards long one, the distance larger then potassium enters which gives rise to depolarization – Hyperpolarization when leaning away from long hair Afferents – influx of Efferents – amplify the sound by Prestine (motor proteins) which cause cell to change length due to hyperpolarization or depolarization Article – mammano and Ashmore – outer hair cells with amplification – contract or expand – hair cell moves around (twitches) when exposed to sound – especially when putting pipette near outer hair cells, you get mechanical response – opposite effect of RL and BM since both are contracting so both more in opposite directions but one is stronger than the other which is why one is more than the other – Voltage-dependent – the more depolarization more displacement and different on both – triangle of Corti – fulcrum system – outer hair cells pull on Triangle of Corti and the Basiler membrane is pulled up – the sound of that goes in and then if the sound that comes out is different they use this to see if this is a normal ear
Central auditory processes – more complex than visual pathways – do with as few synapse as possible because synapsebare where disturbance and noise appear – MGN – medial geniculate nucleus – slide 32 – image on exam – tonotopy – physical properties of basilar membrane – red – more intense, more action potentials, more louder but you cannot distinguish frequencies – Burst of action potential – right after the maximum peak of frequency sound pressure waves – this is called phase lock – volley principal – phase locking over series of neurons – sound localization – direction is good to hear but elevation is not very good (up down arrow) because ears are in not in (up down arrow) dimension – direction – sound appears at one ear earlier and a little louder (not because it is closer but because the other ear is in the shadow of your head blocking the sound waves to that ear!!!) Superior olive – stimulate at different times (first 1, then 2, then 3) in the opposite side then 3, then 2, then 1 – Depend on which cones first where the two action potentials meet and become additive – in this one is at the third one – as sound enter the pinna, it doesn't go straight in, it gets either amplified or reduced depending on frequency and direction and the brain uses this to tell direction Auditory cortex – primary auditory area – only stimulated by one modality only and nothing else (the definition of primary) – neurons are tuned to frequencies Deficiencies are very subtle because other ear compensates
The vestibular system – Eye movement, posture – 6th sense – because rather subtle – performs sensory transduction for acceleration (positive or negative) – sense velocity with quick adaptation – a difference in time is important – utricle and saccule are little bubbles which oriented in 3-D main axis X, Y, Z and both three rotations so three semicircular canals – as gravity imposes force and person moves, the otoliths sense change – semi circle canals – like three-quarter circles – have endolymph in canal and takes longer for endolymph to move – As it moves (floats) it pushes against the ampula and cupulla then you can sense rotation by translating the movement of this fluid – we have 2 vestibular systems – one in each ear – horizontal canal is different – auditory nerve – cranial nerve 8 Vestibulo-ocular reflex – if it doesn't work in people in a coma means brain is swelling – sea sick – Head rotation counterclockwise – you fixate eyes on point so eyes rotate clockwise – Eye muscles (lateral and medial) so medial contract and lateral will relax for the left eye and opposite for right eye (to look to the right) – the left vestibular nucleus innervates left oculomotor nucleus – abducens pulls away from nose – drugs affect vestibular system – e.g. alcohol – Know this image and what happens and which nerves are activated and inhibited in each situation!!!!
– hundreds of taste buds per papillae – microvilli allow to sense taste using receptor potential Taste receptor cells – Tuning – typically tastes cells are not only for one taste (sweet or salty) but have different levels of tuning to all tastes. Taste – mechanism for taste transduction sensory transduction – 3 mechanisms for 5 types of taste 1. through ion channels 2. block ion channels 3. bind to G protein coupled receptors Saltiness – mostly sense NaCl – special sodium channels (insensitive to voltage) cause depolarization – then open voltage gated sodium channels – and calcium vesicles fusion – cation and anion– anion have inhibitory effects to the point that you don't perceive sodium saccharine at salty but as sweet. Sourness – low pH Bitterness – poison detection – to G protein coupled receptors – Perceive different poisoning – T1R, T2R – different receptors but we don't really care what type of poison just that it is poison Sweetness – pair of receptors T1R2, T1R3 same 2nd messenger systems as bitterness Umami – pair of receptors T1R1, T1R3
- detect amino acid Taste Central Pathways -Three cranial nerves (VII, IX, X) – Information about taste travels on three cranial nerves - goes to gustaory nucleus – then to the thalamus, ventromedial nucleus, primary gustaory cortex Lesions – Ageusia – the loss of taste Labeled line hypothesis – selective Population coding – information is actually not encoded in only one cell but an entire set of neurons Pheromones – smell – ID information, food, survival, aggression, territory etc. – basal cells – future or olfactory cells – mucous layer – molecules of smell called odorants enter mucous layer to activate sensory receptors – cilia in mucus are the dendrites of the cell – axons are thin but also slow because they enter through the skull - very susceptible to damage Within the cilia – olfactory transduction Humans 300-400 smell receptor genes Adaptation – smell after effect – decreases response, less sensitive to odors after smelling for a while Rats have a very large snout to have a large nasal olfactory receptive area Glomeruli – there are inhibition between Glomerulus to enhance some things for over another
Smell and memory have a projection between them – you remember the smell you recognize Thalamus – not controlling smell – when you sleep, the thalamus shut down but since smell is not controlled by thalamus, it does not shut down when sleeping What is flavor? Not same as taste – retronasal olfaction – based on olfaction but it isn't smell, the brain make sense of it in a different way – involves touched (to the mouth), smell and taste Ventriloquism – audio-visual illusion – the system that is more reliable will dominate so vision dominates which is why the puppet moving his mouth we see and perceive it as it talking. Multisensory – flavor of food seems to come from mouth actually from the nose by retronasal olfaction taste – only sweet or sour flavor – if it tastes like apples or bananas Food appears to come from mouth because you sense that there is something in your mouth Multiplication - more salt or sugar is added so your brain believes more food is in your mouth so stronger flavor Flavor is ONLY when you sense that there is food in your mouth
Lecture 2 - vision
– Contrast than relative Optics – Light is waves – wavelength, frequency (brightness) and amplitude (color) – Polarity of light – Birds use, humans cannot – Three concepts: 1. reflection 2. absorption 3. refraction (transparent surfaces) - depends on which of the two mediums denser Anatomy of the eye – Pupil, sclera, Iris, cornea, optic nerve – cornea is important for the focus of light – only the cornea cannot change shape (like the lens) which is also important for focus – Optic disk = blind spot – macula – acute (good) vision – fovea – best vision here – helpfullness of iris – you can tell if the person is looking at you or what they are looking at (difference between Iris and Sclera) – contraction of the ciliary fibers stretches the lens flat – pressure of vitreous humor gives the eye round shape Eye disorders – Strabism: one eye becomes weak and affects oculomotor so you have double vision so you pick one eye causing oculardominance and eventually that becomes blind (the week eye) (cross eyes) – Cataracts - clouding of the lens – needs to replace the lens (artificial lens) – Glaucoma – the vitreus pressure if there is too much then you get glacoma and this is usually in the blind spot so usually don't even notice – Detached retina - the retina detaches from the back of the eye- this can be lasered back to the eye
– Retinitis pigmentosa - hereditary autoimmune disease where the body attacks the area right around the retina so you lose your sight starting with night vision. Spatial vision -Light that comes from a single source comes and collects at the cornea and then refracts the light – The cornea cannot change shape but the lens can – When the cilliary fibres relax, the lens stretches and thinner for far images – When the ciliary fibers contract, the lens relaxes (back to regular form) and thicker for images closer. Vision correction – Emmetropia – normal – Hyperopia – myopia – astigmatism – Cornia not being completely properly structured - not spherical The pupillary light reflex – the smaller the pupil, the more focused the vision is – the pupil controls the level of light going into the eye – consensual – both pupils should construct/relax at the same time – If the pupils are not consensual, it is a find that something is not right in the brainstem The visual field Visual acuity: the minimum distance between two dots that you can still see both dots. Anatomy of the retina Vertical pathway – photoreceptors– bipolar cells – ganglion cells Horizontal pathway Light enters from the ganglion cell layer and ends at the photoreceptor layer photoreceptors are special types of neurons
Graph – 0= the fovea – the blue curve equals count of cones – red is count of rods – so in the fovea there are only cones and no rods – in the peripheral retina, the further you go, the less light there is so you see less (almost blind) – there are more rods in the retina than cones 1 photoreceptor is attached to 2 bipolar cells is attached to it 1 ganglion cell – with the more photoreceptors/ bipolar/ ganglion cells, the more you can see (sensitive) but the less acuity so sensitivity and acuity are opposite. Pit shape of fovea – more visual acuity (find out why it is pit shaped) Phototransduction of rods – Rods are in the dark – don't send out action potentials, they send out graded potentials – since it is graded potential, it is more detailed and more sensitive to how much light is there and not just the presence or absence of light. – In dark, the sodium channels are open and let sodium flow in the depolarize the cell – Photodiesterase (PE) – know what happens in rods and cones when in the light and dark situations – Cones have different colors for different wavelengths so all three cones (for red, green, and blue) are all needed to perceive all the colors - Depending on how much each is activated or inhibited – Blue cones = 430 – green cones = 530 – red cones = 560 – rods (only see grey, black, and white) in the dark Light and dark adaptations – the light difference is 16
– regeneration of unbleached opsin – when photoreceptor is more bleached, it is more sensitive to light – you have maximum sensitivity after 20 to 30 minutes because it takes some time for the rods and cones to adjust – in daylight, the rods completely bleached because there's so much light – it takes the rods some time to adjust from being completely bleached to go back to being sensitive when going from light to dark (see graph) – nocturnal animals – only have rods – animals who cannot stay in the night (e.g. salamanders) only have cones – There is some plasticity in the retina – the retina is mostly designed to pick up differences or contrast in light calcium regulates photoreceptors – affects sensitivity to changes in light – in the dark calcium increases to a certain level so that cGMP levels decrease (mechanism goes against itself) because it slows down the depolarization – in light calcium release slows down hyperpolarization because less calcium increases cGMP production which then opens sodium channels again Retinal computations – a system with very many photoreceptors – 125 million – perception begins at a very early stage – photoreceptors are what are actually sensitive to light – the other cells are also sensitive but because they get a signal from the photoreceptors and not because they are receptive to light – depolarization in darkness - releases glutamine – in light, the horizontal cell is activated and the bipolar cell is inactivated (inhibited) – activate the light bipolar cell – each photoreceptor is attached to 1 ON and 1 OFF bipolar cell – on center ganglion cells and off center ganglion cells
– visual illusions Ganglion cells – M type and P type (parvo) Article on bipolar cells: introduction – 10 types of bipolar cells in vertebrate – 20 types of ganglion cells – piece of salamander retina and put an electrode to stimulate bipolar cells – 1 bipolar cell stimulated cause 2 different effects on 2 ganglion cells – this is due to the amacrine cells – so they block the amacrine cells – they found the greater action potential and now both ganglion cells are almost the same – so amacrine cells are found to be inhibitory
– Different types of lesions causing blindness Akinetopsia– in MT and lesions – regions in both affect motion perception Optic agnosia – difficulty with recognizing shapes – rare and might be memory or attention problems so these need to be ruled out before hand – They can have some shape awareness however, they cannot recognize the object but can use the object correctly (action can do but not name) Prosopagnosia – cannot recognize faces – but you know it is a face Capgras delusion – like opposite of prospoagnosia – no emotional response to looking at a face – delusion that person looks like the person but are actually imposters – only to someone close to them and not just anyone they know
Lecture 4– auditory and vestibular system Describe 3 pathways of visual system that are differently specialized for motion, colour, and shape – Magnocellular, Parvocellular, Conocellular Hearing and Balance – based evolutionary (still in fish) called lateral lines system – helpful to sense acceleration – response to differentenents Sound – air molecules that bunch together in regions of lower and higher air pressure – Amplitude – air pressure – Max - Min = intensity – pitch – perception of frequency – amount of physical energy (sound level on graph) – The one ( dot blue) that are at the same horizontal dimension but since the second is on a higher level, it will be perceived as louder – Outer ear – pinna and auditory canal – Tympanic membrane – sound pressure waves – three bones – smallest bone in body – ossicles – oval window – cochlea – Auditory vestibular nerve Function of bones – Since the surface area of the needle is smaller than the surface area of the other end of needle then it goes into the arm of the boy and not into hand of physician even though the pressure is the same The attenuation reflex – we listened to louder, higher sound and ignore lower sounds – High potassium in endolymph is important! Usually potassium goes out and not in
– basal membrane images stretched out – the cochlea is wide at the beginning and small at the end but the basal membrane (blue) is narrow at beginning and large at the end and floppy (floppy = lower frequency detection end and higher frequency at beginning) – Stapes causes pressure waves – Frequencies move the basilar membrane – different neurons respond to different frequencies along basilar membrane – Organ of Corti – inner hair cells – touch techtorial membrane – as basilar membrane moves, the organ of corti touches the techtoral membrane TRPAI channels – if brushing towards long one, the distance larger then potassium enters which gives rise to depolarization – Hyperpolarization when leaning away from long hair Afferents – influx of Efferents – amplify the sound by Prestine (motor proteins) which cause cell to change length due to hyperpolarization or depolarization Article – mammano and Ashmore – outer hair cells with amplification – contract or expand – hair cell moves around (twitches) when exposed to sound – especially when putting pipette near outer hair cells, you get mechanical response – opposite effect of RL and BM since both are contracting so both more in opposite directions but one is stronger than the other which is why one is more than the other – Voltage-dependent – the more depolarization more displacement and different on both – triangle of Corti – fulcrum system – outer hair cells pull on Triangle of Corti and the Basiler membrane is pulled up – the sound of that goes in and then if the sound that comes out is different they use this to see if this is a normal ear
Central auditory processes – more complex than visual pathways – do with as few synapse as possible because synapsebare where disturbance and noise appear – MGN – medial geniculate nucleus – slide 32 – image on exam – tonotopy – physical properties of basilar membrane – red – more intense, more action potentials, more louder but you cannot distinguish frequencies – Burst of action potential – right after the maximum peak of frequency sound pressure waves – this is called phase lock – volley principal – phase locking over series of neurons – sound localization – direction is good to hear but elevation is not very good (up down arrow) because ears are in not in (up down arrow) dimension – direction – sound appears at one ear earlier and a little louder (not because it is closer but because the other ear is in the shadow of your head blocking the sound waves to that ear!!!) Superior olive – stimulate at different times (first 1, then 2, then 3) in the opposite side then 3, then 2, then 1 – Depend on which cones first where the two action potentials meet and become additive – in this one is at the third one – as sound enter the pinna, it doesn't go straight in, it gets either amplified or reduced depending on frequency and direction and the brain uses this to tell direction Auditory cortex – primary auditory area – only stimulated by one modality only and nothing else (the definition of primary) – neurons are tuned to frequencies Deficiencies are very subtle because other ear compensates
The vestibular system – Eye movement, posture – 6th sense – because rather subtle – performs sensory transduction for acceleration (positive or negative) – sense velocity with quick adaptation – a difference in time is important – utricle and saccule are little bubbles which oriented in 3-D main axis X, Y, Z and both three rotations so three semicircular canals – as gravity imposes force and person moves, the otoliths sense change – semi circle canals – like three-quarter circles – have endolymph in canal and takes longer for endolymph to move – As it moves (floats) it pushes against the ampula and cupulla then you can sense rotation by translating the movement of this fluid – we have 2 vestibular systems – one in each ear – horizontal canal is different – auditory nerve – cranial nerve 8 Vestibulo-ocular reflex – if it doesn't work in people in a coma means brain is swelling – sea sick – Head rotation counterclockwise – you fixate eyes on point so eyes rotate clockwise – Eye muscles (lateral and medial) so medial contract and lateral will relax for the left eye and opposite for right eye (to look to the right) – the left vestibular nucleus innervates left oculomotor nucleus – abducens pulls away from nose – drugs affect vestibular system – e.g. alcohol – Know this image and what happens and which nerves are activated and inhibited in each situation!!!!
