16 + 20. Vision, Auditory and Vestibular Systems Flashcards

Question

What can cataracts lead to?

Answer 1

Straightforward to treat by removing the lens surgically and replacing it with an artificial lens. BUT cataracts still cause millions to be blind.

Answer 2

* Tends to occur in old age * Higher incidence near the equator -\> May be due to severe dehydration

Answer 3

It is the watery fluid that fills the anterior and posterior chamber of the eye. It is not to be confused with the vitreous fluid behind the lens.

Answer 4

* Produced by the ciliary body * Flow through the posterior then anterior chambers * Flows out through the trabecular meshwork in the corner of the anterior chamber

Answer 5

Around 16.5mmHg

Answer 6

Usually it is due to decreased drainage of aqueous humour (e.g. due to blockage of the trabecula meshwork).

Answer 7

Damage to the optic nerve caused by raised intraocular pressure (\>20mmHg). It can lead to blindness.

Answer 8

Ophthalmoscope

Answer 9

Near the optic disc. (It is also worth noting that almost no vessels go to the macula).

Answer 10

* When viewing the retina, the doctor's eye is in the way of the source (figure a) * Therefore, an ophthalmoscope uses a beam splitter to ensure that the doctor is aligned with the source practically but not literally

Answer 11

* Rods * Cones

Answer 12

Cones: * Colour vision * Centre of the eye (in fovea) Rods: * Night vision * Periphery of eye (Just remember: CCC)

Answer 13

* 100 million rods * 7 million cones

Answer 14

* 1.5mm * Equal to 5\* of visual angle

Answer 15

Retinal nerve cell bodies are shifted aside from the central fovea, so light has a more direct path to photoreceptors.

Answer 16

No, it is slightly off to the side. (Check if this is due to the angling of the lens)

Answer 17

* Photoreceptors (cones and rods) at the back of the retina detect light * This information is passed to bipolar neurons * This information is then passed to ganglion cells -\> These form the fibres that flow out as the optic nerve Photoreceptors -\> Bipolar neurons -\> Ganglion cells (Note: The front of the retina is at the bottom)

Answer 18

* Horizontal cells -\> Connect laterally between pedicles of the photoreceptor cells * Amacrine cells -\> Connect across ganglion cells

Answer 19

* Bipolar cells -\> Connect between photoreceptors and ganglion cells * Horizontal cells -\> Connect laterally between pedicles of the photoreceptor cells * Amacrine cells -\> Connect across ganglion cells

Answer 20

Ganglion cells

Answer 21

* Astrocytes * Muller glial cells [EXTRA] * Pigment epithelial cells

Answer 22

* Increase contrast via lateral inhibition -\> Leading to centre-surround receptive fields. * Adapting both to bright and dim light conditions. Horizontal cells provide inhibitory feedback to rod and cone photoreceptors.

Answer 23

* Intercept retinal ganglion cells and/or bipolar cells * Create functional subunits within the receptive fields of many ganglion cells * Vertical communication within the retinal layers * Paracrine functions -\> e.g. Release of dopamine and acetylcholine * Through their connections with other retinal cells at synapses and release of neurotransmitters, contribute to the detection of directional motion, modulate light adaption and circadian rhythm, and control high sensitivity in scotopic vision through connections with rod and cone bipolar cells

Answer 24

Maintain the structural and functional stability of retinal cells: * Uptake of neurotransmitters * Removal of debris * Regulation of K+ levels * Storage of glycogen * Electrical insulation of receptors and other neurons * Mechanical support of the neural retina

Answer 25

* There is a straight-through pathway from receptor to bipolar cell to ganglion cell * There are also two lateral pathways: * Horizontal cells communicate between receptors (sending signals between them) * Amacrine cells serve a similar function between ganglion cells

Answer 26

* Centre-surround receptive field * This is where the receptive field consists of a centre (on) and surround (off) region * If photoreceptors in the centre of the receptive field are stimulated, then there is excitation of the ganglion cell * If photoreceptors in the edge of the receptive field are stimulated, then there is inhibition of the ganglion cell * If both are stimulated, then the excitatory response is weak

Answer 27

* Horizontal cells * When exposed to light, a photoreceptor releases less glutamate onto the horizontal cell * This causes hyperpolarisation of the horizontal cell * The horizontal cell is connected to other adjacent photoreceptors and leads to their depolarisation (remember that activation of photoreceptors leads to hyperpolarisation) * Thus, horizontal cells provide negative feedback to nearby photoreceptors, meaning that a spot of light will have a ring of inhibition around it.

Answer 28

ON bipolar cells: * When the photoreceptors are activated and hyperpolarise, ON bipolar cells depolarise * They synapse in sublamina B of the inner plexiform layer OFF bipolar cells: * When the photoreceptors are activated and hyperpolarise, ON bipolar cells hyperpolarise * They synapse in sublamina A of the inner plexiform layer It is worth noting that the photoreceptors all release glutamate, it is just the way the bipolar cells respond to it that differs (different receptors?)

Answer 29

* ON bipolar cells have an on-centre, off-surround field * OFF bipolar cells have an off-centre, on-surround field

Answer 30

No, they receive input from only one type of bipolar cell, which is why we also sometimes talk about ON and OFF ganglion cells (since they are corresponding).

Answer 31

The process through which photons are converted into electrical signals in photoreceptors.

Answer 32

Light causes HYPERPOLARISATION of the photoreceptors: * Light causes isomerisation of photopigment * This leads to transducin (G-protein) activation * Transducin activates a phosphodiesterase (PDE) * PDE reduces levels of cGMP * Reduced cGMP causes sodium channels to close * Therefore, the membrane is hyperpolarised This enables large and adjustable amplification.

Answer 33

* It is the depolarising inwards sodium current in photoreceptors while it is dark. * Upon sensing light, the sodium channels are closed and the current stops.

Answer 34

* Rods -\> Rhodopsin * Cones -\> Other opsins (3 different types -\> Red, green and blue)

Answer 35

Different opsins have different spectral sensitivities.

Answer 36

Consist of two parts: * Opsin (a type of protein) -\> Determines the type of photopigment * Chromophore (in the human retina, the type is called 'retinal')

Answer 37

Retinal (the chromophore in animal photopigments) is an aldehyde of vitamin A. Therefore, vitamin A deficiencies can lead to visual defects.

Answer 38

It leads to isomerisation of retinal (the chromophore), which triggers the transducin pathway that hyperpolarises the cell (phototransduction).

Answer 39

* It takes about 20 minutes for sensitivity to reach maximal values after lights turned off. * This corresponds to the time needed for rhodopsin in rods to regenerate (rhodopsin isomerises when activated, so it must regenerate for full dark vision) * The sensitivity to light also depends on the colours shown, since rods are less sensitive to red light

Answer 40

Sensitivity to colour shifts towards red on moving from dim (‘scotopic’) light, where only rods are active, to bright (‘photopic’) light, where cones are used. This is due to difference in the shapes of their spectral curves.

Answer 41

* Deuteranomaly -\> Abnormal green-absorbing pigment (5% -\> Most common) * Protanomaly -\> Abnormal red-absorbing pigment * Protanopia -\> Absence of red-absorbing pigment * Deuteranopia -\> Absence of the green-absorbing pigment

Answer 42

* Commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision * It is a measure of spatial resolution

Answer 43

Using a Snellen chart: * The patient is presented with a set of letters of different sizes * They stand at a set distance, usually 6m or 20ft * They read to the smallest text they can comfortably read * Each lines is labelled with a number * The visual acuity can be quoted as a fraction -\> Distance from object / Number of line * 6/6 or 20/20 vision is normal vision

Answer 44

* Gaps of about 1 min arc (1/60 degree) can just be read. * But under ideal conditions, gaps of 0.5 min can be resolved.

Answer 45

The spacing of cones in the fovea -\> The width of individual foveal cone outer segments is 2 microns.

Answer 46

* Magnocellular * Parvocellular Note that each of these can be either ON or OFF-centre cells.

Answer 47

Magnocellular: * Transient responses * High temporal resolution * Low spatial resolution * Monochrome Parvocellular: * Sustained responses * Low temporal resolution * High spatial resolution * Colour In other words, magnocellular cells are useful for detecting movement, while parvocellular are useful for detecting colour, texture and depth.

Answer 48

* The diagrams in the middle show the way in which banded lines of line are moved back and forth between two positions * The graphs on each side show the firing of magnocellular and parvocellular cells in response to each diagram * This shows that the magnocellular cells have better temporal resolution and can therefore detect movement better -\> This is shown by the fact that there are peaks every time the light changes * It also shows that the parvocellular cells have better spatial resolution and essentially produce an average of the receptive field -\> This is shown by the fact that there are peaks when there is either light or dark, but not both

Answer 49

* High blood glucose damaged blood vessels * This causes proliferation of blood vessels, which become swollen and damage the retina * There is loss of vision

Answer 50

* Damage to the macula (part of the retina) that occurs with age. * The pathophysiology is not known, but theories have been suggested, relating to oxidative stress, mitochondrial dysfunction, and inflammatory processes. * This results in blurred or no vision in the centre of the visual field.

Answer 51

Lateral geniculate nucleus (LGN)

Answer 52

* It is a relay center in the **thalamus** for the visual pathway. * It receives a major sensory input from the retina.

Answer 53

* Layers 1-2 receive input from magnocellular ganglion cells * Layers 3-6 receive input from parvocellular ganglion cells * The layers alternate inputs from the two eyes (so 3 layers per eye) * There are also extensive inputs from the brainstem and from V1 It is also worth noting that there are koniocellular cells in the interlaminar spaces.

Answer 54

* It was first thought that it was nothing more than a relay of visual information to the visual cortex, but it is now thought to play a far more complex role as a gate for controlling the passage of signals. * For example, it can cause fewer signals to pass through during sleep.

Answer 55

To the primary visual cortex (V1) via the optic radiations.

Answer 56

* The retinal (hereafter called "retinotopic") map is preserved. Axons from the retina preserve their order. * There is an entire map of a visual hemi-field in each layer of the LGN.

Answer 57

* Prior to the LGN -\> Left or right eye defects * After the LGN -\> Left or right field defects

Answer 58

Nasal retina

Answer 59

* Optic nerve * Optic chiasm * Optic tract * Visual cortex So no optic radiations or LGN.

Answer 60

Loss of vision in one eye

Answer 61

Bitemporal hemianopia (vision loss in the outer half of both the left and right visual fields)

Answer 62

Contralateral homonymous hemianopsia -\> Loss of one half of visual field. If right side affected, sight is lost of left side of visual field (and vice versa).

Answer 63

* Dependent on what part of the optic radiations are lesioned -\> This is because the radiations do not all run together * e.g. Meyer’s loop -\> Loss of vision in the upper quadrant on the opposite side of the visual field to the injury. Also known as pie in the sky disorder. * Lesion of upper optic radiation -\> Pie in the floor * Complete lesion causes contralateral homonymous hemianopsia -\> Loss of half of visual field (opposite side to lesion)

Answer 64

* Complete unilateral damage -\> Contralateral homonymous hemianopsia (Loss of one half of visual field on the opposite side to lesion) * Macular sparing (preservation of the centre of the field of view) can occur in some cases, such as posterior cerebral artery stroke -\> Proposed to be due to double blood supply to the macular region from the posterior and middle cerebral arteries. * Damage to just the lower bank of calcarine fissure -\> Pie in the sky * Damage to just the upper bank of calcarine fissure -\> Pie on the floor

Answer 65

Inflammation of the optic nerve

Answer 66

* Superior colliculus -\> Eye and head movements * Suprachiasmatic nucleus -\> Circadian rhythms * Pre-tectal nucleus -\> Pupillary light reflex These should be covered more in other lectures -\> If not, add more flashcards.

Answer 67

The striate cortex -\> It is given this name because it has this pale stripe along it, which is formed by small granule cells. The boundary between V1 and V2 is shown by the end of the pale stripe, as indicated by the red arrows.

Answer 68

It is in the occipital lobe of the cerebral cortex.

Answer 69

* Like all parts of the cerebral cortex, it has 6 layers (layer 1 not shown here) * In layers 2 and 3, there are cytochrome oxidase 'blobs', which receive input from koniocellular neurons from the LGN (these are the interlaminar neurons that are not usually considered as the 6 layers of the LGN) * In layer 4, the axons of parvocellular LGN neurons terminate deeper than those of magnocellular LGN neurons

Answer 70

* They are regions of the primary visual cortex (V1), which are most clearly seen in layers 2 and 3 * The neurons in the blobs are sensitive to COLOUR * The blobs can be detected histologically by staining with cytochrome oxidase stain

Answer 71

* Studying the visual field losses caused by bullet & shrapnel wounds in the war between Russia and Japan early in the 20th century; and in WW1 (by Gordon Holmes) * The parts of the brain that were damaged were compared with the parts of the visual field that were lost, allowing the map of the visual field in V1 to be detected

Answer 72

* They tend to lead to blindness, as would be expect * However, if it is only V1 that is lesioned, sometimes there is a condition called blindsight * This is where they can respond to visual stimuli that they do not consciously see. * In studies, when a stimuli is shown in the blind parts of their visual field, they have a higher than chance likelihood of guessing when the stimulus is.

Answer 73

* Central field -\> Posterior pole of the occipital lobe * Upper field -\> Lower bank of the calcarine fissure * Lower field -\> Upper bank of the calcarine fissure * Peripheral field -\> Deep in the calcarine fissure

Answer 74

(Hubel and Wiesel, 1968): * Found that each V1 neuron responds to a bar of light differently depending on the bar's orientation * Each neuron has an orientation at which it fires most rapidly, and the it fires less at other orientations

Answer 75

Each V1 neuron receives inputs from multiple receptive fields arranged in a line, meaning that the neuron only achieves peak activation at a certain orientation, when all of the receptive fields are fired.

Answer 76

* Simple cells -\> These are the orientation-selective neurons that respond to a line at a given orientation * Complex cells -\> Like simple cells, but they have a high degree of spatial invariance, such that there is a large receptive field, and the line can be responded to regardless of the exact position * Hypercomplex cells -\> Like complex cells, but they are excited specifically by short bars or corners

Answer 77

* Ocular dominance columns -\> These are alternating stripes of neurons that respond preferentially to input from one eye than the other * Orientation columns -\> These are columns of neurons that are excited by line stimuli at a specific orientation These are arranged at right angles to the layers of cortex.

Answer 78

No, they receive information from both eyes, but they preferentailly respond to input from one, resulting in ocular dominance columns. The fact that they can receive information from both eyes is because of partial decussation at the optic chiasm.

Answer 79

* Two-photon calcium imaging * This is where a mouse is modified so that neurons in V1 show colour upon calcium entry (when the neuron is excited) * This allows the researchers to see how excited individual cells get when exposed to given orientations of lines

Answer 80

* The ocular dominance columns can change sizes in an adaptive manner. * If one eye is deprived of light, then its ocular dominance columns shrink and the other eye takes over parts of them.

Answer 81

* One eye in a monkey can be covered from birth til 8 weeks * The ocular dominance columns in that monkey will be much larger for the dominant eye than for the covered eye, especially when compared to a control monkey

Answer 82

* It is a disorder when the visual cortex fails to process input from one eye as strongly as input from the other eye (a.k.a. lazy eye) * Causes include: Poor alignment of the eyes, an eye being irregularly shaped such that focusing is difficult, one eye being more nearsighted or farsighted than the other, or clouding of the lens. * Symptoms may not be noticeable, but can include poor depth perception, poor pattern recognition, poor visual acuity, and low sensitivity to contrast and motion. * Treatment can be done by wearing an eye patch over the stronger eye to allow the weaker eye to take over more of V1.

Answer 83

* Strabismus is a condition in which the eyes do not properly align with each other when looking at an object. * It can lead to amblyopia.

Answer 84

* Many cells in the V1 are disparity-selective. * The receptive fields are in slightly different horizontal positions on the two retinae. * Hence they respond best to single objects at particular distances.

Answer 85

* Double-opponent cells -\> Found in blobs (in layers 2 and 3) * Single-opponent cells -\> Found in the rest of V1 and as retinal ganglion/LGN cells

Answer 86

* Cells in blobs of V1 that are, for example, excited by green and inhibited by red in the receptive field centre, and excited by red and inhibited by green in its receptive field surround. * They are important in detecting colour contrast, such as in patterns, textures and boundaries.

Answer 87

* Cells in V1 that are, for example, excited by green in its receptive field centre, and inhibited by red in its receptive field surround. * They are important in responding to large areas of colours, such as in large colour scenes and atmospheres.

Answer 88

* Double opponent cells do not respond to monochromatic and black-white contrast illumination since the signals from the centre and surround would cancel each other out each time. * Single opponent cells respond to monochromatic colour and also to a white spot in its centre against a black surround.

Answer 89

They can be differentiated by their: * Cytoarchitecture (different cell types and distributions) * Myeloarchitecture (different myelination) * Connectivity

Answer 90

No, there are multiple cortical areas for vision.

Answer 91

* They are in the occipital lobe * V1 is intact, but the other parts are split on either side of it

Answer 92

"What" pathway: * Via V4 to inferotemporal cortex (in temporal lobe) * Involved in colour and pattern recognition, as well as memory (such as recognising known faces and objects) "Where" pathway: * Via V5 to the posterior parietal cortex * Involved in location, motion and space sense

Answer 93

Receptive fields increase in size since each neuron at each level integrates information from multiple neurons, so that there is progressive integration.

Answer 94

* Visual agnosia is where a patient can see objects as normal, and in general their vision is unimpaired, but they are unable to recognise what each object is * This is usually due to damage to the "what" visual pathway (such as in the lateral occipital cortex)

Answer 95

* The wave period is the time it takes to complete one cycle. * The standard unit of a wave period is in seconds.

Answer 96

* The opening and closing of the vocal cord produces sound waves * They are not sinusoidal and there is a range of frequencies * The pitch can be changed by changing the tension in the muscles

Answer 97

* Outer ear * Middle ear * Inner ear

Answer 98

It is everything outside of the ear drum (i.e. ear canal and auricle).

Answer 99

* Pinna/Auricle -\> This is the whole part that is visible from the outside * Tragus -\> The small prominence on the anterior side of the pinna, which slightly covers the ear canal * External auditory meatus (ear canal) * Tympanic membrane (ear drum)

Answer 100

* Collection of sound -\> The pinna catches sounds and deflects them into the external auditory meatus. * Acoustic gain -\> The auricle and start of the ear canal have resonant properties that increase the amplitude of sounds of certain frequencies * Sound location -\> Identical sounds from different directions will elicit different frequency spectra when passing through the pinna.

Answer 101

Sounds from different locations produce different frequency spectra.

Answer 102

Secretions of the ceruminous gland (ear wax).

Answer 103

Outer third is cartilaginous, continuous with the pinna, whilst the inner two thirds are formed by the temporal bone.

Answer 104

* Trigeminal (V) * Vagus (X) * Facial (VII) -\> Contributes to tympanic membrane

Answer 105

It is an air-filled cavity between the ear drum and cochlea. It contains the auditory ossicles.

Answer 106

* Auditory ossicles (malleus, incus and stapes) * Stapedius muscle + Tensor tympani muscle * Pharyngotympanic tube connection * Oval and round windows

Answer 107

Pharyngotympanic tube (Eustachian tube) -\> Connects the ear to the nasopharynx for pressure equalisation

Answer 108

* Malleus -\> Largest of the ossicles and is attached to the tympanic membrane at its handle. * Incus -\> Shaped rather like a pre-molar tooth and has a long limb terminating at the stapes. * Stapes -\> Has two limbs and a base which connects to the oval window (i.e. the inner ear).

Answer 109

* The middle ear must match low-impedance sounds from the air to the higher impedance of the fluid in the inner ear. * Impedance describes a medium's resistance to movement. * Normally, when sound travels from a low-impedance medium like air to a much higher-impedance medium like water, almost all of the acoustical energy is reflected.

Answer 110

* Difference in membrane area -\> The tympanic membrane (eardrum) is much larger than the footplate of the stapes, so that the pressure transferred to the inner ear is increased * The ossicles act as levers, multiplying the force * The tympanic membrane buckles as it moves, increasing the force transferred to the inner ear

Answer 111

* Oval window -\> Membrane made to vibrate by the stapes * Round window -\> Membrane vibrates with opposite phase to the oval window, so that the cochlear fluid can move

Answer 112

Stapedius muscle: * Connects to the stapes * Innervated by the facial nerve (VII) Tensor tympani muscle: * Connects to the malleus * Innervated by the trigeminal nerve (V) When the muscles contract, they increase the tension in the auditory ossicles, so that there is less transmission of sound.

Answer 113

* The contraction of the stapedius muscle by loud, low-frequency sounds. * The contraction causes stiffening of the auditory ossicles in the middle ear, so that low frequency sounds are not as easily transmitted through the middle ear. * Because of latency, this is not that useful in protecting against loud external noises, but it is triggered in advance of your own speech to protect against that

Answer 114

Everything inwards of the cochlea.

Answer 115

* Internal acoustic meatus * Cochlea * Cochlear nerve * Spiral ganglion * Vestibular apparatus

Answer 116

Petrous part of the temporal bone

Answer 117

Internal acoustic meatus (this is a canal in the temporal bone)

Answer 118

Not really, it is just to make it compact.

Answer 119

* It is coiled about 2.5 times * If we now consider any given spiral: * On the very outside, there is the bony labyrinth, containing perilymph * In the perilymph, there is the membranous labyrinth, containing the endolymph

Answer 120

* Scala vestibuli (perilymph) * Scala media (endolymph) * Scala tympani (perilymph)

Answer 121

* The membranous labyrinth is the structure that surrounds the scala media (contain endolymph) in the cochlea. * It is made up of the basilar membrane and Reissner's membrane

Answer 122

* Perilymph is high in sodium (like normal extracellular fluid) * Endolymph is high in potassium, which is pumped in through the stria vascularis (which contains ATPases)

Answer 123

* It is the potential difference of 80mV between the (more positive) endolymph and the perilymph, across the basilar membrane. * The high potassium in the endolymph enables transduction of the mechanical signal into an electrical one.

Answer 124

The conversion of a mechanical signal into an electrical one.

Answer 125

In the hair cells of the organ of Corti, on top of the basilar membrane in the scala media.

Answer 126

It contains hair cells and support cells, and is covered by the tectorial membrane.

Answer 127

* Note how there is no axon (just like with photoreceptors), since the hair cells do not fire action potentials. Instead there is an afferent fibre that innervates the cell. * There is also efferent innervation. * There are stereocilia on the surface that are arranged by height.

Answer 128

* Inner hair cells -\> Only one row, stereocilia not embedded in tectorial membrane * Outer hair cells -\> 3 rows, stereocilia embedded in tectorial membrane

Answer 129

* When the stapes vibrates, it moves the membrane in the oval window (connected to the scala vestibula) * Since the membrane in the round window at the other end (connected to the scala tympani) can also move, pressure waves are sent through the perilymph * The basilar membrane separates the scala tympani (containing perilymph) and the scala media, so it is deflected as the pressure waves pass * The hair cells, fixed to the basilar membrane, have stereocilia that are deflected as they brush against the tectorial membrane above them

Answer 130

* The stereocilia are arranged from shortest to longest, and the tip of each cilia is attached to its longer neighbour * When the sterocilia are brushed in the direction of the longest stereocilia (as the basilar membrane moves up), the tip-links are stretched * Stretching of the tip-links leads to opening of transduction channels, TMC1 and TMC2 (transmembrane channel-like 1 and 2) * This leads to entry of potassium into the hair cell (due to electrical gradients) and therefore depolarises the hair cell * Voltage-gated calcium channels open and there is an influx of calcium, which triggers neurotransmitter release onto the afferent nerve fibre * On the other hand, when the sterocilia are brushed in the direction of the shortest stereocilia (as the basilar membrane moves down), the tip-links are relaxed. This leads to hyperpolarisation.

Answer 131

Its high potassium concentration means that there is fast influx of potassium into hair cells, when they are stimulated by pressure waves. This makes the hair cells very sensitive.

Answer 132

No, they are also found in the vestibular system.

Answer 133

* The stiffness of the basilar membrane decreases as you go along the cochlea * This means that as the wave of displacement travels along it, the point at which it peaks will be different for every frequency * This means that specific hair cells detect specific frequencies, based on their position along the cochlea

Answer 134

* It is a graph of the minimum amplitude of a sound at a range of frequencies that is required to activate hair cells * It is done for a single point along the basilar membrane in the cochlea

Answer 135

* Stiffness of the basilar membrane changes along its length -\> So that peak deflection occurs at a specific point along the cochlea (and therefore at corresponding hair cells) * Amplification of the sound (at the right frequencies) by outer hair cells Note: The importance of amplification is shown by the kanomycin, which is an ototoxic drug.

Answer 136

* Outer hair cells become longer when hyperpolarised and become shorter when depolarised * This means that when they are stimulated in the cochlea, they appear to bounce * SInce their stereocilia are embedded in the tectorial membrane, this causes it to move * Therefore all of the hair cells are deflected more and therefore activated more Note how this is selectively amplifiying the sound at the right frequencies since it only happens at points where the outer hair cells are already being stimulated.

Answer 137

Prestin is the protein in the basolateral membrane responsible for the changes in size.

Answer 138

* Almost all of the afferent innervation is of the inner hair cells * Many of the inner hair cells are innervated by multiple afferent fibres

Answer 139

* The frequency of sound that AUDITORY NERVE FIBRES (that innervate hair cells in the cochlea) are most sensitive to * Since auditory nerve firbes only innervate one hair cell in the cochlea, the graph shown should correspond to the frequency tuning curve of the hair cell (which is in turn dependent on its position along the basilar membrane)

Answer 140

* No, the vibration of the tectorial membrane eventually becomes saturated (CHECK THIS), so that at a certain amplitude the response plateaus. * This is shown on the graph, where the line flattening out shows that the ear cannot detect difference in amplitude of the sound beyond that amplitude.

Answer 141

* When a sound in the grey area is played simultaneously with the one at the characteristic frequency, the response of the auditory nerve to the characteristic frequency sound is decreased. * This is not mediated by inhibitory synapses, but is due to the non-linear response of the basilar membrane (i.e. the amplification mechanism is saturated).

Answer 142

It is the spatial arrangement of where sounds of different frequency are transduced, transmitted to and processed in the brain. (i.e. Since the hair cells in the cochlea pick up different frequencies based on their position, and they are innervated by corresponding nerve fibres, this results in tonotopy)

Answer 143

Glutamate is the excitatory neurotransmitter released.

Answer 144

* It is the way in which the frequency of the sound corresponds to how frequency the firing rate of an auditory nerve fibre alternates between high and low. * i.e. An auditory nerve fibre will only fire at moments when the basilar membrane deflects upwards, which occurs at the peaks of the waves -\> This happens at constant intervals

Answer 145

* It can be considered by looking at the firing rates of all of the different nerve fibres, each of which has a characteristic frequency * It can also be considered by phase locking, where the frequency of the sound determines how rapidly the nerve fibre oscillates between a high and low firing rate

Answer 146

Auditory nerve (a.k.a. vestibulocochlear nerve)

Answer 147

VIII (a.k.a. vestibulocochlear nerve)

Answer 148

Spiral ganglion

Answer 149

(Cochlear nucleus of the) Medulla.

Answer 150

* Cochlea * Spiral ganglion In brainstem: * Cochlear nucleus * Superior olivary complex (including the medial nucleus of trapezoid body) In midbrain: * Inferior colliculus In cerebrum: * Medial geniculate nucleus * Auditory cortex (in the superior temporal gyrus)

Answer 151

* Dorsal and ventral cochlear nuclei * The auditory nerves enter at the ventral cochlear nuclei

Answer 152

* Each hair cell can receive afferent innervation from about 10 auditory nerve fibres * Each of these bundles corresponds to a different characteristic frequency, and these areas are topologically organised in the brain (e.g. in the cochlear nucleus) * Therefore, there is essentially a map of different frequencies on the brain

Answer 153

* The cells all differ in their morphology and pattern of firing in response to a tone burst * Their pattern of firing is partly dependent on the physical properties of the membrane channels they have, and partly dependent on local inhibitory neurons that affect the appearance of their frequency response areas

Answer 154

No, each cochlear nucleus receives input from the cochlea on the same side of the body.

Answer 155

Both of the cochlear nuclei.

Answer 156

* Medial superior olive * Receives excitatory input from the cochlear nuclei on contralateral AND ipsilateral side * EE (excitatory-excitatory) * Lateral superior olive * Receives excitatory input from the cochlear nucleus on the ipsilateral side and inhibitory input from the cochlear nucleus on the contralateral side (via the medial nucleus of the trapezoid body) * EI (excitatory-inhibitory) * Medial nucleus of the trapezoid body * This is where some fibres from one cochlear nucleus synpase and inhibitory neurons continue to innervate the contralateral superior olive

Answer 157

* It is the site in the pons where fibres from the cochlear nuclei decussate to the other side * The medial nucleus of trapezoid body is where some of these fibres synapse and continue as inhibitory neurons to the contralateral lateral superior olive

Answer 158

In the lateral and medial superior olives, since they receive auditory information from both ears, so they can compare the sounds reaching each ear.

Answer 159

To the inferior colliculus in the midbrain, via the lateral lemniscus.

Answer 160

Medial geniculate body (a.k.a. nucleus)

Answer 161

Auditory cortex

Answer 162

In the superior temporal gyrus.

Answer 163

Yes, all the way to the auditory cortex.

Answer 164

* There are isofrequency bars. * On top of these are mapped areas of EE (excitatory input from both ears), EI (excitatory from one ear, inhibitory from the other) and frequency modulated (changing frequencies). Note that this is not a very well understood mapping.

Answer 165

* Posterior parietal cortex (parietal lobe) -\> "Where" a stimulus is * Inferotemporal cortex (temporal lobe) -\> "What" a stimulus is

Answer 166

The range of sound intensities that can be perceived between the lowest detectable sound pressure and the threshold of pain.

Answer 167

* Threshold of hearing -\> 0dB * Threshold of pain -\> 140dB

Answer 168

* Each hair cell in the cochlea has its own dynamic range * The minimum deflection of sterocilia required for depolarisation determines the minimum amplitude detected, while the maximal opening of channels determines the maximum amplitude detected * Thus, the dynamic range of hearing is the sum of all of these dynamic ranges

Answer 169

* It is a graph of the minimum amplitude of sound that an individual can hear at a range of frequencies. * It is useful in diagnosing hearing conditions.

Answer 170

20Hz to 20kHz

Answer 171

* 1dB * 2Hz

Answer 172

* The cochlea's properties (length and stiffness) determine the range of frequencies the ear can detect * The external ear amplifies all sound entering the ear, but it is done in a frequency-dependent manner based on the physical properties of the external ear, meaning the ear is most sensitive around 2-5kHz

Answer 173

Temporal coding, since the amplitude of the wave may affect that rate at which action potentials are fired. Phase locking simply means that the action potentials will be fired in bursts at set intervals depending on the frequency.

Answer 174

Up to 4kHz (roughly)

Answer 175

* “Tonotopic” organisation of the auditory system -\> i.e. The parts of the cochlea that the sound of that frequency stimulate * "Phase locking" of auditory neurons -\> The time between bursts of auditory neuron firing, which corresponds to the time between peaks of the sound wave

Answer 176

* It is the smallest change in position of a sound source (angle) that we can detect. * It is about 1-2 degrees.

Answer 177

They are difference in the sound perceived by each ear, which allow us to detect the position of a sound.

Answer 178

* Interaural time differences (ITDs) -\> The difference in arrival time of the sound at each ear * Interaural level differences (ILDs) -\> The difference in amplitude of the sound at each ear

Answer 179

Just like it the sound practicals we did.

Answer 180

* ILDs -\> 1dB * ITDs -\> 10-20 microseconds Note that these are dependent on frequency!

Answer 181

ILDs: * Low-frequency waves (with longer wavelengths) can diffract around the head and enter the acoustic shadow cast by the head, so that the ILD is reduced * Thus, ILDs are only used over about 3kHz. ITDs: * ITDs with high frequency waves are essentially interaural phase differences. If there is more than one wave cycle between the ears, then the brain has no way of telling the true phase difference. * Thus, ITDs are only used below about 1500Hz.

Answer 182

* The left MSO * This is because the sound arrives at the right ear first, so it must be delayed slightly (via the longer route) in order for the action potentials to arrive at the MSO at a similar time * Thus, each MSO processes sounds located on the contralateral side of the body

Answer 183

* ITDs -\> In the medial superior olive * ILDs -\> In the lateral superior olive

Answer 184

* The MSO receives signals from both the contralateral and ipsilateral ear * Each MSO uses a counterflow delay system so that signals arrive at each MSO neuron at different times * The more a sound is on the contralateral side (and therefore the greater the ITD), the higher the rate of firing of neurons is at the MSO, since (in net) the signals converge at the MSO at closer intervals and therefore there is more firing * Thus, ITD is estimated by comparing the activation of the two MSO channels

Answer 185

* Each LSO receives stimulatory inputs from the ipsilateral side and inhibitory inputs from the contralateral side * This means that if a sound is on the ipsilateral side to a LSO, then the excitatory response dominates, while if it is on the contralaterl side, then the inhibitory response dominates * Thus, the LSO neurons fire more when the sound is on the ipsilateral side

Answer 186

* The external ear provides cues about the direction of the sound. They are also useful for the vertical direction of the sound. * These cues are processed largely in the dorsal cochlear nucleus, which contains type 4 cells.

Answer 187

* Superior colliculus * This is involved in producing a sensory map of the directions of various modalities of stimuli (sound, vision, somatosensory)

Answer 188

* It receives sensory input from the auditory, visual and somatosensory systems * It has maps of all of these, superimposed on each other * Thus, it integrates the positions of all of these stimuli * It also has a corresponding motor map, so that fast responses (such as eye movements towards a stimulus) can be coordinated Note that the superior colliculus is not essential for sound localisation however.

Answer 189

* Conductive -\> Problems with sound conduction in the external or middle ear * Neural -\> Problems with sound transduction and processing (e.g. hair cells, etc.) in the inner ear or further downstream

Answer 190

Weber's test: * Press a vibrating tuning fork against the patient's forehead (so that the bone conducts it to the inner ear). * If there is unilateral CONDUCTIVE hearing loss, the sound is heard louder in the DEAF ear (suprising, perhaps) * If there is unilateral NEURAL hearing loss, the sound is heard louder in the NORMAL ear Rinne's test: * Press a vibrating tuning fork against the mastoid (so that the bone conducts it to the inner ear). * Compare the thresholds with airborn sounds. * If there is NEURAL hearing loss, the air thresholds are lower, since the air conducts the sound better. * If there is CONDUCTIVE hearing loss, however, the bone thresholds are lower.

Answer 191

* Eardrum pop * Occlusion due to wax build-up * Middle ear filling up with fluid

Answer 192

Middle ear disease (otitis media): * An infection of the middle ear that causes inflammation and a build-up of fluid behind the eardrum. * If the fluid does not clear eventually, it may have to be drained.

Answer 193

* It accounts for the normal U-shaped curve of human hearing. * Therefore, it just shows the deviation from normal hearing at each frequency and gives ranges for different types of hearing loss.

Answer 194

* The hearing loss is around constant at every frequency * Therefore, the audiogram is almost a flat line

Answer 195

Presbycusis -\> This is the progressive hearing loss at high frequencies as you age.

Answer 196

The highest frequencies of hearing are most affected.

Answer 197

* They induce metabolic changes that cause loss of outer hair cells -\> These are responsible for cochlear amplification. * They also cause swelling of the auditory nerve fibres.

Answer 198

* Tinnitus -\> This is a ringing in the ears in the absence of sound. * It is due to central auditory system plasticity.

Answer 199

* They use a microphone outside of the head to detect sounds * These sounds are then transduced using an electrode array that is inserted into the scala tympani. * This is done in situations where cochlear hair cells are lost and therefore transduction is the problem, so that no amount of amplification using a hearing aid will help.

Answer 200

* This is also known as the scleral venous sinus * Circular canal found in the posterior part of the corneoscleral junction * Allows the collection of aqueous humour from the anterior chamber of the eyeball and for it to be delivered to the veins of the of the eyeball

Answer 201

* A mesh-like structure that occupies the hole in the sclera through which optic nerve fibres and the central retinal artery and vein pass * Formed by a multilayered network of collagen fibres that insert into the scleral canal wall * Thought to support the optic nerve as it leaves the eyeball

Answer 202

* This is the part of the eye that connects the iris to the choroid * Secretes aqueous humour * Made up of the ciliary muscle, the ciliary ring and the ciliary processes * Ciliary muscle adjusts the curvature of the lens (contraction causes lens to become more spherical and increases focussing power) * Ciliary ring joins the ciliary body to the choroid * Ciliary processes are radial structures from which the lens is suspended by ligaments

Answer 203

* This is the tissue that lines the insides of the eyelids and covers the sclera * Composed of unkeratinised, stratified squamous epithelium with goblet cells, and stratified columnar epithelium * Provides and lubrication of the eye through the production of mucus and tears * Also provides an anti-microbial barrier and aids in immune surveillance

Answer 204

* Pigmented region of the eye which regulates the amount of light that is allowed to enter the eye * Made up of circular and radial muscles (is a functional sphincter) * When circular muscles contract, the aperture radius decreases * When radial muscles contract, the aperture radius increases

Answer 205

* The aperture in the eye through which light can enter * Size is governed by the muscles in the iris * Aperture is smaller in bright light, wider in dim light * Responds during the pupillary light reflex

Answer 206

* Thin layer of tissue that makes up the innermost layer on the back of the eye * Contains rod and cone cells, which are able to transduce light into neural signals, which can then be transmitted to the brain via optic nerve fibres * The retina does not cover the entirety of the eye, the innermost layer on the iris and more anterior structures of the eye is the choroid * Junction between the two layers is the ora serrana

Answer 207

* Also known as the optic nerve head * This is the point of exit for ganglion nerve cells as they leave the eye * These cells form the optic nerve once they have left the eye * There are no overlying rods or cones, so this region is a blind spot on the retina

Answer 208

* This is a tiny pit located in the macula of the retina * The macula is the functional centre of the retina * Provides the clearest vision possible in the eye, as the other layers of the retina are not present at this region, allowing light to fall directly onto the cones * These cells have the highest acuity, and so a clear image is formed

Answer 209

* Transparent biconvex structure that helps to refract light to be focussed onto the retina * Can change shape depending on the optical power needed/distance from the object * This is achieved through the action of surrounding structures (ciliary bodies and suspensory ligaments)

Answer 210

* Also known as the zonule * Series of fibres that connects the ciliary body to the lens, holding it in place * When the ciliary muscle contracts, the ligaments are allowed to loosen and the lens bunches back into its natural shape (thicker and more spherical) * When the ciliary muscle relaxes, the ligaments become stretched/become tight, and the lens is also stretched into a thinner and flatter shape

Answer 211

* The anterior chamber is between the cornea and the iris * Chamber is filled with aqueous humour, which is produced by the ciliary bodies, but first passes into the posterior chamber before entering the anterior chamber via the pupil * The posterior chamber is between the suspensory ligaments and the iris * Chamber is also filled with aqueous humour

Answer 212

* One of the layers of the eye, containing some blood vessels that then augment the main blood vessels found in the retina * Also mostly made up of connective tissues * Is the middle layer of the eye * Is pigmented to limit reflection of light within the eye that would otherwise cause the image to be degraded * Fused with the ciliary body * The junction between the retina and the choroid is the ora serrata

Answer 213

* This space is filled with vitreous humour (transparent, 'glass-like') * Region between the lens and the retina * Has protective functions and also gives the eye its spherical shape

Answer 214

* This is the angle between the iris and the cornea (red region on diagram) * Lies external to the lens and is responsible for the outflow of aqueous humour from the anterior chamber (into the canal of Schlemm)

Answer 215

* External stratified epithelial layer * Thin anterior limiting lamina (aka Bowman's membrane, free of fibroblasts) * Stroma of the cornea (thick layer of parallel running collagen fibrils, interspersed with fibroblasts) * Posterior limiting lamina (Descemet's membrane) * Layer of endothelial cells

Answer 216

* Photoreceptor layer is lined by a thin sheet, which forms the **pigmented epithelium** * Beneath this layer is the choroid, which contains many blood vessels * Outer and inner segments of the photoreceptive **rods** and **cones** lie interally to this layer, and their nuclei lie in the outer nuclear layer * Cell-free layer lying internally is the **outer plexiform layer**, which contains the processes of the **horizontal** and **bipolar** cells, and synaptic processes of photoreceptors * Horizontal and bipolar cells both synapse with rods and cones, but horizontal cells also synapse with bipolar cells (thought to intergrate information laterally) * Bipolar cells contact ganglion cells directly to receive from cones, others form contacts with amacrine cells to receive from rods * Bipolar cells form contacts with amacrine and ganglion cells in the **inner plexiform layer** * Amacrine cells are also associated with lateral integration, and their cell bodies are either in the **inner nuclear layer** or the **ganglion cell layer** * **Ganglion cell layer** is largely made up of ganglion cells, which send their axons to the visual layers * Between the ganglion cell layer and vitreous humour, there is a thick fibre layer of ganglion cell axons which converge on the optic disc to form the optic nerve * These fibres are unmyelinated, but become myelinated as they leave the eye * **Fovea** has the thinnest inner cell layers, allowing this region to be the most sensitive to light, but the macula is also rod-free/there are only cones present in this location * Fovea lies in the temporal retina, which is lateral to the optic disc * Other regions of the retina are comparatively thick * Muller cells are vertically orientated glial cells with end feet forming a layer adjacent to the **inner limiting membrane** of the retina * These cells are equivalent to astrocytes, and are important in maintaining the ionic composition of extracellular fluid

Answer 217

* Red square: pigmented epithelium * Red bracket: choroid layer * Yellow highlight: rods * Black outline: cones * Blue bracket: outer nuclear layer * Blue square: outer plexiform layer * Black bracket: inner nuclear layer, containing horizontal, amacrine and bipolar cells * Black square: Inner plexiform layer * Red triangle: ganglion cell layer * Red circle: ganglion cells

Answer 218

Muller cells

Answer 219

* There are 6 oculomotor muscles * The are innervated by 3 muscles: * Oculomotor - the largest of the three, supplies all of the eye muscles except for the lateral rectus and superior oblique * Trochlear - innervates the superior oblique muscle * Abducens - innervates the lateral rectus muscle

Answer 220

* Transparent region of the eye covering the iris, pupil and anterior chamber * Able to refract light, and accounts for approx 2/3rds of the eye's total optical power * Contains collagen fibres that will stain green using Masson's trichrome * Has five layers: * External stratified epithelial layer * Thin anterior limiting lamina (aka Bowman's membrane, free of fibroblasts) * Stroma of the cornea (thick layer of parallel running collagen fibrils, interspersed with fibroblasts) * Posterior limiting lamina (Descemet's membrane) * Layer of endothelial cells

Answer 221

* White, tough, fibrous outer layer of the eyeball, which is continuous with the cornea at the front of the eye and the sheath covering the optic nerve at the back * Provides protection and form to the eye

Answer 222

* Innervated by the parasympathetic supply of the oculomotor nerve * This ganglion controls pupil constriction and the smooth muscle of the ciliary body * Contraction of the ciliary muscle reduced the diameter of the ring of muscle formed by the ciliary body * This reduced tension in the lens, causing it to relax and become spherical

Answer 223

* Central artery of the retina * Branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath on the way to the eyeball * Supplies the inner layers of the retina

Answer 224

* Lateral rectus muscle -\> Abduction * Medial rectus muscle -\> Adduction * Superior rectus muscle -\> Elevation + Adduction * Inferior rectus muscle -\> Depression + Adduction * Superior oblique muscle -\> Depression (counter-intuitive) + Abduction + Inward rotation * Inferior oblique muscle -\> Elevation (counter-intuitive) + Abduction + External rotation

Answer 225

LR₆SO₄O₃-\> This is a mock formula mnemonic for remembering: * Lateral rectus -\> 6th cranial nerve (abducens) * Superior oblique -\> 4th cranial nerve (trochlear nerve) * Others -\> 3rd cranial nerve (oculomotor nerve)

Answer 226

* The abducens nerve usually causes contraction of the lateral rectus muscle, causing the eye to be abducted/turn outwards * With a lesion, the eye deviates towards the midline

Answer 227

* The optic nerve disc/head can be viewed using an ophthalmoscope * Ophthalmascope is a tool that introduces light into the back of the retina to allow visualisation by eye (large light aperture requires the pupil to be dilated using mydriatic drops) * Compression of the optic nerve onto the lamina cribrosa causes cupping of the optic nerve head * Nerves fibres in the optic nerve begin to die, causing the cup around the disc to become unstable and appear larger than the disc, since support has been lost * The optic disc/nerve head appears pale as the small capillaries of the nerve are compressed

Answer 228

* The optic nerves pass first to the **ventral diencephalon**, where they form the **optic chiasm** * Retinal ganglion cells in the **temporal** half of each retina (which, due to the reversing lens, views the nasal part of each visual field) send their information to the **same** part of the brain (ipsilateral) * Retinal ganglion cells on the **nasal** retina cross to the contralateral side * This partial decussation results in each side of the brain receiving information from the opposite side of our visual fields * After the optic chiasm, the nerve fibres become the optic tracts * The optical tract runs to the **lateral geniculate body** (**LGN**) * This is the main visual relay in the thalamus * From the LGN, fibres sweep rostrally and laterally to the **retrolentiform** part of the **internal capsule**, passing around the concave surface of the ventricle where the body runs into the **inferior horn** * Fibres spread into a broad sheet, **superior** and **lateral** to the **lateral ventricle**, and the inferior fibres sweep far **rostrally** on the **superior aspect** of the **inferior horn** of the **lateral ventricle** * This causes upper visual field neurons to project onto the lower banks of the calcarine fissure, and the lower visual field to project onto the upper banks * The macula has a relatively large representation on the cortex and projects to the caudal pole of the occipital cortex

Answer 229

* Laminated structure * Outer two cell layers are made up of large cells * **Magnocellular** * Inner four cell layers are made up of smaller cells * **Parvocellular**

Answer 230

* The optic nerve is surrounded by the subarachnoid space, which is continuous with that around the brain and contains CSF * Therefore if pressure increases within the CNS, it will affect this compartment and then cause the optic disc to bulge into the eye, also raising intraoptic pressure * Through observing the optic disc, the intracranial pressure can also be observed and monitored

Answer 231

* Swelling of the optic nerve disc due to raised intracranial pressure * The dural anatomy of the optic nerve shows that it is continuous with the subarachnoid space, therefore subject to changes in intracranial pressure (ICP) * If the ICP increases, it is transmitted to the optic disc, causing it to bulge outwards Image shows unilateral papilloedema (healthy retina on the left)

Answer 232

* Papillodema - this is the swelling of the optic nerve as a result of increased pressure in or around the brain * This also causes the bulging inwards of the optic disc * Disturbances to vision (especially visual field) * Dilation of retinal veins - this occurs do to occlusion of the exiting veins, as these travel in the same channel as the optic nerve, so the increased pressure will reduce flow

Answer 233

Lateral rectus muscle * Origin: Lateral part of the tendinous ring * Insertion: Anterolateral region of the sclera * Innervation: Abducens nerve Medial rectus muscle * Origin: Medial part of the tendinous ring * Insertion: Anteromedial region of the sclera * Innervation: Inferior division of the **oculomotor nerve** Superior rectus muscle * Origin: Superior part of the tendinous ring * Insertion: Superior and anterior part of the sclera * Innervation: Superior division of the **oculomotor nerve** Inferior rectus muscle * Origin: Inferior part of the tendinous ring * Insertion: Inferior and anterior region of the sclera * Innervation: inferior branch of the **oculomotor nerve** Superior oblique muscle * Origin: Body of the sphenoid bone * Insertion: Anteriorly and parallel to the medial wall of the orbit, inserts on the equator of the eye between the superior and lateral rectus muscles * Innervation: Trochlear nerve Inferior oblique muscle * Origin: Maxillary bone * Insertion: Posterior, inferior, lateral surface of the eye * Innervation: Inferior branch of the **oculomotor nerve**

Answer 234

* Leaves the brain at the rostral border of the pons, just lateral to the midline * Runs rostrally across the apex of the petrous temporal bone and passes in the lateral wall of the cavernous sinus to enter the superior orbital fissure * Divides into inferior and superior orbit as it enters the orbit

Answer 235

Superior branch: * Superior rectus muscle * Levator palpebrae muscle of the upper eyelid Inferior branch * Medial rectus * Inferior oblique * Inferior rectus muscle * Parasympathetic supply to the ciliary ganglion

Answer 236

* Dilation of the pupil * This is due to now unopposed sympathetic tone in the iris * Ptosis (drooping of the upper eyelid) * This is due to the paralysis of levator palpebrae * Lateral diversion of the eye * This is due to the unopposed action of lateral rectus

Answer 237

* Arises dorsally, just posterior to the inferior colliculus * Only nerve to arise from the dorsal side of the brain * Axons of each nerve cross the midline just prior to leaving the brain * Courses arounded the cerebral peduncle and travels rostrally to the superior orbital fissure in the lateral wall of the cavernous sinus

Answer 238

* Innervates the superior oblique muscle * Lesion in the nerve is difficult to detect but will prevent the eye from moving down and out

Answer 239

* Abducens nerve leaves the brainstem at the junction between the pons and the medulla (medial to the facial nerve, CNVII) * It runs upwards and forwards from this position to reach the eye, entering the orbit through the superior orbital fissure to innervate the lateral rectus muscle

Answer 240

* Abducens (CN VI) acts synchronously with the oculomotor nerve (CN III) * This is important in congruent eye movements, as lateral gaze involved equal and opposite contraction of the lateral and medial rectus muscles of the two eyes

Answer 241

* The superior colliculus, oculomotor nuclei, vestibular system and motor systems of the neck are all interconnected to coordinate head and neck movement * These reflexes allow for the fovea to maintain focus on visual targets and for the head to move at the same time * The tract connecting these systems is called the medial longitudinal fasciculus and forms a pair of prominent fibre bundles that pass either side of the midline of the dorsal brainstem

Answer 242

Medial longitudinal fasciculus

Answer 243

* Abnormally high pressure in the eye/increased intraocular pressure * Often causes damage to the optic nerve * [Is one of the leading causes of blindness for people over the age of 60] * Mostly caused by a failure of fluid drainage, causing the pressure buildup Extra: * **Open angle glaucoma** is where the drainage angle (iridocorneal angle) remains open, but the trabecular meshwork is partially blocked, preventing drainage * **Closed angled glaucoma** is where the iris bulges forwards to block or narrow the drainage/iridocorneal angle, preventing the drainage of fluid

Answer 244

* Raised intraocular pressure (as occurs in glaucoma) results in the compression of the retinal axons onto the collagen lattice of the lamina cribrosa * This causes conduction blockade (not unlike pins and needles caused by peripheral nerve block) that can result in permanent damage and blindness

Answer 245

* Forms a boundary to **oligodendrocytes** so that they do **not** migrate into the retina * Myelination would degrade the optical transparency of the retina, and so this is only allowed to occur within the optic nerve

Answer 246

* Axons are arranged in bundles surrouded by astrocytes * Axons fall into different categories, reflecting both the size of the soma, the relative axon diameter and therefore the degree of myelination and speed of conduction

Answer 247

* Retinal afferents from the **ipsilateral** eye terminate in layers 2, 3 and 5 * Retinal afferents from the **contralateral** eye termine in layers 1, 4 and 6 * In each layer, there is complete retinotopic (and therefore visuotopic) representation of each hemifield * Each of the layers are in register, so a knitting needle passing through the whole structure would represent one point in visual space * Similarly, a point lesion through all six layers of the LGN would result in a **focal scotoma** (fixed blind spot)

Answer 248

* Responsible for maintaining and supporting the position of the eyeball in its normal upward and forward position in orbit * Also prevents downward displacement * Forms a hammock, stretching down and below the eyeball * Encloses the inferior rectus and inferior oblique muscles of the eye

Answer 249

* Elevates the superior/upper eyelid, skeletal muscle * Innervation: Oculomotor nerve (CN III) EXTRA: * Origin: Lesser wing of the sphenoid bone, just above the optic foramen * Insertion: Skin of the upper eyelin and the superior tarsal plate

Answer 250

* Smooth muscle that is attached to the levator palpebrae superioris * Helps to raise the upper eyelid through keeping it raised after levator palpebrae superioris has completed its raising action * Innervation: Sympathetic innervation, postganglionic sympathetic fibres that originate in the superior cervical ganglion * There is some communication with the oculomotor nerve also, and continue with the superior division of the nerve to enter the orbit EXTRA: * Origin: Inferior aspect of levator palpebrae superioris * Insertion: Superior tarsal plate of the eyelid

Answer 251

* Horner's syndrome is damage to a particular sympathetic pathway through a number of ways: * Lung cancer (Pancoast's tumour, to the apex of the lung) * Schwannoma (cancer of the myelin sheath) * Damage to the aorta * Traumatic injury * Surgery in the chest cavity * Lesion/damage to this path of the SNS causes: * Miosis (constriction of the pupil) * Ptosis (drooping eyelid, due to interruption of innervation to the superior tarsal muscle) * Anhidrosis (lack of sweating on the face) * Enophthalmos (sinking of the eye into the orbit)

Answer 252

As an outgrowth of the forebrain.

Answer 253

* An opacification of the lens, which leads to decreased vision * Can be bilateral or unilateral * Most develop due to changes in the tissue due to injury or ageing * There are some inherited genetic disorders that cause other health problems and increase your risk of cataracts * Can also be caused by other eye conditions, previous eye surgery or medical conditions such as diabetes

Answer 254

* Afferent innervation: Ophthalmic branch of trigeminal (CN V) * Efferent innervation: Parasympathetic facial (CN VII) via the pterygopalatine ganglion * When something irritates the cornea or conjunctiva, an impulse passes along CN V to the midbrain * Efferent (autonomic) innervation stimulates the lacrimal glands of the orbit, causing the outpouring of tears * Production of tears helps to protect the eye and potentially remove any irritants present

Answer 255

* Paired exocrine glands that secrete the aqueous layer of the tear film * The glands continuously release fluid which cleanses and protects the eye's surface as it lubricates and moistens it * Situated in the upper lateral region of each orbit, int he lacrimal fossa of the orbit formed by the frontal bone

Answer 256

* Also known as the tear duct * Carries tears from the lacrimal sac of the eye into the nasal cavity * Duct begins in the eye socket (between the maxillary and lacrimal bones), from where it passes posteriorly and inferiorly * This duct allows the draining of tears into the nasal cavity, where they will then be removed or ingested and components broken down in the stomach * [This means that if there is a blockage in the duct, the eyes are not drained, causing them to become watery and at higher risk of infection]

Answer 257

* Afferent innervation: Ophthalmic (CN V) * Efferent innervation: Facial (CN VII) to orbicularis oculi * This reflex is an involuntary blinking of the eyelids in response to stimulation of the cornea (e.g. by touching or by a foreign body), although can be in response to any foreign stimulus (e.g. quick movement towards the eye) * This reflex has a protective function

Answer 258

* The muscles are dually innervated by the autonomic nervous system * Parasympathetic innervation activates the muscle for contraction * Sympathetic innervation has an inhibitory effect on the level of parasympathetic activity * Contraction and relaxation of the ciliary muscles changes the thickness and curvature of the lens, therefore controlling the focussing power of the eye * Contraction of the muscle allows for the lens to bunch up, increasing its focussing power (the suspensory ligaments are allowed to become slack) * Relaxation of the ciliary muscles causes the lens to become thinner and flat, decreasing the focussing power (the suspensory ligaments become stretched/tight)

Answer 259

* This is the radial muscle of the iris that is able to dilate the pupil * It receives sympathetic innervation (long ciliary nerves, non-myelinated sympathetic fibres) * Its parasympathetic innervation appears less significant

Answer 260

* This is a muscle that controls the size of the pupil * The sphincter muscles are located near the pupillary margin and contraction of this muscle will cause the pupil to become smaller * The muscle is innervated by parasympathetic fibres (short ciliary nerves)

Answer 261

* This controls the diameter of the pupil in response to the light that falls onto the retinal cells * Greater intensity of light causes the pupil to constrict (sphincter pupillae constricts) * Lower intensity of light causes the pupil to dilate (dilator pupillae constricts) * Light shone into one eye will cause both pupils to constrict * Afferent innervation: Optic nerve (CN II) to the pretectal nucleus in the midbrain * Efferent innervation: Oculomotor nerve (CN III) -\> Edinger-Westphal nuclei (also in the midbrain) give rise to preganglionic parasympathetic nerves which then synapse with postganglionic parasympathetic neurons in the ciliary ganglion (this causes constriction)

Answer 262

* **Alpha-adrenergic agonists** and **muscarinic antagonists** (e.g. phenylphrine and tropicamide respectively) -\> Together these are called alpha muscarinics (?) * **Cyclopentolate** -\> Muscarinic antagonist, commonly used as an eye drop during paediatric eye examinations to dilate the eye (mydriatic) and prevent focussing (cycloplegic) * Many recreational drugs that are commonly misused cause dilated pupils: * Amphetamines - increased production of dopamine * Cocaine - inhibition of NA uptake (In bold are on the spec)

Answer 263

* It is part of the inner ear, continuous with the cochlea. * It is responsible for detecting motion, head position and spatial orientation.

Answer 264

It is within the temporal bone and it lies adjacent to the cochlea.

Answer 265

* 3 semi-circular canals -\> Each involved in detecting the angular acceleration of the head in a different plane (rotation) * Utricle -\> Detects acceleration in the horizontal plane + head position * Saccule -\> Detects acceleration in the vertical plane + head position

Answer 266

A swelling called the ampula, which contains the hair cells.

Answer 267

* They detect head acceleration in all 3 planes of rotation * In the ampula (swelling) of each canal, there are hair cells which function like in the cochlea * Stereocilia in the hair cells project into the cupula (somewhat analogous to the tectorial membrane in the cochlea) * When the head accelerates in one direction, the sterocilia are deflected, activating the hair cells

Answer 268

* Utricle -\> Detects acceleration in the horizontal plane + head position * Saccule -\> Detects accleration in the vertical plane + head position * Movement causes the otolith (calcium carbonate) layer to move, displacing the fluid below it * This deflects the sterocilia, activating the hair cells

Answer 269

The vestibular portion of the vestibulocochlear nerve (CN VIII).

Answer 270

In the vestibular ganglion.

Answer 271

Cell bodies of ganglion cells that receive neurotransmitter from hair cells.

Answer 272

* Vestibular nuclei in the brainstem * Cerebellum

Answer 273

They are at the junction between the pons and medulla: * Medial and lateral * Superior * Inferior (descending)

Answer 274

* Towards kinocilium = Excitation (higher discharge rate) * Away from kinocilium = Inhibition (lower discharge rate)

Answer 275

* Type I hair cells have a large afferent calyx surrounding their base * Type II hair cells do not

Answer 276

Vestibular nerve cells

Answer 277

* The cupula * It is a structure analogous to the tectorial membrane, but in the ampulla of the semi-circular canals * Hair cells are embedded within the cupula * When the head rotates, the endolymph lags behind and drags the cupula within it, which deflects the hair cells that are embedded in the base

Answer 278

* The hair cells in the semicircular canals are only activated upon acceleration, not stationary movement or constant speed * Thus, the graph shows that there is a spike in firing rate when the head accelerates * There is a time constant for the decay of this spike once the head reaches a constant velocity (about 6 seconds) * Note how the spikes are in opposite directions on each side of the head

Answer 279

* Semi-circular canal afferents terminate mainly in the superior and medial nuclei * Afferents from the utricle and saccule terminate mainly in the inferior and medial nucleus * The lateral nucleus receives afferents from both

Answer 280

It is the reflex that enables you to keep your gaze fixed on an object when you rotate your head.

Answer 281

No, it works in the dark.

Answer 282

* The cranial nerves that control the extraocular muscles -\> Abducens, Oculomotor and Trochlear * The nerves involved depend on the direction of head rotation

Answer 283

Note that this is for horizontal head rotation. Other axes of rotation will involve different nuclei and nerves.

Answer 284

Vestibulocerebellum (flocculonodular lobe): * Visual feedback is useful for calculating errors in the VOR. * Although this is too slow to correct these errors in real time, there are connections to the cerbellum, which is responsible for adaptive changes to the VOR.

Answer 285

It receives direct afferents and also indirect inputs from the vestibular nuclei.

Answer 286

The vestibular system outputs to the vestibular nuclei, which then output to: * Vestibulo-ocular reflex pathways * Vestibulocerbellum (also directly) * Thalamus, then to cortex * Spinal cord

Answer 287

* The saccule sounds like "sack", which hangs vertically. * Therefore it detects acceleration in the vertical plane, while the utricle detects acceleration in the horizontal plane.

Answer 288

The otolithic membrane that surrounds the otoliths (a.k.a. otoconia).

Answer 289

* Calcium carbonate structures within the utricle/saccule that have inertia and are moved by linear acceleration. * They are surrounded by a gelatinous otolith membrane that hair cells are embedded in.

Answer 290

* They can also detect head position (e.g. tilt of the head) * This is because when the head is tilted, the otolith moves, disrupting the stereocilia on hair cells

Answer 291

* Both the utricle and saccule are zoned with central specialisations “strioli” which have type I hair cells whereas the extra striolar region has type II hair cells. * The hair cells are arranged in complementary sets on each side of the stiola, with each set arranged along a certain direction * The cells are mirrored across the striola, such that a movement will excite cells on one side and inhibit those on the other side * This means that the cells can respond to changes in motion in any given direction

Answer 292

* In head tilt, gravity causes displacement of the otolithic membrane * This leads to firing of the hair cells

Answer 293

* When inputs from vestibular system do not match environment (i.e. visual inputs). * This leads to the sensation of spinning.

Answer 294

* Benign paroxysmal positional vertigo (BPPV) * Pieces of otolithic membrane break off and fall into semicircular canal displacing fluid. Common in elderly. * Benign paroxysmal positional vertigo is commonly treated by allowing gravity to move the dislodged otoconia from the canals

Answer 295

* Normal physiological nystagmus is part of the vestibulo-ocular reflex (VOR) * It involves alternating smooth pursuit in one direction and saccadic movement in the other direction -\> i.e. The eye moves slowly as you rotate your head and then when you run out of space the eyes quickly snap to a new point [CHECK] * The direction is named according to the quick phases * Nystagmus is a problem when it happens without moving the head (i.e. the eyes flicker on their own) * If lesion is peripheral, nystagmus can be suppressed by vision and will recover over time. * If lesion is in vestibular nuclei, there is little suppression and less recovery.

Answer 296

1. Must maintain a steady stance against gravity 2. Must anticipate goal-directed movements 3. Must be adaptive

Answer 297

* Relative position of parts of body with respect to each other (egocentric coordinate system) * Relative position of body with respect to environment (exocentric coordinate system) * Orientation of body in gravitational field (geocentric coordinate system)

Answer 298

When a leg moves, the remainder of the body needs to reposition such that the centre of gravity of the body is above the remaining leg.

Answer 299

Vestibular and proprioceptive -\> These input to the vestibular nuclei, which control muscles via the vestibulo-spinal tracts.

Answer 300

* Lateral vestibulospinal tract * Descends to lumbar regions to influence limb extensors involved in balance. * Medial vestibulospinal tract * Projects bilaterally to the cervical spinal cord to mediate the vestibulocollic reflex (a neural reflex that activates neck muscles when head motion is sensed by the vestibular organs in the inner ear).

Answer 301

Vestibular nuclei

Answer 302

* Neck muscle proprioceptors send signals to vestibular nuclei. * Here the information integrates with the information from the vestibular systems. * The vestibulospinal tracts then project downwards and control posture via the muscles.

Answer 303

* The subject is made to stand on a platform that moves forwards or backwards, causing the person to lean over * They must compensate for this or they fall over * Over multiple trials, the compensatory response becomes faster and stronger, demonstrating adaptive learning

Answer 304

Cerebellum

Answer 305

They are postural reflexes in response to changes in head position detected by the vestibular system, with the motor component via the vestibulospinal tracts.

Answer 306

* Pressure on feet causes placing reaction * Static vestibular reflexes cause extension of forelimbs and flexion of hindlimbs when head tilted down at the nose, and opposite when head tilted up (i.e. vestibulospinal reflexes - IMPORTANT) * Static neck reflexes cause forelimb extension and hindlimb flexion when neck flexed and opposite when neck extended. Only the vestibulospinal reflexes are mentioned in the spec.

Answer 307

When there are shifts in the centre of gravity, such that there is more pressure on one of the sets of limbs, those limbs detect the extra pressure and the response is to extend those limbs.

Answer 308

* When the head is tilted downwards/upwards, it is detected by the vestibular system * If the head is tilted downwards, there is reflex extension of the forelimbs and retraction of the hind limbs * This is mediated by the vestibular nuclei outputting to the vestibulospinal tracts that affect muscles

Answer 309

Tonic neck reflex causes extension of forelimbs and retraction of rear limbs when neck flexed.

Answer 310

When a person is sat in a fixed position in a room that is rotating, they may feel as if they are spinning even though they are not.

Answer 311

Complex (this means that any spoken sound is the sum of various frequencies of sine wave)

Answer 312

* Speech is produced by exhaling air from the lungs through the trachea into the larynx * The larynx consists of the glottis (an opening) and the vocal folds (two flaps of muscle) * During voiced (nonwhispered) speech, the vocal folds are stretched over the glottis. Air pressure from the lungs causes them to vibrate rapidly, producing a sound. * As we make our vocal folds more tense, they vibrate faster, producing a higher perceived pitch. * Above the larynx there are several chambers: the throat, the nasal /oral cavity, and the lips. Each chamber allows some frequencies to flow through while filtering others. * Speech production involves altering the shape and size of these chambers (e.g. by moving the tongue and lips), to alter the resonant frequencies (formants) produced, in order to produce different speech sounds (phonemes).

Answer 313

* The fundamental frequency is the lowest frequency heard in the complex sound that is speech * It determines the pitch at which we perceive the sound * The harmonics are frequencies that are multiples of the fundamental frequency * When the vocal cords are made more tense, they vibrate faster, producing a higher fundamental frequency and thus a higher perceived pitch. The harmonics are still multiples of the fundamental frequency.

Answer 314

Articulation

Answer 315

* Parts of speech that are properties of syllables and larger parts of speech. They include intonation, tone, stress, and rhythm. * For example, intonation is important for understanding the context of speech, such as whether something is a question (rising pitch).

Answer 316

* Identifying the speaker (male/female adults) * Interpreting their mood * Attending to a voice in a noisy background

Answer 317

* A vowel is a relatively long-lasting, unchanging speech sound * The oral tract is kept mostly open from the glottis to the lips and there are segments of time during which the articulators do not move * Each vowel can be detected by peaks of energy called “formant” frequencies (F1, F2, F3, etc). * The first 2 formant frequencies are usually sufficient to characterize each vowel. The rest are useful for identifying a speaker's voice.

Answer 318

* Consonants are formed by blocking passage of air, either partially or completely. * The constonants are in pairs, with each pair distinguished by the place of articulation and manner of articulation. * In each pair, one of the phonemes is unvoiced and one is voiced

Answer 319

For stop consonants (b-p, d-t, and g-k): * Place of articulation -\> This produces different formant frequencies (similar to vowel perception - see flashcard), which must be learned. * Voice Onset Time (VOT) -\> The duration of the period of silence between the stop consonant and the proceeding vowel (e.g. the gap between the d and a in "da" is shorter than the gap between t and a in "ta"). This allows two sounds within a phoneme pair to be differentiated.

Answer 320

(Kuhl, 2006): * The sounds r and l in English can be distinguished by their formant frequencies resulting from their place of articulation * Over time, the ability of English infants to discriminate the two sounds increases, while the ability of Japanese infants to do so decreases * This shows the learning of consonant formant frequencies

Answer 321

1. It is rapid: 25-30 phonetic segments per second 2. A continuous signal must be perceived as segments (i.e. words) 3. The acoustics are unreliable, both within and across speakers (i.e. Phonemes vary with speaker mood, gender, identity, accent, grammatical context, nasal cold, etc…) 4. In the real world, speech is present with background noises, requiring us to attend to different sound sources. Listening in noise is particularly challenging for older listeners, even if they show a normal audiogram. It also exacerbates developmental language impairments.

Answer 322

(Rasmussen & Milner, 1977): * Anaesthetised either the left or right hemisphere by injection of sodium amobarbital into the carotid artery through a catheter. * Then scored the patient’s ability to understand and produce speech is scored. * About 90% of all right handed patients and ~75% of all left handed patients display “left hemisphere dominance” for speech. * The remaining patients are either “mixed dominant” (i.e. they need both hemispheres to process speech) or they have a “bilateral speech representation” (i.e. either hemisphere can support speech without necessarily requiring the other). * Right hemisphere dominance is rare (1-2% of the population)

Answer 323

1. Acoustic / phonetic representation -\> Can the patient tell whether two speech sounds or syllables presented in succession are the same or different? 2. Phonological analysis -\> Can the patient tell whether two words rhyme? Or what the first phoneme (“letter”) in a given word is? 3. Semantic processing: Can the patient understand “meaning”, e.g. follow spoken instructions?

Answer 324

(Boatman, 2004): * Used microelectrodes to disrupt the function of different parts of the brain * Only the primary auditory cortex was required for acoustic tasks (e.g. differentiating syllables) * Both the primary and secondary cortices were required for phonological tasks (e.g. telling whether words rhyme or determining the first letter in a word) * The primary cortex, secondary cortex and language areas (e.g. Broca's and Wernicke's) were required for semantic tasks (e.g. understanding meaning)

Answer 325

* Broca's aphasia (non-fluent) * Wernicke's aphasia (fluent) * Conduction aphasia

Answer 326

* Lesions of Broca's area * Features: * Disjointed speech * Uses mostly content words (nouns, names, etc.), not many function words * Poor articulation, but this is not consistent between patients so it is not a motor problem * Repetition of speech is impaired * Patients struggle to find words or name objects * Comprehension is spared, but have problems understanding syntax (i.e. may struggle with certain sentence structures) * Patient is aware of deficit

Answer 327

Left inferior frontal gyrus (Brodmann areas 44 and 45) of left cerebral hemisphere

Answer 328

Posterior part of superior temporal gyrus (Brodmann area 22) of left cerebral hemisphere

Answer 329

* Lesions of Wernicke's area * Features: * Fluent speech * Impaired comprehension * Repetition of speech is impaired * Normal articulation * Grammatically correct sentences without meaning * Patient is unaware of deficit

Answer 330

Geschwind model (1960s) explains that when speaking a heard word: * Auditory cortex passes auditory information to Wernicke's cortex * Wernicke's cortex accesses the meaning of the word * Wernicke's area communicates with Broca's area via the arcuate fasciculus * Broca's area stores motor information associated with that word and outputs to the motor cortex * This leads to the speech of that word

Answer 331

* It is an aphasia due to lesions in the arcuate fasciculus (connecting Wernicke's and Broca's areas). * More recently this idea has been challenged and it is thought that it could also be due to lesions of other areas such as the left superior temporal gyrus/left supramarginal gyrus. * The superior temporal gyrus/left supramarginal gyrus are involved in phonological working memory (processes that underlie the short-term maintenance of language sounds for processes like memory during a sentence), while the arcuate fasciculus is involved in integrating the auditory and motor systems. * These lesions result in an inability to repeat things exactly (e.g. "the football player celebrated" becomes "the sportsman cheered") * Also show impaired naming, especially phonemic paraphasis (e.g. they may say "wife" instead of "knife") * Speech is fluent and grammatical, and auditory comprehension normal -\> Since Wernicke's and Broca's areas are mostly undamaged

Answer 332

(Buchsbaum, 2011): * Mapped the areas of lesion in patients with conduction aphasia and found the most common areas of overlap * Mapped the active areas in healthy patients performing a phonological working memory task * The area that was most overlapping between the two groups was determined to be Area Spt (which is involved in phonological working memory)

Answer 333

* Semantic paraphasia -\> When an entire word is substituted for the intended word (e.g. orange instead of apple) * Phonemic paraphasia -\> When part of a word is substituted with a non-word that preserves at least half of the segments and/or number of syllables of the intended word (e.g. wife instead of knife). * Neologisms -\> Making up a word.

Answer 334

* Hemiplegia is paralysis on one side of the body. * It causes weakness, problems with muscle control, and muscle stiffness. * It is more commonly associated with non-fluent (Broca's) aphasia, because Broca's area is much closer to the motor cortex, so it is more likely to be lesioned too.

Answer 335

* Although patients with lesions in Broca’s area generally have relatively normal comprehension, they are impaired at syntactic processing due to their problems with grammar * Much like with their use of mostly content words in speech, they also struggle to understand grammar (e.g. some tenses) when listening * (Caramazza & Zurif, 1976): * Presented patients with three simple sentences like “the boy ate the apple”, “the boy kissed the girl” and “the boy was kissed by the girl” * The patients understood the first two sentences, since they can understand the subject words and can infer the meaning from the word order and logic * However, they struggle to understand the third sentence due to the passive voice * The two explanations are: * The object of the verb has moved (Trace-deletion hypothesis, Grodzinsky, 1990) * There is a lack of working memory to process this syntax

Answer 336

* Broca's area is involved in speech production * Wernicke's area is involved in language comprehension

Answer 337

* There is involvement of the visual cortex. * There is also involvement of parasympathetic and sympathetic fibres.

Answer 338

Sympathetic supply (as in Horner's syndrome)

Answer 339

It can lead to bitemporal hemianopia.

Answer 340

* Glaucoma -\> Can lead to blindness * Cataract -\> Spots of lost vision and colour changes * Macular degeneration -\> Blurred or no vision in the centre of the visual field

Answer 341

* Gentamicin * Furosemide * Aspirin * Quinine

Answer 342

* It is a benign tumour of the Schwann cells of the vestibulocochlear nerve * It is also known as a vestibular schwannoma, which is a better name because the tumour usually arises on the vestibular division and from the Schwann cells in particular * The pressure on the nerve from the tumor may cause hearing loss and imbalance.

Answer 343

Due to a difference between actual and expected motion.

Answer 344

Superior colliculus

Answer 345

* It is a heightened sensitivity to particular sounds that are not usually a problem for others. * This is due to damage to the facial nerve (CN VII)

16 + 20. Vision, Auditory and Vestibular Systems Flashcards

(418 cards)