Wk 8 - Non-Visual Systems Flashcards
The former model of sensory processing held that the system was… (x3)
With which five stages?
Hierarchical
Functionally homogenous
Serial
Receptor - thalamus - primary sensory cortex - secondary - association
The current model of sensory processing holds that the system is… (x3)
Meaning that?
Hierarchical
Functionally segregated
Parallel
There are many lateral connections and feedback after receptors send info to thalamus, primary, secondary, association cortices
The pina is…(x1)
Which functions to…(x2)
The external part of ear
Catch passing sound waves
Help with locating sound source
The first point of contact inside the ear canal is the…(x1)
Which is responsible for…(x1)
Tempanic membrane (eardrum) Transfer mechanical energy to the ossicles
Ossicles are…(x1)
Three tiny bones transferring energy from eardrum (tempanic membrane) to cochlea
The organs of Corti consist of…(x3)
And are responsible for… (x1)
Tectorial membrane, lying above the
Basilar membrane, in which are embedded
Hair cells
The transduction of sound energy to nerve impulses
Mechanisms of sound transduction are… (x6)
Stapes attached to base of cochlea
Sets fluid in cochlea into waves
Organ of Corti vibrates -
Tectorial and basilar membranes joined at base, and
Shearing motion against each other leads to
Changed electrical properties on membrane = excitatory action potentials
Sound signals hitting the tympanic membrane are amplified… (x3)
1.3 times by the vibrations of the ossicles, and
17 times by the concentration of tympanic vibrations to very tiny part of oval window
For a total of 22 fold increase in vibration strength
At the auditory threshold, the hair cells of the basilar membrane displace…(x1)
Which is the equivalent of.. (x1)
With such fine distinctions contributing to… (x1)
100 picometers
The top of the Eiffel Tower bending 10mm
Detection of faint sounds (esp when combined with properties of oval window/middle ear amplification)
Frequency theory of pitch perception covers which frequencies, by what mechanism?
0 -100 Hz
Neurones firing at direct equivalent rate per second to frequency
Volley theory of pitch perception covers which frequencies, by what mechanism?
100 - 5000 Hz
Teams of neurons firing in sequence to add up to necessary rate per second
Place theory of pitch perception covers which frequencies, by what mechanism (x5)?
5000 - 23 000 Hz
Based on mechanical properties of basilar membrane
High frequency sounds cause displacement, maximal at the base, like skipping rope;
So hair cells at that point code for high frequencies
At each point along membrane, coded for lower frequency
So if wave makes it right to the tip, will be coded as much lower freq than at base
What two methods allow sound localisation?
Interaural time differences
Interaural intensity differences
Explain the use of interaural time differences in sound localisation (x3)
Sound in front hits both ears at the same time
But off to side - detectable diff in time taken to travel width of the head
Brain compares arrival times, calculates where sound came from
Explain the use of interaural intensity differences in sound localisation (x3)
Particularly for higher frequencies, intensity of sound from one side is different to intensity on other side
Coz head forms a buffer
Brain calculates difference to localise sound source
Mechanisms of coding sound location through interaural time differences (x5)
Loudspeaker closer to left ear - sound arrives slightly sooner to left ear
Coincidence detector – fires maximally to simultaneous signal arrival, connections at a,b,c,d,e
A through D don’t fire, because only hit from left signal, which has head start
E fires because it gets simultaneous signal – the last from the left ear and first from the right,
Codes that sound came from left
Mechanisms of coding sound location through interaural intensity differences (x5)
Sound into left ear, stimulates cochlea, sends neural impulse along to olivary nucleus
Excites it to send excitatory signal from left superior olive to A1
Same time, another pathway sends inhibitory signal to trapezoidal body
Stimulates it to inhibit right olivary nucleus
Giving a push/pull mechanism based on the intensity of the sound
Describe two principles of the organisation of the auditory cortex
Tonotopic organisation: adjacent regions stimulated on basilar membrane stimulate adjacent regions in cortex
Columnar organisation: columns respond to different frequencies
To guard against hearing loss, we should have no more than 5 hrs/wk exposure to noise levels above…(x1)
88 db
Conduction deafness results from…(x1 plus eg)
But does not involve… (x1)
Damage to the tympanic membrane and ossicles
Eg ossicles become fused, no longer transmit vibrations from the outer ear to the cochlea
The nervous system
Sensorineural deafness results from…(x1 plus 4 eg causes)
Auditory nerve fibres not stimulated properly = permanent deafness
Infection, trauma, toxic exposure, loud noise
Tuberculosis patients treated with streptomycin suffered its ototoxic properties in that it lead to …(x2)
Cochlear damage
Some cases, all hair cells destroyed = total sensorineural deafness
Central deafness is caused by…(x1)
Resulting in…(x1 plus 2 egs)
Brain lesions in temporal lobes of cortex (ie stroke)
Loss of specific function
Language processing (left lobe) or
Discrimination of non-language sounds (right lobe)
The meaningful sounds test measures… (x1)
By… (x1)
Showing which pattern of deficits? (x2)
Ability to match correct semantic meaning to a sound
Get played a sound, eg braying donkey, then have to point out similar sound/category or unrelated sound
Need to identify, assign semantic meaning, so left temporal damage affects
Whereas right side doesn’t
The meaningless sounds test measures…(x1)
By…(x1)
Showing which pattern of deficits? (x2)
Perceptual ability to discriminate between sound patterns
Ps indicating whether pairs of sound identical, similar, different
Right temporal damage = poor performance
Left doesn’t affect ability
The vestibular system is critical for… (x2)
Keeping you balanced/oriented
Maintaining stable visual world
The semicircular canals are…(x1)
And are responsible for… (x1)
Three fluid filled tubes of the inner ear, oriented roughly orthogonally
Coding for rotary accelerations
Mechanisms for semicircular canals coding for rotary accelerations (x5)
Cupola in the ampulla (swelling in each canal)
Endolymph fluid has inertia -reluctant to move
Results in bending of the cupula
Hair cells at the base change firing rate when bending
When we reach constant speed, fluid catches up, cupula stop firing
Neural firing pattern of response of vestibular nerve from semicircular canal organ (x5)
Pretty high firing rate at rest
Acceleration bends hairs in one direction = increased firing
Constant velocity reduces back to baseline, then
When slowing hairs bend in opposite direction, firing decrease
Codes for acceleration/deceleration
Alcohol affects our balance/makes room spin because…(x3)
Cupula in ampulla of semicircular canal is in state of neutral buoyancy
Alcohol changes this balance
Leads to cupula flopping about
Otoliths are…(x2, plus function)
Utricles detect linear acceleration (aligned horizontally)
Saccules align with gravity
Mechanisms of otolith encoding for linear acceleration (x4)
But note that…(x1)
Hair cells stick up from membrane, with little calcium stones atop each one
Stones have inertia relative to body,
So forward movement means they stay put for a second, bending cells back
Provides stimulus for neural impulse
Head tilts produce displacement similar to certain accelerations
We know we’re standing upright because…
Saccules (otoloths in inner ear) align with gravity
Hair cells are constantly bent downward = firing
Neural firing pattern of response of vestibular nerve from an otolith organ (x3)
Get constant output throughout the stimulation due to gravity continuing to bend the hairs
Increase or decrease (sustained table-top graph function) from baseline encodes the two states
But actual acceleration/deceleration would look more like the up and down spikes shown by semicircular canal organs
The vestibulo-ocular reflex and vestibulo-ocular nystagmus both involve…(x2)
And are necessary for… (x1)
Rhythmic movement of the eyes -
A slow, tracking phase, and
A fast, return phase (saccade)
Maintaining a steady visual world
Vestibulo-ocular nystagmus is… (x1)
And is driven by…(x1)
Rhythmic eye movements that compensate for movements of visual scene relative to the viewer
Motion across the retina
Vestibulo-ocular reflex is driven by… (x1)
Stimulation of semi-circular canal and utricles
The connections underlying the vestibulo-ocular reflex are (x4)
Which function to…(x1)
From vestibular nucleus
Through Pons
Midbrain
To lateral and medial rectus muscles of eye
Keep the visual world stable while you move about
Loss of the vestibulo-ocular reflex results in (name and describe)
Oscillopsia Bouncing vision Sensation of world moving when head does Vestibular organ info unavailable Compensatory eye movements not made
The somatosensory system is comprised of which three systems?
Exteroceptive system - stimuli to skin
Proprioceptive system - position of limbs
Interoceptive system - internal conditions, temp, blood pressure etc
Name and describe four cutaneous receptors of the interoceptive somatosensory system
Free nerve ending - no specialised structure, temp and pain
Pacinian corpuscles - pressure, rapid adaptation
Merkel’s disks - gradual pressure, slower adaptation
Ruffinin endings - gradual pressure or stretch, slow adaptation
A dermatome is…(x1)
Convergence of afferent nerve fibres from specific body area in dorsal root of spinal column
Somatosensory info ascends from each side of body to cortex via which two major somatosensory pathways…
Dorsal column media-lemniscus
Anterolateral system
The dorsal column medial-lemniscus is… (x1)
Which…(x1)
A major ascending somatosensory pathway
Carries info about touch and proprioception
The anterolateral system is… (x1)
Which…(x1)
A major ascending somatosensory pathway
Carries info about pain and temp
The dorsal column medial-lemniscus runs…(x4)
Up dorsal column of spine
To hindbrain where they cross over, decuscate
Then ascend through medial lemniscus path via thalamus
To somatosensory cortex
The anterolateral system (ascending somatosensory pathway) runs through which three separate tracts? (name and descirbe)
With such diffusion meaning that…(x1)
Spinothalamic tract: up spine to first synapse at thalamus
Spinoreticular tract: First synapse at tectum, then thalamus etc
Spinoreticular: first synapse at reticular formation
If one tract is damaged, vital pain system still works
The sensory homunculus is…(x1)
The organisation of the somatosensory cortex into regions according to map of the body
Damage to the primary somatosensory cortex results in…(x1)
Probably because…(x1)
No major deficits in sensation
Of numerous parallel pathways in the dorsal column-medial lemniscus and anterolateral system
Cortical representation of pain is…(x1)
Meaning that…(x1)
Diffuse
Removal of S1, S2, or even entire hemisphere has little effect on perception
Describe Miss C, the woman who felt no pain (x4)
Constant injuries
Not even an autonomic reaction
Multiple health problems, and
Eventual death from infection at age 29
The anterior cingulate gyrus has been implicated in…(x1)
Because…(x1)
But…(x1)
Perception of pain
PET studies show increased activation when Ps touch hot/cold
Is more likely involved in the emotional response to pain
Body has internal pain management through…(x1)
Because…(x2)
Periaqueductal grey’s analgesic effects
Has receptors for opiates
Endorphins modulate PAG activity
