sensory Flashcards
(smell and taste) where do these mechanisms send information
send information to phylogenetically old areas of the brain associated with memory and emotion
(smell and taste): why is there a suggestion that there is an overlapping central processing between these 2 mechanisms
because they are closely linked even though they involve different receptors and receptive processes.
(taste) what does this regulate
to a lesser extent smell, regulate gastrointestinal
secretions
(smell) what are olfactory receptors confined to
confined to about 5 cm2 of the olfactory mucosa
(smell) where do olfactory receptors lie
lie deep within the nasal cavity
(smell) what do the cilia bind to during olfaction and what system does this involve
Cilia on the olfactory receptive neurones bind with odorants and the transduction process involves a G-protein second messenger system
(smell) name the 7 subdivision of smell
peppermint, musk, floral, ethereal, pungent, putrid and camphoraceous
(smell) what do odours project to
Specific odours map to specific regions within the olfactory trac
(smell) where do the output from the olfactory BULB project via what and to where
Output from the olfactory bulbs project via olfactory tracts to both the ipsi- and contralateral regions of the olfactory cortex.
(smell) what are bipolar olfactory cells linked to and via what
the bipolar olfactory cells are linked to the olfactory bulb via short axons.
(smell) describe where he olfactory PATHWAY project from and to
from the nose project directly to the cortex.
(smell) what gives rise to smell localisation
Bi- directional projections give rise to smell localisation
(smell) what is the role of the cortex
sharpening the odour codes
(smell) what does topographic mapping show\
topographic mapping show which zones project to either the medial and lateral
(smell) true or false: sense of smell has a small range
false: large range and many subdivision/ 7 primary qualities
what does the complementary expression of ligand receptor expression allow for
reverting image within visual system as eye acts a prisms so light that comes in from bottom, will reach the top of the retina and vise versa.
(smell)what is the competition model
by not smelling something for a long time, olfactory receptors will adapt, most used will outcompete the un-used receptors
(smell) describe the Odorant signalling
Ligand bind to receptor on Cilia, activates intracellular G protein, Activates adenylyl cyclase (ATP –>cAMP), cAMP activates CNG calcium channel –> calcium enters into cell –> both depolarisation of cell as positively charged and because of activation of Cl- channels, Cl- leave cell = more positively changed cell, AP in olfactory bulb and cortex
(smell) how to stop activation of olfactory bulb and cortex within odorant signalling
with the feedback loop, Ca2+ ions activates CaM, activates CAMK, which inhibits adenylyl cyclase = no cAMP
true or false: each olfactory neuron can express more than one type of receptor
false: each olfactory neuron can express only one type of receptor
how does sharpening the odour happen
through lateral inhibition
firing of strongly activated cells dampens down neighbouring, hence heightening signal of strongly activated cells
sensory systems - what are they for?
awareness of environment, prevention of harm (e.g. from withdrawal reflex), conscious control and integration (e.g. learning from experience)
name the types of sense receptors
exteroceptors, interreceptor and proprioceptors
what’s the difference between exteroceptors, interreceptor and proprioceptors
Information about external and internal
environments reaches the CNS via a range of sensory
receptors
where are interreceptor found
GIT, respiratory tracts, cardiovascular systems: pH pressure and volume
where are exteroceptors generally found
- hair cells in the inner ear, skin, tongue
exteroceptors examples
olfactory receptors
- taste receptors
- skin receptors: mechanoreceptors, thermoreceptors, nociceptors
photoreceptors
where are proprioceptors generally found and provide examples
- most reflexes at spinal
level: conscious awareness
secondary - joint receptors
what is classification of the sensory systems
Each type of receptor is normally activated by only
one type of environmental energy
what is transduction of the sensory systems
Sensory receptors convert environmental energy into
action potentials in sensory neurons
what do specific receptors associated with
are associated with specific CNS sensory pathways and brain regions
what does the coding of Stimulus Intensity and Duration tell us
Action potentials encode the quality of the stimulus
Sensory Receptors Range in Complexity: what does adequate stimulus mean
Usually respond to one type of stimulus
Sensory Receptors Range in Complexity: true or false:
Can be activated by other types of stimuli if they are strong enough
Sensory Receptors Range in Complexity: do they have specialised nerve endings and why
yes, may be specialised nerve endings/ specialised accessory cells so the response is only to to one type of stimulus
Classification of sensory receptors: name the 4 types of receptors
Mechanoreceptor, chemoreceptors, photoreceptors, thermoreceptors
Classification of sensory receptors: name 4 general classifications of mechanoreceptor
special senses, muscle & joints, skin & viscera, Cardiovascular
Classification of sensory receptors: name 2 general classifications of chemoreceptors
special senses, skin & viscera
Classification of sensory receptors: name general classifications of photoreceptor
special senses
Sensory Organisation: what is a receptive field
is the area where a stimulus activates a sensory neuron
Receptive fields usually overlap
Sensory Organisation: how is a larger secondary receptive field created
Primary neurons from adjacent receptive fields may converge on one secondary neuron, creating a larger secondary receptive field
Sensory Organisation: what does the 2 point discrimination determine
size of receptive field
Sensory Organisation: why does the 2 point discrimination determine the size of the receptive field
In some regions of skin, for example, two distinct stimuli are perceived as a single stimulus because the primary neurons converge on the same secondary neurons
Stimulus Location - Lateral Inhibition Sharpens the Code
(edit !)
Stimulus Location: how does the brain compute location of sound
Brain computes location of sound by comparing the timing of soundwave detection in each ear
Modality and Central Organisation: where does the specific sensory pathways relay information from and to
relay information from only one type of sensory receptor to specific primary areas of the cerebral cortex that receive only a single type of stimulus
Modality and Central Organisation: where does the non-specific sensory pathways relay information from and to
from more than one type of sensory unit to the brainstem reticular formation and regions of the thalamus that are not part of the specific ascending pathways
Modality and Central Organisation: what does the arrangement of sensory pathways give rise to
convergence or divergence of the sensory input
Modality and Central Organisation: what does the convergence/divergence of the sensory inputs influence
influences the quality of the sensation at the conscious or subconscious level within the CNS
Central Organisation: where do the olfactory pathways vs equilibrium vs all other pathways except olfactory go
olfactory: from the nose project directly to the cortex
equilibrium: project to the cerebellum with a branch to the cortex via the thalamus
all other: except olfactory: through thalamus before they project to their relevant cortical area
Inhibitory Modulation: how does one change the perceptual threshold
Higher brain centres can change one’s perceptual threshold
Inhibitory Modulation: what happens in perceptual threshold wihtin the higher brain centres
still receive the information but the brain
‘decides’ what it is necessary to fully perceive
e.g. selectuve hearing
Coding and Processing of the Stimulus: what is a tonic receptors
Slowly adapting receptors continuously signal the intensity and the duration of the stimulus
Coding and Processing of the Stimulus: what is a phasic receptors
Rapidly adapting receptors signal the onset and offset of a stimulus
Coding and Processing of the Stimulus: ho w is the quality of stimulus encoded
encoded in the frequency of the action potentials transmitted down the afferent fibre + the number of sensory receptors activated
Coding and Processing of the Stimulus: what does the structure or the morphology of the sensory receptor’s surrounding tissue associated with
its key property : Adaptive ability
integration of sensory input: what does axonal branches give rise to
give rise to
divergent outputs - diffuses inpu
integration of sensory input: what does secondary order sensory neurons have
Second-order sensory neurones
with convergent excitatory inputs
integration of sensory input: what do inhibitory interneurons give rise to
give rise to lateral inhibition - refines input
integration of sensory input: where dp axons projections go to
Axon projections to third-order sensory neurons
what is the order of integration of sensory input
axonal branches, secondary order sensory neurons, inhibitory interneurons, axon projections
what does sensory discrimination equate to
Sensory units with overlapping
receptive fields. Field size and receptor
density equates to sensory discrimination
true or false: sensory receptors monitory internal environments
false: External & internal environments monitored by sensory receptors
what is transduction
Stimulus converted to an electrical potential
what is the adequate stimulus
Each type of receptor excited most effectively by only one modality of stimulus
true or false: primary afferent fibres convey information from sensory
receptors to specific areas of PNS
false : primary afferent fibres convey information from sensory receptors to specific areas of PNS
where are the the sensory inputs processed
Sensory input processed at both sub-conscious and v conscious levels within the CNS
Classification of sensory receptors: name 2 general classifications of thermoreceptors
skin and CNS
Sensory Receptor Transduction: what is the first stage in sensory transduction
the generation of a graded receptor potential
Sensory Receptor Transduction: what happens if an all or nothing AP is generated
modulated release of transmitter from the receptor cell associated with the primary neuron
Sensory Receptor Transduction: difference between direct and indirect effects of stimulus
direct: acts on opening membrane ion channels (hair cells in the ear)
indirect: mediated by intracellular cell signalling mechanisms (olfactory neurons)
For better visiting, ciliary muscles contract.
How to solve short and short short sightedness
Long-Convex Lens
Short-Concave lens
true or false : Rods and cones contain pigments activated by light at different wavelengths
true yes
why do growth cones receive guidance cues
Growth cones receive guidance cues to guide them to their destinations during embryonic development
which animals has most research on retinotectal projection been carried out in
chick, zebrafish and Xenopus
visionary pathway: where do RGCs send their axons from and to
RGCs send their axons from the retina to the brain
visionary pathway: where do axons converge
All axons converge onto the same point in the eye, the ONH, through which they enter the optic nerve
visionary pathway: where do RGCs project ipsilaterally
In mammals RGCs in the ventrotemporal region of the retina project ipsilaterally (occurring on the same side of the body)
visionary pathway: what is the major decision point
The optic chiasm is a major decision point
visionary pathway: what is the tectum
In lower vertebrates the main target is the tectum
what is the complementary expression of inhibitory ligand’s function
the complementary expression of inhibitory ligand in the tectum, and their receptors expressed in the RGCs, establishes precise positional cues for individual axons relative to their neighbour
describe how the temporal axons are projected within the complementary expression of inhibitory ligand
Temporal axons, having more receptor,
are inhibited from projecting deep into
the tectum
describe how the nasal axons are projected within the complementary expression of inhibitory ligand
Nasal axons, having progressively less
receptor, project progressively further
into the tectum
Complementary expression of ligands and
receptors in the D-V axis
provides a 3-D map ensuring neighbouring axons from the retina project to neighbouring complementary positions within the tectum
establishes precise positional cues for individual axons relative to their neighbour
how are the complementary expression of inhibitory ligand receptors expressed
their receptors expressed in the RGCs
Vision: what are scotomas
defects of central fields
Visual defects: what causes scotoma
- blind spot
Visual defects: what is caused by lesions at fovea
causes greatest lack of visual acuity
Visual defects: what is caused by retinal lesions
occlusion of blood vessels or the
optic nerve
Visual defects: what do drugs cause
vitamin B12 deficiency;
what are other retinal problems
retinal detachment
- glaucoma ( intraocular pressure)
Visual defects: describe the impacts of lesions to any part of the visual system
result in loss of reception of at least part of the visual fields
Extent of defect depends on location and extent of lesion
Visual defects: what could defects be caused by
trauma and tumour compression, atherosclerosis (age/diet) or oedema (swelling).
colour blindness: percentage in each gender
8% males; 0.5% females
colour blindness: what do trichromats suggest
Trichromats are ‘normal’
colour blindness: what do dichromats suggest ,
miss one pigment = red-green blindness
colour blindness: what do monochromats suggest
extremely rare, totally colour blind and perhaps photophobic
what wavelength do the red blue green cones and rods correspond to roughly
Blue 450nm
Rods 525nm
Green 550nm
Red 600nm
what are taste afferents involved in
Taste afferents from the midbrain are involved in visceral reflexes (eg secretion of
gastric juices)
what are chemoreceptive refined into
smell (olfaction) and taste (gustation)
where do smell (olfaction) and taste (gustation) send informtaion
send information to phylogenetically old areas of the brain associated with memory and emotion
true or false : there is suggested overlapping central processing smell (olfaction) and taste (gustation)
true, closely linked even though they involve different receptors and receptive processes, suggest an overlap in central processing.
true or false: Smell regulate gastrointestinal
secretions
False, Taste, and to a lesser extent smell, regulate gastrointestinal secretions
Gustation function
quality and quantity of food, general sensation, flavour, overall appreciation of whether food should be swallowed, chemosensory and somatosensory
information
at least 5 types of taste which are…
- sweet (beneficial)
- salty
- sour
- bitter (possibly toxic)
-umami (“deliciousness”)
(back of pharynx)
Gustation: how are taste buds segregated on tongue
Taste buds segregated into 4 groups on specific regions of the tongue.
Gustation: How is Saltiness and sourness transduced
Saltiness and sourness transduced directly by sodium and hydrogen ions respectively.
Transduction of sweetness and bitterness involves 2nd messengers.
Gustation: what is the criteria for sensing taste
In sensing taste, activity in neurones of all four taste modes, ie the whole population of taste neurones, is compared.
true or false: individual taste cells can respond to more than one modality of taste
Individual taste cells are relatively selective to one particular mode but can respond to more than one modality of taste.
Gustation: What is Umami associated with and where receptors located
Umami (deliciousness), a taste associated with glutamate and other nucleotides, has receptors located at the back of the pharynx.
Gustation: where do the Primary sensory input travel to and via where
Primary sensory input to the cortex travels via the facial (front of tongue), glossopharyngeal (back of tongue) and, vagus (soft palate & mouth) nerves.
what is the role of taste pores
to allow mucus, containing dissolved foods + ions and other molecules in to dendrites neurons
where are the taste buds for salty, sweet, sour and bitter located on the tongue
salty, sweet, sour and bitter
» front to back»
Taste - anatomy: the 3 types of papillae
The four types of papillae on the human tongue have different structures and are accordingly classified as circumvallate (or vallate), fungiform, filiform, and foliate. All except the filiform papillae are associated with taste buds.
Taste - anatomy: describe the difference in structure within circumvallate, foliate and fungiform
circumvallate- with serous gland and wide, deep clefts
foliate - with serous gland and thinner, deep clefts
fungiform - without serous gland and short clefts
taste receptors: what receptors sense sweet and bitter
T1Rs sense sweet stimuli
T2Rs sense bitter stimuli
taste receptors: what receptors sense umami
t-mGluR4 is the candidate umami receptor, and detects glutamate
Taste receptor distribution: what receptors do fungiform papillae have
T1R3 and T1R3 receptors, L-amino acid receptor
taste receptors: what are MDEG/ENaC
receptors belong to a superfamily of ion channels implicated in sodium salt and acid sensation
Gustatory processing: describe the pathway to triggering mood and memory for taste
cranial nerves innovate brain stem –> 2 way signalling to other areas of cortex, integration through the thalamus (triggering mood and memory for taste )
Gustatory processing:
what affects signalling between different taste areas within the brain
Somatosensory/visceral systems- Information from the oral cavity and gut (cutaneous, thermal and nociceptive)
also using thalamus for memory
taste receptors: what type of receptors are all of these 3: T1Rs T2Rs, t-mGluR4
these 3 Rs are 7-pass transmembrane receptors
Taste receptor distribution: what receptors do circumvallate papillae have
T1R3 and T1R2 receptors, SWEET
Taste receptor distribution: what receptors do folate papillae have
T1R3 and T1R2 receptors, SWEET
and T1R3 and T1R3 receptors, L-amino acid receptor
describe the Taste transduction for bitter and sweet ligands
Bitter and sweet ligands use G-protein coupled membrane receptors
The bitter ligand, transducin, releases Ca2+ from intracellular stores
The sweet ligand, gustducin, activates a cAMP second messenger that closes
K+ channels and depolarises the cell
Ionic ligands for sour and salt alter ion channels and depolarise the cell, triggering extracellular Ca2+ entry
In all cases, increased intracellular Ca2+ triggers neurotransmitter release
Hearing: what is it
Hearing is our perception of the energy carried by sound waves over the range 20-20,000 Hz at safe amplitudes of 1-80 dB.
function of sound transduction
Sound transduction turns air waves into mechanical vibrations, then fluid waves, chemical signals, and finally action potentials
name 3 parallel fluid filled channels within the the cochlea of inner ear
the cochlear duct (middle canal), the vestibular duct (vestibular canal), and the tympanic duct (tympanic canal).
Hearing: where is the organ of Corti
The cochlear duct contains the organ of Corti, which lies along the basilar membrane.
Hearing: what is the organ of corti composed of
hair cell receptors and is partially covered by the tectorial membrane.
Hearing: describe how hair cells release neurotransmitters
Hair cells are topped by flexible cilia. When surrounding fluid bends the cilia + the movement of the basilar and tectorial membranes by sound waves, allows for the cells depolarise and release neurotransmitter onto the sensory neurons.
Hearing: Cochlea function
The cochlea is the organ where sound waves are converted first into fluid waves, then into chemical signals and finally into action potentials
The initial processing for pitch, loudness, and duration of sound takes place in the cochlea
Sound transmission: describe 6 step process
- Sound waves in the air strike the tympanic membrane
- Sound wave energy is transferred to bones of the middle ear, which vibrate
- The vibrations are transmitted via the oval window to the fluid within the vestibular duct and create a fluid wave within the cochlea
- The fluid waves push on the flexible membrane of the cochlear duct
- Sound waves are transmitted to the tympanic duct and dissipated back into air by the movement of the round window.
- Deformation of the cochlear duct cause the tectorial membrane to move and activate stereocilia of the hair cells.
Sensory Coding: describe the basilar membrane
The basilar membrane of the cochlear duct is stiff and narrow close to the oval window. It becomes
wider and more flexible near its distal end
Sensory Coding: what is the role of frequency
The frequency of the imposed sound wave determines the displacement of the basilar membrane.
changes when hair bent in opposite dir.
Sensory Coding: what is the impact of specifically high and low frequency
High frequency sound waves displaces the membrane closer to the stapes and lower frequency sounds displaces the membrane closer to its distal end
Sensory Coding: how is amplitude created and signalled
the specific location of hair cells on basilar membrane creates a code that the brain translates about the pitch of the sound. The amplitude is signalled by degree of displacement + coded in AP frequency generated in the sensory neuron
Deafness: how is conductive deafness remedied
Mostly easily remedied by non-invasive methods
Otosclerosis (abnormal bone growth in mid-ear) may require stapedectomy or fenestration
Deafness: what can cause conductive deafness
defects in the conduction of sound to the inner ear
wax build-up blockage of eustachian tube
inflammation (otitis)
otosclerosis (bone growth)
damage to ear drum
Deafness: what causes Sensorineural deafness
hair cell damage in organ of Corti
Meniere’s disease = increase endolymph, trauma, ageing, infection, drugs
Deafness: what causes nerve deafness
damage to the auditory nerve
- lesion (trauma), infection
- ageing–>atherosclerosis (hardening of arteries)
-
Deafness: true or false hair cells can regenerate in all mammals
False: Hair cells do not regenerate in mammals, only birds
Deafness: what is tinnitus
continuous or discontinuous ringing in the ears
Deafness: why does tinnitus occur
- degeneration of organ of corti – especially in elderly
- could also result from external and middle ear problems
- Ménière’s disease, or acoustic neuroma (auditory nerve disease through increase fluid pressure )
Deafness: true or false, there is over 100 mutant genes known involved in Hereditary deafness
true due to wide range of phenotypes
Deafness: what causes Hereditary deafness
wide variety of phenotypes = wide range of impairment: profound congenital deafness (from birth)
- slowly-progressing, adult-onset
(over 100 mutant genes known)
Equilibrium: what is it
Equilibrium is a state of balance that allows us to position our body in three-dimensional space under normal gravitational conditions.
Equilibrium: how is balance maintained
Balance is maintained through the hair cells in the fluid filled vestibular apparatus and the hair cells in the semicircular canals of the inner ear.
Equilibrium: what provides the forces for hair cell movement
- Gravity and acceleration provide the forces that moves the cilia of hair cells, which act as mechanoreceptors.
Equilibrium: name the 2 components
A dynamic component, sensing the rotational movement of the head
a static component that senses head displacement via linear acceleration and the associated gravitational changes.
Equilibrium: how are rotational movements detected
- Rotational movements are detected by hair cells found within the ampulla linked to the semicircular canals.
Equilibrium: how are gravitational changed detected
Gravitational changes are detected by the otolith organs found within the maculae at the base of the semicircular canals.
Vestibular System and Balance: describe the role of the posterior canal of the vestibular apparatus
the posterior canal of the vestibular apparatus sense the tilt of the head toward the right/left shoulder
Vestibular System and Balance: describe the role of the superior canal
senses rotation of the head from back to front
Vestibular System and Balance: describe the role of the horizontal canal
sense as head turns left to right
Vestibular System and Balance: describe the role of the vesitupular apparatus of inner ear
responds to changes in body position in space
Vestibular System and Balance: describe the role of the the maculae sensory receptors and cristae
maculae sensory receptors: linear acceleration cristae sensory receptors: rotational acceleration
Rotation and Gravity: what is the role of the movement of the endolymph
pushes on the gelatinous cupula and activates the receptor cells
Hair cells: how are hair cells linked and what is the function of this
linked by tip links, collective movements for force transduction through openning os ion channels
Rotation and Gravity: what are the otoliths
the otoliths are crystals that move in response to the gravitational force
Cochlea Hair Cells and Rotation: what induces endolymph to bend
Rotation of the head displaces endolymph to bend
hairs in either direction depending on the direction
of rotation
Cochlea Hair Cells and Rotation: what does head rotations do
Head rotation increases the firing frequency in canals on one side and reduces it in the other
describe the CNA Vestibular Pathways
Vestibular apparatus - branch of Vestibulocochlear nerve -
cerebellum –> reticular formation –> thalamus –> cerebral cortex
Vestibular Pathways nuclei of medulla –> somatic motor neurons with eye movement
