Physiology of Balance, Taste and Smell Flashcards
1
Q
Vestibular System: Function:
A
- responsible for balance and spatial
awareness - motor coordination, response
- eye movement
- posture
2
Q
What does the vestibular system consist of?
A
- semicircular canal
- otolith organs
3
Q
Vestibular System: Semicircular Canals: Function:
A
detect angular acceleration
4
Q
Vestibular System: Otolith Organs: Function:
A
detect linear acceleration
5
Q
What are the otolith organs?
A
the utricle and saccule
6
Q
Vestibular System
A
insert diagram
7
Q
Vestibular System: Otolith Organs: Macula:
A
- sensory tissue of utricle and
saccule are respective maculae - macula contains hair cells, which
are sensory mechanoreceptors of
the vestibular system - type I and type II
- macula of saccule is at a right
angle to the macula of the utricle - utricle macula = horizontal plane
- saccule macula = vertical plane
8
Q
Otolith Organ Structure:
A
insert slide
9
Q
Semi Circular Canals:
At each end are the continuations of the utricle or saccule?
A
utricle
10
Q
Where are the sensory cells of the semi circular canal located?
A
in the ampulla
crista ampullaris is cone like stricture in the ampulla
crista ampullaris contains hair cells and is orientated at a right angle to the canal x acis
hair cell cilia are embedded in a gelatinous mass called the cupulla
11
Q
Semicircular Canals:
A
insert diagram
12
Q
Hair cells:
A
insert slide
13
Q
Vestibular System:
Each movement initiates a series of
A
complex excitation and inhibition events at the hair cells
14
Q
Vestibular System: Exiting the Car After Stopping:
- Turn towards the car door:
- Stepping out of the car:
- Raising to a standing position:
A
- Exiting the car after stopping.
- Turn towards the car door:
stimulation of the horizontal
semicircular canals. - Stepping out of the car:
stimulation of the hair cells in the
utricles (left and right). - Raising to a standing position:
stimulation of the hair cells in the
saccules (left and right).
Conclusion of the movement leads to opposite linear and angular accelerations
15
Q
Vestibular system Pathway:
A
- afferent nerves that innervate the
vestibular sensroy receptor carry
stimuli from receptors to the
vestibular nuclei: superior, lateral, medial and inferior - then projects to the abducens nuclei
- via abducens nuclei stimuli are
transported to the trochlear and
oculomotor nuclear complex - projections of the vestibular nuclei
innervate CNIII (oculomotor), IV
(trochlear), VI (abudcens) - coordinate eye, neck and trunk
movement - projections innervate descending
pathways that regulate posture
and muscle tone
16
Q
Vestibular System Pathway:
A
insert diagram
17
Q
Vestibular System Disorder: Vertigo:
A
- caused by accumulation of debris
from the otolithic membrane to
the ampulla - increase sensitivity to angular
movement - can also be caused by nerve or
neural nuclei lesions
18
Q
Vestibular System Disorder: Meniere’s Disease:
A
- vertigo that is intermittent and
relapsing - possible hearing distortion or
tinnitus - thought to be caused by the
accumulation of endolymph due
to poor drainage - damage to hair cells has also been
observed, possibly due to
endolymph oedema
19
Q
Nystagmus
A
- head rotation in one direction is
followed by slow movement of
eyes in the opposite direction,
followed by rapid eye movement
towards the rotation of the head
and fixation in new plane of vision - slow eye movement is controlled
by the vestibular nuclei - nystagmus in the absence of head
movement can indicated
damage/lesion in the vestibular
system
20
Q
How is the vestibular system tested for damage?
A
- caloric test
- ear irrigation with either hot or
cold water - applies to the horizontal
semicircular canals - warm water irrigation of the left
ear causes the firing of hair cells
and activation of vestibular nuclei - stimulates head movement to the
left, eyes slowly deviating to the
right - cold water irrigation of the left ear
does not lead to hair cell firing and
consequently causes head
movement to the right and eye
movement to the left - absence of eye movements can
indicate damage to the vestibular
system
21
Q
The olfactory system relies on ——– sensory neurons receptors?
A
chemical
22
Q
Olfactory receptors are located in
A
the mucosal epithelium of the nasal cavity
23
Q
What is the life span of a chemical sensory olfactory receptor?
A
30-60 days
short life span
24
Q
Olfactory System:
A
insert diagram
25
What occurs at the olfactory bulb?
axons of the bipolar olfactory neuron receptors project to the olfactory bulb where they form synapses with second order olfactory neurons
synapse is a glomerulus
26
The Olfactory Epithelium:
- olfactory sensory neuron
dendrites extend into cilia,
embedded in the nasal mucosal
epithelium
- basal epithelium contains stem
cells that can replace the olfactory
neurons
- olfactory neuron axons are not
myelinated and they form clusters
that synapse with 2nd order
neurons to form CN1
- epithelial cells support in a similar
fashion as neural glial cell s
27
Olfactory Epithelium:
insert diagram
28
Olfactory System: Chemical Signal Generation:
- cilia contain protein receptors that
bind odorant molecules
- metabotropic GPCR receptors
- odorant molecule-receptor
complex activates the Gs system
- GDP excahnged for GTP
- activates adenylate cyclase which
activates cyclic AMP
- cAMP binds to cyclic nucloetide
gated channels causing an influx of
Ca2+ and Na+ and an efflux of Cl-
- leads to depolarisation of cilia and
production of an action potential
29
Chemical Signal Transport:
insert diagram
30
Olfactory System: Summary:
insert diagram
31
Olfactory Pathway:
- olfactory sensory neurons release
glutamate
- olfactory bulb neurons release
GABA and dopamine
- olfactory tract projects to the
olfactory cortex, the enteorhinal
cortex and the amygdala
- and to the frontal cortex,
hippocampus and hypothalamus
32
Olfactory bulb layers:
insert diagram
33
Olfactory Pathway: Summary:
insert diagram
34
Anosmia
loss of smell
35
hyposmia
reduction in smell
36
hyposmia and anosmia can result in
altered consumption of food and drink
37
Causes of loss of smekk:
- head injury that causes movement
of olfactory bulband damage to
the axons of the olfactory neurons
- infection
- nasal polyps
- age; less regeneration of olfactory
sensory neurons
- alzheimer's or parkinsons's
38
Cacosmia:
olfactory hallucination of unpleasant smells
39
Cacosmia: Causes:
- seizures involving the temporal
lobe
- tumour
- parkinson's
- head injury
40
5 basic senses of taste:
- sweet
- sour
- bitter
- salty
- umami (pleasant savoury taste)
(meat, fish, vegetables, breast mill)
41
Receptors in which area of the tongue detect umami?
Receptors on all areas of the tongue can detect each of the five senses of taste
42
What is the sensory organs of the gustatory system?
Taste buds
43
Taste Buds:
- embedded laterally in the margins
of the papillae and they are
surrounded by fluid
- taste bud pore allows fluids from
the oral cavity that contain
chemical substances to enter
- each taste bud contains taste cells
that are the sensory receptors for
taste
- taste cells have a short lie span,
and are regularly replaced
44
Taste Cell: Innervation:
- afferent nerves that project to the
ganglia of CN VII, IX, X
- facial, glossopharyngeal, vagus
45
Taste Receptor: Activation Process:
- chemical substances in saliva
enter the taste bud pore and come
in contact with the microvilli of
taste cells
- initiates cascade events depending
on type of chemical substance
- each cascade leads to the
depolarisation of taste cells and
the release of neurotransmitters
received by afferent neurons that
innervate the taste cells
- in all pathways taste cell
depolarisation opens voltage
dependent Ca2+ channels, influx
of Ca2+ and the release of
neurotransmitters; ATP and
serotonin
46
Taste Receptors: Salty Substances:
- salty substance enters taste bud
pore and comes in contact with
the microvilli
- cascade events
- influx of Na+ ions
- opening of voltage gated Ca2+
channels
- depolarisation, action potential,
neurotransmitter
47
Taste Receptor: Sour Substances:
- sour substance enters the taste
bud pore and comes into contact
with microvilli
- cascade events
- influx of H+ ions and
depolarisation due to the closure
of K+ ion channels
- Ca2+ influx due to opening of
Ca2+ voltage gated channels
- action potential, neurotransmitter
48
Taste Receptor: Sweet Substances:
- sweet substance enters the taste
bud pore and comes in contact
with the microvilli
- GPCR (Gs) activates adenylate
cyclase, and production of cAMP
- cAMP activates PKa, which closes
K+ channels causing
depolarisation
- influx of Ca2+ due to opening of
Ca2+ voltage gated channels
- action potential, neurotransmitter
release
49
Taste Receptors: Bitter Substances:
- bitter substance enters taste bud
pore and comes into contact with
the microvilli
- GPCR (Gq) activated, activated
phospholipase c (PLC) and
catalyses syntehsise of IP3
- IP3 causes the release of Ca2+
from intracellular storage
- depolarisation, neurotransmitter
release
50
What taste pathway is shown below?
salt
51
What taste pathway is shown below?
sour
52
What taste pathway is shown below?
sweet
53
What taste pathway is shown below?
bitter
54
The Gustatory Pathway:
- chordae tympani of facial nerve,
glossopharyngeal nerve and vagus
nerve project to the gustatory
cortex via the nucleus of solitary
tract and the thalamus
55
Why might chordae tympani become damaged during ear surgery?
Causes?
passes through the middle ear
dygeusia
56
Ageusia
loss of taste (rare)
57
Hypogeusia
partial loss of taste
58
Dysgeusia
sensation of unpleasant tastes
59
Gustatory Pathway:
insert diagram
60
Which of the following systems have similar receptors and pathways?
- auditory
- visual
- vestibular
- olfactory
- gustatory
The olfactory and gustatory sensory receptors are chemical receptors that follow a different pathway of activation compared to the mechanoreceptors of the auditory and vestibular systems.
