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Module 202 Neuroscience & behaviour > T2 L13 Physiology of balance, taste & stimuli > Flashcards

T2 L13 Physiology of balance, taste & stimuli Flashcards

1
Q

What is the endolymph in the scala media continuous with?

A

Apical surface of vestibular hair cells

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2
Q

Describe the 6 semi-circular canals

A

At right angles to one another to detect head rotation in all directions
Left & right lateral semi-circular canals are functionally pairs

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3
Q

Describe the 4 otolith organs

A

Aren’t at right angles to resolve head tilt & linear acceleration in all directions

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4
Q

What are the sensory cels in the ampullae of the semi-circular canals embedded in?

A

Cupula

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5
Q

What are the sensory cells in the otolith organs embedded in?

A

Gelatinous sheet covered with heavy crystals of calcium carbonate

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6
Q

What does Newton’s second law show?

A

Gravity & linear acceleration provide same stimulus to otolith organs

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7
Q

What is Newton’s second law?

A

F = m x a

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8
Q

Describe type II vestibular hair cells

A

Most common

Receive afferent & efferent innervation

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9
Q

Describe type I vestibular hair cells

A

Surrounded by afferent nerve calyx

Not direct contact with efferent nerve fibres

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10
Q

Which type of vestibular hair cell appears to be more sensitive?

A

Type II

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11
Q

What is nystagmus?

A

Slow eye movements followed by fast ones during a continuous head rotation

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12
Q

When does physiological nystagmus occur?

A

When rotating the head

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13
Q

What is spontaneous nystagmus?

A

Eyes move rhythmically side to side in absence of head movements

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14
Q

When does spontaneous nystagmus occur?

A

When one of the canals is damage
There is difference in the vestibular nerve firing rates when the head is stationary as the vestibular nerve innervating the intact canal is still firing

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15
Q

What is caloric testing used for?

A

Test brainstem function in unconscious patient

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16
Q

What happens during caloric testing if the brainstem is intact?

A

Both eyes move toward the side of the cold water

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17
Q

What happens during caloric testing if there is a lesion of the medial longitudinal fasciculus?

A

Movement of eye only on the irritated side

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18
Q

What is the diagnosis if neither eyes move during caloric testing?

A

Low brainstem lesion

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19
Q

Why does cold water irrigation cause eye movements?

A

Increases density of water in semi-circular canals –> convection currents in canal that mimic endolymph movement induced by turning head

20
Q

What is the result of warm water irrigation?

A

Endolymph rises

Increased firing

21
Q

What is the result of cold water irrigation?

A

Endolymph falls

Decreased firing

22
Q

What are some causes of vestibular disorders?

A 
Ear infection
Head injury
Whiplash
Ageing
Certain drugs
23
Q

What are some causes if the patient complains of dizziness?

A

Light headed - check cardiovascular

Vertigo - check vestibular

24
Q

What is benign paroxysmal positional vertigo?

A

Vertigo caused by changes in head position

25
Q

What is Meniere’s disease?

A

Progressive disease

Episodes of vertigo, tinnitus & progressive hearing loss

26
Q

Why is smell important?

A

Social interactions - perfumes, deodorants
Avoidance of poisons / noxious gases
Enjoyment of food

27
Q

How many odourant receptor proteins are there?

A

More than 1000

Each receptor cells expresses just 1 of these proteins

28
Q

What is olfactory information coded by?

A

Pattern of stimulation that the brain learns to interpret

Not coded by individual receptor types

29
Q

What does olfactory transduction depend on?

A

Second messenger process with cAMP being activated in response to an odourant molecule

30
Q

What happens after the opening of cAMP-dependent ligand gated ion channels?

A

Non-selective cation channels permeable to Na+ & Ca2+
Influx of Na+ & Ca2+ –> depolarisation of olfactory receptor cells which signals binding of odourant molecule –> action potentials
Ca2+ influx indirectly opens Cl- channels –> high intracellular Cl- concentration of olfactory receptors –> contributes to depolarisation

31
Q

What can cause issues with olfaction?

A 
Upper respiratory tract infection
High age
Nasal polyps
Diabetes mellitus
Head trauma
High dose radiation at nasal epithelium
Some drugs
32
Q

What is the function of taste?

A

Evaluate nutritious content of food & prevent ingestion of toxic substances

33
Q

What are the 5 different modalities of taste that can be distinguished?

A 
Salty
Sour
Sweet
Bitter
Umami
34
Q

What is the function of a sweet taste receptor?

A

Identify energy-rich nutrients

35
Q

What is the function of a umami receptor?

A

Recognition of amino acids

36
Q

What is the function of a salty receptor?

A

Ensures proper electrolyte balance

37
Q

What is the function of the sour & bitter receptors?

A

Warn against intake of potentially noxious and/or poisonous chemicals

38
Q

What is the mechanism for salt taste transduction?

A

Depends on equilibrium potential for Na+ across taste receptors

39
Q

What is the mechanism for sour taste transduction?

A

Depends on pH with H+ closing K+ channels either directly or indirectly via cAMP as a second messenger

40
Q

What is the mechanism for sweet taste transduction?

A

Via second messenger system which closes K+ channels –> depolarisation of taste receptors

41
Q

What is the mechanism for bitter & umami taste transduction?

A

Second-messenger induced increase in intracellular Ca2+ receptors –> neurotransmitter release

42
Q

What cranial nerves signal taste to the nucleus of solitary tract in the brainstem?

A

VII
IX
X

43
Q

Where do the fibres from 2nd order taste neurons project to in primates?

A

Ipsilaterally to ventral posterior nucleus of thalamus

44
Q

Where do thalamic efferents project to?

A

Insula, defining primary gustatory cortex which projects to orbitofrontal cortex

45
Q

Describe the parabrachial nuclei in pons in rodents

A

Dorsal thalamic projection & ventral projection that terminates in amygdala & hypothalamic nuclei

46
Q

What are the main causes of issues with olfaction?

A

Prior upper respiratory tract infection
Head injury
Poor oral hygiene

Module 202 Neuroscience & behaviour (39 decks)

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