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Flashcards in Physiology Deck (67):
1

What type of receptors are used for taste and smell?

Chemoreceptors.

stimulated by binding to particular chemicals

2

Stimulation of taste and smell receptors induces a...or... sensation

Pleasurable or objectionable

3

What does taste and smell influence further down in the digestive tract?

Flow of digestive juices

4

Gustation

physiology of taste

5

Where are sensory taste receptor cells mainly found?

TASTE BUDS

6

What type of cells do Taste buds consist of?

How are they arranged?

> Sensory receptor cells
> Support cells

> Like slices of an orange

7

Life span of taste receptor cells?

Where are they replaced from?

10 days

They are continuously replaced from BASAL CELLS within the taste buds

8

Taste receptor cells synapse with

Afferent nerve fibres within the taste buds

9

Where are majority of taste buds found?

PAPILLAE in the tongue

10

What are the papillae of the tongue

Finger-like structures

Give rough appearance of the dorsum of tongue.

Little red dots/raised bumps.

11

How many types of papillae?

What are the types?

4 types

Filiform: most numerous – do not contain taste buds

Fungiform

Vallate

Foliate

12

Which papillae do not contain taste buds?

Filiform

13

Gustation - mechanism of action

> Binding of taste provoking chemical (tastant) to receptor cells alters cell ionic channels and produces depolarising receptor potential

> Receptor potential initiates action potentials in afferent nerve fibres which synapse with receptor cells

> Signals conveyed by cranial nerves via brainstem and thalamus to cortical gustatory areas

> Afferent taste fibres reach the brainstem via:

VIIth cranial nerve (chorda tympani branch of facial nerve) - anterior two-thirds of the tongue

IXth cranial (glossopharyngeal) nerve - posterior third of the tongue

Xth caranial (vagus) nerve - areas other than tongue, including e.g. epiglottis and pharynx

14

Which cranial nerve supplies the anterior 2/3 of the tongue?

CN VII

Chorda tympani branch of facial nerve

15

Which cranial nerve supplies posterior 1/3 of tongue

CN IX (glossopharyngeal)

16

5 primary tastes.

What is each stimulated by?

SALTY: stimulated by chemical salts especially sodium chloride (NaCl)

SOUR: stimulated by acids which contain free hydrogen ions (H+)

SWEET: stimulated by configuration of glucose

BITTER: stimulated by diverse group of tastants, including e.g. alkaloids, poisonous substances and toxic plant derivatives

UMAMI (meaty or savoury): triggered by amino acids especially glutamate

17

Ageusia

What is it
Causes

Loss of taste function

e.g. of causes:
> nerve damage
> local inflammation (glossitis, radiation, tobacco)
> some endocrine disorders

18

Hypogeusia

Reduced taste function.

e.g. of causes:
> chemo
> medications

19

Dysgeusia

Distortion of taste function

Often related to a metallic taste in the mouth

e.g. of causes

glossitis; gum infections; tooth decay; reflux; upper respiratory infections; medications; neoplasms; chemotherapy; zinc deficiency

20

Where is olfactory mucosa found?

Three cell types

Patch of mucosa found in the CEILING (dorsal roof) of nasal cavity

Cell types:

1. Olfactory receptor cells
2. Supporting cells
3. Basal cells (secrete mucous)

21

Olfactory receptors

Specialised endings of renewable afferent neurons.

Each neurone has a thick, short DENDRITE and expanded end called an OLFACTORY ROD

From olfactory rods, CILIA project to surface of olfactory mucosa

Odorants bind to the cilia

22

Lifespan of olfactory receptors

2 months.

23

Which cells act as precursors for new olfactory receptor cells

Basal cells.

24

Axons of olfactory receptors collectively form?

Which structure do they then pierce?

Afferent fibres of olfactory nerve

Pierce the cribriform plate of ethmoid bone and enter the olfactory bulbs in the inferior surface of the brain.

25

Olfactory bulbs transmit...

Smell information to the brain

26

Where do neurons pass from the olfactory bulb?

Pass along OLFACTORY TRACT to reach temporal lobe and olfactory areas

27

How to odourants reach smell receptors during quiet breathing?

Why

By diffusion

Olfactory mucosa is above normal path of airflow

28

Sniffing

Enhances smelling by drawing air currents upwards within the nasal cavity

29

To be smelled, a substance must be:

(1) sufficiently volatile i.e. some of its molecules can enter the nose with inspired air

(2) sufficiently water soluble i.e. can dissolve in the mucus coating of olfactory mucosa

30

Anosmia

Inability to smell

Temporary or permanent

Causes
- viral infections
- allergy
- nasal polyps
- head injury

31

Hyposmia

which disease may it be an early sign of?

Reduced ability to smell.

Causes
- similar to those for anosmia

Parkinson's

32

Dysosmia

Altered sense of smell.

Differently interpreting some odours;

hallucinations of smell avoid

33

Range of human hearing in Hz?

20Hz - 20,000Hz

34

External ear/pinna acts as a...

Receiver.

35

Middle ear acts as an

Amplifier mechanism

36

Middle ear contains which bones

Malleus
Incus
Stapes

The ossicular chain

Acts as a piston with varying efficiency depending on frequency of sound transmitted.

37

Which part of the stapes is in the oval window?

Stapes FOOT PLATE

38

Which part of malleus interacts with the tympanic membrane

Handle of the malleus

Head of malleus interacts with the incus

39

Eustachian tube

Ventilation pathway for middle ear mucosa

Bony & cartilaginous portions

Resting state of cartilaginous tube is CLOSED but opened by tensor veli palatini & levator palatine muscles

‘equalise ears’

Dysfunction leads to middle ear negative pressure

40

Resting state of eustachian tube?

Closed

41

Which muscles open the eustachian tube?

Tensor veli palatini

Levator palatine muscles

42

Oval Window & Round window

Two openings of the cochlea to the middle ear.

Oval window superiorly
Round window inferiorly

In-phase movements of windows

Permit transmission of pressure wave in enclosed canal and vibration of the basilar membrane

Stapes foot plate transmits force onto oval window, and the round window moves to allow movement of the fluid inside the cochlea. If this did not occur, the fluid would be in-compressible.

43

How many times is the cochlea "rolled up"?

2 and a half times around central modiolus

44

Where do low frequency sounds localise in the cochlea?

Apex

45

Where do high frequency sounds localise in the cochlea?

Base (near oval/round window)

46

The scala media is filled with?

Endolymph

Suspended between scala tympani and scala vestibuli (perilymph)

47

What is suspended between the scala tympani and scala vestibuli?

Scala media

48

What is contained within the scala tympani and scala vestibuli

Perilymph

49

Organ of Corti

the sensory epithelium, a cellular layer on the basilar membrane, in which sensory hair cells are powered by the potential difference between the perilymph and the endolymph

50

Hair cell function

Transduction: conversion of mechanical ‘bending force’ into electrical impulse

Stereocilia arranged in height order with tip links connecting them together.

Depolarisation occurs when deflected towards longest,

Hyperpolarisation occurs when deflected away.

51

When does Depolarisation occur in hair cells?

When hair cells are deflected towards the longest hair cells

52

When does hyper polarisation occur in hair cells?

When hair cells are deflected AWAY from the longest hair cells

53

Where is the primary auditory cortex

Left posterior superior temporal gyrus

54

ECOLI-MA mnemonic

??

55

Balance systems (6)

Visual
Proprioceptive
Vestibulospinal tract
Vestibular
Cardiovascular
Vestibule-Ocular reflex

56

What is Oscillopsia

Oscillopsia occurs when we have no vestibular input – eye movement with the head instead of fixing on an object.

57

What are the vestibular end organs (5)

Maculae of the utricle and saccule - OTOLITH ORGANS

Ampullae of lateral, posterior and superior semicircular canals

58

What are the Otolith organ.

What are the maculae of these organs

Utricle and saccule

Maculae (concentrations of hair cells) have sterocilia projecting upwards into a gelatinous matrix with otoconia.

These lend weight and brain perceives movement when tilting head (gravity) or linear motion.

Stereocilia orientated in all directions so all movements perceived by depolarisation/hyperpolasrisaion

Firing stops with linear motion so you know movement has stopped

BUT it continues its head tilt

59

Otoconia

Calcium carbonate crystals

Embedded in gel membrane

60

When does firing continue in otolith organs?

Head tilting

(stops with linear motion)

61

How are otolith organs orientated?

360 orientation

All planes of motion are detected.

62

How are semi-circular canals arranged

Oriented at 90° to each other

Paired, equal and opposite

63

Where does the cupola of the a semi-circular canal sit?

Cupula

64

Deflection of the cupula is caused by

Deflection by perilymph

Bending causes stereo cilia to deflect

65

Vestibule-Ocular Reflex (VOR)

Move head to the right

Semicircular canal in that plane on the right hand side will be excited, and the left hand side will be inhibited.

Eyes move to the left (to stay fixed on an object)

Static head - left and right are equally excited

Turning left - left hand side is excited more

66

Spontaneous nystagmus

Flicking of eye in direction they are trying to fix

67

Central pathways - series of communications in vestibular nuclei with outputs to...

> Vestibulospinal tract - motor output to neck, back and leg muscles

> Medial longitudinal fascicles and ocular muscles - motor output to eyes

> Medial lemniscus and thalamus to cerebrum