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MBChB Glasgow Year 1 Phase 1 > PBL 10 > Flashcards

PBL 10 Flashcards

1
Q

What are the two systems that the ear can be split into functionally?

A

Auditory and vestibular

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2
Q

What is the auditory system responsible for?

A

hearing

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3
Q

When does the auditory system begin?

A

As soon as sound waves enter the ear

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4
Q

What does the auditory system consist of?

A

The external, middle and inner ear

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5
Q

What is the external ear made up of?

A

The auricle (pinna) and the external acoustic meatus (auditory canal)

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6
Q

What are the auricles/pinnae made of?

A

They are composed of and shaped by elastic cartilage that is covered with skin

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7
Q

What is the function of the auricles/pinnae?

A

To direct sound into the external acoustic meatus

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8
Q

What are the three parts of the auricles/pinnae?

A

The helix, tragus and lobule

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9
Q

What is the external acoustic meatus?

A

An S-shaped passage that begins as an opening in the auricle

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10
Q

Where does the external acoustic media travel?

A

about 4 cm through the tympanic portion of the temporal bone to terminate at the tympanic membrane

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11
Q

What is The external acoustic meatus lined with?

A

mucous membrane containing sebaceous glands and modified sweat glands known as ceruminous glands

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12
Q

How is earwax (cerumen) formed?

A

when the secretions of ceruminous and the sebaceous glands combine

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13
Q

What is the function of earwax?

A

prevents the entrance of foreign particles into the ear and reduces the risk of bacterial and fungal infection

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14
Q

Where does the external acoustic meatus direct the sound waves to?

A

The tympanic membrane

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15
Q

what is contained in the middle ear?

A

The structures that amplify sound. these include the ossicles and auditory muscles

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16
Q

What is the tympanic membrane?

A

A thin, semi-transparent concave sheet.

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17
Q

What is the function of the tympanic membrane?

A
  • separates the external and middle ear

- transmits vibrations from sound to the ossicles (malleus)

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18
Q

What is the tympanic cavity?

A

The cavity of the middle ear that contains the three ossicles

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19
Q

What is the tympanic cavity connected to?

A

The nasopharynx by the eustachian tube

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20
Q

What is the tensor tympani

A

a small muscle in the middle ear

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21
Q

Where is the tensor tympani?

A

it originates from the eustachian tube and sphenoid bone and inserts into the malleus

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22
Q

What is the function of the tensor tympani muscle?

A

To tense the tympanic membrane in response to abrupt noise and in anticipation to loud vocalization

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23
Q

What is the stapedius?

A

A small muscle in the middle ear

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24
Q

Where is the stapedius?

A

Attached to the temporal bone and the neck of the neck of the stapes

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25
Q

What is the function of the stapedius?

A

To dampen the vibrations of the ossicles by contracting in response to high intensity sound

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26
Q

What are the ossicles?

A

Three tiny bones found in the middle ear

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27
Q

What are the three ossicles?

A

The malleus, the incus and the stapes

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28
Q

What is the function of the ossicles?

A

They transmit and magnify sound from the tympanic membrane and across the tympanic cavity

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29
Q

What is the malleus?

A

largest and most lateral of the ossicles, It is attached to the tympanic membrane and articulates with the incus

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30
Q

What is the incus?

A

the middle ossicle and is located in the epitympanic recess of the tympanic cavity (middle ear) and it articulates with the stapes

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31
Q

What is the stapes?

A

the smallest and most medial ossicle of the middle ear. it articulates with the oval window of the inner ear

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32
Q

What is the function of the Eustachian tube?

A
  • Connects the middle ear to the nasopharynx

- Allows the pressure within the cavity to remain equal to local barometric pressure

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33
Q

What is the oval window?

A

an opening between the middle and inner ear that articulates with the footplate of the stapes

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34
Q

What is the function of the oval window?

A

Allows the footplate of the stapes to transmit the sound vibrations from the middle ear to the inner ear

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35
Q

What is contained in the inner ear?

A

The sensory structures for both hearing and balance

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36
Q

What does the inner ear consist of?

A

A network of bony canals contained deep within the temporal bone

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37
Q

What are the parts of the bony labyrinth?

A

The cochlea and the semi-circular canals

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38
Q

How are the cochlea and semi-circular canals connected?

A

A centrally placed vestibule

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39
Q

What is the bony labyrinth?

A

a tube of bone that coils around a central pillar called the modiolus. It resembles a snail shell. Between the bony labyrinth and membranous labyrinth, sit two fluid-filled spaces: the scala vestibuli and scala tympani

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40
Q

What is the scala vestibuli?

A

A fluid filled space that passes the entire length of the cochlea.

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41
Q

What is the scala tympani?

A

A fluid filled space that passes through the entire length of the cochlea.

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42
Q

What is the fluid in the scala vestibuli and the scala tympani known as?

A

perilymph

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43
Q

What is perilymph maintained by?

A

The secretory epithelial cells that line the canals

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44
Q

What does the scala vestibuli connect to?

A

The oval window sits at the base of the canal, where it connects to the tympanic cavity.

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45
Q

What is the scala tympani connected to?

A

At its base sits the round window, which connects it to the tympanic cavity, and at its apex the helicotrema joins it to the scala vestibuli

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46
Q

What is the membranous labyrinth?

A

A coiled tube that contains the cochlear duct

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47
Q

What is the cochlear duct (scala media)?

A

The middle triangular canal that contains the organ of corti

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48
Q

What forms the roof and floor of the cochlear duct?

A

Roof - vestibular membrane

Floor - basilar membrane

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49
Q

What fluid does the cochlear duct contain?

A

Endolymph

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50
Q

What is the vestibule?

A

The central part of the bony labyrinth

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51
Q

What does the vestibule do?

A

connects the inner ear with the middle ear and has a supportive role

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52
Q

what does the vestibular membrane do?

A

Separates the cochlear duct from the scala vestibuli

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53
Q

What is the vestibular membrane?

A

a thin transparent membrane that stretches obliquely from the inner membrane of the modiolus

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54
Q

How does the vestibular membrane contribute to hearing?

A

When vibrations of the tympanic membrane are felt in response to sound waves, the pressure waves created are transmitted through the vestibular membrane to the basilar membrane

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55
Q

what does the basilar membrane do?

A

Supports the organ of corti and separates the cochlear duct (scala media) from the scala tympani

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56
Q

What is the structure of the basilar membrane like?

A

It is not uniform in width or thickness, as it is wider, thinner, and more pliant at the apex than at the base

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57
Q

What is the spiral ganglion?

A

The group of nerve cells that serve the sense of hearing by sending a representation of sound from the cochlea to the brain

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58
Q

Where is the spiral ganglion found?

A

The modiolus. Fewer ganglion cells are found in the middle turn compared with the apical and basal turns

59
Q

What is found within the spiral ganglion?

A

the cell bodies of the cochlear branch of the vestibulocochlear nerve (VIII)

60
Q

What is the cochlear nerve?

A

A branch of the vestibulocochlear nerve (VIII)

61
Q

Where do the nerve fibres of the cochlear nerve pass?

A

from the hair cells of the organ of Corti and through the modiolus as the spiral ganglia, before continuing onto the internal auditory meatus

62
Q

What is the function of the hair cells on the organ of corti?

A

They act as sensor transducers

63
Q

Where are the hair cells of the organ of corti found?

A

They rest on the basilar membrane with their stereocilia (hairs) embedded in the underside of the tectorial membrane.

64
Q

What types of hair cell are there?

A

There are three or four rows of outer hair cells but only a single row of inner hair cells

65
Q

What are stereocilia?

A

Membrane bound cellular projections of inner and outer hair cells

66
Q

What is the role of the stereocilia?

A

they create a streaming movement in the surrounding fluid

67
Q

where are the stereocilia found?

A

protrude from hair cells through the reticular membrane and point towards the tectorial membrane that lies above

68
Q

How do the stereocilia contribute to hearing?

A

The bending movement causes them to depolarize and send information to the rest of the hair cell, turning the mechanical energy of a sound wave into a neural signal

69
Q

What is the tectorial membrane?

A

a semi-transparent, fibro gelatinous structure that overlies the hair cells of the organ of Corti

70
Q

What is the function of the tectorial membrane?

A

it withstands the mechanical stresses associated with cochlear fluid vibrations

71
Q

What are the supporting cells of the organ of corti?

A

a series of specialized epithelial cells that provide mechanical support to the sensory cells that they surround.

72
Q

what are sound waves?

A

oscillations of pressure in a medium, such as air or liquid

73
Q

Where do external sound waves travel?

A

Through the external and middle ear to the auditory receptors in the cochlea

74
Q

What is the pathway of sound in the external ear?

A

sound waves are directed by the auricle through the external acoustic meatus, to the tympanic membrane

75
Q

What do the sound waves do to the tympanic membrane?

A

They cause it to vibrate

76
Q

What does the tympanic membrane articulate with?

A

The ossicles

77
Q

What happens when the tympanic membrane vibrates?

A

The ossicles transmit these vibrations to the cochlea

78
Q

Where do the vibrations travel in the perilymph?

A

up the scala vestibuli and down the scala tympani

79
Q

What happens when the vibrations arrive back at the round window?

A

it bulges out into the middle ear

80
Q

Where is the cochlear duct?

A

Between the scala vestibuli and scala tympani

81
Q

What are the two branches of the vestibulocochlear nerve?

A

The vestibular and cochlear

82
Q

What parts of the ear are involved in balance?

A

The vestibule and semi-circular canals

83
Q

What does the vestibule contain that helps with balance?

A

Mechanoreceptors called maculae that detect static equilibrium

84
Q

What is static equilibrium?

A

The movements of the body relative to the forces of gravity

85
Q

What do the semi-circular canals contain that helps with balance?

A

mechanoreceptors called crista ampullaris that detect dynamic equilibrium

86
Q

What is dynamic equilibrium?

A

The angular movements of the body

87
Q

What is Acute otitis media?

A

A painful infection of the Middle ear

88
Q

What happens in Acute otitis media?

A

The middle ear becomes inflamed and infected

89
Q

What can cause Acute otitis media?

A

a primary or secondary bacterial infection or a virus

90
Q

What is a secondary bacterial infection?

A

Occurs after or because of a primary infection

91
Q

What happens if the swelling in the ear is too great?

A

the blood vessels in the ear drum are compressed, local tissue necrosis and the ear drum bursts, letting out pus and relieving the pain

92
Q

What is the standard treatment of Acute otitis media?

A

The prescription of an antibiotic even though 80%of all acute otitis media resolve spontaneously without treatment

93
Q

What happens if the inflammatory exudate causes the tympanic membrane to rupture?

A

The inflammatory exudate may spread to the mastoid air cells, causing acute mastoiditis

94
Q

What is serous otitis media?

A

When fluid accumulates in the middle ear as a consequence of eustachian tube obstruction

95
Q

What is another cause of serous otitis media?

A

It can also occur following otitis media, when the fluid in the ear, formed by the infection, does not drain spontaneously

96
Q

What does serous mean?

A

of, resembling, or producing serum

97
Q

What are the possible complications of serous otitis media?

A

risk for further infection and worsens hearing by about 30 dB

98
Q

How can serous otitis media be resolved?

A

by removing the obstruction e.g. in patients with tonsillar hyperplasia

99
Q

What is chronic otitis media?

A

persistent or repeated acute bacterial infections

100
Q

Why is there hearing loss if the tympanic membrane is perforated?

A

there is not enough area of the tympanic membrane to catch sound

101
Q

What are 4 common complications of chronic otitis media?

A
  • Tympanic perforation and discharge
  • Aural polyps: granulation tissue in the middle ear
  • Disarticulation and resorption of ossicles, with conductive hearing loss
  • Cholesteatoma
102
Q

What is Cholesteatoma?

A

accumulation of keratin derived from squamous epithelium spreading in from the external auditory canal following tympanic perforation

103
Q

What is labyrinthitis?

A

An infection of the inner ear/labyrinth

104
Q

What is the usual cause of labyrinthitis?

A

Virus

105
Q

Why are children more likely to get ear infections than adults?

A
  • their eustachian tubes are smaller and more level
  • Childrens immune systems aren’t as well developed as adults
  • Sometimes bacteria get trapped in the adenoids causing chronic infection that can pass to the ear
106
Q

What does the structure of children’s eustachian tube have to do with the increased likelihood of them getting an ear infection?

A

smaller and more level, which makes it difficult for fluid to drain out of the ear.

107
Q

What is thermoregulation?

A

a process that allows your body to maintain its core internal temperature

108
Q

What is the aim of all thermoregulation mechanisms?

A

to return your body to homeostasis

109
Q

How can muscles increase metabolic heat production?

A

They contract e.g. shivering

110
Q

What is non-shivering thermogenesis?

A

The breakdown of brown fat / brown adipose tissue

111
Q

Who has the most brown fat?

A

Babies - its prevalence decreases as humans age but there is still a small amount in adults

112
Q

What is vasoconstriction?

A

Shrinking the diameter of blood vessels that supply the skin

113
Q

What is vasodilation?

A

blood vessels get wider, or dilate, increasing blood flow to the skin

114
Q

What is counter-current heat exchange?

A

a circulatory adaptation that allows heat to be transferred from blood vessels containing warmer blood to those containing cooler blood

115
Q

How does counter-current heat exchange work?

A

As warm blood passes down the arteries, the blood gives up some of its heat to the colder blood returning from the extremities in these veins.

116
Q

What are the four ways heat can be lost?

A

convection, conduction, radiation, and evaporation

117
Q

What happens in hot conditions?

A
  • Eccrine sweat glands under the skin secrete sweat
  • The hair on the skin lie flat, preventing heat from being trapped by the layer of still air between the hair
  • Arteriolar vasodilation, redirecting blood into the superficial capillaries in the skin increasing heat loss by convection and conduction
118
Q

What happens in cold conditions?

A
  • Sweat production is decreased
  • hair erector muscles contract causing a layer of air to be trapped, insulating the skin
  • arteriolar vasoconstriction
  • shivering and muscle contraction to generate heat
  • non-shivering heat production through brown adipose tissue
119
Q

What is thermogenin?

A

The uncoupling protein used to generate heat by non-shivering thermogenesis

120
Q

Where is thermogenin found?

A

The mitochondria of brown adipose tissue

121
Q

What is a fever?

A

having a temperature above the normal range

122
Q

What are pyrogens?

A

Chemicals in the bloodstream that cause fevers

123
Q

What are fevers caused by?

A

Pyrogens

124
Q

What are the two types of pyrogens?

A

Endogenous and exogenous

125
Q

What is an endogenous pyrogen?

A

Internal

126
Q

What is an exogenous pyrogen?

A

external

127
Q

What is a common example of a pyrogen?

A

Interleukin-1 (IL-1)

128
Q

What are most endogenous pyrogens?

A

Cytokines

129
Q

How is IL-1 produced?

A

By macrophages when they come into contact with certain bacteria and viruses

130
Q

What do pyrogens cause the release of?

A

Prostaglandin E2 (PGE2)

131
Q

What does PGE2 do?

A

acts on the hypothalamus, which creates a systemic response in the body causing heat-generation effects to match a new higher temperature set point.

132
Q

What is the ultimate mediator of the fever?

A

PGE2. The set point temperature of the body will remain elevated until PGE2 is no longer present.

133
Q

What does the hypothalamus act as?

A

A thermostat

134
Q

What causes the hypothalamus to change set point?

A

Prostaglandins

135
Q

What is thought to be the purpose of a fever?

A

to raise the body’s temperature enough to kill off certain bacteria and viruses sensitive to temperature changes

136
Q

What does the increase in set point trigger?

A

increased muscle contractions and a feeling of cold

137
Q

Why does paracetamol not work as an anti-inflammatory?

A

It does not appear to inhibit the function of any cyclooxygenase (COX) enzyme which is what NSAIDs such as aspirin do

138
Q

How does paracetamol work?

A

It appears to inhibit COX in the brain selectively

139
Q

How does paracetamol inhibit COX?

A

This does not appear to be by direct inhibition (by blocking an active site), but by reducing COX which must be oxidised in order to function.

140
Q

How is paracetamol thought to relieve pain?

A

by reducing the production of prostaglandins in the brain and spinal cord, increasing our pain threshold

141
Q

When are prostaglandins produced?

A

by the body in response to injury and certain diseases

142
Q

What is one of prostaglandins actions?

A

to sensitise nerve endings, so that when the injury is stimulated it causes pain

143
Q

How does paracetamol work on a fever?

A

It acts as an antipyretic and reduces fever by promoting heat loss and thus helps reset the hypothalamic thermostat

MBChB Glasgow Year 1 Phase 1 (10 decks)

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