Case 16 questions 1-15

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Question 1

Select the correct statement regarding the auditory pathway.

  1. The vestibular nerve supplies the organ of Corti in the inner ear.
  2. Most fibres decussate at the superior olivary complex and predominantly ascend in the contralateral lateral lemniscus.
  3. The primary auditory cortex is situated in the inferior temporal gyrus.
  4. From the inferior colliculus in the midbrain, the fibres project to the ipsilateral lateral geniculate body in the thalamus.
  5. Expressive dysphasia results from damage to Wernicke’s area.

The correct answer is option b.

The vestibular nerve supplies the utricle, saccule, and semi-circular ducts as part of the vestibular system. Most fibres decussate at the superior olivary complex but remember that some fibres ascend ipsilaterally (on the same side). The primary auditory cortex is situated in the superior temporal gyrus. From the inferior colliculus in the midbrain, the fibres project to the ipsilateral medial geniculate body in the thalamus.

A good way to remember this is music goes to medial, and light goes to lateral. Expressive dysphasia (speech production) results from damage to Broca’s area, whilst receptive dysphasia (speech comprehension) is due to damage to Wernicke’s area.

Question 2

Which of the following statements is true regarding the tympanic membrane?

  1. The deepest part of the tympanic membrane is called the umbo.
  2. The cone of light is at the 5 o’clock position in the left ear.
  3. The cone of light is at the 7 o’clock position in the right ear.
  4. A normal tympanic membrane is pearly grey and translucent with retraction.
  5. Only the pars tensa and cone of light is seen during otoscopy.

The correct answer is option a (The deepest part of the tympanic membrane is called the umbo)

The tympanic membrane is a flattened cone pointing towards the middle and inner ear, and is therefore concave. The deepest part of this concavity is the umbo which is located centrally. The cone of light is at 5 o’clock in the right ear and 7 o’clock in the left ear.

A normal tympanic membrane is shiny, pearly grey and translucent in colour but there is no retraction or bulging or tears in the membrane. During otoscopy, the pars tensa, pars flaccida, lateral process of malleolus, the umbo and the cone of light can be visualised.

Question 3

Which part of the ear transmits sound vibrations directly to the oval window?

  1. Pinna
  2. Incus
  3. Tympanic membrane
  4. Stapes
  5. Cochlea

The correct answer is option d, stapes

The middle ear transmits vibrations from the tympanic membrane to the inner ear via the oval window. The ossicles in the middle ear are the malleus, incus, and stapes. The stapes attaches to the oval window and so transmits vibrations to it.

Question 4

Select the correct statement regarding the mechanism of encoding sound frequency.

  1. The loudness of sound correlates with a pressure wave’s frequency.
  2. The mechanoelectrical transduction channels associated with the tip links on stereocilia are opened when the stereocilia are displaced towards the smallest rank.
  3. The apex of the basilar membrane in the cochlea is tuned to high frequency sounds.
  4. Nerve fibres arising from the base of the cochlea carrying high frequency sounds penetrate the posterior cochlear nucleus.
  5. Outer hair cells are the primary sound transducers.

The correct answer is option d

The loudness of sound correlates with a pressure wave’s amplitude. The MET channels open when the stereocilia are displaced towards the tallest rank. The apex of the basilar membrane is tuned to low-frequency sounds, whereas the base is tuned to high-frequency sounds.

Low frequency sounds correspond to the anterior cochlear nucleus, whilst high frequency sounds correspond to the posterior cochlear nucleus. Here is an image below to help visualise this. Inner hair cells are the primary sound transducers, outer hair cells are involved in amplifying and finetuning the auditory signals.

Question 5

The attenuation reflex is triggered by loud sounds and when we talk, which cause the muscles of the middle ear to contract and stiffen the ossicular chain, attenuating the transmission of sound.

Which of the following statements regarding the muscles in the middle ear is true?

  1. The stapedius muscle anchors the malleus to the wall of the middle ear.
  2. The stapedius is innervated by the trigeminal nerve.
  3. The tensor tympani is innervated by the mandibular nerve.
  4. The tensor tympani is innervated by the facial nerve.
  5. Of the muscles in the middle ear, only the tensor tympani is involved in the attenuation reflex.

The correct answer is option c, ‘The tensor tympani is innervated by the mandibular nerve’.

The tensor tympani is innervated by the mandibular nerve (V3) which is a branch of the trigeminal nerve (CN V). The stapedius muscle is innervated by the facial nerve (CN VII). The tensor tympani anchors the malleus to the wall of the middle ear, whereas the stapedius muscle attaches to the stapes. Both muscles are involved in the attenuation reflex.

Question 6

Which of the following ions is found in high concentrations in the endolymph?

  1. Na+
  2. Ca2+
  3. K+
  4. Cl-
  5. PO43-

The correct answer is option c,K+

The endolymph is a K+-rich fluid produced by the stria vascularis.

Question 7

Which of the following structures is not found in the vestibular system?

  1. Kinocilia
  2. Utricle
  3. Macula
  4. Striola
  5. Tectorial membrane

The correct answer is option e, Tectorial membrane

The gelatinous tectorial membrane is part of the organ of Corti, which is the organ of hearing, and therefore part of the auditory system, not the vestibular system. The tectorial membrane covers the tips of the outer hair cells’ stereocilia as they protrude through the reticular lamina into the endolymph.

Question 8

Which of the following is most sensitive to angular acceleration?

  1. Macula
  2. Utricle
  3. Saccule
  4. Organ of Corti
  5. Crista

The correct answer is option e, Crista

The utricle and saccule are most sensitive to gravity, for example changes in head position from an upright position (utricle) and changes from a lying down position (saccule). The organ of Corti senses sound. The macula are more sensitive to linear acceleration.

Question 9

Which of the following is true about the structure of the herpes virus?

  1. A single type of capsomer stacked around a central axis gives the herpes virus its helical morphology.
  2. The herpes virus consists of single-stranded DNA surrounded by the capsid.
  3. The herpes virus consists of single-stranded RNA surrounded by the capsid.
  4. The protein cage surrounding the herpes virus is called the envelope.
  5. The herpes virus has an outer lipid bilayer derived from the host cell membrane.

The correct answer is option e, The herpes virus has an outer lipid bilayer derived from the host cell membrane.

The herpes virus consists of double-stranded DNA surrounded by the protein cage (capsid) which is surrounded by an outer lipid bilayer derived from the host cell membrane (envelope). The capsid is icosahedral in shape.

Question 10

What types of vaccines will induce a CD8 T cell response?

  1. Killed bacterial vaccine
  2. Peptide or polysaccharide vaccine
  3. Toxoid vaccine
  4. Live attenuated vaccine
  5. Killed viral vaccine

The correct answer is option d, live attenuated vaccine

Only live vaccines have a strong enough T cell response resulting in longer term protection
Options 1-3 and 5 are all inactivated vaccines which do not induce a CD8 response.

Question 11

How does the secondary response to an antigen differ from the primary (first response)?

  1. Mainly IgG from long lived plasma cells, stronger and faster response
  2. Mainly IgG from long lived plasma cells, weaker and slow response
  3. Mainly IgM from short lived plasma cells, weaker and slow response
  4. Mainly IgM from short lived plasma cells, stronger and faster response
  5. Mainly IgM from long lived plasma cells, weaker and slow response

The correct answer is option a, Mainly IgG from long lived plasma cells, stronger and faster response

IgG is released from long lived plasma cells. The secondary response is associated with higher levels of IgG and lower levels of IgM which is released from short lived plasma cells. There is a stronger secondary response with a higher production of total antibodies produced

Question 12

Which of these characteristics is true regarding inactivated vaccines?

  1. They offer long term protection
  2. They are more likely than live vaccines to cause mild symptoms of the disease
  3. They produce a better T cell response
  4. They ussally offer short term protection
  5. They are made from an attenuated virus

The correct answer is option d,They ussally offer short term protection

The other characteristics are true of live vaccines

Question 13

Which one of these answers is not a stage in the viral life cycle?

  1. Attachment
  2. Assembly
  3. Release
  4. Degradation
  5. Replication and protein synthesis

The correct answer is option d, Degradation

The life cycle of a virus consists of:Attachment -> Entry -> Replication and protein synthesis -> Assembly -> Release

Question 14

A virus spread ‘from one person to another person in the same generation’ best describes

  1. Vertical transmission
  2. Horizontal transmission
  3. Zoonoses
  4. Diagonal transmission
  5. Backwards transmission

The correct answer is option b, Horizontal transmission

Horizontal transmission is the transmission of organisms (e.g. viruses) between those who do not have a mother-ofspring relationship e.g. Fecal oral, contaminated blood products
Vertical transmission is between a mother and fetus/ baby
Zoonoses are viruses spread from a non-human animal to a human
Diagonal and backwards transmission are not methods of viral transmission

Question 15

Which one of these viruses is spread via faecal oral transmission?

  1. Hepatitis A
  2. Chickenpox (varicella zoster)
  3. Smallpox (variola virus)
  4. Rhinovirus
  5. Influenza

The correct answer is option a, Hepatitis A

Hepatitis A typically causes an acute hepatitis and is endemic in many reigons arround the world. Prevention is through good sanitaitation.
Chickenpox (varicella zoster), Smallpox (variola virus),Rhinovirus and Influenza are all spread via the respiratory system (via respiratory droplets).

Credits

  • 1-10 (Jenita James, 3rd year),
  • 11-15 ( Hannah Elkatkat, 4th year)