Week 3

Question 1

Which system in the head detect rotational and linear acceleration?

Answer 1

Rotational = Semi-circular canals

Linear = Utricle and saccule

Question 2

What structures in the semi-circular canal are responsible for detecting rotational acceleration?

Answer 2

Hair cells called crista which project cilia into the gelatinous matrix of the cupula.
During rotation the matrix of the cupula pulls the cilia of the crista

Question 3

Describe the pathway of nerve impulses from the semi-circular canals to the brain

Answer 3

From hair cells through the vestibular part of CN VIII, synapse with the vestibular nuclei in the pons

Question 4

How does the structure of the utricle and saccule detect linear acceleration?

Answer 4

Hair cells project cilia into a gel matrix. On top of the matrix sit otoliths, which are heavy. When gravity acts on the otoliths it pulls the gelatinous matrix and therefore the cilia too.

Question 5

What is the role of the vestibule ocular reflex?

Answer 5

maintains visual fixation to sudden input from the vestibular system (not the same as fix and follow reflex)

Question 6

Define vertigo

Answer 6

Sensation of movement in absence of external stimuli

Question 7

How is the Romberg test performed?

Answer 7

• Have patient stand with feet together and arms by their side
• Ask them to close their eyes for 1 minute
• If they fall then the test is positive

(can make the test harder by having them cross their arms and legs)

Question 8

Define pathological nystagmus and its potential causes

Answer 8

Definition = Eyes repeatedly flick in one direction

can be caused by central (brain) or peripheral (vestibule) problem

Question 9

Name the bones of the middle ear in order

Answer 9

• Malleus
• Incus
• Stapes

Question 10

What are the roles of the ear canal?

Answer 10

contributes to shaping and amplification of sound

Protection of tympanic membrane from microbes and insects

Question 11

Name the air filled space that connects the nasopharynx and middle ear

Answer 11

The Eustachian tube

Question 12

Name these structures of the cochlea

Answer 12

Question 13

The organ of corti has different types of hair cells.

What are they, how many per row, and what are their functions?

Answer 13

Inner hair cell (1x row)
- detect sound by depolarising when stereocilia are deflected

Outer hair cells (3x Row)
- Discriminate between frequencies and amplify sound by altering the amount of vibration on the basilar membrane

Question 14

Describe the pathway from the cochlea to the brain

Answer 14

Hair cells => first order neurons => spiral ganglia => cochlear nerve => CN III
=> through the internal acoustic meatus => synapse with cochlear nuclei

Question 15

What are the 2 types of hearing loss?

Answer 15

Conductive hearing loss
- mechanical problem of outer/middle ear

Sensorineural hearing loss
- Cochlear/nerve damage

Question 16

How is a pure tone audiogram performed?

Answer 16

Sounds of various tones are played and patient pushes a button if they can hear the sound. done with both headphones and bone conductors.

Question 17

How are results form pure tone audiogram interpreted?

Answer 17

Abnormal of headphones, but normal for bone conduction = conductive hearing loss

Abnormal for both headphones and bone conduction = sensorineural hearing loss

Question 18

What are the two types of intracranial haematomas you might see with head injuries, and how would you recognise them from a CT?

Answer 18

Extradural/epidural
- bleed between the skull and dura mater
- lens shaped as blood is contained between skull sutures

Subdural
- Between dura and arachnoid
- lens shaped as not contained within sutures

Question 19

Describe the Monroe-kellie principle

Answer 19

The volume of the intercranial space must remain constant. therefore if a mass/lesion takes up volume blood and CSF is lost to compensate. Only 120ml can be lost before intracranial pressure rises

Question 20

What is cerebral perfusion pressure?

Answer 20

It is a measurement of blood flow in the brain

Question 21

How can Cerebral perfusion pressure (CCP) be calculated?

Answer 21

CPP = MAP x ICP

MAP = Mean arterial pressure

ICP = Intercranial pressure

Question 22

What are the signs of increasing intercranial pressure?

Answer 22

Decreasing Glasgow comma scale

Diminished pupillary light response

Lateralising signs

Question 23

What is measured in the Glasgow comma scale and what are the potential scores?

Answer 23

GCS (3-15)
- Eye opening (1-4)
- Verbal response (1-5)
- Motor response (1-6)