Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Block 3 > Special Senses > Flashcards

Special Senses Flashcards

1
Q

What structure allows us to smell?

A

CN I innervates olfactory mucosa of superior concha (part of ethmoid bone) and then travels to olfactory bulb via the cribriform plate carrying sensory neurons to orbital + piriform cortexes with pathways linking to brainstem, limbic system and hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is special about olfactory neurons?

A

They can regenerate - may not if cribriform plate becomes fractured damaging them severely

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why might someone get unilateral anosmia?

A

Meningioma

Anterior cranial fossa trauma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do you clinically test olfaction?

A

Test EACH nostril individual with familiar scents e.g. orange, coffee (dont use smelling salts as ammonia may irritate nasal mucosa causing false +ve ‘sense of smell) - ask can you smell it? What is it?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the words for smelling things that aren’t there?

A

Phantosmia

Cacosmia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When do you test a patients olfaction?

A

Not routinely testing in absence of other signs/issues - patient may complain of loss of taste and/or smell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why might a patient experience anosmia?

A

Viral infection
Parkinson’s + AD (early sign)
Meningioma (olfactory groove)
Anterior cranial fossa fracture (may present with CSF rhinorrhoea)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is the piriform cortex?

A

Part of temporal lobe medially including the amygdala and parahippocampal gyrus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What might happen to olfaction in epileptic patients?

A

Unpleasant olfactory aura preceding a seizure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where are the taste receptors?

A

On the tongue but also some in the palate/pharynx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What cranial nerves (CNs) innervate the tongue?

A

Taste sensation:
Anterior 2/3rd - CNVII (facial n. via Chorda Tympani n.)
Posterior 1/3rd - CNIX (glossopharyngeal n.)
CNX’s provides a little bit of taste too

Somatic sensory:
CNVc (lingual)
CNIX

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the different taste receptors for?

A
  1. Sweet
  2. Sour
  3. Salty
  4. Bitter
  5. Umami (savoury)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the structure of the tongue?

A

Covered in papillae e.g. fungiform, filiform (no taste buds) and vallate (across sulcus terminalis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What sensory nucleus do the cranial nerves (CNs) carrying taste synapse on when they come into the brainstem?

A

Nucleus solitarius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why does the tongue have different innervations?

A

During embryological development, the tongue develops from different pharyngeal arches so it will have different nervous innervations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can become damaged in a 3rd molar extraction?

A

Branch of CNVc - inferior alveolar nerve as both provide somatic sensory (lingual) innervation to tongue so patient may not know if they are biting tongue for e.g.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the structure of the eyeball?

A

3 layers:

  • Retina (photo-receptive/sensory region)
  • Choroid
  • Sclera (white outer layer)

Fovea centralis = region of greatest visual acuity sitting in middle if macula

Optic papilla = blind spot where all nerves (CNII) and vessels come in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do you examine the retina?

A

Fundoscopy: first examine cornea and lens when patient is gazing into distance - approach from temporal field (L-L eye, R-R eye), red fundus reflex seen so then move in and adjust dioptre to examine back of eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is an example of a condition that can cause blindness?

A

Central retinal arterial occlusion

Pituitary tumours (compress optic chiasm)

LGB damage

Glaucoma (reduces fields)

Retinal issues e.g. retinitis pigmentosa causes tunnel vision, papilloedema (raised disc, engorged veins), retinopathy, emboli, haemorrhage + scars

20
Q

How is light detected by the eye?

A
  1. Light passes through neuronal layers to get to photoreceptors (different cells detect different colours)
  2. Neural cells come together off of retina to back of eye to form CNII through optic canal of sphenoid bone
  3. Goes through optic chiasm and tract through lateral geniculate body of thalamus
  4. Optic radiation (Meyer’s loop) and then loop arches inferiorly down into temporal lobe
  5. Projects to primary visual cortex (occipital lobe) gyri around calcarine sulcus
21
Q

What does the visual pathway do to what we see?

A

Everything ‘seen’ by eye is inverted and flipped as it passes through the lens of the eye and visual field split into a R (L side of retina) and L (R side of retina) half for each eye

22
Q

What are retinal fields?

A

Anatomical regions of retina named according to its position relative to nose or temporal regions for e.g. in L eye:
Temporal retinal field on L whereas nasal retinal field on R (vice versa for visual fields)

23
Q

How are visual field deficits presented?

A

Described and drawn from patients POV as if you are seeing as the patient does although patient will not see black as drawn, they will see nothing - depending on size of defect, patient may not be aware of problem

24
Q

How does visual information end up when it reaches the visual cortex?

A

Information from L side of visual field from both eyes ends up on the R/contralateral side of the brain upside down (vice versa for R visual field) as optic radiation of lower visual field is higher in the brain that fibres portraying upper visual field

25
Q

How is the visual field further split into quadrants?

A

Meyer’s loop = upper visual field (1/4 on each side)

Lower visual field above it (1/4 on each side)

Macula + foveal vision = tip of occipital pole/lobe/striate area - centre middle circle of visual field

26
Q

What can happen in central scotoma?

A

Loss of central macula vision so highest area of visual acuity is lost indicating a problem at the occipital lobe (striate area)

27
Q

What can a vascular lesion of the occipital lobe primary visual cortex cause?

A

Homonymous hemianopia: damage to top and bottom visual fields on same side BUT sparing the central circle i.e. macula sparing where tip of occipital pole (striate area)receives a different blood supply to rest of occipital cortex so escapes harm

28
Q

How do you test the visual fields (CNII)?

A

Confront patient staring directly ahead at arms length, cover one eye and compare R-L and L-R comparing to own visual field using a large red coloured pin

29
Q

How do you test visual acuity?

A

Snellen chart: compares what we see at 6m at 6m away from chart (if patient reads 20ft-6m line they have 20/20 vision) - wear glasses/contacts when doing test

Under 40s should be able to read 1st 6 lines - acuity of less than 6/9 lines needs investigation

When there is poor acuity (e.g. due to optic neuritis, refractive lens error or PS issues) ask patient to count digits, see movement or perceive light

30
Q

How can you clinically test CNII?

A 
Visual acuity (Snellen chart)
Visual fields
Pupil light reflex
Accommodation
Fundoscopy
31
Q

What does the pupillary light reflex test?

A

Functioning of retina, midbrain and CNII and III as shining light in 1 eye should make both pupils contract (consensual light reflex) due to bilateral distributions of brainstem fibres

32
Q

How does the pupillary light reflex come about?

A
  1. Some retinal cells send afferent info to PTN via CNII
  2. PTN linked to eachother by PC and linked to both EWN by interneurons
  3. Pre-ganglionic PS fibres enter CNIII synapsing in ciliary ganglion
  4. Post-ganglionic PS fibres in short ciliary nerves enter iris controlling sphincter pupillae
33
Q

What should be thought if one function of a CN e.g. visual acuity is not working?

A

Think WHERE the functions are separate e.g. nuclei, lens of eye etc.

34
Q

What is accommodation?

A

What enables us to look at and focus upon objects that are close to the eye via vergence, pupillary constriction and lens fattening

35
Q

How does accommodation occur?

A
  1. Retina projects information to 1o visual cortex which affects frontal eye fields
  2. CNIII nucleus contracts medial rectus causing vergence
  3. EWN has 2 effects on ciliary ganglion:
    - Contracts sphincter pupillae causing pupil constriction
    - Contracts ciliary body, relaxing suspensory ligaments enabling lens to recoil + relax making it fatter
36
Q

What are the vestibular and cochlea apparatus?

A

Structures containing fluid (endolymph and perilymph) that transmit vibrations and shared between the 2 systems - housed in a perfect bony deficit creating a snugly space that fits its contours in the petrous temporal bone within a bone labyrinth

37
Q

How is the cochlea arranged?

A

In a spiral where the sensory part is the Organ of Corti that has sensory hair cells detecting vibrations so spiral ganglion come together to form the cochlear nerve (part of CNVIII) which transmits back to pons/medulla

38
Q

Where are vibrations transmitted?

A

From the oval window in the middle ear to the perilymph of the cochlea

Vibrations passed to endolymph via vestibular membrane

39
Q

How is high and low frequency sound detected?

A

When the membrane is narrow and stiff HIGH frequency sound is detected whereas when the membrane is wide and flexible LOW frequency sound is detected

40
Q

How is auditory information transmitted to brain?

A

Ascends and distributed bilaterally to cortexes with multiple nuclei and decussation points (e.g. auditory relay station inferior colliculus) so primary auditory cortex receives bilateral auditory sensory input so patient will not go deaf if one side is damaged, may just lose sensitivity and stereo placing of sounds

41
Q

What are some examples of hearing disorders?

A
  • Conductive
  • Sensorineural (drug-linked, viral rubella in utero or mumps)
  • Loss of stereo-placement sound can indicate cortical/thalamic pathology
  • Tinnitus (Meniere’s, URTI, following exposure to loud sounds or tensor tympani/stapedius myoclonus)
42
Q

What are the 2 parts of the vestibular system?

A
  1. Dynamic: formed from semi-circular canals and crista acting mainly on eye movement via medial-longitudinal fasciculus
  2. Static: formed from maculae (utricle + saccule) acting via vestibulospinal pathway picking up static changes of position of head even when still + linear acceleration of head
43
Q

What are maculae?

A

Provide information relating to head position relative to trunk and sense linear acceleration (e.g. walking, driving, falling)

44
Q

What are the 2 types of macula?

A
  1. Utricle: detect horizontal acceleration (e.g. driving) so active with head in flexion or extension
  2. Saccule: detect vertical acceleration (e.g. falling) - extensor activation in a fall (strong extensor thrust) activates vestibulospinal pathway - active with head held to side
45
Q

Where is the vestibular nuclei? What happens when inputs go wrong?

A

In pontomedullary brainstem with 3 main inputs:
1. Visual via ocular movement
2. Proprioception via cerebellar modulation
3. Vestibular via vestibulospinal tract (1/3 major descending tracts) and neck movement
= 1 input can be lost but if 2 are lost, we become unstable losing postural control

46
Q

What is the Romberg test?

A

Patient closes eyes whilst standing taking away the visual input to the vestibular nuclei and if they sway/fall this is a +ve test whereas if they remain steady, its a -ve test

47
Q

What might be damaged in a positive Romberg test?

A

Dorsal column can become degenerated in syphilis

Fracture through petrous portion of temporal bone which damage inner ear and vestibular system

Block 3 (40 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions