Senses ✅ Flashcards
How do the senses vary?
- Between different individuals
- Within the same individual, depending on emotional state
What nerves are involved in taste?
Cranial nerves 7 and 9, and partly 10
What detects taste?
Chemoreceptors in the form of papillae distributed over the tongue
How many tastes can be detected?
5
What tastes can be detected?
- Salty
- Sweet
- Sour
- Bitterness
- Umami (savoury/meaty taste of foods)
Why is MSG used as a flavour enhancer?
Receptors for the umami taste are activated by MSG (monosodium glutamate)
Damage to what surfaces might affect taste?
- Damage to cranial nerve 7
- Damage to tongue surface
How does smoking affect taste?
Seems to dull sense of taste, but may be more via its effects on smell
What % of what is interpreted as taste is actually smell?
80-90%
What nerve is responsible for smell?
CN 1
How does CN 1 detect smell?
Axons from thousands of cells expressing the same odour receptor converge in the olfactory bulb
What is the theory behind smell being a potent emotional and memory trigger?
The olfactory systems proximity to the limbic system and hippocampus, which are involved in emotion and memory
Give an example of a cause of temporary loss of smell?
Common cold
What can cause permanent loss of smell?
- Head injuries
- Intracranial tumours
- Kallmann syndrome
What is Kallmann syndrome associated with?
Absent or incomplete pubertal development
What might trigger a false sense of smell?
Some forms of temporal lobe epilepsy - odd smell prior to or during attack
What is a significant feature of olfactory neurones?
Their capacity to regenerate
What does good visual function depend on?
Combination of good visual acuity and sensitivity to targets in the peripheral visual field
What is visual acuity defined as?
Minimal distance that 2 targets need to be separated in order to be seen as distinct
What is considered to be ‘perfect’ vision with regards to visual acuity?
Able to resolve 2 targets separated by one minute of arc (i.e. 1/60 of a degree) - equivalent to 6/6 Snellen vision
How is the Snellen chart used?
It is usually viewed from 6m, and gives the numerator - the denominator is the number printed beneath the smallest line a child can read, e.g. 6/36 means child can read from 6m what most people can read from 36m.
What is the expected visual acuity at birth?
<6/60
How is visual acuity tested at birth?
Fixation to lights
How are visual fields tested at birth?
Not possible
What is the expected visual acuity of a 0-3 month old?
6/60-6/38
What is the expected visual acuity of a 3-24 month old?
6/38, improving to 6/12
What is the expected visual acuity of a 2-4 year old?
6/12-6/9
How is visual acuity measured at 0-3 months old?
Fixation to faces/large toys
How is visual acuity measured at 3-24 month old?
Preferential looking cards (Teller/Cardiff)
How is visual acuity measured at 2-4 years old?
Picture optotype charts
How are visual fields measured up to 4 years (but not newborns)?
- Visually elicited eye movement
- Confrontation techniques
What is the expected visual acuity in 5+ years?
6/9-6/6
How is visual acuity tested in 5+ years?
Letter optotype charts
How are visual fields tested in 5+ years?
Goldmann perimetry/automated perimetry sometimes possible
What are Snellen charts being replaced by?
LogMAR charts (logarithmic minimal angle of resolution)
What logMAR score is equivalent to 6/6 vision on a Snellen chart?
0.0
What does a higher logMAR number mean in terms of visual acuity?
Higher number = worse visual acuity