Tag: taste

Posted in Psychology & Medicine

Cranial Nerves

Posted on by Jinavie

Nerves can be divided broadly as spinal nerves and cranial nerves: the latter which is directly from the brain. There are 12 pairs of cranial nerves:

  1. CN I – Olfactory nerve (smell)
  2. CN II – Optic nerve (sight)
  3. CN III – Oculomotor nerve (eye movements, control of pupil and lens)
  4. CN IV – Trochlear nerve (eye movements)
  5. CN V – Trigeminal nerve (sensory information from face and mouth, chewing)
  6. CN VI – Abducens nerve (eye movements)
  7. CN VII – Facial nerve (taste, tear and salivary glands secretion, facial expressions)
  8. CN VIII – Vestibulocochlear nerve (hearing and sense of balance)
  9. CN IX – Glossopharyngeal nerve (taste, swallowing, parotid gland secretion, sensory information from oral cavity, information about blood)
  10. CN X – Vagus nerve (sensory and motor signals to and from many internal organs, glands and muscles)
  11. CN XI – Accessory nerve (movement of SCM and trapezius, which are neck/shoulder muscles)
  12. CN XII – Hypoglossal nerve (tongue movements)

As there are so many nerves and the names are all varied, there is a simple (yet very obscene) mnemonic to help medical students remember the names and order of nerves:

Oh, Oh, Oh, To Touch And Feel Virgin Girls’ Vaginas And Hymens
or
Oh, Oh, Oh, To Touch And Feel A Girl’s Very Soft Hands
(where vestibulocochlear -> auditory)

It is also worth noting the mnemonic for the types of nerves is:

Some Say Marry Money, But My Brother Says Big Boobs Matter More

Perhaps the only way to survive medical school is through humour.

Posted in Psychology & Medicine

Sensory Illusion

Posted on by Jinavie

The five senses we use to experience the world are simply wondrous. However, thanks to our not-so-perfect brain, these senses can easily be distorted. Illusions are a very good way to show how the brain processes sensory information and there are many fascinating examples.

Almost everyone has seen an optical illusion before, such as Penrose’s endless stairs or the Muller-Lyer illusion. There are countless more examples such as static pictures that appear to be moving and illusions in colour perception (A and B are the same colour). This is caused by the brain not recording images like a camera, but rather processing visual information and reconstructing an image. There are four main types of optical illusions: ambiguous (e.g. rabbit or duck), distortion (Café wall illusion), paradoxical (Penrose triangle) and fictional (only seen in hallucinations or by schizophrenics).

(Do you see the dolphins? Children cannot see the man and woman because they cannot comprehend it, whilst adults cannot overpower the sexual image)

Like vision, every other sense can be fooled in a similar fashion.
Auditory illusions that distort what we hear are fairly common, a good example being the infinitely ascending Shepard scale (which are just a series of the same ascending octave scale). Also, the McGurk effect shows how the brain uses a multimodal approach where it involves both hearing and vision when listening.

There are also tactile illusions. For example, if you pull your top lip to left and the bottom lip to the right, then prod the middle of the lips with a pencil, it feels like there are two. However, the more famous case is of the Phantom Limb, where an amputee’s brain still believes that the limb is there, causing it to “feel” the limb or even feel pain.

The other two senses aren’t as famous in terms of illusions, but definitely exist.
Smell is easy to fool through chemicals as it is the physiological method of detecting smell. It also exhibits olfactory fatigue where it becomes desensitised to a strong smell.
Taste illusions are more fascinating and easily seen. They are caused by two or more tastes forming a synergy to produce a completely different taste. For instance, mixing barley tea and milk produces a coffee milk taste, while cucumber and honey tastes like melons.
A more fascinating illusion involves Miracle Fruit Berries, which contain a substance called miraculin that distorts the taste of sourness to sweetness.

This shows how we can fool all five senses, and learn more about the mysterious organ that is the brain.