Tag: nervous

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

Babinski Reflex

Posted on by Jinavie

Normally when you tickle or stroke the sole of your feet, the toes flex inwards. However, when a newborn’s feet are tickled or stroked, the toes spread outwards. This is known as the Babinski reflex, or Babinski sign. It is a primitive reflex that disappears before 12 months of age.
If this reflex is seen after that, including adults, it is a sign there is something wrong with the nervous system, especially the brainstem or the spinal cord.

A primitive reflex is one shown by newborns but disappears gradually as they develop. These include reflexes such as the walking reflex, swimming reflex and crawling reflex that shows actions that they have not yet learnt, or the rooting reflex and sucking reflex that ensures the baby’s survival.

Posted in Psychology & Medicine

Vertex

Posted on by Jinavie

The vertex, also known as the crown of the head, is the uppermost point on the human body on the top of the head. It is the part of the body that comes out first (usually) during childbirth.

There are some interesting properties regarding this anatomic location.

Firstly, if one places a cellphone on top of their head, they cannot feel the vibration when they receive a call or text message. Almost every other part of the body can feel the vibration, but not the vertex. This is because the top of the skull is not covered by any muscles, which have receptors that sense vibrations. Ergo, no vibrations can be felt.

Secondly, when one places their hand on top of their head, they experience a sudden drop in muscle strength. This applies to the whole body and can be seen through basic activities such as lifting weights or even through arm-wrestling. The degree of weakness can be up to 10~15% of the muscle’s normal strength. 

The reason for this is slightly more complicated. The nervous system remembers trauma and responds to it, such as childbirth where almost everyone (assuming they were born through vertex presentation, the most common) experiences trauma on the top of the head. For example, as labour is quite an intensive procedure, significant pressure is placed on top of the baby’s head as it tries to push out.
Because of this, when pressure or electric signals are exerted on the vertex, the nervous system responds negatively, remembering the trauma from childbirth, and “weakens” throughout the body. This results in decreased force exertion by muscles. The same effect can be achieved when a cellphone is placed on top of the head, as it emits electric signals.

Lastly, the top of the head is not sealed until a few months after birth. This makes a baby’s skull very malleable, and two fontanels, which are gaps between pieces of the skull, remain open for that time. This is seen as “soft spots” on the head which pulsates as there is no bone beneath it.