PYB102 – Week Six Revision
The Orienting Senses
Acceleration is an increase in the velocity of the body. Movements such as running forward
and even tilting your head require acceleration. It is the vestibular systems of our bodies
which are designed to detect these various accelerations.
Functions of the Vestibular System
Semicircular canals are small canals inside the temporal bone (behind the ear).
These are fluid-filled and help us detect movement and motion. This is done through
the inertia of the fluid in these canals, which pushes against the cupula, which
stimulates the tiny hair cells within it and transmits the notion of rotary movement
to the brain.
Within around 25 – 30 seconds of acceleration, the fluid inside the canals catches up
with the motion of the body, which prevents the cupula from being pushed any longer.
Thus, the sensation of acceleration disappears.
Saccule and utricle
Two small organs in the vestibule (behind the ear). These detect gravity and
movement of the entire body. They do so in a way similar to the semicircular canals.
The hairs rest in a gelatinous substance and are moved by inertia when the body
moves or is subjected to gravity changes.
Where are the messages sent?
The crista and macula send this sensory information to the brainstem via the eighth cranial
nerve. Most fibres project to the vestibular nuclei in the brainstem. From here, this
information is sent to a number of places including the cerebellum and cortex.
Most of the fibres leaving the vestibular nuclei are efferent fibres (i.e. muscle control).
Some of these motor control fibres project to the eye muscles which control eye
Different types of papillae on the tongue:
Fungiform – the main tastebuds we see on our tongue
Circumvallate – the big tastebuds towards the back
Foliate – the frilly sides of the tongue at the back
Filiform – the tiny buds on the front edges of our tongue – no tastebuds
Anatomy of a tastebud
Each papilla contains a tiny cave surrounding it, in which the taste buds are contained.
When we eat so