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Senses

5 SENSES

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S enses are the physiological methods of perception. The senses and their operation, classification,

and theory are overlapping topics studied by a variety of fields. Sense is a faculty by which outside
stimuli are perceived.

We experience reality through our senses. A sense is a faculty by which outside stimuli are
perceived. Many neurologists disagree about how many senses there actually are due to a broad
interpretation of the definition of a sense. Our senses are split into two different groups. Our
Exteroceptors detect stimulation from the outsides of our body. For example smell,taste,and
equilibrium. The Interoceptors receive stimulation from the inside of our bodies. For instance, blood
pressure dropping, changes in the gluclose and Ph levels. Children are generally taught that there are
five senses (sight, hearing, touch, smell, taste). However, it is generally agreed that there are at least
seven different senses in humans, and a minimum of two more observed in other organisms. Sense can
also differ from one person to the next. Take taste for an example, what may taste great to me will taste
awful to someone else. This all has to do with how our brains interpret the stimuli that is given.

Chemoreception

The senses of Gustation (taste) and Olfaction (smell) fall under the category of Chemoreception.
Specialized cells act as receptors for certain chemical compounds. As these compounds react with the
receptors, an impulse is sent to the brain and is registered as a certain taste or smell. Gustation and
Olfaction are chemical senses because the receptors they contain are sensitive to the molecules in the
food we eat, along with the air we breath.

Gustatory System

In humans, the sense of taste is transduced by taste buds and is conveyed via three of the twelve
cranial nerves. Cranial nerve VII, the facial nerve, carries taste sensations from the anterior two thirds
of the tongue (excluding the circumvallate papillae, see lingual papilla) and soft palate. Cranial nerve
IX the glossopharyngeal nerve carries taste sensations from the posterior one third of the tongue
(including the circumvallate papillae). Also a branch of the vagus nerve carries some taste sensations
from the back of the oral cavity (i.e. pharynx and epiglottis). Information from these cranial nerves is
processed by the gustatory system. Though there are small differences in sensation, which can be
measured with highly specific instruments, all taste buds can respond to all types of taste. Sensitivity to
all tastes is distributed across the whole tongue and indeed to other regions of the mouth where there
are taste buds (epiglottis, soft palate).

Papilla

Papilla are specialized epithelial cells. There are four types of papillae: filiform (thread-shape),
fungiform (mushroom-shape), foliate (leaf-shape), and circumvallate (ringed-circle). All papillae
except the filiform have taste buds on their surface. Some act directly by ion channels, others act
indirectly.

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