W8 - Special sense P1 gustation, olfaction,

Question 1

Define a sensation and list different types of sensory receptors based on their functions

Answer 1

Question 2

Classification of Sensory Receptors

Answer 2

Question 3

Understand the general classification of senses

Answer 3

General Senses

Receptors distributed over a large part of the body

Somatic senses

Provide sensory information about the body and the environment

Visceral senses

Provide information about various internal organs involving pain and pressure

Special Senses

More specialised in structure and localised to specific parts of the body

Smell, taste, sight, hearing and balance

Question 4

Briefly describe the receptors for olfaction and the olfactory pathway

Answer 4

Because some nerve impulses for smell and taste propagate to the limbic system, certain odors and tastes can evoke strong emotional responses or memories.

The olfactory epithelium occupies the upper portion of the nasal cavity.

It contains olfactory receptor cells (olfactory neurons), which are first-order neurons of the olfactory pathway. 

Question 5

Olfactory receptor cells

Answer 5

Olfactory receptor cells are bipolar neurons.

Their distal processes (dendrites) have cilia, olfactory hairs that project into the olfactory epithelium and get stimulated by inhaled chemicals, the odorants.

The proximal processes (axons) of olfactory sensory neurons extend from olfactory epithelium to the olfactory bulb.

There are about 40 bundles of these short, slender, unmyelinated axons coursing through about 20 holes in the cribriform plate of ethmoid bone.

These bundles of axons collectively form the right and left olfactory nerves that are referred to as Cranial Nerve I (CN I).

Question 6

Olfactory nerves

Answer 6

Question 7

primary olfactory cortex

Answer 7

Question 8

Briefly describe the receptors for gustation and the gustatory pathway

Answer 8

Taste or gustation allows us to feel tastes such as sour, sweet, bitter, salty and umami (meaty/savory)

Odors from the mouth passes into the nasal cavity where they stimulate olfactory receptors as well.

Question 9

Taste receptors

Answer 9

Question 10

Vallate papillae

Answer 10

Question 11

Gustatory receptor cells

Answer 11

Question 12

Gustatory pathway

Answer 12

Primary neurons extend from gustatory cells of the tongue through the cranial nerves CN VII and CN IX, and synapse in the nucleus solitarius located in the medulla oblongata.

Secondary neurons extend from the nucleus in the medulla oblongata and synapse in the thalamus. 

Tertiary neurons extend from the thalamus and terminate in the primary gustatory cortex in the insula of the cerebrum.