BPK 105 Midterm: Module 5 - Objectives - Part 2

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Module 5 - Objectives - Part 2
Describe how molecules in the air stimulate action potential in the olfactory
neuron.
- sense of smell: olfaction
- occurs in response to airborne molecules (odorants) that enter the nasal cavity.
-Olfactory neurons: bipolar neurons within the olfactory epithelium, which lines the
superior part of the nasal cavity (figure 9.4a
).
-dendrites of the olfactory neurons extend to the epithelial surface, and their ends are
modified with long, specialized cilia that lie in a thin mucous film on the epithelial
surface.
- mucus keeps the nasal epithelium moist, traps and dissolves airborne molecules (then
airborne molecules bind to receptor molecules which initiate AP), and facilitates the
removal of molecules and particles from the nasal epithelium.
- once odorant binds to receptors, desensitized with refractory period (adaptation to odors)
- Airborne odorants (odorants) become dissolved in the mucus on surface of epithelium +
bind to receptor molecules on the membranes of the specialized cilia.
- binding of the odorant to the receptor initiates action potentials, which are then
conducted to the olfactory cortex of the cerebrum by sensory neurons.
- olfactory receptor can bind multiple types of odorants; each type of odorant can bind to
multiple olfactory receptors.
- Once an odorant has bound to its receptor, that receptor is desensitized and does not
respond to another odor molecule for some time, which helps with adaptation to a
particular odor.
- threshold for the detection of odors is extremely low, so very few odorants bound to an
olfactory neuron can initiate an action potential.
Describe the structure and function of a taste bud.
Taste buds: sensory structures that detect taste stimuli
- oval structures located on the surface of certain papillae, which are enlargements on the
surface of the tongue (figure 9.5).
- distributed throughout other areas of the mouth and pharynx, such as on the palate, the
root of the tongue, and the epiglottis.
- Each taste bud consists of two types of cells. Specialized epithelial cells form the
exterior supporting capsule of each taste bud, and the interior consists of about 40 taste
cells.
- Each taste cell contains hairlike processes (taste hairs), that extend into a tiny opening
in the surrounding stratified epithelium (taste pore).
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