Ch.15 Flashcards
Olfaction
sense of smell
in response to odors that stimulate sensory receptors in the olfactory region
Where is the olfactory region and what is it lined with?
Olfactory region is located in the extreme superior area of nasal cavity and lined with specialized epithelium called the olfactory epithelium
The olfactory epithelium contains approx ________ olfactory neurons, which are ________ _________ cells
10 million
Olfactory receptor cells
Olfactory vesicles
Bulbous enlargements of dendrites of olfactory neurons that extend into the epithelial surface of the nasal cavity
Olfactory hairs
Cilia on the olfactory vesicles which lie in thin mucous film on epithelial surface
Olfactory neurons are considered what type of receptor?
Chemoreceptor
Odorants
Airborne molecules that enter the nasal cavity and are dissolved into the fluid covering the olfactory epihelium
Bind to odorant receptor molecules
What is the process for a binding of an odorant to activating a olfactory neuron?
- Odorant binds to receptor molecule
- Receptor molecule activates G protien, which activates adenylate cyclase.
- Adenylate cyclase catalyzes the formation of cAMP from ATP
- cAMP in these cells causes Na+ and Ca2+ channels to open
- The influx of ions causes depolarization and an action potential
What are the 7 primary smells?
Camphoraceous (mothballs)
Musky
Floral
Pepperminty
Ethereal (fresh pears)
Pungent
Putird
Can a olfactory receptor react to more than one odorant?
yes
What is the neuronal pathway for olfaction?
Axons from the olfactory neuron which forms olfactory nerve, project through small foramina in the bony cribiform plate to the olfactory bulb where olfactory neurons synapse with 2ndry neurons which relay olfactory info to the brain via olfactory tracts
Olfactory stimuli cause not only perception of odors but also a emotional and autonomic responses. What parts of the brain do the olfactory neurons lead to?
Central olfactory cortex areas in temporal and frontal lobes
Also to the hypothalamus, hippocampus, and structures of limbic system
What are the structures that dectect taste or gustatory stimuli?
Taste buds
Papillae on tounge
bumps on tounge / not taste buds
What are the 4 major types of papille and where are they located?
- *Filiform** - most numerous but no tastebuds/rough surface helping with food
- *Vallae** - Surrounded by a wall/largest and least numerous, V shape separeting anterior and posterior tounge
- *Foliate** - leaf shaped / sides of tounge and most sensative taste buds
- *Fungiform** - mushroom shaped / scattered irregulary
Taste buds are associated with vallate, foliate, and fungiform papillae
What is the life span of a taste cell?
10 days
Each of the 10,000 taste buds found in the oral cavitiy consists of what 3 types of specialized epithelial cells?
Taste cells - sensory
Basal cells - non sensory
Supporting cells - non sensory
Each taste cell has several microvilli, called?
Tastants
Substances dissolved in saliva which enter taste pores and stimulate the taste cells
What are the 5 classes of tastants?
Salt
Sour
Sweet
Bitter
Umami
How does the taste of Salt occur?
When Na+ diffuses through Na+ channels resulting in depolarization of taste cells
How do we taste sweet ?
bind to receptor molecules and cause depolarization through G protien mechanisms
How do we taste Sour ?
Results when H+ of acids cause depolarization 1 of 3 ways
- enter through H+ channels
- Bind to ligand gated K+ channels and block the exit of K+
- open ligand gated channels for other positive ions and allow them to diffuse into the cell
How do we taste Bitter ?
Simular to how we taste sweet, through G protiens
How do we taste Umami ?
results when amino acids bind to receptors and causes depolarization through g protien mechanisms
What other factors can affect the perception of taste?
Texture
hot or cold temp
What are the neuronal pathways for taste?
Facial nerve VII - Chorda tympani transmits taste sensations from anterior 2/3s of tounge, except from vallae papillae
Glossopharyngeal nerve IX - carries taste sensations from posterior 1/3 of tounge, the vallate papillae and superior pharynx
Vagus nerve X - carries fibers from epiglottis
*The fibers then go to Medulla oblongata then decussate then go to thalamus. then go to cerebrum
The visual system includes
Eyes
Accessory structures
Optic nerves, tracts and pathways
What are the accessory structures of the visual system?
Eyebrows
Eyelids
Eyelashes
conjuntiva
Lacrimal apparatus
Extrinsic eye muscles
What is the function of eyebrows?
Prevent perspiration from running down forehead and shade eyes from sunlight
What is the function of the eyelids?
Palpebrae
their eyelashes protect eyes from foriegn objects
What are the 5 layers of tissue that make up eyelids
- thin layer of skin on external surface
- thin layer of aerolar connective tissue
- layer of skeletal muscle containing orbicularis oculi and levator palpebrae superior muscles
- cresent shaped layer of Dense connective tissue which helps maintain shape of eyelid
- Palpebral conjunctiva which lines inner surface of eyelid and anterior surface of eyeball
Ciliary glands
modified sweat glands that open into the follicles of the eyelashes to keep them lubricated
*A sty forms when one of these glands becomes inflamed