Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
44 Cards in this Set
- Front
- Back
|
Are smell and taste sensitive or not? |
Extremely sensitive |
|
|
Why is it difficult to study the transduction process in smell and taste? |
Cells are inaccessible |
|
|
How many odors and flavors can be discriminated? |
Thousands |
|
|
How do smell and taste sense odors and flavors? |
They recognize discrete chemical structurres |
|
|
What is the los of the sense of smell? |
Anosmias |
|
|
Where is the sensation of smell transduced? |
Within the olfactory epithelium |
|
|
Where is the olfactory epithelium? |
Dorsal posterior recess of the nasal cavity |
|
|
What does the nasal epithelium contain? |
Receptor cells, supporting cells, and basal cells |
|
|
Describe the smell receptors. |
Bipolar cells with a short peripheral process and a long central process |
|
|
Describe the peripheral process of the receptor neuron. |
Extends to surface of the mucosa, ends in an expanded olfactory knob giving rise to several cilia that interact with odorants within the layer of mucus |
|
|
Describe the longer central process. |
Unmyelinated axon, projects through cribiform plate to ipsilateral olfactory bulb |
|
|
How are olfactory neurons different from most other neurons in mammals? |
They are generated throughout the life of the mature animal |
|
|
What feature must cells in the olfactory bulb have do to olfactory neuron regeneration? |
Must continually accept new synapses |
|
|
Describe the path of odorants from the air to the olfactory neuron. |
First absorbed into mucous layer that either diffuse to the cilia or are presented attached to binding proteins that may filter, protecting olfactory neurons from exposure to excessively high concentrations of odorants |
|
|
What types of ion channels are present in olfactory transduction? |
Second messenger-regulated (Indirect) |
|
|
Describe sensory transduction in the olfactory neuron. |
Odorant causes depolarizign receptor potential that causes a graded increase in frequency of AP Opening of ion channels specific for Na+ Increase the level of cAMP by enhancing the activity of adenylyl cyclase GTP-binding protein (Golf) and an olfactory-specific adenylyl cyclase Increase in cAMP opens Na+ channel directly |
|
|
How many different receptors are there? |
Hundreds |
|
|
Do individual olfactory neurons have multiple receptors? |
Not known, probably |
|
|
Is the epithelium homogenous or are there some areas that respond better to an odorant than others? |
Hot spots |
|
|
What happens when stimulus intensity is increased? |
Previously silent olfactory receptors are activated, changing the overall firing pattern |
|
|
What is the pathway for olfactory information? |
Axons of olfactory neurons terminate in the olfactory bulb (glomeruli) where axons synapse on dendritic arbors of large mitral cells and small tufted cells (main output cells) that then project in olfactory tract to second olfactory areas of olfactory cortex |
|
|
Is there a relationship between the arrangement of the projections of olfactory neurons in the olfactory bulb and the regions of mucosa from which they originate? |
No |
|
|
How would you perform functional mapping of the projections of olfactory neurons? |
2-deoxyglucose autoradiography after exposure to various odorants |
|
|
What happens when functional mapping used? |
Activity of cells in specific glomeruli increase in response to certain odorants, as concentration increased, additional glomeruli are active (groups of cells with higher thresholds) |
|
|
Which neurons constitute local inhibitory circuits? |
Periglomerular and granule neurons |
|
|
Is olfactory information relayed through the thalamus? |
Ultimately, yes on its way to orbitofrontal cortex |
|
|
What does the orbitofrontal cortex do? |
Conscious perception of smell |
|
|
What is the amygdala's role in smell? |
Relay center that connects olfactory cortex with the hypothalamus |
|
|
What is the diminished sense of smell? |
Hyposmia |
|
|
Describe taste receptor cells. |
Epithelial cells clustered in taste buds |
|
|
What is contained in taste buds? |
50 to 150 receptor cells, basal cells and supporting cells |
|
|
Describe basal cells. |
Located at the base of the taste bud Interneurons Differentiate to become new receptor cells |
|
|
Describe supporting cells. |
Glial-like properties Provide structural or trophic support |
|
|
What is the only part of the taste receptor cell exposed? |
Microvilli (sites of sensory transduction) |
|
|
Describe taste receptor innervation. |
Each receptor cell innervated at base by peripheral branch of primary afferent fiber that innervates several taste buds and receptor cells Anterior two thirds innervated by VII Posterior third innervated by IX |
|
|
Do taste receptor cells generate action potentials? |
No, graded receptor potentials that increase intracellular Ca2+ and release transmitter |
|
|
What are the four basic taste qualities? |
Bitter Salty Sour Sweet |
|
|
Describe bitterness. |
Associated with harmful stimuli Releases Ca2+ from intracellular stores (triggered by IP3 or cAMP, which releases neurotransmitter |
|
|
Describe sweetness. |
Two possible mechanisms: 1) Na+-selective, voltage-independent channel 2) Closure of a voltage-dependent leakage K+ channel (closed by elevations in cAMP) |
|
|
Describe sourness. |
Acids Penetrate the membrane of the cell directly and block voltage-dependent Na+, Ca2+, and K+ channels |
|
|
Describe saltiness. |
Passage of ions through voltage-independent cation channels, directly altering the membrane potential Doesn't require existence of specific membrane receptors |
|
|
Where do afferents from taste buds project? |
Gustatory nucleus |
|
|
Describe the taste pathway. |
First synapse at taste bud Complex overlapping RFs CN VII, IX, X enter solitary tract in medulla and synapse on gustatory nucleus then to thalamus to two regions of cortex: gustatory region of post-central gyrus and innerface of insula |
|
|
What are the two theories of taste perception? |
1) Specific pathway theory: single class of neurons signal one basic taste quality (labeled line) 2) Across-fiber pattern coding: central neurons compare inputs from a whole population of afferent fibers, each of which responds preferentially to a certain stimulus but also have significant sensitivity to other stimulus types Both correct |
