Specialized Tissues, Stem Cells, and Tissue Renewal II: Renewal of Olfactory Epithelium Flashcards
What is sensory epithelia?
A specialized epithelium that covers certain parts of the body (sensory tissue of the nose, ears, and eyes).
What embryological tissue is sensory epithelia derived from?
ectoderm
What is the function of sensory epithelia of the nose, ears, and eyes?
Sensory cells present in the sensory epithelium act as TRANSDUCERS, converting signals from the environment into an ELECTRICAL FORM that can be interpreted by the CNS.
True or False:
Sensory epithelia is well conserved through evolution.
True
What sensory cells are found in the nose?
Nose has olfactory sensory neurons.
What sensory cells are found in the ears?
Ears have auditory hair cells.
What sensory cells are found in the eyes?
Eyes have photoreceptors.
What does each sensory cell carry at its apical end?
Apical end has a specialized structure that detects the external stimulus and converts it into a change in membrane potential.
What does each sensory cell have at its basal end?
It makes a synapse with neurons that relay the sensory information to specific sites in the brain.
What type of neurons are olfactory sensory neurons?
Bipolar Neurons
which have a dendrite facing the extracellular environment (interior space of the nasal cavity) and an axon that travels along the olfactory nerve to the olfactory bulb in the brain
How many olfactory neurons does each human have?
40 million olfactory neurons
True or False:
Bipolar neurons (olfactory sensory neurons) have a dendrite facing the extracellular environment (interior space of the nasal cavity) and an axon that travels along the olfactory nerve to the olfactory bulb in the brain.
True
many tiny hair-like cilia protrude from the dendrite
What are found between olfactory sensory neurons?
Supporting cells present in between olfactory sensory neurons - hold neurons in place and separate them from one another.
What type of cells are found in the olfactory epithelium, which are in contact with the basal lamina and are a stem cell?
Basal cells in the epithelium.
What type of olfactory receptors are found on the free surfaces of cilia in the nose?
The free surfaces of cilia have odorant receptor proteins (olfactory receptors).
type of G Proteins Coupled Receptor
How many odorant receptor genes do humans have?
350
How many different odorant receptor genes does each neuron express in humans?
Each neuron expresses only one of these genes enabling the cell to respond to only one class of odorant (organic small molecules).
What class of odorant does olfactory neurons only respond to?
organic small molecules
True or False:
A given olfactory receptor can only bind to a single class of odorant molecule, which may include a variety of odor molecules.
True
What is activated by an activated olfactory receptor?
Intracellular G-protein
What ions does the opening of ion channels in the plasma membrane after an intracellular G-protein is activated from binding of an odorant to the olfactory receptor influx into the cell?
influx of sodium and calcium
this influx of positive ions causes the neuron to depolarize, generating an action potential
When dealing with olfactory, what are relay stations in the brain called?
Glomeruli
located in olfactory bulbs
What is a glomeruli in the brain?
Relay station for action potentials.
located in olfactory bulbs
Where are glomeruli, which are relay stations in the brain for action potentials, located?
olfactory bulbs
In the mouse brain, how many glomeruli/bulb are there?
1800
True or False:
Although olfactory neurons expressing the same odorant receptor are located in different places on the olfactory epithelium, their axons converge on the same glomerulus.
True
What is the life span of an individual olfactory neuron?
1 month
What stem cell in the olfactory epithelium generates replacements for olfactory neurons, which survive for only a month?
Basal Stem Cells in contact with basal lamina divide and differentiate into olfactory neurons.
True or False:
Neural stem cells residing in the olfactory epithelium generate replacements for lost neurons.
True
What is the role of odorant receptor proteins in growth cone migration?
Help in axonal guidance and allow the growth cone to migrate to and establish connection with the correct glomerulus in the olfactory bulb.
Give an example of one of the only few instances of adult neurogenesis in the central nervous system (CNS).
regeneration of olfactory receptor cells
this has raised considerable interest in dissecting the pathways for neural development and differentiation in adult organisms
What is the unique relationship between olfaction and people with age-dependent neurodegenerative disorders?
> REDUCED olfaction has been observed in aged individuals and in people with age-dependent neurodegererative disorders.
> In idiopathic Parkinson’s disease reduced sense of smell precedes clinical symptoms of the disease by almost ten years.
> IN Alzheimer’s disease severity of the disease correlates with the degree of loss of olfaction.
In which certain parts of the brain has it been shown to produce new neurons to replace those that die?
- Ventricles of Forebrain (cells from this region migrate to the olfactory bulb)
- Hippocampus (involved in learning and memory)
What is evidence for neural stem cells?
Cultures established from dissociated brain tissue show neurospheres.
What is a neurosphere?
Clusters of neural stem cells.
What is a cluster of neural stem cells called?
neurosphere
True or False:
Neurospheres cannot be propagated through several generations.
False - can be propagated through several generations.
Which two cells types can neurospheres, which is a cluster of neural stem cells, differentiate to produce?
- Neurons
- Glial cells
Give an example of regeneration in non-mammalian organisms.
> Regeneration of a newt limb following amputation.
> Differentiated muscle cells in the stump reenter the cell cycle, de-differentiate, and become embryonic cells and proliferate to form a limb bud similar to the embryo.
> Regenerate the missing limb.
