Specialized Tissues, Stem Cells, and Tissue Renewal II: Renewal of Olfactory Epithelium Flashcards

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1
Q

What is sensory epithelia?

A

A specialized epithelium that covers certain parts of the body (sensory tissue of the nose, ears, and eyes).

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2
Q

What embryological tissue is sensory epithelia derived from?

A

ectoderm

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3
Q

What is the function of sensory epithelia of the nose, ears, and eyes?

A

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.

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4
Q

True or False:

Sensory epithelia is well conserved through evolution.

A

True

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5
Q

What sensory cells are found in the nose?

A

Nose has olfactory sensory neurons.

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6
Q

What sensory cells are found in the ears?

A

Ears have auditory hair cells.

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7
Q

What sensory cells are found in the eyes?

A

Eyes have photoreceptors.

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8
Q

What does each sensory cell carry at its apical end?

A

Apical end has a specialized structure that detects the external stimulus and converts it into a change in membrane potential.

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9
Q

What does each sensory cell have at its basal end?

A

It makes a synapse with neurons that relay the sensory information to specific sites in the brain.

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10
Q

What type of neurons are olfactory sensory neurons?

A

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

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11
Q

How many olfactory neurons does each human have?

A

40 million olfactory neurons

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12
Q

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.

A

True

many tiny hair-like cilia protrude from the dendrite

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13
Q

What are found between olfactory sensory neurons?

A

Supporting cells present in between olfactory sensory neurons - hold neurons in place and separate them from one another.

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14
Q

What type of cells are found in the olfactory epithelium, which are in contact with the basal lamina and are a stem cell?

A

Basal cells in the epithelium.

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15
Q

What type of olfactory receptors are found on the free surfaces of cilia in the nose?

A

The free surfaces of cilia have odorant receptor proteins (olfactory receptors).

type of G Proteins Coupled Receptor

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16
Q

How many odorant receptor genes do humans have?

A

350

17
Q

How many different odorant receptor genes does each neuron express in humans?

A

Each neuron expresses only one of these genes enabling the cell to respond to only one class of odorant (organic small molecules).

18
Q

What class of odorant does olfactory neurons only respond to?

A

organic small molecules

19
Q

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.

A

True

20
Q

What is activated by an activated olfactory receptor?

A

Intracellular G-protein

21
Q

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?

A

influx of sodium and calcium

this influx of positive ions causes the neuron to depolarize, generating an action potential

22
Q

When dealing with olfactory, what are relay stations in the brain called?

A

Glomeruli

located in olfactory bulbs

23
Q

What is a glomeruli in the brain?

A

Relay station for action potentials.

located in olfactory bulbs

24
Q

Where are glomeruli, which are relay stations in the brain for action potentials, located?

A

olfactory bulbs

25
Q

In the mouse brain, how many glomeruli/bulb are there?

A

1800

26
Q

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.

A

True

27
Q

What is the life span of an individual olfactory neuron?

A

1 month

28
Q

What stem cell in the olfactory epithelium generates replacements for olfactory neurons, which survive for only a month?

A

Basal Stem Cells in contact with basal lamina divide and differentiate into olfactory neurons.

29
Q

True or False:

Neural stem cells residing in the olfactory epithelium generate replacements for lost neurons.

A

True

30
Q

What is the role of odorant receptor proteins in growth cone migration?

A

Help in axonal guidance and allow the growth cone to migrate to and establish connection with the correct glomerulus in the olfactory bulb.

31
Q

Give an example of one of the only few instances of adult neurogenesis in the central nervous system (CNS).

A

regeneration of olfactory receptor cells

this has raised considerable interest in dissecting the pathways for neural development and differentiation in adult organisms

32
Q

What is the unique relationship between olfaction and people with age-dependent neurodegenerative disorders?

A

> 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.

33
Q

In which certain parts of the brain has it been shown to produce new neurons to replace those that die?

A
  • Ventricles of Forebrain (cells from this region migrate to the olfactory bulb)
  • Hippocampus (involved in learning and memory)
34
Q

What is evidence for neural stem cells?

A

Cultures established from dissociated brain tissue show neurospheres.

35
Q

What is a neurosphere?

A

Clusters of neural stem cells.

36
Q

What is a cluster of neural stem cells called?

A

neurosphere

37
Q

True or False:

Neurospheres cannot be propagated through several generations.

A

False - can be propagated through several generations.

38
Q

Which two cells types can neurospheres, which is a cluster of neural stem cells, differentiate to produce?

A
  • Neurons

- Glial cells

39
Q

Give an example of regeneration in non-mammalian organisms.

A

> 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.