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

Question 1

What is sensory epithelia?

Answer 1

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

Question 2

What embryological tissue is sensory epithelia derived from?

Answer 2

ectoderm

Question 3

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

Answer 3

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.

Question 4

True or False:

Sensory epithelia is well conserved through evolution.

Answer 4

True

Question 5

What sensory cells are found in the nose?

Answer 5

Nose has olfactory sensory neurons.

Question 6

What sensory cells are found in the ears?

Answer 6

Ears have auditory hair cells.

Question 7

What sensory cells are found in the eyes?

Answer 7

Eyes have photoreceptors.

Question 8

What does each sensory cell carry at its apical end?

Answer 8

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

Question 9

What does each sensory cell have at its basal end?

Answer 9

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

Question 10

What type of neurons are olfactory sensory neurons?

Answer 10

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

Question 11

How many olfactory neurons does each human have?

Answer 11

40 million olfactory neurons

Question 12

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.

Answer 12

True

many tiny hair-like cilia protrude from the dendrite

Question 13

What are found between olfactory sensory neurons?

Answer 13

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

Question 14

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

Answer 14

Basal cells in the epithelium.

Question 15

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

Answer 15

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

type of G Proteins Coupled Receptor

Question 16

How many odorant receptor genes do humans have?

Answer 16

350

Question 17

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

Answer 17

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

Question 18

What class of odorant does olfactory neurons only respond to?

Answer 18

organic small molecules

Question 19

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.

Answer 19

True

Question 20

What is activated by an activated olfactory receptor?

Answer 20

Intracellular G-protein

Question 21

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?

Answer 21

influx of sodium and calcium

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

Question 22

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

Answer 22

Glomeruli

located in olfactory bulbs

Question 23

What is a glomeruli in the brain?

Answer 23

Relay station for action potentials.

located in olfactory bulbs

Question 24

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

Answer 24

olfactory bulbs

Question 25

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

Answer 25

1800

Question 26

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.

Answer 26

True

Question 27

What is the life span of an individual olfactory neuron?

Answer 27

1 month

Question 28

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

Answer 28

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

Question 29

True or False: Neural stem cells residing in the olfactory epithelium generate replacements for lost neurons.

Answer 29

True

Question 30

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

Answer 30

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

Question 31

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

Answer 31

regeneration of olfactory receptor cells **this has raised considerable interest in dissecting the pathways for neural development and differentiation in adult organisms**

Question 32

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

Answer 32

> 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.

Question 33

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

Answer 33

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

Question 34

What is evidence for neural stem cells?

Answer 34

Cultures established from dissociated brain tissue show neurospheres.

Question 35

What is a neurosphere?

Answer 35

Clusters of neural stem cells.

Question 36

What is a cluster of neural stem cells called?

Answer 36

neurosphere

Question 37

True or False: Neurospheres cannot be propagated through several generations.

Answer 37

False - can be propagated through several generations.

Question 38

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

Answer 38

- Neurons | - Glial cells

Question 39

Give an example of regeneration in non-mammalian organisms.

Answer 39

> 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.