Specialized Tissues, Stem Cells And Tissue Renewal II Flashcards
The sensory epithelia is derived from?
Ectoderm
What does the sensory epithelia contain?
Elaborate devices that collect signals from the external environment and deliver them to the CNS
Function of sensory cells in the sensory epithelia?
Act as transducers, converting signals from the environment into an electrical form that can be interpreted by the CNS - well conserved
What are the 3 sensory cells ?
Olfactory sensory neurons; auditory hair cells; photoreceptors
The apical end of sensory cells contains?
A specialized structure that detects the external stimulus and converts it into a a change in membrane potential
The basal end of epithelial cells contains what?
Where it makes synapse w/ neurons that relay the sensory info to. Specific sites in the brain
Describe an olfactory neuron
Bipolar neurons w/ a dendrite facing the extracellular environment (interior spcce of the nasal cavity) and an axon that travels along the olfactory nerve to the olfactory bulb in the brain
What protrudes from the dendrite of olfactory neurons?
Many tiny hair-like cilia
What types of cells are present between the olfactory neurons and what is their funtion?
Supporting cells - hold nuerons in place and separate them from one another
What do the free surfaces of cilia contain?
Odor and receptor proteins (olfactory receptors)
What type of receptor is the olfactory receptor?
GPCR
Why can the cell only response to 1 class of odorant?
Because each neuron only expresses one odor receptor gene
What does the receptor recognize from the odorant?
The odorants structural features
What is the result of an activated olfactory receptor?
It activates intracellular G protein which activates adenylate cyclase which produces cyclic AMP. Opening of ion channels in the pm results in an influx of NA and Ca in to the cells which causes the neuron to depolarize generating an action potential.
When an action potential is relayed via the axon to the brain, what are the relay stations in the brain called?
Glomeruli
Where are glomeruli located?
In olfactory bulbs - one on each side of the brain
How many glomeruli/bulb in the mouse brain?
1800
Olfactory neurons expressing the same odorant receptor can be located in different places on the olfactory epithelium - so where do their axons converge?
On the same glomerulus
How long to individual olfactory neurons survive?
One month
What generates replacements for lost olfactory neurons?
Neural stem cells residing in the olfactory epithelium
What is the function of the odorant receptor proteins in the regeneration of olfactory neurons?
They help in axonal guidance and allow the growth cone to migrate to and establish connection w/ the correct glomerulus in the olfactory bulb.
What is one of the few instances of adult neruogenesis in the CNS?
Recreation of olfactory receptor cells
What is the relationship b/w olfaction and age and neurodegenerative disease?
Reduced olfaction has been observed in aged individuals and in people w/ age-dependent neurodegenerative disorders
What is the trend seen with smell and idiopathic Parkinson’s disease?
Reduced sense of smell precedes clinical symptoms of the disease by almost 10 years
In Alzheimer’s disease, its severity correlates with what?
The degree of loss of olfaction but mechanism isn’t understood
What system is the most difficult to contruct in adult life?
CNS
Adult brain and spinal cord have ________ ___________ to self-repair or regenerate.
Little capacity
It was recently discovered that the brain has stem cells - they can make what 2 cells?
Neurons and glial cells
Regeneration of cells in the brain only happens in what 2 parts?
Ventricles of the forebrain - cells from this region migrate to the olfactory bulb. And Hippocampus - region involved in learning and memory.
What are neuro spheres?
Clusters of neural stem cells; can be propagated through several generations and can differentiate to produce both neurons and glial cells
A transformation is common in non-mammalian species which are able to regenerate lost tissues and organs - what is an example of this?
Regeneration of a newt limb following amputation.
Describe the process of regeneration of a newt limb
Differentiated muscle cells in the stump renter the cell cycle, de-differentiate and become embryonic cells and proliferate to form a limb bud similar to the embryo. Regenerates the missing limb.
Sensory epithelia
Specialized epithelium that covers certain parts of the body (sensory tissue of the nose, ears and eyes)
