Lecture 33: Stem Cells And Tissue Renewal II Flashcards
Sensory epithelium is a specialized epithelium that covers certain parts of the body like the nose, ears, and eyes. What germ layer is it derived from?
Ectoderm
Sensory epithelial contains elaborate devices that collect signals from the external environment and deliver them to the _______
CNS
What are the “transducers” of the sensory epithelium, which are responsible for converting signals from the environment into an electrical form that can be interpreted by the CNS
Sensory cells
What are the sensory cells of the eyes?
Photoreceptors - rods and cones
What are the sensory cells of the ears?
Auditory hair cells
What are the sensory cells of the nose?
Olfactory sensory neurons
Which end of the sensory cell has a specialized structure that detects the external stimulus and converts it into a change in membrane potential?
Apical end
Which end of a sensory cell makes the synapse with neurons that relay the sensory info to specific parts of the brain?
Basal end
Describe olfactory neurons
Bipolar
Dendrites face EC environment with cilia coming off
Axon travels along the olfactory nerve to olfactory bulb
What type of cells are present in between olfactory neurons, which hold the neurons in place and separate them from one another?
Supporting cells
What cells associated with olfactory neurons are associated with the basal lamina?
Basal cells
What is the function of the mucus overlying olfactory neurons?
Keeps sensory surfaces of epithelium moist and protected
Where are the odorant receptor proteins located?
The free surfaces of the cilia (coming off the dendrites)
What type of receptors are odorant receptor proteins?
GPCRs
What type of features of the operant are recognized by the GPCR?
Structural features
Each olfactory neuron expresses only one odorant receptor gene, enabling the cell to respond to ______ class(es) of oderant
One
True or false: All olfactory neurons respond by a common mechanism
True
What is the sequence of events after an odorant ligand binds to a GPCR?
Intracellular G-protein (Golf) is activated
Activates adenylate cyclase -> produces cAMP
Ion channels open -> influx of Na and Ca into cell
Positive ion influx -> action potential
The action potentials generated at the olfactory receptors are relayed via the axon to the brain. What are the relay stations in the brain?
Glomeruli
Where are olfactory glomeruli located?
In olfactory bulbs, one on each side of the brain
Although olfactory neurons expressing the same odorant receptor are located in different places on the olfactory epithelium, what do their axons do?
Converge on the same glomerulus
How long do individual olfactory neurons survive?
1 month
What type of cells reside among the basal cells in the olfactory epithelium and generate replacements for lost neurons?
Neural stem cells (come from basal stem cells that lose contact with basal lamina and differentiate into olfactory neurons)
Odorant receptor proteins help in a process called ___________ ___________ and allow the growth cone to migrate to and establish a connection with the correct glomerulus in the olfactory bulb
Axonal guidance
True or false: Regeneration of olfactory receptor cells is one of many instances of adult neurogenesis in the CNS
False!
It is one of very few examples, which has raised interest in dissecting the pathway for neural development and differentiation in adult organisms
What is thought to serve as a potential biomarker for neurodegenerative diseases like Parkinson’s and Alzheimer’s?
Loss of olfaction
What part of the nervous system is the most difficult to construct in adult life?
CNS - the adult brain and spinal cord have little capacity to self-repair or regenerate
What two cell types can neural stem cells make?
Neurons and glial cells
Stem cells are only prevalent in what two parts of the brain?
Ventricles of forebrain (migrate to olfactory bulb)
Hippocampus
What are the hippocampal stem cells involved in?
Learning and memory formation - contributes to plasticity of adult brain function
One potential for therapy for neurodegenerative disease is activation of the endogenous population of quiescent stem cells in the adult hippocampus. What would this do to help these conditions?
Enhancement of neurogenesis through activation of these stem cells. This may facilitate neuronal repair and recovery of cognitive function
What is known to induce long-term potentiation (LTP) and in vitro depolarization to potently activate the quiescent stem cells in the brain to proliferate?
Neuronal activity, such as what occurs in learning
A different subpopulation of stem cells is activated following exposure to _____________, and it is thought that this population responds to NE-mediated antidepressant treatment which can alleviate clinical depression
Norepinephrine
What method, which is currently used to treat many neurodegenerative and psychiatric conditions, has been shown to promote proliferation of stem cell pools in animal models?
Electrical stimulation, such as deep brain stimulation and electroconvulsive shock
Cultures established from self renewing regions of brain and fetal brain tissue show something called _______________, which are made up of clusters of neural stem cells, neural cells, and glial cells
Neurospheres
What would happen if neural stem cells were grafted into an adult brain?
They have the ability to adjust their behavior to match their new location
Briefly describe regeneration and repair in non-mammalian organisms like flatworms
A small tissue fragment can form a complete animal
When it is starved, it gets smaller, reducing its cell numbers while maintaining body proportions
When it is fed, it will return to normal size
Cycle can repeat over and over without harming organism
Along with differentiated cells are undifferentiated cells called ________, aka stem cells
Neoblasts
Neoblasts are stem cells, continually differentiating into body cells which are continually dying via apoptosis. What happens to these apoptotic cells?
Their corpses are phagocytosis and digested by neighboring cells = cell cannibalism
Cell birth, cell death, and cell cannibalism are well coordinated - How do starvation and fed states affect this balance?
Starvation = tilted towards cannibalism
Fed state = cell birth
If an organism is exposed to X-ray radiation to the point that it loses its ability to undergo cell division, what would be the effect of injecting a single neoblast?
It would rescue the organism, and help develop the full organism with all of its body parts
Transformation is common in non-mammalian species which are able to regenerate lost tissues and organs. For example, a newt can form a new limb after amputation. How does this occur?
Differentiated muscle cells in the stump re-enter the cell cycle, de-differentiate, and become embryonic stem cells which can proliferate and regenerate the limb
