Lecture 33: Stem Cells And Tissue Renewal II

Question 1

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?

Answer 1

Ectoderm

Question 2

Sensory epithelial contains elaborate devices that collect signals from the external environment and deliver them to the _______

Answer 2

CNS

Question 3

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

Answer 3

Sensory cells

Question 4

What are the sensory cells of the eyes?

Answer 4

Photoreceptors - rods and cones

Question 5

What are the sensory cells of the ears?

Answer 5

Auditory hair cells

Question 6

What are the sensory cells of the nose?

Answer 6

Olfactory sensory neurons

Question 7

Which end of the sensory cell has a specialized structure that detects the external stimulus and converts it into a change in membrane potential?

Answer 7

Apical end

Question 8

Which end of a sensory cell makes the synapse with neurons that relay the sensory info to specific parts of the brain?

Answer 8

Basal end

Question 9

Describe olfactory neurons

Answer 9

Bipolar

Dendrites face EC environment with cilia coming off

Axon travels along the olfactory nerve to olfactory bulb

Question 10

What type of cells are present in between olfactory neurons, which hold the neurons in place and separate them from one another?

Answer 10

Supporting cells

Question 11

What cells associated with olfactory neurons are associated with the basal lamina?

Answer 11

Basal cells

Question 12

What is the function of the mucus overlying olfactory neurons?

Answer 12

Keeps sensory surfaces of epithelium moist and protected

Question 13

Where are the odorant receptor proteins located?

Answer 13

The free surfaces of the cilia (coming off the dendrites)

Question 14

What type of receptors are odorant receptor proteins?

Answer 14

GPCRs

Question 15

What type of features of the operant are recognized by the GPCR?

Answer 15

Structural features

Question 16

Each olfactory neuron expresses only one odorant receptor gene, enabling the cell to respond to ______ class(es) of oderant

Answer 16

One

Question 17

True or false: All olfactory neurons respond by a common mechanism

Answer 17

True

Question 18

What is the sequence of events after an odorant ligand binds to a GPCR?

Answer 18

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

Question 19

The action potentials generated at the olfactory receptors are relayed via the axon to the brain. What are the relay stations in the brain?

Answer 19

Glomeruli

Question 20

Where are olfactory glomeruli located?

Answer 20

In olfactory bulbs, one on each side of the brain

Question 21

Although olfactory neurons expressing the same odorant receptor are located in different places on the olfactory epithelium, what do their axons do?

Answer 21

Converge on the same glomerulus

Question 22

How long do individual olfactory neurons survive?

Answer 22

1 month

Question 23

What type of cells reside among the basal cells in the olfactory epithelium and generate replacements for lost neurons?

Answer 23

Neural stem cells (come from basal stem cells that lose contact with basal lamina and differentiate into olfactory neurons)

Question 24

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

Answer 24

Axonal guidance

Question 25

True or false: Regeneration of olfactory receptor cells is one of many instances of adult neurogenesis in the CNS

Answer 25

False!

It is one of very few examples, which has raised interest in dissecting the pathway for neural development and differentiation in adult organisms

Question 26

What is thought to serve as a potential biomarker for neurodegenerative diseases like Parkinson’s and Alzheimer’s?

Answer 26

Loss of olfaction

Question 27

What part of the nervous system is the most difficult to construct in adult life?

Answer 27

CNS - the adult brain and spinal cord have little capacity to self-repair or regenerate

Question 28

What two cell types can neural stem cells make?

Answer 28

Neurons and glial cells

Question 29

Stem cells are only prevalent in what two parts of the brain?

Answer 29

Ventricles of forebrain (migrate to olfactory bulb)

Hippocampus

Question 30

What are the hippocampal stem cells involved in?

Answer 30

Learning and memory formation - contributes to plasticity of adult brain function

Question 31

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?

Answer 31

Enhancement of neurogenesis through activation of these stem cells. This may facilitate neuronal repair and recovery of cognitive function

Question 32

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?

Answer 32

Neuronal activity, such as what occurs in learning

Question 33

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

Answer 33

Norepinephrine

Question 34

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?

Answer 34

Electrical stimulation, such as deep brain stimulation and electroconvulsive shock

Question 35

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

Answer 35

Neurospheres

Question 36

What would happen if neural stem cells were grafted into an adult brain?

Answer 36

They have the ability to adjust their behavior to match their new location

Question 37

Briefly describe regeneration and repair in non-mammalian organisms like flatworms

Answer 37

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

Question 38

Along with differentiated cells are undifferentiated cells called ________, aka stem cells

Answer 38

Neoblasts

Question 39

Neoblasts are stem cells, continually differentiating into body cells which are continually dying via apoptosis. What happens to these apoptotic cells?

Answer 39

Their corpses are phagocytosis and digested by neighboring cells = cell cannibalism

Question 40

Cell birth, cell death, and cell cannibalism are well coordinated - How do starvation and fed states affect this balance?

Answer 40

Starvation = tilted towards cannibalism

Fed state = cell birth

Question 41

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?

Answer 41

It would rescue the organism, and help develop the full organism with all of its body parts

Question 42

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?

Answer 42

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