Zaidi - Stem Cells 1 + 2

Question 1

Cells from a zygote, including extra-embryonic placenta tissue, is ___.

Embryonic Stem Cells are ___.

Adult Stem Cells, those within a given dermal layer, are ___.

Answer 1

Totipotent.

Pluripotent.

Multipotent.

Question 2

Cell division from a stem cell can occur in these two ways. Briefly describe these two mechanisms.

Which model seems to be the more acceptable one?

Answer 2

Asymmetric division: 2 cells are created and one maintains stem cell characteristics.

Independent choice: division makes 2 identical cells and the outcome is determined by the environment.

Independent choice (more flexible and explains the sharp increase in stem cell numbers).

Question 3

Each organ/tissue has a fixed number of ___, which have a programmed, fixed number of divisions.

These cells can divide to one daughter cell and another that remains a ___.

Answer 3

founder stem cells.

stem cell.

Question 4

Mixed with stem cells are other cells that divide frequently, called ___. These cells come from stem cells and are programmed to divide a limited number of times.

Answer 4

transit amplifying cells.

Question 5

From outer to inner, the three layers of the skin are __, __, and __. Give a unique characteristic of each.

Answer 5

epidermis (continuously repaired and renewed), dermis rich in collagen), and hypodermis (fatty subcutaneous layer).

Question 6

The only dividing cells in the epidermis are found in the __ layer.

Answer 6

basal cell.

Question 7

What are the layers of the epidermis, from superficial to deep?

The __ layer forms boundary between inner metabolically active strata and outer dead epidermis cells.

The __ layer has numerous desmosomes that attach tufts of keratin filaments.

Answer 7

squame (keratinized), granular cell layer, prickle cell layer, basal cell layer, basal lamina.

granule

prickle

Question 8

T/F: As basal cells divide and move superficially away from the basal cell layer, a change in gene expression occurs at each layer.

Answer 8

True.

Question 9

High levels of ___ are correlated with being a stem cell.

Answer 9

Beta integrin.

Question 10

Overactivation of ___ pathway makes cell continue to divide even after exit from basal layer. Deficit of hedgehog signal leads to loss of __ glands.

Up-regulation of __ signaling causes extra hair follicles to develop and can give rise to tumors.

Answer 10

hedgehog.

sebaceous.

Wnt.

Question 11

___ signaling and lateral inhibition restricts size of stem cell population and causes neighbors of stem cells to become transit amplifying cells.

___ plays a key role in repair of skin wounds, promoting formation of collagen rich scar tissue.

Answer 11

Notch.

TGFBeta.

Question 12

Of the three sensory cells, photoreceptors, auditory hair cells, and olfactory sensory neurons, which one is self-renewing? Which one is neuron-like?

Answer 12

olfactory sensory neurons.

photoreceptors.

Question 13

Olfactory sensory neurons are ___ neurons, with a dendrite facing the ___ environment and an axon that travels along the ___ nerve.

___ cells are present in between neurons, holding the neurons in place and separate from one another.

Answer 13

bipolar.

extracellular.

olfactory.

Supporting.

Question 14

Olfactory neurons respond to only one __ of odorant. The odorant receptor, a type of GPCR, once activated then activates a series of reactions that lead to depolarization. Describe this series.

Answer 14

class.

GPCR activates intracellular Golf (adenylate cyclase and then cAMP).

Then it opens cAMP gated ion channels, causing an influx of sodium and calcium, causing depolarization and an AP.

Question 15

Relay stations in the brain are called ___ and are located in the olfactory bulbs.

There are approximately ___ glomeruli per bulb and axons of neurons of the same odorant receptor converge on the same glomerulus.

Answer 15

Glomeruli.

1800.

Question 16

T/F: regeneration of olfactory receptor cells is one of the only few instances of adult neurogenesis in the CNS.

Answer 16

True.

Question 17

Stem cells in the brain are located in these two locations.

Answer 17

Ventricles of forebrain and the hippocampus.

Question 18

T/F: Individual olfactory neurons survive for only one month.

Answer 18

True.

Question 19

Stem cells in the lining of the ___ continuously divide and produce new stem cells. Then, they migrate to the ___ where they differentiate into olfactory neurons.

Answer 19

brain ventricles.

olfactory bulb.

Question 20

Approximately how many neurons are generated every day in the hippocampus, contributing to plasticity?

Answer 20

1400.

Question 21

Cultures established from self renewing regions of brain and fetal brain tissue show ___, which are clusters of neural stem cells, neural cells, and glial cells.

Cells in these areas can stay as stem cells or differentiate into ___.

Answer 21

neurospheres.

neurons and/or glial cells.

Question 22

These three mechanisms can stimulate quiescent, non-dividing stem cells into proliferating precursors and newborn neurons.

Answer 22

LTP, Deep Brain Stimulation, antidepressants (norepinephrine).

Question 23

T/F: Planaria have an extraordinary capacity to regenerate and under starvation conditions, they can reduce to 1/20th of its size by reducing cell numbers and maintaining body proportions.

Answer 23

True.

Question 24

20% of cells in the body are ___, stem cells that continually differentiate into body cells which are dying via apoptosis. Corpses are phagocytosed and digested by neighboring cells in a process called ___.

Answer 24

neoblasts.

cell cannibalism.

Question 25

When a newt limb is cut off, differentiated muscle cells re-enter the ___, de-differentiate and become ___ to form a limb bud and regenerate the missing limb.

Answer 25

cell cycle.

embryonic cells.