answer the questions below:
A. Define stem cells and differentiation, and describe the different types and the extent to which they are
present during the life of an individual (include the fertilized egg as well as the adult that eventually
results).
B. Which of the four tissue types contain populations of stem cells of known function, and what is that
function? Which types of tissue have stem cells of unknown function? Do any types of tissue lack stem cells?
C. How do fully differentiated cells differ from stem cells? How can stem cells be used in medical treatment?
Give examples.
A. Stem cells are cells that are mitotic and not fully differentiated. Differentiation is the process cells undergo as
they become more and more specialized in structure and function as is typical of the specific tissues they compose.
The fertilized egg and the cells resulting from the first few cleavage divisions after fertilization are totipotent, which
means they can ultimately produce all the types of cells in an adult. Within the first week after conception, the cells
begin differentiation and become capable of producing many types of cells but not all. These cells are pluripotent.
By adulthood, stem cells can be described as multipotent, which are stem cells that can produce many of the cell
types in a specific tissue, and committed stem cells, which can only become one specific cell type within that tissue.
B. Epithelial and connective tissues have active populations of multipotent stems cells, which replace cells lost to
damage or normal turnover. Muscle and nervous tissues contain stem cells but appear to be unable to replace lost
cells. They were once thought to lack stem cells altogether.
C. Once cells are fully differentiated, they can no longer divide to produce more cells. Disease conditions or injuries
that result in cell loss may be remedied by treatment with appropriate stem cells. Examples are neurological injuries
and diseases marked by irreversible damage to cells that cannot (yet) be replaced by new cells.
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Which of the following is not a property of the blood-brain barrier?
A) The capillary endothelial cells are interconnected by tight junctions. B) It is very permeable to many water and lipid-soluble compounds. C) Astrocytes surround the CNS capillaries. D) It is absent in portions of the hypothalamus. E) It is intact except in areas known as circumventricular organs.
________ is characterized by a thickened alveolar membrane, slowing respiratory gas exchange.
Fill in the blank(s) with the appropriate word(s).
A threshold potential is
a. the potential achieved when two opposing forces acting upon an ion (concentration and electrical gradients) achieve a state of equilibrium b. the peak potential achieved during an action potential c. the point at which there is an explosive increase in Na+ or Ca2+ permeability d. the potential at which K+ permeability increases e. always a positive potential
The monomer of the carbohydrates is __________.
Fill in the blank(s) with the appropriate word(s).