Action potentials are the primary electrical responses of neurons and other excitable tissues, and they are the main form of communication within the nervous system.

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#Id: 191

#Unit 5. Developmental Biology

At slightly lower concentrations (intermediate concentrations), activin (about 100 molecules per cell) activated the Xbra gene and instructed the cell to become muscle.

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#Id: 192

#Unit 5. Developmental Biology

At lower concentrations of activin, genes were not activated, and the “default” gene expression instructed the cells to become blood vessels and heart.

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#Id: 930

#Unit 5. Developmental Biology

Stem cells are sometimes referred to as “undifferentiated” due to this maintenance of proliferative properties.

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#Id: 931

#Unit 5. Developmental Biology

Stem cell potential refers to the range of cell types a stem cell can produce. 

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#Id: 932

#Unit 5. Developmental Biology

A totipotent stem cell can generate all cell types of both embryonic and extraembryonic lineages. 

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#Id: 933

#Unit 5. Developmental Biology

The niche employs a variety of mechanisms of cell-to-cell communication to regulate the quiescent, proliferative, and differentiative states of the resident stem cell.