Session 7 - Cellular Adaptations Flashcards
What is Paracrine signalling?
Cell secretes molecules that act on nearby cells
What is endocrine signalling?
Cells release molecules that travel in the bloodstream to a distant target cell
What is Intracrine signalling?
Molecules are made within the cell and act on receptors within the same cell
Describe Growth Factors
- local mediators involved in cell proliferation
- polypeptides that act on cell surface receptors
- coded for by pronto-oncogenes
- stimulate transcription of genes that determine whether the cell entered the cell cycle or not
Name some processes that growth factors have an influence on
- cell proliferation + inhibition
- locomotion
- contractility
- differentiation
- angiogenesis
Give some examples of growth factors
- Epidermal GF
- Vascular endothelial GF
- Platelet derived GF
- Granulocyte colony stimulating factor
Where are the three checkpoints of the cell cycle?
- End of G2
- End of G1
- R point
How is the R point passed in the cell cycle?
Hint: action of CDKs and Cyclin
- Cyclin binds to CDK, and activates it
- Complex can then phosphorylate RB protein
- Then the R-point can be passed
Describe Labile tissue, their normal state in the cell cycle and give some examples.
- Tissues that undergo rapid proliferation usually
- Normally involved in active cell division G1->M->G1
- E.g epithelial cells + Haematopoietic
Describe Stable cells, their normal state in the cell cycle and give some examples.
- Cells that state of division can be varied
- resting state is G0
- E.g Hepatocytes, osteoblasts, fibroblasts
Describe Permanent cells, their normal state in the cell cycle and give some examples.
- Unable to regenerate
- G0
- E.g Neurones, cardiac myocytes
Define Regeneration
Replacement of cell losses by identical cells to maintain tissue or organ size
Name some tissues that can regenerate well
Very well - Bone, Epithelia, Liver, smooth muscle
Well - Mesothelia
Melanocytes tend to over or under regenerate
Name some tissues that do not regenerate well
Poorly - Tendons, articular cartilage, striated muscle
Not at all - Adipocytes, CNS
Define Hyperplasia
Increase is tissue or organ size due to an increasing NUMBER of cells