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
Name a physiological and pathological example of hyperplasia
Physio…- Proliferative endometrium + Bone marrow at altitude
Patho…- Thyroid Goitre
Define Hypertrophy
Increase in size of tissue or organ due an increasing SIZE of cells
Name a physiological and pathological example of Hypertrophy
Physio…-Skeletal muscle+pregnant uterus (hyperplasia as well)
Patho…- Ventricular cardiac muscle + bladder smooth muscle
What is compensatory Hypertrophy?
If we remove an organ which we have two of, the other will undergo Hypertrophy to compensate for the increasing workload
Define Atrophy
Shrinkage of a tissue or organ due to an acquired decrease in size and/or number of cells
Name a physiological and pathological example of Atrophy
Physio…- Ovarian atrophy in post-menopausal women
Patho…- Muscle atrophy due to Denervation + cerebral atrophy in Alzheimer’s
Define Metaplasia
Reversible change of one DIFFERENTIATED cell type to another
When is Metaplasia most common and what cell type changes into what?
In smokers
Pseudo stratified cilated epithelia become squamous to be more robust against the smoking toxins
Define Reconstitution
Replacement of a lost part of the body
