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
Give an example of reconstitution in humans
Small blood vessels + In small children if a fingertip is cleanly cut off
Define aplasia
Complete failure of a specific tissue or organ to develop
Give an example of aplasia
Kidney may not develop embryonically
Define involution
Normally programmed shrinkage of an organ
Give an example of involution
Uterus after childbirth, thymus in early life
Define Hypoplasia
Incomplete development of a tissue or organ
Give an example of Hypoplasia
Testes in Kleinfelter’s syndrome, chambers of heart
Define atresia
Abnormally closed or blocked orrifice or passageway
Give an example of atresia
Ovarian, tricuspid valve, segments of the bowel
Define Dysplasia
Abnormal maturation of cells within a tissue
What is Autocrine secretion?
Cell secretes molecules that act on its own cell surface receptors
