Pathology- Tissue and Cell Injury Flashcards
Homeostasis
Steady state which is closely maintained
Hyperplasia
Increase in number of cells
Must be in response to an external stimulus and will regress if withdrawn
Hypertrophy
Increase in cell size
Atrophy
Decrease in cell size
Metaplasia
When one mature cell type transitions into another
Three categorises of growth receptors
- receptors with intrinsic tyrosine kinase activity
- seven transmembrane GPCRs
- Receptors without intrinsic tyrosine kinase activity
Main stages in the cell cycle
- Growth 1
- Synthesis
- Growth 2
- Mitosis
What happens in G1 stage?
CDK4 is activated by Cyclin D and phosphorylates Rb
Cells get bigger with increased protein synthesis
What happens in S stage?
E2F initiates DNA replication and increases cyclin A levels
Cyclin A activates CDK2, which also promotes DNA replication
By end of this stage, the cell should contain 2 copies of its genome
What happens in G2 stage?
Cell gets bigger and more protein synthesis occurs
Main checkpoint occurs at the end of this stage
What happens in M stage?
Copied DNA and cytoplasm is divided
2 new cells are made, which go to stage G1
Role of retinoblastoma protein
Usually bound to E2F in order to prevent initiation of cell division
Rb cannot bind to E2F when phosphorylated by CDK4
What is the main checkpoint protein?
P53
What does P53 do?
Checks for mistakes in cell cycle
if the cell cannot be repaired, it is instructed to self destruct
If not able to divide, what do cells do?
They are terminally differentiated ie they exhibit replicative senesence
