Session 7-Cellular Adaptations Flashcards
How is cell proliferation controlled?
- chemical signals
- when signalling molecule binds to receptor -> modulation of gene expression
What can the chemical signals make the cell do?
1) survive - resist apoptosis
2) divide - enter cell cycle
3) differentiate - take on specialised form and function
4) die - undergo apoptosis
How can a cell population increases its numbers?
- shortening cell cycle
- conversion of quiescent cells to proliferating cells by making them enter the cell cycle
Can cells with damaged DNA replicate?
No - if damaged DNA cannot be fixed, cell goes into apoptosis
What is the restriction (R) point?
Point near the end of G1 - if cells pass R point, they will complete the cell cycle (point of no return)
Which is the most commonly altered checkpoint in cancer cells?
R point - checkpoint activation delays cell cycle and triggers DNA repair mechanisms or apoptosis via p53
How is the cell cycle controlled?
cyclins or cyclin dependent kinases (CDKs)
How do CDKs become active?
Binding with cyclins
How can cells adapt?
1) hyperplasia
2) hypertrophy
3) atrophy
4) metaplasia
What is the least reversible cellular adaptation?
Atrophy
What is hyperplasia?
Increase in tissue or organ size due to increased cell numbers
In which types of tissues does hyperplasia occur?
Labile or stable tissues
What causes hyperplasia?
Increased functional demand or hormonal stimulation
True or false: hyperplasia remains under physiological control and is reversible
TRUE
What does repeated cell division expose the cell to?
Risk of mutations and neoplasia
What are some examples of physiological hyperplasia?
1) proliferative endometrium under the influence of oestrogen
2) bone marrow produces erythrocytes in response to hypoxia
What are some examples of pathological hyperplasia?
1) eczema
2) thyroid goitre
What is hypertrophy?
Increase in tissue or organ size due to increased cell size
In which types of tissue does hypertrophy occur?
Labile, stable but especially permanent tissues
How is workload shared by a greater mass of cellular components in hypertrophic cells?
Cells contain more structural components
What are some examples of physiological hypertrophy?
1) skeletal muscle in body builders
2) pregnant uterus (hypertrophy and hyperplasia)
What are some examples of pathological hypertrophy?
1) hypertension -> ventricular hypertrophy
2) enlarged prostate
3) proximal tissue to stricture in bowel hypertrophies to push food through
Why do patients with systemic hypertension/valvular disease have greater cardiac hypertrophy than athletes?
Patients’ heart never rests so more hypertrophy than athletes
How can systemic hypertension lead to fibrosis?
Cardiac muscle hypertrophies and heart responds by growing more capillaries but never enough to compensate so heart is hypoxic -> fibrosis -> problems with electrical conduction in heart
