Cell Adaptations Flashcards
What does the size of a cell population depend on? (3)
- Rate of proliferation
- Rate of differentiation
- Rate of apoptosis
What molecules can stimulate or inhibit cell proliferation?
Growth factors
How to growth factors affect cell proliferation?
Bind to specific receptors on the cell surface membrane and stimulate transcription of genes that regulate entry into the cell cycle and the cell’s passage through it
Where is the R point in the cell cycle? Why is it significant?
- R point is at the end of G1 before S phase
- Point of no return - devotes the cell into the cell cycle
- Checkpoint activation delays cell cycle and triggers DNA repair or apoptosis via p53
- Most commonly altered checkpoint in cancer cells
What gene inhibits entry into the cell cycle?
Retinoblastoma gene (RB)
When do cellular adaptations occur?
In response to changes in homeostasis in order to prevent cell injury and cell death
Name the 5 main types of cell adaptations
- Regeneration
- Hyperplasia
- Hypertrophy
- Atrophy
- Metaplasia
What is regeneration? What tissues can this occur in?
- Replacement of lost/damaged cells with new functional differentiated cells
- Can occur in labile and stable tissues (not permanent tissues)
What are the outcomes of regeneration? (2)
- RESOLUTION if the harmful agent is removed
- TISSUE DAMAGE AND SCAR FORMATION if the harmful agent persists
When can newly regenerated cells which are not fully matured be advantageous?
- Influenza viral infection
- Influenza virus infects and multiplies in many cells, causing cell death
- Replaced by immature cells which do not have the receptor for influenza so are not harmed
What is reconstitution? Is this common in mammals?
- Replacement of a lost body part
- Not common in mammals, but can occur in other organisms e.g. Lizard tail can reconstitute itself after being severed
What is the difference between hyperplasia and hypertrophy?
- Hyperplasia is increase in tissue size due to increase in the NUMBER of cells, whereas hypertrophy is increase in tissue size due to increase in CELL SIZE
- Hyperplasia cannot occur in permanent cell populations as there are no stem cells present, so cells must undergo hypertrophy to increase organ size
Give 2 physiological examples of hyperplasia
- Proliferation of the endometrium under the influence of oestrogen
- Erythropoiesis in bone marrow in response to hypoxia at high altitudes
Give 2 pathological examples of hyperplasia
- Proliferation of epidermal basal layer in skin conditions such as eczema and psoriasis
- Hyperplasia of thyroid in iodine deficiency (goitre)
Why do permanent cells undergo hypertrophy instead of hyperplasia to increase organ size?
- Permanent cell types cannot regenerate or proliferate in post natal life as there are no stem cells present in the tissue
- Must undergo increase in cell size in order to increase organ size
- Hypertrophy results in more structural components so workload is shared