Cellular Adaptations Flashcards
What does the size of cell populations in adults depend?
The rate of cell proliferation, cell differentiation and cell death by apoptosis
What are increased cell numbers seen with?
Increased cell proliferation or decreased cell death
What may cell proliferation occur as the result of?
Physiological or pathological conditions
Give an example of where excessive physiological stimulation can become pathological
Prostatic hyperplasia
What do proto-oncogenes do?
Regulate normal cell proliferation
How do cells in a multicellular organisms communicate?
Through chemical signals
How is cell proliferation largely controlled?
Largely by signals (soluble or contact dependant) from the microenvironment which either stimulate or inhibit cell proliferation
What are the potential final outcomes of signalling biochemistry?
Divide
Differentiate
Survive
Die
How do cells divide?
They enter the cell cycle
What happens when cells differentiate?
They take on a specialised form and function
How do cells die when signalled?
They undergo apoptosis
What are the types of cell signalling?
Autocrine
Paracrine
Endocrine
What is autocrine signalling?
Cells respond to the signalling molecules that they themselves produce
What is intracrine signalling?
A type of autocrine signalling whereby the cell synthesises a factor which has an effect by binding to intracellular receptors within the cell.
The factor is therefore not secreted by the cell
What is paracrine signalling?
A cell produced the signalling molecule, which acts of adjacent cells
Where are the effector cells in paracrine signalling?
Close to the secreting cell
Are the cells affecting by paracrine signalling the same as the one secreting?
No, they are often of a different type
What is endocrine signalling?
Hormones are synthesised by cells in an endocrine organ, and then conveyed in the blood stream to target cells to effect physiological activity
What happens when a signalling molecule binds to a receptor?
It causes a series of events, which results in modulation of gene expression
Where are the receptors to signalling molecules located?
Usually in the cell membrane, but can also be in the cytoplasm or nucleus
Give an example of a type of receptor located in the nucleus?
Steroid hormone receptors
What can cell to cell signalling be via?
Local mediators
Direct cell-cell or cell-stroma contract
Hormones
What is particularly important amongst local mediators for cell proliferations?
Growth factors
What are growth factors?
Polypeptides that act on specific cell surface receptors