MoD Session 7- Cellular Adaptations Flashcards
What regulates normal cell proliferation?
Proto oncogenes
What is the size of cell populations dependent on?
The rate of:
- cell differentiation
- cell proliferation
- apoptosis
What are the 4 outcomes for cells?
- differentiate (become specialised)
- divide (enter cell cycle)
- survive (resist apoptosis)
- die (apoptosis)
What are the three types of cell signalling?
- autocrine
- paracrine
- endocrine
What is autocrine signalling?
Where the cells respond to the signalling molecules that they themselves produce.
What is intracrine signalling?
Where the cell is affected by the signalling molecule that it produces, but this signal binds intracellularly and is never secreted.
What is paracrine signalling?
Where the signalling molecule produced by a cell acts on neighbouring cells.
What is endocrine signalling?
The cell secretes a hormone which travels in the blood stream to a distant target cell/ organ.
Cell to cell signalling can be via… (3)
- hormones
- local mediators
- direct cell-cell or cell-stroma contact
What codes for growth factors?
Proto Oncogenes
What distance do growth hormones act over?
Short distance
Apart from cell proliferation and inactivation, what else do growth hormones affect? (6)
- locomotion
- differentiation
- angiogenesis
- contractility
- activation
- viability
With respect to the cell cycle, how does increased tissue growth occur? (2)
- shortening the cell cycle
- conversion of quiescent cells to proliferating cells by causing them to enter the cell cycle.
Which phase of the cell cycle is distinctive under the light microscope?
M
What does phase M include?
- mitosis (nuclear division)
- cytokinesis (cell division)
What is the rest of the cell cycle called?
Interphase
What is cell progression controlled by and what do they do?
Checkpoints. They sense damage to DNA and ensure that damaged DNA does not replicate.
Wait is the most critical checkpoint and where is it found?
The restriction (R) checkpoint. It is found at the end of G1.
What happens if checkpoint activation occurs?
The protein P53 comes into play and suspends the cell cycle and triggers DNA repair (if poss) or apoptosis.
Which protein and its associated enzyme control the cell cycle progression?
Cyclins
Cyclin-dependent kinases (CDKs)
What do activated CDKs do
Phosphorylate proteins so that they can move to the next stage of the cell cycle.
What is the activity of cyclin-CDK complexes regulated by?
CDK inhibitors
What are labile cells and give 2 examples.
Ones that continue to multiply throughout life.
Bone marrow and epithelium.
What are stable cells and give 2 examples.
Stable cells are ones that both mature and stem cells can proliferate if needed, in regenerative bursts. They are usually quiescent.
Examples liver and kidney cells.
Define quiescent.
Dormant
What are permanent cells and give 3 examples.
They are cells that are permanently differentiated and therefore cannot proliferate.
Examples are cardiac muscle, skeletal muscle and neural tissue
What are stem cells?
Cells with prolonged proliferation activity that show asymmetric replication.
What is asymmetric replication?
Where one daughter cell remains as a stem cell and the other goes on to differentiate into another cell type.
Are stem cells present in permanent cell populations?
Yes but they cannot amount an effective proliferative response to significant cell loss.
What is cell adaptation?
It is the state between a normal, unstressed cell and an over stressed injured cell. It is reversible.
What is regeneration?
The replacement of cells by identical ones to maintain organ/tissue size.
What is the hayflick number?
The number of cell divisions possible.
What is the human hayflick number?
61.3
What is reconstitution?
The replacement of a lost part of the body.
What is hyperplasia?
An increase in organ/tissue size due to increased cell numbers.
What does hormonal hyperplasia lead to?
Increase in functional capacity
What does compensatory hyperplasia lead to?
Increased tissue mass after injury.
What 2 cell populations can hyperplasia occur in?
Labile and stable.
Give an example of physiological hyperplasia
Increased bone marrow production of erythrocytes in response to hypoxia conditions.m
Give an example of a pathological hyperplasia
Epidermal thickening in chronic eczema and psoriasis.
What is hypertrophy?
An increase in organ/tissue size due to increased cell size.
Why are cells bigger in hypertrophy?
They have more structural components
What cell population is hypertrophy seen in?
Permanent
Give 2 physiological examples of hypertrophy
- skeletal muscle hypertrophy of a bodybuilder
- smooth muscle hypertrophy of a pregnant uterus
Give a pathological example of hypertrophy
Ventricular cardiac muscle hypertrophy in response to hypertension.
What is the disadvantage of cardiac hypertrophy?
Anoxia occur because although the number of capillaries increases, this is insufficient to satisfy the increased muscle mass.
What is compensatory hypertrophy and when does it happen?
It happens when you remove one of a pair of organs- the other organ increases in size to compensate for the loss of its partner.
What is atrophy?
A shrinkage of a tissue/organ due to reduced cell size and/or number.
What is cellular atrophy?
A decrease in cell size.
What is organ or tissue atrophy due to?
A decrease in cell size and apoptosis.
How does cells shrinkage occur?
By self-digestion. (Autophagosomes)
Give 2 physiological examples of atrophy.
- decrease in size of the uterus following parturition
- ovarian atrophy in post menopausal women.
Give 3 of the 7 listed examples of pathological atrophy. (See workbook for more)
- muscle atrophy due to disuse
- denervation atrophy. E.g in the hand due to median nerve damage
- peripheral vascular disease due to inadequate blood supply
- wasting of muscles due to malnutrition
- loss of endocrine stimulation
- persistent injury
- senile atrophy
What is metaplasia?
The replacement of one cell type with another cell type with a different phenotype.
Wha is the difference between metaplasic and dysplasic epithelium?
Metaplasic is fully differentiated
Dysplasic is disorganised and has an abnormal differentiation.
Give an example when metaplasia useful.
When bone marrow is destroyed by disease, splenic tissue undergoes metaplasia to bone marrow.
Give an example when metaplasia is not useful.
When cigarette smoke causes pseudostratified columnar epithelia in the oesophagus to change into stratified squamous epithelia.
What Is Aplasia?
The complete failure of a tissue or organ to develop, or an organ whose cells have ceased to proliferate.
It is an embryonic developmental disorder.
What is involution?
It is the normal, planned shrinkage of an organ.
E.g the uterus after childbirth.
What is hypoplasia?
The congenital underdevelopment or incomplete development of an organ or tissue. There are therefore an inadequate number of cells.
It is an embryonic developmental disorder.
What is atresia?
When there is no orifice produced. E.g the anus or vagina.
What is dysplasia?
The abnormal maturation of cells within a tissue.
