Cell Adaptations

Question 1

What does the size of a cell population in adults depend on?

Answer 1

Rate of proliferation
Rate of differentiation
Rate of cell death

Question 2

What are the possible outcomes of signalling?

Answer 2

Divide (enter the cell cycle)
Die (apoptosis)
Differentiate
Survive (resist apoptosis)

Question 3

What is autocrine signalling?

Answer 3

When the cell responds to the signal that itself produces

Question 4

What is paracrine signalling?

Answer 4

A cell produces a signalling molecule which acts on adjacent cells.

Question 5

What is endocrine signalling?

Answer 5

When a hormone is produced by an endocrine organ and this is converted in the blood stream to target cells.

Question 6

What modes of cell to cell signalling are there?

Answer 6

Hormones
Direct cell-cell or cell-stroma contact
Local mediators

Question 7

What do growth factors affect?

Answer 7

Proliferation
Cell locomotion 
Contractility
Differentiation
Angiogenesis

Question 8

Mechanism of action for growth factors?

Answer 8

Bind to receptors and stimulate the transcription of genes that regulate the entry of the cell into the cell cycle and the cell’s passage through it.

Question 9

Epidermal growth factor

• produced by?
• cells it acts on?
• receptor?
• what it does

Answer 9

Produced by macrophages, keratinocytes, inflammatory cells
Acts on epithelial cells, hepatocytes, fibroblasts
Binds to epidermal growth factor receptor
Mitogenic for the above cells

Question 10

What does vascular endothelial growth factor do? Which situations?

Answer 10

Induces blood vessel development (vasculogenesis) and blood vessel growth (angiogenesis)
Works in tumours, wound healing and chronic inflammation

Question 11

What is platelet-derived growth factor produced by?

Answer 11

Stored in alpha granules in platelets. Released on platelet activation. Also produced by macrophages, endothelial cells, smooth muscle cells and tumour cells.

Question 12

What does platelet-derived growth factor do?

Answer 12

Causes migration and proliferation of fibroblasts, smooth muscle cells and monocytes.

Question 13

Phases of the cell cycle?

Answer 13

G1 - S - G2 - M

Question 14

What is interphase?

Answer 14

Contains the stages G1, S and G2

Question 15

What happens in G1?

Answer 15

Cell growth

Question 16

What happens in S?

Answer 16

DNA is replicated

Question 17

What happens in G2?

Answer 17

Cell prepares to divide

Question 18

When are the different check-points?

Answer 18

R - towards the end of G1
G1/S
G2/M

Question 19

What happens at the G1/S checkpoint?

Answer 19

Checks DNA damage before DNA replication

Question 20

What happens at the G2/M checkpoint?

Answer 20

Checks DNA damage after DNA replication

Question 21

What happens if there is something wrong at the checkpoint?

Answer 21

p53 protein delays the cell cycle and triggers DNA repair mechanisms or apoptosis if DNA cannot be repaired.

Question 22

What regulates progression through the cell cycle?

Answer 22

Cyclin proteins

Cyclin-dependent kinases (enzymes)

Question 23

What does labile mean? Example?

Answer 23

Stem cells divide persistently to replenish losses

Surface epithelial such as epidermis, gut epithelium and bone marrow cells

Question 24

What stage of the cell cycle are stable cells in?

Answer 24

G0

Question 25

What does stable mean?

Answer 25

Cells which are in G0 but can enter G1 by activation of a large number of genes such as proto-oncogenes

Question 26

Examples of stable cells?

Answer 26

``` Hepatocytes Bone osteoclasts Fibroblasts Vascular endothelial cells Smooth muscle cells ```

Question 27

Examples of permanent cell populations?

Answer 27

Cardiac and skeletal muscle | Brain neurones

Question 28

What are permanent cell populations?

Answer 28

Stem cells cannot mount an effective, proliferative response to significant cell loss. The mature cells have left the cell cycle and cannot replicate.

Question 29

What replaces neurones if they are destroyed?

Answer 29

Glial cells

Question 30

What is asymmetric replication?

Answer 30

When stem cells divide, they produce two daughter cells - one a stem cell - one differentiates into a mature, non-dividing cell

Question 31

What is cell adaptation?

Answer 31

The state between a normal, unstressed cell and an injured, overstressed cell

Question 32

What is regeneration?

Answer 32

The replacement of cell losses by identical cells in order to maintain the size of a tissue or organ

Question 33

Under what conditions can regeneration and resolution not occur?

Answer 33

If the harmful agent persists If there is extensive tissue damage If the tissue damaged is permanent tissue

Question 34

Give two examples of when regeneration is seen

Answer 34

In the liver after a hepatectomy | In the epidermis by keratinocytes after a burn

Question 35

What is hyperplasia?

Answer 35

Increase in tissue or organ size due to an increase in cell numbers

Question 36

In which types of populations can hyperplasia occur in?

Answer 36

Labile and stable cell populations

Question 37

Two types of physiological hyperplasia?

Answer 37

Hormonal - increase in function capacity | Compensatory - increase in tissue mass after tissue damage

Question 38

Examples of physiological hyperplasia?

Answer 38

Increased production of erythrocytes in bone marrow due to low oxygen content of blood Proliferation of endometrium under influence of oestrogen

Question 39

Examples of pathological hyperplasia?

Answer 39

Epidermal thickening in eczema and psoriasis | Enlargement of the thyroid gland in response to iodine deficiency

Question 40

What is hypertrophy?

Answer 40

Increase in organ/tissue size due to an increase in cell size, not cell number!

Question 41

What makes the cells bigger in hypertrophy?

Answer 41

More structural components

Question 42

What is hypertrophy done in response to?

Answer 42

Increased functional demand | Hormones

Question 43

Examples of physiological hypertrophy?

Answer 43

Skeletal muscle - body builders | Smooth muscle in a pregnant uterus

Question 44

Examples of pathological hypertrophy?

Answer 44

Ventricular cardiac muscle hypertrophy

Question 45

What is atrophy?

Answer 45

Shrinkage of a tissue/organ due to an decrease in cell size/number.

Question 46

What is atrophy due to?

Answer 46

A decrease in supply of growth factor/nutrients

Question 47

Example of physiological atrophy?

Answer 47

Ovarian atrophy in post-menopausal women | Decrease in size of uterus after parturition

Question 48

Causes of pathological atrophy?

Answer 48

``` Denervation Disuse Inadequate blood supply Inadequate nutrition Loss of endocrine stimulation Persistent injury Ageing Pressure ```

Question 49

What is metaplasia?

Answer 49

The reversible change of one differentiated cell type to another

Question 50

Examples of metaplasia?

Answer 50

Bronchial pseudostratified columnar epithelium to stratified squamous in the lung from cigarette smoke Change of oesophageal stratified squamous to gastric-type epithelium with persistent acid reflux

Question 51

What is aplasia?

Answer 51

The complete failure of a tissue/organ to develop | It is an embryonic developmental disorder

Question 52

What is hypoplasia?

Answer 52

The under development or incomplete development of a tissue/organ

Question 53

What is dysplasia?

Answer 53

The abnormal maturation of cells within tissues

Question 54

How do CDKs drive the cell cycle?

Answer 54

Phosphorylate proteins that are critical for the progression of the cell into the next stage of the cycle