MoD 8 Cellular Adaptations

Question 1

What is the most critical checkpoint in the cell cycle?

Answer 1

Restriction (R) point towards end of G1

Question 2

What different methods of cell signalling are there?

Answer 2

Autocrine- cell reponds to signalling molecules its made itself
Paracrine- cell produces signalling molecule that acts on ajacent cells which are often a different type
Endocrine- response to hormones

Question 3

What happens is G1?

Answer 3

Cell grows

Question 4

What happens in S?

Answer 4

DNA replicates

Question 5

What happens in G2?

Answer 5

cell prepares to divide

Question 6

What happens at R?

Answer 6

Cell is checked for damage, passage governed by phosphorylation of Retinoblastoma protein pRB
p53 acts here to delay cell cycle, trigger reparative mechanisms or apoptosis if DNA cant be repaired

Question 7

How does pRB regulate R?

Answer 7

cyclin dependent kinases bind to cyclins, activating them and these phosphorylate rPB which allows cycle to continue

Question 8

What are labile cells?

Answer 8

e.g epithelial or haematopoeitic
normal state active cell division
usually rapid proliferation

Question 9

What are stable cells?

Answer 9

e.g hepatocytes, osteoblasts, fibroblasts
resting state- G0
Variable regeneration speed

Question 10

What are permanent cells?

Answer 10

e.g neurones, cardiac mycocytes
unable to divide G0
unable to regenerate

Question 11

What do stem cells do in labile cell populations?

Answer 11

Divide persistently to replenish losses

Question 12

What do stem cells so in stable cell populations?

Answer 12

Normally quiescent(dormant) or proliferate very slowly 
proliferate persistently when required

Question 13

What do stem cells do in permanent cell populations?

Answer 13

Present but can’t mount an effective proliferative response to significant cell loss (none present in cardiac muscle

Question 14

What is regeneration?

Answer 14

Replacement of cell losses by identical cells to maintain tissue or organ size

Question 15

What is hyperplasia?

Answer 15

Increase in tissue or organ size due to increased cell numbers
Can only occur in labile and stable populations
Physiological- proliferative endometrium
bone marrow at altitude
Pathological- thyroid goitre

Question 16

What is hypertrophy?

Answer 16

Increase in tissue or organ size due to increased cell size
Permanent cells cant divide so increase in size
In cells that can divide may occur alongside hyperplasia
Physiological- skeletal muscle
pregnant uterus (hyperplasia and hypertrophy)
Pathological- ventricular cardiac muscle hypertrophy
Bladder smooth muscle hypertrophy

Question 17

What is atrophy?

Answer 17

Shrinkage of tissue or organ due to decrease in size and/or number of cells
Organ/tissue atrophy typically due to a combo of atrophy and apoptosis
Physiological- ovarian atrophy postmenopause
Pathological- Muscle atrophy (denervation)
Cerebral atrophy (alzheimer’s)

Question 18

What is metaplasia?

Answer 18

Reversible change of one differentiated cell type to another
change in epithelium to be more suited to new environment
e.g smoker pseudostratified ciliated->squamous (robust)
sometimes prelude to dysplasia and cancer

Question 19

What is aplasia?

Answer 19

complete failure of a specific tissue or organ to develop

Question 20

What is hypoplasia?

Answer 20

Incomplete development of a tissue or organ

Question 21

What is dsyplasia?

Answer 21

Abnormal maturation of cells within a tissue

Question 22

Give some causes of pathological atrophy

Answer 22

reduced functional demand (disuse) e.g muscle
Denervation
inadequate blood supply e.g thinning of leg skin in peripheral vascular disease
Inadequate nutrition e.g muscle wasting
Loss of endocrine stimualtion
Persisitent injury
Aging (senile atrophy)
pressure