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Flashcards in Cell injury Deck (38)
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1
Q

What is homeostasis?

A

The maintenance of a steady state/closely maintained

2
Q

What does the body do if there is increased demand?

A

Hyperplasisa and hypertrophy

3
Q

What will the body do if there is decreased demand?`

A

Atrophy

4
Q

What will the body do if there is altered stimulus?

A

Metaplasia

5
Q

What is hypertrophy?

A

Cells get bigger

6
Q

What is hyperplasia?

A

More cells grow - this will only occur if there is specific cell signals and increased cell division

7
Q

What are signals that can lead to hyperplasia?

A

More growth factor production

More growth factor receptor production

8
Q

What are the three types of growth receptors?

A

Receptors with intrinsic tyrosine kinase activity
7 transmembrane G-protein couples receptors
Receptors without intrinsic tyrosine kinase activity

9
Q

What happens if there are mistakes in the signals for growth and cell cycle development?

A

Cancer development

10
Q

How id the cell cycle controlled?

A

It is a stepwise progression through a series of stages that has various checkpoints that ensure faulty cells are not made. Faulty cells may predispose to cancers

11
Q

What are the 4 stages to the cell cycle?

A

G1, S, G2, M

12
Q

What controls the cell cycle?

A

Cyclin dependent kinases (CDK’s) that will activate each other and other enzymes in a step wise fashion. Each CDK is activated by a specific cyclin. Can be Cyclin D, E, A or B

13
Q

What occurs during G1?

A

The cell increases in size with increased protein synthesis

14
Q

How is G1 controlled?

A

During G1 CKD4 is activated by cyclin D. CDK4 phophorylates retinoblastoma

15
Q

What is retinoblastoma?

A

An important protein needed for normal cell growth. Normally Rb is bound to E2F

16
Q

What is E2F?

A

A protein that will kick off cell division but is prevented to by Rb. When phosphorylated by CDK4, Rb can’t bind to E2F and therefore E2F is free to give a green light to cell division

17
Q

What occurs during the S phase?

A

DNA synthesis occurs. E2F initiates DNA replication and increases levels of cyclin A.

18
Q

What does cyclin A do?

A

Activated CDK2

19
Q

What does CDK2 do?

A

Promotes DNA replication

20
Q

What occurs during G2?

A

Second growth phase where the cell gets bigger and more protein synthesis occurs. Main checkpoint for cell cycle.

21
Q

What is the main checkpoint protein at G2?

A

p53

22
Q

What does p53 do?

A

Checks cell for mistakes
Pauses cell cycle to allow for DNA repair
Initiate apoptosis

23
Q

What can a terminally differentiated cell not do?

A

Divide, an example is a neuron. These cells exhibit replicative senesence by qhich other cells must divide many times to either grow or replace lost cells

24
Q

What is a telomere?

A

The caps on chromosomes to provide protection and to stop the chromosome ends from degradation and fusion

25
Q

What does a telomere consist of?

A

A TTAGGG repeats and with every division , the number of repeats gets smaller

26
Q

What is an example of normal hyperplasia?

A

Hormonal such a during puberty the growth of breast tissue or during pregnancy, the growth of the lining of the womb

27
Q

What tissues will show compensatory hyperplasia?

A

Liver and bone marrow

28
Q

What are some examples of pathological hyperplasia?

A

Excess oestrogen will lead to endometrial hyperplasia and abnormal menstrual bleeding - usually post menopausal.
Hormonally induced prostatic hyperplasia in response to androgen’s

29
Q

What will occur during an infection?

A

The lymph nodes will undergo hyperplasia in response to an infection

30
Q

What will occur if the stimulus is withdrawn in hyperplasia?

A

It will be reversed as hyperplasia is reversible growth. Hyperplastic tissue however is at a risk for developing cancer

31
Q

When will hypertrophy occur?

A

Usually in conjuction with hyperplasia and often in isolation in non-divding cells e,g, cardiac myocytes or skeletal muscle
Often in response to mechanical stress

32
Q

When will hypertrophy become pathologic?

A

When the heart can no linger function and requires more blood supply than it is given. The muscles will also become less function when hypertrophy has occured

33
Q

What are physiolocical atrophy examples?

A

Embryological structures and the uterus after birth

34
Q

What are examples of pathological atrophy?

A

Decreased workload - e.g. if a limb has been in a cast
Loss of innervation
Loss of function after a nerve supply is removed
Blocked blood supply
Loss of hormonal stimulation e.g. a post menopausal uterus
Inadequate nutrition
Ageing
Pressure due to endogenous or exogenous structures

35
Q

What is the mechanism of atrophy?

A

The cellular components will be reduced and protein degradation will occur . The proteins will be digested in lysosomes.

36
Q

What hormones promote degradation?

A

Thyroid and glucocoricoids

37
Q

What hormones oppose atrophy and promote growth?

A

Insulin

38
Q

What retains homeostasis?

A

A balance of growth and atrophy