Life and Death

Question 1

What are the two types of cell death?

Answer 1

Necrosis

Apoptosis

Question 2

When do these Adaptive Responses occur:
Hypertrophy
Hyperplasia
Atrophy
Metaplasia

Answer 2

Hypertrophy - if more work is required
Hyperplasia - more work
Atrophy - less work (reduction in cell size and can be physiological or pathological)
Metaplasia - different work

Question 3

What happens if stress is too severe in terms of quantity of stress?

Answer 3

Hyperplasia and hypertrophy only cope so far.
They also take time to happen.
Therefore the cell undergoes cell death in the form of necrosis or apoptosis.

Question 4

What are the two options for Cell Death?

Answer 4

Necrosis or Apoptosis

Question 5

What is Necrosis?

Answer 5

Requires no energy
Always pathological (Abnormal. It does not occur normally).
Never occurs as a physiological phenomenon

Question 6

What is Coagulative Necrosis?

Answer 6

Preservation of cell outline.
Dead cells are consumed by various enzymatic processes and cells.
Microenvironment too toxic for proteolysis etc.
Common.
Often seen in cardia muscle. Myocardial infarction.

Question 7

What is Liquefactive Necrosis?

Answer 7

Liquid viscous mass - no cell structure remains.
Pus.
Associated with localised bacterial and fungal infections.
Necrosis within the brain.

Question 8

What is Caseous Necrosis?

Answer 8

Caseous necrosis (Cheesy necrosis).
Microscopic.
Usually associated with Tuberculosis.
Granulomatous inflammation with central necrosis.
If someone mentions caseous necrosis - think TB
Ask for culture, PCR and look for result of Ziehl Neelson stain.

Question 9

What is Apoptosis?

Answer 9

Programmed cell death in response to specific signals.
Requires Energy (ATP).
Sometimes cell death is physiological and we need cells to die off.
Counter-intuitively it may be a part of normal growth.
Removal of self reactive lymphocytes.
Hormonal-dependent involution.

Question 10

When does pathological apoptosis occur?

Answer 10

In response to injury.
Radiation (including UV light).
Chemotherapy.
Viral infection - hepatitis.
Cancers.
Graft versus host disease.

Question 11

What do mechanisms rely on?

Answer 11

All mechanisms rely on activating caspases.
This can be through 2 pathways:
Extrinsic
Intrinsic

Question 12

What is an Extrinsic Pathway?

Answer 12

Death receptor initiated pathway.
Cell membrane receptors with “death domain”.
Death receptors - Tumour necrosis factor (TNF), Fas.

Question 13

What is Fas and what can it lead to?

Answer 13

Fas - recognition of self
Apoptosis in lymphocytes.
People with Fas mutations often get autoimmune diseases.
TNF - complex but indices apoptosis in association with inflammatory conditions.

Question 14

What is an Intrinsic Pathway

Answer 14

Mitochondrial pathway.
Growth signals promote anti-apoptotic molecules in mitochondrial membrane.
When removed - replaced by Bax, Bak.
Increase permeability of mitochondria.
Release of proteins that stimulate caspases.
Cytochrome C.

Question 15

What is the role of p53

Answer 15

DNA damage.
Cells “sense” damage.
p53 halts cells cycle.
If DNA can’t be repaired then p53 stimulate caspases and induces apoptosis.

Question 16

What can Apoptotic abnormalities cause?

Answer 16

Too little - cancers, autoimmune diseases.
Too much - neurodegenerative disorders.
Ishaemic injury (heart attacks), viral infections (hepatitis).

Question 17

What is Morphology?

Answer 17

Cells shrink - pyknosis.
Chromatin condensation - nucleus clumps and breaks up.
Cytoplasmic blebs - cytoplasm breaks up.
Macrophages - come in to hoover everything up.

Question 18

What is Cellular Ageing?

Answer 18

Many causes.
Oxidative stress - free radical damage.
Accumulation of metabolism by-products.
- lipofuscin (is sometimes how it is seen down the microscope).