Cellular Response to Stress and Toxic Insults Flashcards
What are four types of cellular adaptations to stress?
Atrophy - shrinkage of cells
Hypertrophy - increase in the size of cells which results in enlargement of the organs
Hyperplasia - increased number of cells in an organ or tissue
Metaplasia - transformation or replacement of one adult cell type with another
What are the mechanisms of atrophy?
Increased catabolism of cell organelles
Decreased protein synthesis
Increased protein degradation via ubiquitin-proteasome pathway
Increased autophagy
What is Brown atrophy?
During atrophy, undigested lipids are stored as residual bodies called Lipofuscin granules that impart a brown coloration to the tissue
What causes hypertrophy?
Response to increased workload; induced by growth factors produced in response to mechanical stress or other stimuli
Occurs in tissues incapable of cell division
What triggers the molecular pathogenesis of cardiac hypertrophy?
The integrated actions of mechanical sensors (triggered by increase workload), growth factors, and vasactive agents
These activate complex signal transduction pathways
What is the result of the activation of the signal transduction pathways associated with cardiac hypertrophy?
Muscle cell synthesize more proteins and the number of myofilaments increases
a isoform of myosin heavy chain is replaced by B form
Atrial natriuretic factor is re-induced, causing decrease in blood volume
What is physiologic hyperplasia?
Caused by the action of hormones or growth factors that occurs:
when there is a need to increase functional capacity
or when there is a need for compensatory increase after damage or resection
What is pathologic hyperplasia?
Usually due to excessive hormonal stimulation and/or effects of growth factors
What is the cause of metaplasia?
Usually results from chronic irritation
Seem to precede development of cancer
Thought to arise from reprogramming of undifferentiated cells
When does metaplasia from columnar to squamous occur?
Occurs in respiratory tract in response to chronic stress (e.g. smoking) and vitamin A deficiency
Stones in excretory ducts can also cause this type of metaplasia
What is Barrett esophagus?
Esophageal squamous epithelium is replaced by intestinal-like columnar cells under the influence of refluxed gastric acid
What is Connective tissue metaplasia?
Formation of cartilage, bone, or adipose tissue in tissues that normally do not contain these elements
What is cellular adaptation?
Cells are capable of adjusting their structure and functions in response to various physiological and pathological conditions
What are four ways that cell injury can result from oxygen deprivation?
Hypoxia
Ischemia
Hypoxemia
Perfusion defects
What are the four principal targets and biochemical mechanisms of cell injury?
Mitochondria and their ATP and ROS under pathologic conditions
Damage to cellular membranes
Disturbance in calcium homeostasis
Damage to DNA and misfolding of proteins
