6-Adaptive Tissue Responses Flashcards
Define adaptive changes.
Changes in mature cells and tissues after growth has occurred
What are the factors that determine a cells ability to adapt?
Vulnerability to certain agents State of differentiation (labile/stable/permament) Blood supply Nutrition Previous state of the cell
What are the different types of changes a cell/tissue can undergo?
Atrophy
Hyperplasia
Hypertrophy
Metaplasia
What is atrophy?
Reduction in the size of the organ or tissue due to decrease in size/number of its specialised cell
What can cause atrophy of an organ/tissue?
Decreased blood supply Loss of innervation Decreased workload (disuse) Prolonged pressure Loss of hormonal/endocrine stimulation Lack of nutrition Physiological Senile atrophy (aging)
Give an example of a physiological change that causes atrophy of a tissue/organ
Thymus undergoes involution during puberty
Uterus decreases in size after parturition
What is the process involved in atrophic changes of a cell/tissue/organ?
Apoptosis
Explain the mechanism of atrophic changes in cells/tissues
Apoptosis: decrease I’m the number if cells (decreased number of organelles)
Reduction cell size due to catabolic > anabolic processes (increased proteolysis/protein degradation by ubiquinisation stimulated by growth hormones and cytokines) - fewer mitochondria, myofilaments, ER and increased autophagic vacuoles
Define hyper trophy
Increase In size of an organ/tissue due to an increase in size of the specialised cells
Generally what causes an increase in size during hypertrophic changes?
Increased workload on cells that cannot divide to form new cells
Increased number of organelles that are limited by the SA:Vol therefore results in increase in size
What are the two categories of the causes of hypertrophic changes?
Compensatory (increased functional demand)
Hormonal (specific hormonal stimulation)
What are the compensatory causes of hypertrophy?
Removal of a kidney
Heavy work load of skeletal muscles
Increased BP in myocardium
What is are the hormonal causes of hypertrophy?
Pregnancy - hypertrophy of the uterus
What can stimulate the signal transduction pathways that cause increase in organelles and cell size during hypertrophy?
Mechanical/physical triggers
Tropic triggers
Give example(s) of mechanical or physical triggers in hypertrophic changes
Stretching of myocardium
What are some of the trophic triggers of hypertrophy?
Growth factors Vasoactive factors (cytokines and hormones)
What are the two possible forms of cardiac muscle hypertrophy?
Eccentric cardiac hypertrophy
Concentric cardiac hypertrophy
What is concentric cardiac hypertrophy?
Cardiac muscle hypertrophy with narrowing of heart chamber due to chronic pressure overloaded and increased resistance Reduced compliance (stiff) Reduced filling and diastolic dysfunction (shorter)
What is a possible outcome of the reduced filling and diastolic dysfunction consequence of concentric cardiac hypertrophy?
Possible cell death and ischemia
What type of cardiac hypertrophy occurs when there is chronic pressure overload and increased resistance (I.e. Vascular disease)?
Concentric cardiac hypertrophy
What type of cardiac hypertrophy occurs during exercise?
Increased blood supply to the heart results in eccentric cardiac hypertrophy
What occurs during eccentric cardiac hypertrophy?
Increased blood flow to the heart
Stress on heart due to volume overload
Lengthening of cardiomyocytes (not thickening)
Ventricular dilation
Normal relative sarcomere lengths - expansion to receive greater volume of blood
walls thicken in proportion to radius of chamber (dilation) therefore total size of chamber is relatively larger
What is the compensatory response to increase cardiac output in eccentric cardiac hypertrophy?
Dilation while stretching of cardiomyocytes allows increase in stroke volume
What will happen if cardiomyocytes are stretch beyond their limitations?
Decreases contractile strength (long term effects)
