If the harmful agent is removed, damage is limited and regeneration can occur, resulting in full resolution of the damage. When a tissue is exposed to a harmful agent, it undergoes some tissue damage. Usually, regenerated cells are functionally identical to the cells they replace, however some cells take time to reach functional maturity. Regeneration is the replacement of cell losses by identical cells to maintain tissue or organ size. However, if the stimulus continues these adaptations may be inadequate and the cell may become permanently injured or die. These adaptations can usually be reversed if the stressor is removed. When cells experience environmental stressors or other stimuli, they undergo adaptations to allow them to function better and survive in this new environment. Stem cells are present but cannot proliferate effectively to replenish lost cells Stem cells proliferate very slowly or lie dormant, but can rapidly proliferate when required Stem cells divide repeatedly to replenish losses Tissues can be classified into 3 types depending on the ability to self-repair, which depends on their stem cell activity: Tissue type Thus where stem cells are present, new cells can be formed in response to disease, environmental stressors or normal replenishment of cells at the end of their lifespan. They are key to determining a tissue’s ability to replenish lost cells, as they are able to self-renew indefinitely. Stem cells are immature cells that can go on to differentiate into various specialised, mature cell types within a certain lineage. Cell differentiation – cell takes on specialised form and function. Cell division – cell enters the cell cycle.Ultimately, cell signalling results in one of four outcomes: Examples of growth factors include epidermal growth factor, vascular endothelial growth factor and platelet-derived growth factor. Growth factors act on cell surface receptors, stimulating transcription of genes that regulate the cell cycle. If cell proliferation becomes uncontrolled, and cells no longer respond to inhibitory signals, cancer can develop. Signalling may be via hormones, local mediators such as growth factors or direct cell to cell contact. Physiological cell proliferation is primarily regulated by chemical signals which either promote or inhibit proliferation. Increased cell numbers are therefore seen with either increased cell proliferation or decreased cell death.Ĭell proliferation occurs both in both physiological and pathological conditions. O'Connor CM, Whellan DJ, Lee KL, Keteyian SJ, Cooper LS, Ellis SJ, Leifer ES, Kraus WE, Kitzman DW, Blumenthal JA, Rendall DS, Miller NH, Fleg JL, Schulman KA, McKelvie RS, Zannad F, Pina IL (2009) Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial.The size of cell populations depends on the rate of 3 factors: Cardiovasc Res 73:10–18īernardo BC, Weeks KL, Pretorius L, McMullen JR (2010) Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies. Ventura-Clapier R, Mettauer B, Bigard X (2007) Beneficial effects of endurance training on cardiac and skeletal muscle energy metabolism in heart failure. Lippincott Williams & Wilkins, Philadelphia Katz AM, Konstam MA (2008) Heart failure: pathophysiology, molecular biology, and clinical management. Lorell BH, Carabello BA (2000) Left ventricular hypertrophy: pathogenesis, detection, and prognosis.
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