The Decline of Physiological Effectiveness

The Decline of Physiological Effectiveness  Rate of cell division and number of cells reduce o All cells are capable to divide during embryological development o Cells lose ability to divide after birth or have a lower growth rate o Born with a fixed number of neurones → cannot divide/be replaced  Decline in functional effectiveness of cells and organ systems o Deterioration in cells / slower responds to stimuli / slows homeostatic mechanism / increases change of dysfunction and death  Ageing is controlled by genes but can be slowed down by o Regular (and adequate) sleep, (well balanced) meals, exercise o Refrain from smoking and alcohol o Keep body mass close to desirable mass for your height Effect of Age on  BMR o Number of cells decreases during ageing → lowers BMR o BMR decreases by ≈ 5% every 10 years above the age of 55 o 10-20 years - rapid decrease associated with adolescent growth spurt o 20-35 - no change as body same size / same level of activity o 30-70 - slow decrease associated with loss of muscles / gain of fat / reduced activity  CARDIAC OUTPUT = STROKE VOLUME x HEART RATE o Cardiac output decreases even though heart rate does not decline o Due to cardiac muscle fibres weaken (mainly left ventricle) o Decreases stroke volume of ventricles/volume of blood pumped per beat/cycle  NERVE CONDUCTION VELOCITY o Cells in peripheral nervous system and brain get less  Neurones (nerve cells) are lost and cannot d