The Decline of Physiological Effectiveness Rate of cell division and number of cells reduce All cells are capable to divide during embryological development Cells lose ability to divide after birth or have a lower growth rate Born with a fixed number of neurones → cannot divide/be replaced Decline in functional effectiveness of cells and organ systems 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 Regular (and adequate) sleep, (well balanced) meals, exercise Refrain from smoking and alcohol Keep body mass close to desirable mass for your height Effect of Age on BMR Number of cells decreases during ageing → lowers BMR BMR decreases by ≈ 5% every 10 years above the age of 55 10-20 years - rapid decrease associated with adolescent growth spurt 20-35 - no change as body same size / same level of activity 30-70 - slow decrease associated with loss of muscles / gain of fat / reduced activity CARDIAC OUTPUT = STROKE VOLUME x HEART RATE Cardiac output decreases even though heart rate does not decline Due to cardiac muscle fibres weaken (mainly left ventricle) Decreases stroke volume of ventricles/volume of blood pumped per beat/cycle NERVE CONDUCTION VELOCITY Cells in peripheral nervous system and brain get less Neurones (nerve cells) are lost and cannot divide Effect of cell loss depends on cells location Brain loses ≈25% of cells that control muscular movement but hardly any that control speech → changes muscle coordination but not ability to speak LOSS OF MYELIN: no saltatory conduction / impulses cannot jump from node to node / impulses must pass through greater amount of membrane INCREASED WIDTH OF SYNAPSES: longer needed for diffusion/movement/greater distance to receptors/further to stimulate post-synaptic membrane/further diffusion distance of transmitter (across synapse) SLOWER SYNAPTIC TRANSMISSION: presynaptic neurones produce less neurotransmitter Female reproductive capacity → MENOPAUSE (45-55 year old women) Ovaries gradually become insensitive to FSH / secretion of oestrogen becomes less / ovulation becomes less / menstrual cycle becomes less / vagina walls become thinner / woman is infertile when oestrogen secretion stops Levels of gonadotrophins (FSH, LH) rise to a peak after menopause At menopause, oestrogen no longer secreted FSH and LH no longer inhibited by negative feedback SYMPTOMS: due to loss of oestrogen Intense sweating / uncomfortable warmth / psychological problems Increase risk of osteoporosis (loss of bone tissue) and heart diseases TREATMENT: Hormone replacement therapy (HRT) Postmenstrual woman take in small doses of oestrogen and progesterone As tablets (orally) or apply implants beneath skin (skin patches)