Lecture Eleven

• Adulthood = Age 20 to death • Young adulthood = 20-40 yrs • Middle Aged = 40-65 yrs • Older Adult = 65 yrs to death • Three generations: • 65-75 • 75-85 • 85+ • Ageing = the process of ageing • Senescence = the process of deterioration with age

o Our cells constantly divide to replace and build -The chromosomes in those cells become damaged and deteriorate -Therefore, our new cells are not what they used to be o Free radical theory of ageing -Free radicals can alter the structure of molecules -Resulting in damage/dysfunction o Decline of mitochondrial DNA -Result in a decline in ATP production o Immune system becomes less efficient o Genetic traits o Reduced ability to maintain homeostasis

-We do know it is: o Complex and o Multifactorial -Three stages of ageing: o Basic homeostasis -e.g. body temp, pH o Decrease in organ mass o Decline in function -Behavioural adaptations

-Reduction in arterial elasticity o = increased stiffness of arteries and aorta = elevated aortic pressure = left ventricular hypertrophy -Can cause an increase in increased

-Cardiac tissue o Accumulation of lipids and collagen = Increase in cardiac muscle stiffness and less compliant

-Heart valves become less flexible o Primarily the semilunar valves = abnormal functioning

-SA node cells decrease o Electrical activity alters

-HR o Maximum HR declines -220 - age -Response to epinephrine and norepinephrine declines

-SV o Can decline due to heart being less compliant therefore less blood being ejected o Can also stay the same

-CO o Declines with age

-VO2 o Declines from aged 50 -Due to increased fat tissue -Decreased CO -Decrease in Physical activity

-Vital capacity decreased o Decreased ability to fill lungs -Inspiratory reserve volume decreases o Decreased ability to empty lungs -Expiratory reserve volume decreases

-Weakened respiratory muscles -Decreased thoracic cavity compliance (ability to stretch and expand) o Stiffening of cartilage and ribs

-Residual volume increases o Dead space increases -Due to bronchioles and alveolar ducts expanding -Loss of elasticity

-Decreased gas exchange across respiratory membrane o Alveolar walls are reduced (decreased surface area) and thickened -Gradual rise in tidal volume -Mucus builds up o Cilia decrease in number and movement

-Kidneys decrease in size -Amount of blood flowing through decreases -Afferent and efferent arterioles twist and become irregular -Glomeruli are destroyed o By 80, 40% are not working -Nephrons and collecting ducts structure alter by becoming shorter, thicker and irregular -The ability to secrete and absorb declines = ability to produce concentrated urine declines o Decreases ability to get rid of toxins o Increased risk of dehydration -Loss of responsiveness to ADH and Aldosterone -Decreases in renin secretion

-Thinning of the mucosa and submucosa o Less mucous secreted -Reduced protection from toxins from the outside -Reduced ability of the liver to detoxify -Susceptibility to infections -Decrease in blood supply -Decrease in smooth muscle cells o Reduced mobility -Less secretions from major secretory organs -Muscles of mastication are weakened o Less mechanical digestion

• Gradual decrease in secretory activity in some glands - This maybe secondary to a general decline in physical activity

• GH levels decrease - may explain the decline in muscle and bone mass in the elderly. Greater in those that don’t exercise. • Thyroid hormones decrease slightly – may be because of a decline in lean body mass. Damage by the immune system, due to aging, may also occur and cause a decline in T3 and T4 production.

• Increase in parathyroid hormone but reduced blood levels of Ca2+ due to reduced dietary intake = loss of bone matrix to maintain blood levels. • Thymus gland secretes thymosin = development and maturation of the immune system • Secretion decreases with age causing a reduced efficiency of the immune system and subsequent increase in susceptibility of infection

Integumentary System -Skin is easily damaged due to: o Collagen decreases o Epidermis thins -Skin sags and is wrinkled due to: o Loss of subcutaneous adipose tissue o Loss of dermis elastic fibres

-Sebaceous gland secretions decrease -Reduced peripheral blood flow o Reduced ability to regulate temperature -Increased risk of heat exhaustion and illness

-Disturbed sleep patterns o Possibly due to a decrease in melatonin Melatonin -Simulation o A decrease in light entering the eyes -Response o Increase in Melatonin o = inhibit GnRH and may regulate the sleep cycle -Melatonin increased at night = helps us to sleep -Melatonin decreased in the morning = helps us wake