1. AGING & DEATH
Unit 6: Biology 30S

2. AGING The study of aging is known as gerontology
Aging involves progressive and ongoing changes that lead to increased risk of acquiring disease and eventual death

3. WHY DO WE AGE?
1. Genetics
The number of times a cell divides is species specific. For humans, the maximum number of divisions is about 50 times.
Some cells may stop dividing before the maximum number is reached due to the accumulation of DNA mutations, while other cells may surpass the maximum number (cancer cells do this).
Children of long-lived parents also tend to live longer than those of short-lived parents, thus supporting a hereditary link.

4. WHY DO WE AGE? 2. Whole body processes
A decrease in hormones and immune system functioning occurs with aging.
The loss of elasticity of connective tissues (ligaments, tendons…) and blood vessel walls (atherosclerosis)

5. WHY DO WE AGE? 3. Extrinsic factors
Poor health habits (ex. Lack of calcium in the diet, heavy alcohol intake, high fat diet, lack of exercise, smoking) can contribute to early aging and early death. It is said that behaviour accounts for 40% of why we age
Osteoporosis is quite common in many aging people. It involves bone loss that may be accelerated by having poor health habits in ones youth (lack of milk in diet and lack of exercise).

6. HOW AGING AFFECTS BODY SYSTEMS
SKIN
PROCESSING & TRANSPORTING
Becomes thinner and less elastic
Has fewer sweat glands
Sags due to loss of adipose tissue (fat) – leads to a bony appearance and sensitivity to cold
Heart size shrinks from the reduction of cardiac muscle cell size
Arteries become more rigid and narrowed due to plaque build up (Arteriosclerosis)
Blood pressure may increase because of the arteriosclerosis
Reduced metabolic rate - resulting in reduced energy levels, weight gain and reduced ability of the liver to process drugs and toxins
Lungs become less elastic leading to decreased lung capacity
Kidneys become smaller and less efficient at filtering blood
Prostate gland in males enlarges and makes urination difficult
Digestive system slows down

7. HOW AGING AFFECTS BODY SYSTEMS
INTERGRATING & COORDINATION
REPRODUCTIVE SYSTEMS
No new muscle or nerve cells are formed by adults
Loss of short term memory is common due to loss of neurons in the cerebral cortex 
Reaction time slows down
Hearing decreased after age 50, especially of high frequency sounds
Cataracts may form in the lens of the eye
Skeletal muscle mass decreases – though this can be controlled by regular exercise 
Bone mass decreases
Development of arthritis in joints
Females undergo menopause – the walls of the oviducts and vagina narrow and female sex hormone levels fall dramatically.
Males undergo andropause – the levels of male hormones (androgens) falls gradually. Males continue to produce sperm until death.
Females may live longer than males due to the protective effect of estrogen against cardiovascular disease.

8. DEATH & DYING Physiology of dying
Somatic death (death of cells) involves a series of irreversible events, leading to cell destruction and death.
Physiological death (death of whole body) comes after the irreversible death of all vital body systems.

9. DEATH & DYING
The body goes through many physiological changes that occur along with the event of death:
Respiratory System
The lungs become unable to oxygenate the body enough for adequate gas exchange.
Breathing becomes noisy.

10. DEATH & DYING Cardiovascular System
The body goes through many physiological changes that occur along with the event of death:
Cardiovascular System
The heart is unable to pump strongly enough to keep blood moving fast enough – blood begins to back up in the heart and ultimately backs up into the lungs and liver, causing congestion/fluid build up – the pulse will be weak.
The decreased blood supply to the body causes the skin to become cool to the touch and pale in color.
The metabolic rate will also decrease as the cardiovascular system fails – listlissness due to lack of energy.
A few hours before death occurs, the pulse will also become irregular.

11. DEATH & DYING
The body goes through many physiological changes that occur along with the event of death:
Urinary System
Urine production and output decreases, as the kidneys will not be filtering blood very fast.
A person will become incontinent – lose control over their bladder.
Digestive System
Since the digestive system will be working very slowly, there will be a decreased production of feces. A person will eventually lose control over their bowels.

12. DEATH & DYING Urinary System
Urine production and output decreases, as the kidneys will not be filtering blood very fast.
A person will become incontinent – lose control over their bladder.
Digestive System
Since the digestive system will be working very slowly, there will be a decreased production of feces. A person will eventually lose control over their bowels.
Nervous System
Decreased oxygen to the brain will result in a decrease in brain functions.

13. THE DEFINITION OF DEATH
The study of death is known as Thanatology
There is some difference between medical/clinical, legal and biological definitions of death – it has not been easy to establish the definition.
Legal death has been defined as the irreversible cessation of all functions of the entire brain – that is, brain death - when the whole brain, including the brain stem (medulla and pons) have stopped functioning and cannot exhibit control over the lungs or heart.
Medical/Clinical death - the standard criteria for establishing death is when the heart, lungs and brain – vital organs - stop working – and cannot start working again – that is, when these processes become irreversible:
absence of respiration without assistance
absence of heart beat without assistance
flat EEG

14. THE DEFINITION OF DEATH
When the above signs are present along with the absence of papillary (eye) reflexes, the clouding of the cornea, as well as the absence of movement, death has certainly occurred. 
Studies show that medical/clinical death (which has been described above) is not the same as biological death.
BIOLOGICAL DEATH: termination of all biological functions that sustain a living organism.

15. THE DEFINITION OF DEATH
For example the following were THOUGHT to continue to occur for several hours after medical/clinical death:
Hair and nails continue to grow (This is false – dehydration makes the skin shrink away ) 
Liver continues to convert glycogen to glucose (TRUE)
Muscles continue to contract – leading to rigor mortis (lactic acid accumulates in the muscles, leading to their stiffness). (TRUE)

16. THEORETICAL STAGES OF DEATH
Descent
Through death’s portals; defined by its irreversibility in which individual is
in death’s grip and cannot escape; the irreversibility is due to failure of a
one or small number of vital systems such as brain, kidney, heart, lungs. II
Systems collapse
Spiraling or cascading effect of failure of all vital systems; the failure of one
or a few systems in Phase I leads to cascade-like shutting down.
III
Mortification
Final death throes; immobilization; onset of lethargy, morbidity, and/or paralysis.
This is a continuation of the collapse but here it occurs in the non-vital systems such as sensory, visual and so forth that cannot be sustained due to collapse of vital systems in Phases I and II. IV
Expiration
Final release; extinction of all signs of life of individual as a whole. A few
twitches so this phase too occurs over a period of time and is not instantaneous.