PYC2603 CHAPTER 02 SUMMARIZED
ADULT DEVELOPMENT AND AGEING
CHAPTER 02: PHYSICAL DEVELOPMENT AND SEXUALITY
2.1 Introduction
Physical development and changes have important psychological implications. Physical development
constitutes an important force in the development of an individual. For example:
The senses – such as the eye and the ear, detect or “capture” the different forms of stimuli
from our bodies or from the environment. The senses then send the information to the brain
where it is interpreted. The inability of the senses to detect stimuli adequately could have a
significant impact on an individual’s functioning and even on the ability to survive.
The central nervous system – especially the brain, is responsible for the interpretation of
this incoming information. It therefore plays a crucial role in all aspects of the cognitive
functioning of an individual.
The endocrine glands – which secrete hormones, play an important role in a variety of
developmental changes. For instance, hormones can influence the sexual behaviour,
metabolism and energy levels of individuals.
It is generally accepted that most of us reach the peak of our muscle power, stamina, elasticity,
agility, sensory perception and other aspects of physical development between 20 and 30 years of
age. Thereafter there is a gradual decline, which usually only becomes noticeable after the age of 40.
As in other developmental stages, individual differences regarding physical development are also
found during adulthood. For example, the South African Wally Hayward was 80 years old when he
completed the Comrades Marathon in 1989. [Page 46 for other examples]
From these examples it is clear how scientifically dangerous it is to classify people according to rigid
criteria such as age. The golden rule in psychology – every person is unique.
2.2. Biological Theories of Ageing
Biological theories of ageing includes a variety of theories that address the ageing process at
organismic, molecular and cellular levels. Most of these theories fall into two general categories:
programmed ageing theories and random error theories.
Programmed ageing theories are based on the assumption that ageing and death are built
into the genetic blueprint of all organisms. These theories propose a variety of viewpoints
regarding the ageing process, such as that the length of life is genetically programmed; that
ageing is programmed to start after reproductive ability ends; that molecular changes cause
cells to age and lose their ability to divide and reproduce; that changes occur in the
hypothalamus causing changes in the hormones that eventually bring about ageing in the
organism; and that loss of neurons in the brain cause ageing. The genetic programming
theory is discussed:
, The genetic programming theory. One explanation of ageing according to this theory is that
the cells constitute the body age in accordance with a master genetic programme innate to
every specific species. This means that every species has its own programme of ageing and
life expectancy, subject to only minor individual differences. For example, the approximate
maximum life span for rats is 4 years, sheep 15, cows 120 and humans 120 (the figures in
this regard depend on various factors and should be seen only as a broad indication).
Another viewpoint relates to cell-division. There is a limit to the number of times a cell can divide:
approximately 50 times in the case of a young human being. As the individual grows older, this
ability of cells to divide decreases; the cells therefore deteriorate until the person dies. It is unknown
how this self-destructing programme is activated or how it works. One theory suggests that
telomeres, the small tips of the chromosomes, play a major role.
Telomeres contain an important enzyme called telomerase which is needed to replicate the
telomeres and thus the cells. However, telomeres are shortened with each cell division and the
result is that telomeres eventually become so short and contain so little telomerase that cell division
cannot continue.
The genetic programming theory has an interesting link with cancer. Cancer cells seem to be
immortal; they do not stop dividing normally and they have no upper limit as far as dividing is
concerned. According to some researchers, the reason for this is that the cancer cells can keep the
telomerase level intact, which ordinary cells cannot.
The genetic programming theory is one of the most popular biological theories of ageing. One
reason or this is that it is logical and simple. However, does not mean the theory provides all the
answers. For example, brain cells do not typically divide but still deteriorate.
Random error theories are based on the assumption that ageing reflects unplanned changes
in an organism over time. This class of theories explains ageing as a result from the
accumulation of ‘insults’ from the environment which eventually reach a level incompatible
with life. For example, the stress of everyday life erodes biochemical processes in the cells
and interferes with their operation of basic functions, and chemical reaction with oxygen
causes unstable ‘free radicals’ that unite with other molecules and interfere with their
functioning.
The wear and tear theory. This theory argues that bodies age as a result of constant use,
more or less like machines, rather than being attributable to an innate genetic programme.
Decades of illnesses, injuries and wear and tear cause damage to the cell tissues and organs.
The inevitable result is that the body becomes progressively less able to repair the damaged
and worn out components. Eventually we die of, for example, heart, kidney and lung failure;
diseases that we could resist when we were younger. Note that environmental factors such
as toxins, radiation and poor diet can exacerbate (worsen) the wear and tear process. An
example of the wear and tear theory is osteo-arthritis where the cartilage protecting the
joints wears out and the joints become stiff and painful.
The free radical theory. The nucleus of an atom (the smallest part of any material) is
surrounded by a cloud of electrons, which could be described as elementary particles.
These electrons surround the nucleus in pairs, but occasionally an atom loses an electron,
leaving the atom with an unpaired electron. The atom is then called a ‘free radical’. These free
radicals have been described as scavengers that attack the structure of the cell membranes, thus
ADULT DEVELOPMENT AND AGEING
CHAPTER 02: PHYSICAL DEVELOPMENT AND SEXUALITY
2.1 Introduction
Physical development and changes have important psychological implications. Physical development
constitutes an important force in the development of an individual. For example:
The senses – such as the eye and the ear, detect or “capture” the different forms of stimuli
from our bodies or from the environment. The senses then send the information to the brain
where it is interpreted. The inability of the senses to detect stimuli adequately could have a
significant impact on an individual’s functioning and even on the ability to survive.
The central nervous system – especially the brain, is responsible for the interpretation of
this incoming information. It therefore plays a crucial role in all aspects of the cognitive
functioning of an individual.
The endocrine glands – which secrete hormones, play an important role in a variety of
developmental changes. For instance, hormones can influence the sexual behaviour,
metabolism and energy levels of individuals.
It is generally accepted that most of us reach the peak of our muscle power, stamina, elasticity,
agility, sensory perception and other aspects of physical development between 20 and 30 years of
age. Thereafter there is a gradual decline, which usually only becomes noticeable after the age of 40.
As in other developmental stages, individual differences regarding physical development are also
found during adulthood. For example, the South African Wally Hayward was 80 years old when he
completed the Comrades Marathon in 1989. [Page 46 for other examples]
From these examples it is clear how scientifically dangerous it is to classify people according to rigid
criteria such as age. The golden rule in psychology – every person is unique.
2.2. Biological Theories of Ageing
Biological theories of ageing includes a variety of theories that address the ageing process at
organismic, molecular and cellular levels. Most of these theories fall into two general categories:
programmed ageing theories and random error theories.
Programmed ageing theories are based on the assumption that ageing and death are built
into the genetic blueprint of all organisms. These theories propose a variety of viewpoints
regarding the ageing process, such as that the length of life is genetically programmed; that
ageing is programmed to start after reproductive ability ends; that molecular changes cause
cells to age and lose their ability to divide and reproduce; that changes occur in the
hypothalamus causing changes in the hormones that eventually bring about ageing in the
organism; and that loss of neurons in the brain cause ageing. The genetic programming
theory is discussed:
, The genetic programming theory. One explanation of ageing according to this theory is that
the cells constitute the body age in accordance with a master genetic programme innate to
every specific species. This means that every species has its own programme of ageing and
life expectancy, subject to only minor individual differences. For example, the approximate
maximum life span for rats is 4 years, sheep 15, cows 120 and humans 120 (the figures in
this regard depend on various factors and should be seen only as a broad indication).
Another viewpoint relates to cell-division. There is a limit to the number of times a cell can divide:
approximately 50 times in the case of a young human being. As the individual grows older, this
ability of cells to divide decreases; the cells therefore deteriorate until the person dies. It is unknown
how this self-destructing programme is activated or how it works. One theory suggests that
telomeres, the small tips of the chromosomes, play a major role.
Telomeres contain an important enzyme called telomerase which is needed to replicate the
telomeres and thus the cells. However, telomeres are shortened with each cell division and the
result is that telomeres eventually become so short and contain so little telomerase that cell division
cannot continue.
The genetic programming theory has an interesting link with cancer. Cancer cells seem to be
immortal; they do not stop dividing normally and they have no upper limit as far as dividing is
concerned. According to some researchers, the reason for this is that the cancer cells can keep the
telomerase level intact, which ordinary cells cannot.
The genetic programming theory is one of the most popular biological theories of ageing. One
reason or this is that it is logical and simple. However, does not mean the theory provides all the
answers. For example, brain cells do not typically divide but still deteriorate.
Random error theories are based on the assumption that ageing reflects unplanned changes
in an organism over time. This class of theories explains ageing as a result from the
accumulation of ‘insults’ from the environment which eventually reach a level incompatible
with life. For example, the stress of everyday life erodes biochemical processes in the cells
and interferes with their operation of basic functions, and chemical reaction with oxygen
causes unstable ‘free radicals’ that unite with other molecules and interfere with their
functioning.
The wear and tear theory. This theory argues that bodies age as a result of constant use,
more or less like machines, rather than being attributable to an innate genetic programme.
Decades of illnesses, injuries and wear and tear cause damage to the cell tissues and organs.
The inevitable result is that the body becomes progressively less able to repair the damaged
and worn out components. Eventually we die of, for example, heart, kidney and lung failure;
diseases that we could resist when we were younger. Note that environmental factors such
as toxins, radiation and poor diet can exacerbate (worsen) the wear and tear process. An
example of the wear and tear theory is osteo-arthritis where the cartilage protecting the
joints wears out and the joints become stiff and painful.
The free radical theory. The nucleus of an atom (the smallest part of any material) is
surrounded by a cloud of electrons, which could be described as elementary particles.
These electrons surround the nucleus in pairs, but occasionally an atom loses an electron,
leaving the atom with an unpaired electron. The atom is then called a ‘free radical’. These free
radicals have been described as scavengers that attack the structure of the cell membranes, thus
