Download THE CELL THEORY

[Frequently Asked Questions]
Ageing – Concepts & Models
Subject:
Zoology
Course:
B.Sc. 3rd Year
Paper No. & Title:
Z-305B
Developmental Biology
Topic No. & Title:
Topic – 10
Ageing – Concepts &
Models
Lecture Title:
Ageing – Concepts &
Models
Frequently Asked Questions
Q1. What is the difference between cellular and extracellular theories of ageing?
A1. The major theories explaining ageing are broadly
categorized into two groups: the first deals with ageing at the
level of the cell and is called as the cellular theory and the
second is the extra-cellular theory or systemic theory that
takes into account the entire body for an understanding of
the ageing process.
Q2. What type of cells in body does not lose their
youthful vigor?
A2. There are certain cells in the body which never lose their
youthful vigor or capacity to divide, even in aged adults.
Examples of such cells are the germinal epithelium of the
skin and the intestine, the stem cells of the bone marrow,
the spleen cells, etc. Certain example suggests that man
survives his longevity even with one kidney or one lung.
Therefore loss of some cells or even an organ does not
materially affect his longevity.
Q3. Explain systemic theory of ageing.
A3. According to the systemic theory, changes causing
ageing are systemic in nature and occur in organ systems.
These changes are not the same as those ones arising due to
cell death or loss. The tissues which form organs interact
with each other and thus one tissue if injured will cause
defects in the dependent system. Organic bulk is made up of
extra-cellular matrix consisting of collagen fibers, ground
substance
and
connective
tissue.
Ageing
in
these
components leads to an effect of the entire body leading to
degeneration.
Q4. What is the role of collagen and ground substance
in ageing?
A4. Ageing of collagen in mammals begins when growth
ceases and synthesis of collagen stops. During growth period,
the proportion of collagen fibers and ground substances in
the
extra-cellular
matrix
changes
such
that
fibers
predominate at the cost of the ground substance. This badly
affects the normal functions of the matrix such as the
capacity of water retention, transport of oxygen, nutrients,
metabolites, hormones, antigens, etc. Brain is subject to the
stress of hypoxia resulting in a decrease in its physiological
and psychological efficiency.
Q5. What is autoimmune phenomenon?
A5. With age, defects in the immune response system cause
decrease in body capacity for defense and in production of
antibodies against organism’s own antigens. This effect of
ageing is called autoimmune phenomenon. Rheumatoid
arthritis is an autoimmune disease common in man.
Q6. Why are wrinkles formed in skin on ageing?
A6. Collagen constitutes about a third of the total body
protein in skin, muscles, tendons and skeletal tissues of bone
and cartilage as an extra-cellular filler substance. Ageing
changes
in
collagen
arise
by
thermal
denaturation
of
macromolecules resulting from sustained exposure to high
temperature
Insolubility
of
of
body
in
warm-blooded
macromolecules
brings
about
vertebrates.
rigidity
of
organs, badly affecting their elasticity and contractility. This
is clearly manifested in skin and blood vessels. Skin shows
wrinkles and the diffusion of substances between blood and
surrounding tissues gradually decreases.
Q7. Enumerate certain changes during ageing in man.
A7. Changes during ageing in man can be enumerated as
follows:
•Changes in physical appearance like skin becoming wrinkled
and less elastic, producing a typical “old man” look.
•Changes in physiological abilities such as lowered energy
reserve, decrease in perceptual acuity and loss in defense
mechanism.
•Decline in mental abilities leading to psychological ageing.
•General atrophy of body organs leading to greater infirmities
like decline in muscular strength and coordination between
activities, bones susceptibility to easy fracture, loss in
flexibility of joints, etc.
•Depression, anger, fear, anxiety and apprehension are
emotional stresses affecting mind and behavior.
Q8. What are the biochemical changes associated with
ageing?
A8. Some biochemical changes associated with ageing are:
 Increase in cholesterol and triglyceride level,
 Increase in Blood globulin levels,
 Decrease in alkaline and acid phosphatases,
 Decrease in cellular respiration and
 Increase in serum creatinine.
Q9. What are the symptoms of ageing in brain?
A9. The symptoms of ageing in brain includes atrophy of the
brain and increase in size of brain ventricles, loss of brain
weight (1400 gms at age 20 to 1334 gms at age 60), loss of
white matter, shrinkage of dendrites, loss of nerve cells,
accumulation of age pigment- lipofuscin, increase in cerebral
amyloid, decrease in synaptic density in cerebellum, loss of
cerebellar purkinje cells, decline in cerebellar integrative
functions, decline in learning, decline in short term memory
and recall from long term storage.