Old Skin and Old Muscles: What Happened and Why
For
more detailed information, go to http://www.biologyofhumanaging.com/
1.
Why
does skin wrinkle?
a. less water in the skin - The skin thins and wrinkles like a grape becoming a raisin.
b.
damaged
elastin fibers - The skin holds less water and is less elastic, pliable, and
resilient
c.
damaged collagen fibers - The skin holds less water and is less
elastic, pliable, and resilient.
d.
less fat, especially in the face, hands, arms, feet, and legs - There
is less fat under the skin to keep it plump and prevent it from sagging and
sinking.
2.
What are age spots (liver spots)?
a.
uneven
distribution of pigment cells (melanocytes) and brown skin pigment (melanin) -
Some areas make more pigment and some areas make less.
3.
Why
do bruise marks occur more easily?
a.
decreased
sensation
-> increased incident of injuries
b.
less
water
in the skin -> less cushioning
c.
thinning fat, especially in the hands, arms, feet, and legs ->
less cushioning
d. weaker collagen fibers, especially in the very elderly -> easier injury
e.
stiffer elastin fibers -> easier injury
f.
fewer
blood vessel ->
weaker skin -> easier injury
g.
slower
healing -> skin stays fragile longer after each small injury, so the damage
accumulates
h. medications (“blood thinners”) -> slower clotting -> large black and blue marks
4.
What
does sunlight do to skin?
a.
free
radicals
and cross-linking caused by UV light damage molecules and genes in the
skin
1.
more
irregular keratinocytes (skin cells in the outer layer of the skin
{epidermis})
2.
increases
in the
uneven
distribution of pigment cells and pigment (melanocytes and melanin)
3.
reduces
immune
system cells (Langerhans cells) -> more risk of infection and skin
cancer plus reduced warning from inflammation
4.
increases
irregularities
in elastin
5.
reduces
blood vessels -> less
inflammation for warning of injury, reduced
regulation of body temperature,
reduced
vitamin D production and removal
6. thicker capillary walls -> reduced supply of nutrients and removal of wastes and Vitamin D from the epidermis and the dermis {inner layer of skin})
7.
enlarged
sebaceous glands -> adverse cosmetic effects (i.e., blackheads)
5.
What
does healthy skin do for the rest of the body and the person?
a.
barrier
1.
microbes (bacteria and viruses)
2.
water (retains body water while preventing absorption of excess water
{e.g., from rain, showers, baths)
3.
chemicals (retains body substances while preventing absorption of
harmful substances {e.g., soaps, toxins, wastes, pollutants})
4.
abrasion and trauma (e.g., scraping, rubbing, bumping)
(a)
epidermis
(b)
dermis
(c)
fat tissue
(d)
hair
(e)
nails
5.
light, especially UV light
b.
defense
1.
Langerhans cells for immune responses protect against microbes and
harmful substances
2.
white blood cells and macrophages
protect against bacteria, viruses, and harmful substances
3.
vessels and inflammation protect against many types of injury and
promote healing
c.
information
1.
feeling for
warning
2.
feeling for
enjoyment
d.
temperature regulation
1.
fat tissue insulates
2.
sweat glands cool
3.
blood vessels regulate the rate of heat loss by enlarging or
constricting
e.
Vitamin D production
f.
cosmetic
effects
6.
Why do
muscles get weaker and slower?
a.
reduced ability to be
stimulated = slower starting and
stopping muscle contractions
1.
less
efficient connections of nerves to muscles plus
changes in nerve impulses (weaker, slower, irregular) -> slower starting
and stopping muscle contractions
b.
storing and generating energy
(a) reduced storage of energy molecules (ATP, creatine phosphate, glycogen)
(b)
reduced ability to make energy molecules
(e.g., fewer and weaker mitochondria in muscle cells)
c.
cell thickness
1. with less exercise, muscle cells get thinner and weaker
d.
cell number
1.
loss of muscle cells, unless
exercise enlarges and strengthens the remaining cells
e.
ability to thicken when exercised
1.
slower increase in muscle size and strength
f.
proportions of different fiber types
1.
great decrease in the faster and stronger muscle cells (Type II fibers)
g. motor neurons and nerve impulses
1. fewer nerve cells to stimulate the muscles
2.
slower and less regular nerve impulses
h.
muscle mass
1.
gradual decrease in mass, especially after age 50, and especially with
less exercise
i.
effects
=
1.
less
strength
2.
slower
movements
3.
increased
reaction time (longer to start a motion)
4.
less
coordination
5.
less
stamina (i.e., performing extended
vigorous activity)
(a)
lowered maximum rate of extended work -> must "pace"
slower
(b)
less endurance for extended hard
work -> must "quit" sooner
(c)
longer
recovery time to catch ones breath (e.g., removal of lactic acid)
(d)
more stiffness and soreness after
exercise (from
lactic acid build‑up)
6.
altered posture
7.
altered appearance and body proportions
8.
need for fewer calories and diet modification
9.
need to adjust medications due to altered % body fat
10.
NOTE: great variability among people and among different muscles in a
person because of variable decreases in exercise
7.
Why are
complicated motions and new activities more difficult to learn?
a.
motor neurons and action potentials
1.
less
precision of control (from motor neuron "adoption" of abandoned
muscle fibers -> increased size of motor units)
2.
prolonged contractions (from slower and more varied motor neuron
impulses)
3. effects =
(a) reduced speed of starting motion
(b) reduced speed at repetitive motions
(c) reduced
precision of control
b.
brain and spinal cord
1.
less
coordination
2.
less
short term memory -> takes more time to learn a new motion
8.
Why
does fatigue develops quicker?
a.
decreased
storing and generating energy
b.
declining
cell thickness
c.
declining
cell number
d.
declining fast and strong muscles cells (Type
II fibers)
e. fewer motor neurons and irregular nerve impulses
f. declining efficiency of working
1. less efficient use of oxygen by the heart
2. stiffer respiration
3. stiffer joints
4. less coordination
5. altered movement
patterns (e.g., walking).
g.
age-related
decline in other systems (circulatory,
respiratory, integumentary, joint stiffness)
h.
EFFECTS
1.
lower
maximum rate of extended work -> must "pace" slower
2.
less endurance for extended hard work -> must "quit"
sooner
3.
longer
recovery time to catch one's breath (e.g., removal of lactic acid)
4.
more stiffness and soreness after
exercise (from 8 lactic acid build-up)
5. lower VO2 max (maximum rate at which a person can do very vigorous activity {e.g., run})
(a) effects from reduced VO2 max
If VO2max becomes VERY low, even ordinary activities (e.g., going up stairs, carrying household items, walking, getting up from bed or a chair, eating) become difficult
9.
What do healthy muscles do for the rest of the body?
a.
movement to get what we need and want, and to get rid of or escape from
what we do not want
b.
support so other body parts can work (e.g., bones, circulation,
breathing)
c.
heat production to stay active rather than becoming dormant or
hibernating
d.
weight control by "burning" calories in food
e.
use
glucose (i.e.,
blood sugar) more effectively to prevent diabetes mellitus
10.
What do high levels of blood sugar and oxidants from free radicals
contribute to aging of skin and muscles?
a.
skin
1.
damage keratinocytes
(from free radicals)
2.
damage melanocytes (from free radicals)
3.
damage
Langerhans
cells (from free radicals and high blood sugar)
4.
damage
sebaceous gland
enlargement (from free radicals)
5.
weaken
epidermal/dermal
boundary leading to easier blistering (from free radicals)
6.
less water
content (from free radicals)
7.
slower healing
(from free radicals and high blood sugar)
b.
skin and muscle
1.
damaged
collagen fibers (from
free radicals and high blood sugar)
2.
damaged
elastin fibers (from
free radicals and high blood sugar)
3.
damaged
and fewer blood
vessels (from free radicals and high blood sugar)
4.
thicker
capillary walls ->
less nutrient to the skin cells (from free radicals and high blood sugar)
© Copyright
2000 - Augustine
G. DiGiovanna - All rights reserved.
This material MAY be reproduced or distributed in any
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instructors and students in courses where students are
required to purchase the book HUMAN
AGING: BIOLOGICAL PERSPECTIVES by Augustine G. DiGiovanna,
The McGraw-Hill
Companies, New York, 1994 or 2000; (2) If prior written
permission is obtained from Augustine G.
DiGiovanna, Ph.D., Salisbury University