Key concepts and ageing process

Question 1

Ontogenetic and Phylogenetic differences

Answer 1

Ontogenetic difference
- Alterations that occur during the development of an individual from the immature to the mature biological state.

Phylogenetic difference
- Differences between biologically mature individuals.

Question 2

Developmental Symmorphosis

Answer 2

In any physiologic system the functional capacity of no single component should exceed that of any other part of the system

Question 3

The importance of body size

- Allometric scaling

Answer 3

Allometric scaling

- Approach for studying relationship between body size and shape, anatomy or function

Question 4

Y = aX^b

Answer 4

• Y = body part or function being measured in relation to the size of the organism
• X = measure of size used for basis of comparison (e.g. body mass)
• a = conversion factor
  
  • (size of Y when X = 1)
• b = scaling exponent (tells us how y changes relative to x)

Question 5

b < 1

Answer 5

Y increases at a slower rate than X, i.e. as X increases, Y becomes relatively smaller

Question 6

b > 1

Answer 6

Y increases at a faster rate than X, i.e. as X increases, Y becomes relatively larger

Question 7

Dimensionality theory

Answer 7

Assuming similar geometry between people

• Linear dimensions (e.g. lever arm of a muscle) should relate to body mass by exponent 0.33 (1/3 = 0.33)
• Areas (such as cross-section) should related to mass by 0.67 (2/3 = 0.67)

Question 8

Does Dimensionality Theory hold true for growing children?

- Primary rule in allometry

Answer 8

Primary rule in allometry

• Do not combine phylogenetic and ontogenetic data.
• This means that, when creating allometric equations, data obtained in different mature adults should not be compared with measurements taken over time in growing children.

Question 9

Ageing

Answer 9

Eugeric:
- True ageing; age-related changes that will happen to everyone, inevitably

Pathogeric
- Pathological ageing, not a predestined part of ageing

Question 10

Examples of eugeruc ageing

Answer 10

• Slowed movements
• Impaired hearing
• Reduced ability to adapt to stress
  Decreased resistance to infection
• Loss of elasticity of skin
• Greying of hair
• Fading vision
• Decreased height

Question 11

Ageing process

Answer 11

• Destructive, compromising functionality.
• Progressive, irreversible.
• Instrinsic
• Universal.

Question 12

Loss of function

Answer 12

Function totally lost

• Reproduction, menstruations
• High frequency hearing

Reduced efficiency of a unit
- Decreased nerve conduction velocity

Structural changes

• Number of fast twitch fibres
• Skeletal muscles diameter

Altered control system
- Reduced reserve when under stress (e.g. oestrogen)

Question 13

Ageing & Homeostatis

Answer 13

Ageing → Takes longer to respond and equilibrate

Sensors

• Loss of sensitivity
• Loss of cutaneous receptors

Control

• Small changes in target set point
• Loss of precision

Effector

• Deterioration of function
• Loss of mass
• Reduction in compliance