Growth And Ageing Flashcards
What is an increase in cell numbers called?
Hyperplasia
What is an increase in cell size called?
Hypertrophy
Give an example of a cell type which cannot grow/regenerate
Neuron
What are some factors which can affect growth?
- genes (heredity)
- environment (nutrition, disease, growth factors eg hromones)
What is the order in growth between the brain, height and reproductive organ?
- brain first
- then height/ reproductive organs
Do all cells regenerate and grow at the same rate?
No
Eg RBC take 120 days, but skin/mucosa cells are faster and some eg neurones can’t regenerate at all
What are hormones which influence growth?
- thyroid hormones
- growth hormones
- sex hormones
- insulin
- cortisol
- vitamin D
- parathyroid hormone
Describe the role of the thyroid hormone in growth
- essential for protein synthesis in brain of fetus/infant
- required for normal development of neurons
- needed for childhood growth
- indirect effect on growth
- facilitates actions of growth hormone and sympathetic NS
Which hormone is essential for protein synthesis in the brain of fetus/infant?
Thyroid hormones
Which hormone facilitates the actions of growth hormone and sympathetic NS?
Thyroid hormones
Which hormone has an indirect effect on growth?
Thyroid hormones
What is hypothyroidism?
Deficiency of thymidine hormones
What are consequences of hypothyroidism in a fetus?
- sparse hair
- large tongue
- permanent mental impairments (impedes brain/skeletal development and growth)
- delays tooth eruption
What can be used to treat hypothyroidism?
- growth defects can be rectified by thyroxine supplements
- may not be a complete recovery
- extent of recovery varies with onset and duration of the hypothyroid state
Describe the role of growth hormone in growth
- metabolic and growth-promoting actions
- main growth-promoting effects in postnatal period, infancy and adolescence
- mainly indirect metabolic actions (increase in blood glucose, decrease in glucose uptake in cells, lipolysis, facilitates uptake of amino acids for protein synthesis)
What is lipolysis?
Making fatty acids available for energy production
Which hormone has its greatest growth-promoting effects in postnatal period, infancy and adolescence?
Growth hormone
What are the metabolic actions of growth hormone?
- increases blood glucose
- decreases glucose uptake by cells
- increases lipolysis
- facilitates amino acid uptake for protein synthesis
Dwarfism types
Describe the role of sex hormones in growth
- testosterone and oestrogens
- responsible for pubertal growth spurt
- effects are mediated by increased secretion of growth hormone and IGF-1
- stimulate bone growth but accelerate closure of epiphyseal growth plates
- testosterone has anabolic effects on protein synthesis, increasing muscle bulk
- testosterone is the anabolic steroid
What is the anabolic steroid?
Testosterone
What are the effects of sex hormones mediated by?
Growth hormone and IGF-1
What hormones are responsible for pubertal growth spurt?
Sex hormones
What is IGF-1?
Insulin like growth factors
Where is IGF- 1 produced?
Liver
What are the effects of IGF-1?
- in cartilage, bone, soft tissues, viscera
- IGF-1 leads to cartilage proliferation in long bones until epiphyses close
What are epiphyses?
Growth centres
Describe the role of insulin in growth
- indirect
- promotes foetal growth
- promoting postal-natal growth by stimulating IGF-1 secretion
- facilitating protein synthesis (making glucose available for energy production)
Describe the role of cortisol in growth
- stimulates protein catabolism
- suppresses bone regrowth and promotes bone resorption (osteoporosis)
- raised level of cortisol in stress and illness accounts for growth retarding effects of childhood illnesses
Which hormone if present in higher than normal levels can inhibit growth?
Cortisol
Describe the role of vit D and parathyroid hormone in growth
- ensuring adequate amounts of calcium and phosphate are available for bone formation
Which hormone is responsible for Ca2+ absorption in the gut?
Vitamin D
Which hormone raises plasma Ca2+ levels?
Parathyroid hormones
What is the effect of excess growth hormone in childhood?
Accelerated normal growth
- gigantism
What is the effect of excess growth hormone in adults?
Hands, feet and jaw increase in bulk
- acromegaly
- appositional growth occurs in extremities
What is appositional growth?
Increase in bone diameter
What is acromegaly?
Rare condition in which the body produces too much growth hormone causing body tissues and bone to grow at increased rate
What could the effects of a tumour of the pituitary gland be?
- enlarged sella turcica
- increased growth of mandible
What is achnodroplasia?
Defective cartilage growth
What has happened to lifespan?
- more people living to old age
- population average age has increased
What are the factors which influence an individuals lifespan?
- genetics
- environment (good nutrition, lifestyle, absence of disease)
Describe the biology of ageing
- decline in ability of cells to divide overtime
- as they decline there is an accumulation of damage (errors in protein synthesis, abnormal proteins, damage to organelles)
- free radicals, shortening of telomeres
When does apoptosis occur?
- in development eg tooth germ, nervous system
- to replace worn out cells
- to destroy tumour cells
