Growth & Development Flashcards by Elin H

How can you quantitatively measure growth?

Body weight
Height
Length
Amount of muscle mas

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How can you qualitatively measure growth?

Body proportions & functions (eg muscle mass vs intramuscular fat mass)

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Name some examples of hormone growth factors

Growth hormone / IGF-1
Insulin
Prolactin
Glucocorticoids
Thyroid hormone
NGF
EGF

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What are the direct effects of growth hormone?

Adipocytes:
-reduced lipogenesis
-reduced fat accumulation

Liver + skeletal muscle:
-increased gluconeogenesis
-increased glycogenolysis
-increased blood glucose
-increased blood synthesis

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What are the indirect effects of growth hormone?

IGF-1 mediated local effects (eg bone growth)
IGF-1 mediated endocrine effects (eg bone growth)

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What’s the relationship between growth & insulin-like growth factor (IGF-1)?

IGF-1 levels correlate with adult body size

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What is farm animal growth focussed on?

Ratio of fat & skeletal muscle
Rapid growth selection

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What is an implication of rapid growth selection in farm animals?

Long bone abnormalities

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What 2 processes contribute to the constant changing shape of bones?

Resorption - removing bone matrix
Deposition - replacing with new bone

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What effect does GH and IGF-1 have on bone growth?

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What hormone is plasma IGF-1 dependent on?

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How does IGF-1 regulate bone growth?

Mitogenic
Recruitment of precursor cells
Maintenance of differentiated state

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How do glucocorticoids regulate bone growth?

in pharmacological doses:
-bone loss
-stimulates catabolism

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How do androgens regulate bone growth?

Testosterone surge during puberty induces closure of growth plate
(pre-pubertal castration increases long bone growth)

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How do growth factors regulate bone growth?

-Local (autocrine/paracrine) in all tissues
-Mitogens (not tissue specific)
-Growth & remodelling of bone

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What is the purpose of muscle?

Provide strength, elasticity & contraction

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What are the 2 types of muscle fibres?
List some characteristics of each

WHITE
-fast twitch
-sprinting, fine motor control, reflexive action

RED
-slow twitch
-contain myoglobin
sustained contraction (eg posture)

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What is myogenesis?

Muscle formation
myoblasts proliferate, differentiate & fuse to generate myofibres

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At what stage of development is the NUMBER the myofibres determined?

During gestation

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What determines the SIZE of myofibres?

Genetics
Nutrition
Exercise
Endocrine environment

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When does hyperplasia of myofibres occur?

During development & tissue repair

What causes hypertrophy of myofibres?

Genetics
Nutrition
Exercise

How does IGF-1 regulate muscle growth?

Locally produced (stimulated by GH)
Increase glucose & amino acid uptake
Decrease proteolysis & increase protein synthesis > hypertrophy
Effects on muscle precursor cells (eg increase myoblast proliferation) > hyperplasia (during development)

How do glucocorticoids regulate muscle growth?

in pharmacological doses:
-glucose sparing (eg protein catabolism)

How do beta-adrenergic agonists regulate muscle growth?

Repartitioning agents - redirect nutrients to skeletal muscle (not adipose tissue) Increase rate of weight gain, by increasing protein deposition

How do androgens & oestrogens regulate muscle growth?

Increased protein deposition

What is the role of brown adipose tissue?

Heat production & weight control

What are some characteristics of brown adipose tissue?

Location is species specific Richly vascularised & many mitochondria for energy production Responds to environmental & nutritional cues (eg hyperplasia with cold exposure)

What is the role of white adipose tissue?

Energy storage

What is the endocrine function of white adipose tissue?

Adipogenesis from stem cells Hypertrophy induces hyperplasia

What are some characteristics of white adipose tissue?

Diffuse (in several locations) Sites are species specific

How does insulin regulate adipose tissue?

Lipogenesis Stimulates proliferation, differentiation & maintenance of differentiated adipocytes

How does GF & IGF-1 regulate adipose tissue?

Reduction of fat mass, due to inhibition lipogenesis (+ stimulation of lipolysis to fuel growth)

How do glucocorticoids regulate adipose tissue?

Stimulate accumulation of visceral fat

How do growth factors regulate adipose tissue?

Fibroblast growth factor (FGF)

How does white adipose tissue act as an endocrine organ?

Secretes factors with important endocrine functions: -appetite regulation -energy homeostasis -immune response -vascular development

How does body composition different between farm animals and animals in the wild/pets?

Farm animals: -control of feed intake -nutrition utilisation -ultimate production of desirable meat product Wild animals/pets: -survival mechanism favour energy storage, weight gain & fat accumulation (pet obesity)

What other health issues are associated with obesity in pets?

Osteoarthritis Heart disease Renal problems Diabetes Respiratory disease

What factors contribute to pet obesity?

Increased dietary fat Improved palatability of food Age Indoor animals Lack of exercise Neutering Glucocorticoids Some breeds genetically predisposed

What nutrient signals contribute to satiety/hunger?

Fatty acids Glucose Amino acids

What nerve signals contribute to satiety/hunger?

Gastric distention

What hormonal signals contribute to satiety/hunger?

Insulin Leptin Ghrelin PYY CCK

What central information inputs to regulates energy homeostasis?

Stored energy status Metabolic status Feeding status

What central response is a result of regulating energy homeostasis?

Alter body's energy intake Alter body's energy use

What signals act positively/negatively on the satiety centre?

+increased glucose (and insulin) +increased CKK (correlates to fat content of meal) +increased stomach distention +increased body fat stores -smell of desirable food -sight of desirable food

What is the effect of ghrelin on regulation of intake?

(from stomach) Levels increase during fasting Stimulates feeding centre Promotes eating

What is the effect of leptin on regulation of intake?

(from white fat) Levels proportionate to fat reserves Stimulates satiety centre Inhibits eating

What is the effect of peptide YY (PYY) on regulation of intake?

(from epithelium of small&large bowel) Release proportional to size of meal Stimulates satiety centre Inhibits eating

What is the effect of CCK on regulation of intake?

(from epithelium of small bowel) Release proportional to fat content of meal Stimulates satiety centre Inhibits eating

Describe the hypothalamic regulation of satiety

What affect does leptin & alpha-MSH & beta-MSH have on the satiety centre?

-Leptin stimulates alpha-MSH & beta-MSH -Alpha-MSH & beta-MSH stimulate MC4 receptor -MC4 receptor (MCR4) stimulation reduces eating (activates satiety centre) -AgRP (agouti) inhibits MC4R (increases feeding)