growth and parathyroid hormones

facilitate active cartilage growth in bone until puberty

chondrocytes

mineralize the growth plate in bone, (Epiphyseal growth plate)

osteoblasts

bone lengthening is under —- regulation

hormonal

Build Bone, Mineralize cartilaginous bone (building bone), Ca²⁺ & PO₄^3- combine to form calcium phosphate crystals (white part of bone), Borders the bone until done growing and then gets trapped inside the bone

osteoblasts

Bone Cells, Sense “pressure” and remodel bone

osteocytes

Break Down Bone, Resorb bone to increase Ca2+, Evil pacman guy, Break down calcium phosphate to just calcium so the body can use it, Ensures you have enough blood calcium

osteoclasts

Adult skeleton is replaced about every —years

10

Partners in crime, Influence musculoskeletal health, part of hormonal influences of bone growth, GH, IGF-1

growth hormone, insulin like growth factor

what are other hormonal influences on bone growth?

thyroid hormone (T3), insulin, sex hormones, cortisol

(Negative Regulator), Catabolic - could be good in short term to break down bone, But chronic stress will impact musculoskeletal health, hormonal influence on bone growth

cortisol

hypothalamus releases growth hormone (GHRH) which binds to the anterior pituitary somatrophs receptor which causes the anterior pituitary to release active growth hormone which binds to receptor on the liver and the liver release insulin like growth factor -1, (HPS)

hypothalamic pituitary somatic axis

inhibitory opposite of growth hormone, inhibits further growth hormones, sets normal range, blocking synthesis and release of GH

somatostatin

promotes growth with IGF-1, stimulate protein synthesis, During fasting, GH increases glucose and lipid availability, but preserves muscle: catabolic side, stimulates gluconeogenesis, decrease in glucose uptake, increase in lypolysis

effects of growth hormone

is growth hormone anabolic or catabolic

both

stimulates Growth at Puberty Through GH, Causes Epiphyseal Closure, Cessation of Long Bone Growth, Time of cessation set by estrogen and other genomic mechanisms

estrogen

Stimulates Growth at Puberty Through GH, Causes Epiphyseal Closure (cessation of long bone growth), Stimulates Protein Synthesis in Males

testosterone

Major Stress Hormone, Inhibits Bone Growth, Stimulates Protein Catabolism, Inhibits GH Secretion

cortisol

effector sites of calcium homeostasis

bone, GI tract, kidneys

Storage vs. Release role in calcium homeostasis, Major site because the bone is made out of calcium phosphate

bone

what role does the GI tract play in calcium homeostasis

absorption

what role do the kidneys play in calcium homeostasis

reabsorption

what are the two major hormones that regulate plasma calcium levels

parathyroid hormone, vitamin D (calcitriol)

what plays a minor role (inhibitory) of regulating calcium levels

calcitonin

secreted by parathyroid glands, Increases Ca²⁺ Availability to Increase Plasma Levels, Increases Ca²⁺ reabsorption in kidneys, Increases osteoclast activity, Increases formation of Vitamin D, which increases uptake of Ca²⁺ in GI tract

parathyroid hormone

Ratio of Ca²⁺ : Phosphate for Optimal for Bone Formation

3:2

Increases Ca²⁺ reabsorption in the kidney, Decreases PO₄^3- reabsorption in the kidney

parathyroid hormone activity in renal system

Active form produced in kidneys

vitamin D

Increases gene expression of Ca²⁺ and PO₄^3- transporters in GI tract

active vitamin D

Secreted by parafollicular cells of the thyroid gland, Decreases plasma Ca²⁺ concentration by inhibiting osteoclasts, Secretion only stimulated by very high plasma Ca²⁺ levels, Inhibits somatostatin

calcitonin