Calcium Regulation Flashcards
(42 cards)
How is growth hormone regulated?
GHRH stimulates the release of GH from the adenohypophysis in response to hypoglycemia, lactation, fasting, exercise.
What does GH stimulate the release of?
Insulin-like growth factors 1 & 2 (IGF-1 and IGF-2)
What does IGF-1 do?
It exerts negative feedback at the hypothalamus.
- Stimulates the release of GHIH (growth hormone inhibiting hormone)
- Increased GHIH decreases GH secretion
What is the effect of dopamine on GH?
Dopamine reduces GH secretion.
What cells secrete GH?
Somatotropes in the adenohypophysis.
What are the effects of IGF-1?
IGF-1 promotes proliferation of chondrocytes in the growth plate and ossification of chondrocytes.
What are the effects of growth hormone on bones?
Promotes growth of long bones through IGF-1.
What are the effects of GH on milk synthesis?
- Promotes galactopoiesis
- Maintains alveolar cell numbers and increases milk synthetic activity per cell
- GH redirects available nutrients towards milk synthesis
Are artificial growth hormones approved in Canada?
Hell no girl
What is an example of an artificial growth hormone?
Recombinant bovine somatotropin (rbST)
What are the metabolic effects of GH?
- Increases rate of protein synthesis in all body cells
- Positive energy balance since GH is anabolic (protein and glycogen synthesis)
- Lipolysis
- Increases blood glucose concentration
Describe postnatal skeletal muscle growth.
Satellite cells can divide under appropriate stimuli (IGF-1) and fuse with the muscle fiber to facilitate muscle hypertrophy. The satellite cell nucleus will be delivered to the muscle fiber so there will be more DNA material in the muscle fiber for its growth and regeneration.
How much of the calcium in blood is bound?
50%
How much of the body’s calcium and phosphate reside in the bone?
99% of calcium and 85% of phosphate
How much calcium is there in the cytosol?
Not much and 99% of it forms insoluble complexes with phosphate
What are the biological functions of calcium?
- Formation of skeletal tissue
- Transmission of nerve impulses
- Cell signalling (important second messenger)
- Modulate activity of many enzymes
- Blood clotting
- Component of milk and egg
What hormones increase calcium in the blood?
- Parathyroid hormone
- Calcitriol
What hormones decrease calcium levels in the blood?
Calcitonin
What cells produce PTH?
Chief cells of the parathyroid gland.
What induces PTH secretion?
Hypocalcemia
What effect does persistent hypocalcemia have on the paratyroid gland?
Hypertrophy of the parathyroid glands.
(More calcium needed, no negative feedback, increased gland size)
How does PTH increase blood calcium levels?
- PTH enhances renal tubular absorption of calcium and excretion of phosphate into urine
- PTH stimulates intestinal calcium absorption (via Calcitriol)
- PTH indirectly activates osteoclasts via osteoblasts
How does PTH cause bone lysis?
Osteolysis (bone breakdown) will be indirectly stimulated in the presence of PTH. There are no receptors of PTH on osteoclasts but there are PTH receptors on osteoblasts. Once PTH activates osteoblasts to secrete various products (to create an acidic environment), osteoclasts will be activated and bone lysis occurs.
What organs are involved in calcitriol synthesis?
Liver and kidney