ENDOCRINOLOGY - Overview and Calcium Homeostasis Flashcards
What are the two classes of hormones?
Steroid hormones
Peptide hormones
Where are steroid hormones synthesised?
Liver
What are steroid hormones synthesised from?
Cholesterol
In vertebrates, which tissues secrete steroid hormones?
Gonads
Adrenal glands
Placenta
Where are steroid hormones metabolised and ultimately secreted?
Steroid hormones are metabolised in the liver and kidneys and excreted in urine, faeces and skin
What are peptides hormones synthesised from?
Amino acid chains
What are tropic hormones?
The hormones secreted from the anterior pituitary gland which stimulates hormone release from target organs
What is the function of the hypothalamus in hormone regulation?
The hypothalamus regulates the secretion of tropic hormones from the anterior lobe of the pituitary gland
What is the function of the anterior lobe of the pituitary gland in hormone regulation?
Secretion of tropic hormones
What is the function of the posterior lobe of the pituitary gland in hormone regulation?
The posterior lobe is made up of axons extending from the hypothalamus which produce hormones, these hormones are secreted by the posterior lobe
List the six physiological processes requiring ionic (free) calcium
Muscle cell contraction
Nerve cell activity
Enzyme activation
Release of hormones and neurotransmitters via exocytosis
Coagulation cascade
Cell membrane stability
List the physiological process requiring bound calcium
Maintaining bone and teeth strength
What are the four pools of calcium found in the body?
Bone calcium
Intracellular calcium
Extracellular calcium
Gastrointestinal tract
How is calcium stored in the bone calcium pool?
Calcium is stored as hydroxyapatite crystals
List the organs involved in calcium homeostasis and their function
Small intestine (absorbs calcium)
Bone (stores calcium)
Kidney (excretes calcium)
What are the glands involved in calcium homeostasis and their function
Parathyroid gland
Thyroid gland
Which hormone is secreted by the parathyroid gland?
Parathyroid hormone
Which hormone is secreted by the parafollicular cells of the thyroid gland?
Calcitonin
List the hormones involved in calcium homeostasis
Parathyroid hormone
Calcitonin
Calcitriol
Which organ secretes calcitriol?
Kidneys secrete calcitriol
Which hormone is stimulated by decreased blood calcium levels?
The parathyroid hormone
Which hormone is stimulated by increased blood calcium levels?
Calcitonin
What are the three processes stimulated by the parathyroid hormone to maintain calcium homeostasis in response to decreased blood calcium levels?
- Increases calcium reabsorption in the kidneys
- Stimulates calcitriol release from the kidneys to stimulate calcium absorption in the small intestine
- Stimulates osteoclasts to mobilise calcium storage in the bone
What are the three processes stimulated by the calcitonin hormone to maintain calcium homeostasis in response to increased blood calcium levels?
- Inhibits calcium reabsorption into the kidneys thus increasing calcium urinary excretion
- Inhibits calcium absorption in the small intestine
- Stimulates osteoblasts to take up circulating calcium to store in the bone
