Calcium Regulation Flashcards
What happens to endocrine target cells that do not receive sufficient hormone
Shrivel and become inactive
Hormones vary in size and composition (4)
Peptide & protein
Amino acid derived
Steroid
Fatty acid compounds
What are the 2 divisions of hormones
Water soluble
Lipid soluble
What is the half life of hormone am and how are they excreted
Short
Removed in faeces and urine
Water soluble directly
Steroids have to be processed by liver
Excretion often occurs after processed in which organs
Lung
Blood
Liver
Kidney
How are proteins transported
Protein carriers
What is necessary for hormones to diffuse
Must be unbound
Often neural stimulation leads to release if hormone what is this type of reflex and give examples of where from
Neurohumoral
Brain hypothalamus
Adrenal medulla
Pituitary
How is the ANS involved in hormones
Modulates secretions
How do genetics play a part in endocrinology
Individuals have varying levels of Size of glands Synthesis and secretion of hormones Elimination rates Sensitivity ti hormones
This is due to size and metabolism
What 2 ions are important in Ca regulation
Calcium
Phosphate
What are the roles of calcium
- skeleton structure
- muscle contraction
- neural excitability
- hormonal release
- membrane permeability
- enzyme activity
- blood coagulation
What are the 3 hormones that alter blood calcium levels
Parathyroid hormone
Calcitonin
Vitamin D
What roles does phosphate play
ATP
Buffer in body and ruin
What is the problem with releasing calcium from bone
Phosphate also released which binds to calcium
What is bone made up of
Calcium phosphate
Limited solubility
PO4 is continually secreted in gut why?
Reuptake is not regulated
What stimulates po4 excretion
Both PTH and CT
Where is parathyroid hormone produced and stored
In parathyroid gland
Next to thyroid gland
Is it normal for hormone to be stored
No
Do parathyroid cells require neural innovation to release PTH
No are sensitive to Ca levels
What stimulates the secretion of PTH
High phosphate
Low calcium
What is the effect of PTH (4)
- Acute - activates osteocytes and osteoblasts to transfer Ca into the blood
- Chronic - stimulates osteoclasts to remodel bone
- Acts on kidney proximal convoluted tubules to decrease reabsorption of PO4 and distal to enhance Ca absorption
- Increases activation of vitamin D = more dietary Ca absorbed
What does CT stand for
Calcitonin
Where is CT secreted from
C-cells in the thyroid
Sparsely spread amongst follicular cells
What stimulates CT
Raises calcium plasma levels
What does CT do
Opposite of PTH
Blocks reabsorption of Ca from bone
Blocks renal absorption of Ca and increases waste of PO4
Blocks vitamin D
How is vitamin D formed
D2 converted to D3 by UV
D3 to 25 hydroxyl cholecalciferol - in liver
Ti 1.25-dihydroxyl cholecalciferol
What is exocrine system
When secretions are released into the surface via duct
What causes hypocalcaemia
High calcium demand in dam
Dietary imbalance Ca/PO4
anorexia - low Ca intake
What causes hypercalcemia
Hyoerparathyroidism
Excessive PTH production causing continual Ca movement from bone
What is the term for softening of bones
Osteomalacia
What causes type 1 and 2 hyperparathyroidism
- Parathyroid adenoma causing direct secreting excess of PTH
- PTH is indirectly raised by renal or dietary cause
Renal
Dietary cause of hyperparathyroidism
Renal - kidney failure to absorb calcium and remove phosphate
Raised phosphate and low calcium trigger PTH
Dietary
Low calcium
High phosphate
Inadequate vitamin D formation
Most hormones if calcium homeostasis are what
Extra cellular
Except vitamin D
