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Endocrine control of plasma calcium - Coggle Diagram
Endocrine control of plasma calcium
Adrenal gland test
Long term chronic stress - cortisol release
Acute stress - adrenaline released
Skeletal muscle breakdown caused by excess cortisol
Calcium
Important in many physiological features
Plays a role in the microscopic and macroscopic level
99% of the structural component of nones and teeth
Maintains normal excitability of nerve and muscle cells
Involved in neurotransmitter and hormone release
Muscle contraction (skeletal and cardiac)
Activation of enzymes
Milk production
Coagulation of blood
Does not exist in nature
Bone dynamic
3 types of cell for bone formation and reabsorption
Osteoblasts
- synthesis and secrete collagen and promote deposition of calcium phosphate crystals - secrete factors that activate osteoclasts
Osteoclasts
- promote reabsorption of bone
Osteocytes
- essential role in exchange of calcium between ECF and bone
Calcium regulation
Acute control
Maintain constant free Ca2+ concentration in the plasma
Most rapid change between bone and ECF
Chronic control
Maintain total level in the body long term
Adjust GIT absorption and urinary exception
Essential that intra and extracellular levels maintained with narrow limits
Plasma Ca2+ conc determined by
Exchange of Ca2+ with bone
Net exception of Ca2+ in urine
Net absorption of Ca2+ from the GIT
Controlled by 3 hormones
Parathyroid hormone - PTH
(most important)
Features
Peptide hormone
Stored within the chief cells
Half life of 5 minutes
Secreted continuously at a low rate
Released in response to low calcium
Exerts in edict on bone, gut and kidneys
What does it do?
Main target tissue is kidney
Increased reabsorption of calcium from the urine
Fast acting - decreased urinary calcium in minutes
Increased the expression of the enzyme 1-alpha-hydroxylase
Bone - increased osteoclast activity (indirecting) causing increase in bone resorption
1,25-dihydroxycholecalciferol
(2nd important)
Calcitonin
(least important)
Parathyroid hormone
Vitamin D
Calcitonin
Actions of calcitriol
Plasma and calcium levels
Protein-bound - calcium cannot diffuse throughout membranes so is not usable by tissues
Ionised or free calcium - physiologically active form
Complex or cheated - calcium is bound to phosphate, bicarbonate, sulphate, citrate and lactate
Regulation
Hypocalcemia
Too low - involuntary muscle contraction
Neuronal hyper-excitability (tetany)
Low ionised calcium levels in the extracellular fluid increase the permeability of neuronal membranes
Essential that intra and extracellular levels maintained within narrow limits
Hypercalcemia
Neurones less exciatble
Too high - depression and kidney damage/stones
Hormone control
Balance between ECH and 3 body compartments
Absorption - via intestines
Excretion - via kidney/urine
Temporary storage
Acute control
Must maintain constant free Ca2+ conc in plasma
Most rapid exchange between bone and ECF
Chronic control
Maintain total level in the body long term
Adjust GIT absorption and urinary exception
Plasma Ca2+ conc is determined by
Net absorption of Ca2+ from the GIT
Net exception of Ca2+ in urine
Exchange of Ca2+ with bone