Lecture 22 _ Calcium

Lecture 22 _ Calcium - o Lecture 22 PTH, Vit D, and Ca+...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 22 – PTH, Vit D, and Ca++ homeostasis Calcium - Calcium salts in bone provide structural integrity of the skeleton - Calcium ions in extracellular and cellular fluids are essential to normal function of a host of biochemical processes - Neuoromuscular excitability o Blood coagulation o Hormonal secretion o Enzymatic regulation - Regulation o The important role that calcium plays in many processes dictates that its concentration, both extracellularly and intracellularly, be maintained within a very narrow range. o This is achieved by an elaborate system of controls. o Control of cellular calcium homeostasis is as carefully maintained as in extracellular fluids o [Ca 2+ ] cyt is approximately 1/1000 th of extracellular concentration o Stored in mitochondria and ER o “pump-leak” transport systems control [Ca 2+ ] cyt Calcium leaks into cytosolic compartment and is actively pumped into storage sites in organelles to shift it away from cytosolic pools. - Extracellular calcium o Three definable fractions of calcium in serum: Ionized calcium 50% Protein-bound calcium 41% 90% bound to albumin Remainder bound to globulins Calcium complexed to serum constituents 9% Citrate and phosphate Calcium and phosphorous - Calcium is tightly regulated with phosphorous in the body. - Phosphorous is an essential mineral necessary for ATP, cAMP second messenger systems, and other roles - Contents and distribution o Total body Ca++>Phosphorus>Mg o % in skeleton Ca++ > P > Mg o Tissues Mg > P > Ca - Renal Excretion The kidneys account for the bulk of regulated calcium excretion Three distinct locations along the renal tubule are involved The regulation of calcium excretion at each of the three renal sites is different - Proximal convoluted tubule o Accounts for 70% of calcium reabsorption o Mainly paracellular pathway - Thick ascending limb o Calcium sensing receptor o 20 % of calcium reabsorption - Distal convoluted tubule o PTH regulation o 8% of calcium reabsorption Phosphate Turnover - Goes into the soft tissue - Bone is major store of phosphate - Favors pushing phosphate out Phosphorous in blood and bone - 87% is diffusible, with 35% complexed to different ions and 52% ionized. -
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

Lecture 22 _ Calcium - o Lecture 22 PTH, Vit D, and Ca+...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online