If Calcium is needed for muscle activity then why are spasms and hyperactivity a sign of hypocalcaeimia?

Question

It makes more sense if those were the symptoms of hypercalcaemia.... what am I missing?

Answer 1

Calcium is needed inside mucle cells for muscle contraction. And you are right that increased (and not decreased) concentratration of calcium inside muscle cells should cause spasms.

But in hypocalcemia (low level of calcium in the blood), the concentration of calcium decreases only in extracellular spaces and not inside muscle cells. Muscle cells use ionic pumps to actively regulate and maintain their calcium concentration, and these pumps prevent any significant decrease of calcium inside the cells.

A decrease of calcium in extracellular spaces makes the neuron-muscle cell junction more excitable and causes muscle spasms to occur because calcium is needed for function of the Cholinesterase enzyme which inactivates neurotransmitter Acetylcholine.

Neurons release Acetylcholine to stimulate muscle contraction. And without calcium, the Cholinesterase enzyme cannot inactivate and remove Acetylcholine. This means that Acetylcholine accumulates and continues to stimulate the muscle for a long time. And it's this lengthy stimulation that causes the muscle cramp.

Answer 2

According to research I have read by Robert Heaney, M.D., former chairman of the dept. of Endocrinology and former chairman of the dept. of medicine at Creighton Medical School, and a leading researcher on Vitamin D, Calcium and Osteoporosis, the mechanism involves the following.

For a muscle cell to contract, calcium is released into the cytoplasm from intracellular stores. So, it is increased INTRAcellular calcium that causes muscle contraction.

Hypocalcemia causes the release of parathyroid hormone (PTH) which stimulates the kidneys to convert vitamin D to its active form (1,25 dihydroxycholecalciferol - 1,25D3). 1,25D3 'pushes' calcium into the cells from the extracellular fluids. So, even though the blood levels of calcium are low, the increased levels of 1,25D3 push high levels of calcium into the cells. This would result in an increased contractile state in the muscle cells - leading to spasms.

Hope this was helpful.

Answer 3

Calcium located outside the cells is needed for maintaining membrane potential of neuronal an muscular cells because signals from neurons to muscles are transmit ed via calcium dependent pathway. Calcium is needed for muscle contraction. It is necessary for calcium to enter a muscle cell in order for muscle to contract. So a deficiency in calcium disrupts the whole system and leads to neuro-muscular iritability that is spasams and tremor.

Answer 4

Too much or too little calcium can have negative effects - the correct balance of calcium is what is needed.

Answer 5

Potassium is what you are missing this is for the muscle spasms.

Bananas are a very good source of potassium as well as other fruits and vegetables.

Answer 6

too much calcium.

Answer 7

well...........