What are the meanings of calcium in physiology?

Physical properties of calcium

Calcium is atomic element number 20. Its consists of a central nucleus and the orbiting shells of 20 electrons. The central nucleus of the most common form, calcium 40 has 20 protons and 20 neutrons. It is believed to be formed in dying stars either in supernova (check: plurality) explosions or in helium burning shells. This is investigated through spectroscopic analysis of starlight, models of nuclear structure and reactions, along with experimental data.

Calcium's nuclear structure is interesting as it is the harmonic series;

This means that it is very likely take part in helium burning and increase the reaction rates of the star. This can decrease or increase the life-span of the star. During a supernova, large amounts of this material is ejected into interstellar space, returning to the galactic clouds from which they came. In evolutionary terms, increasing metallicity in star forming regions leads to different populations of stars (and perhaps planetary formation).

In galactic terms, abundances of elements decrease rapidly with atomic weight, with a secondary peak around Iron 56. Even-numbered atomic weights are favoured over odd weights. Calcium is the 12th most abundant element in the universe and forms 3.2% of the earth's crust (Grolier 1998).

Ecological importance of calcium

In geological terms, calcium is found as calcium carbonate in limestone and chalk. Geographically, limestone and chalk are distributed globally and locally. Evolutionarilly they are distributed temporally. For example, the Combe Martin Beds contain thin bands of limestone, some containing Devonian (400-350 Million Years Before Present) crinoids. Crinoids, or sea lilies, extinct animals related to starfish, attached themselves to rocks by a stalk and waved their arms in the currents to collect food.

Ecologically, calcium rich and calcium poor soils are used to define plant habitats. In Devon, Shining Crane's-bill (Geranium lucidum) a lover of walls and base-rich (calcium-rich) soil, is locally abundant around the south and east of the county where ground water can contain calcium and human activity is high (Ivimey-Cook, 1984). However, there is evidence that intraspecies interactions also affect plant distributions an therefore definitions of calciphile or calciphobe plants (Brewer, 1988, p.16-17).

Agriculturally, calcium is important for plant development and probably milk yield in cattle. Abandoned lime kilns are common on the coast of North Devon; two examples in Ilfracombe can be found at Larkstone Beach and on the Torrs. These kilns burned limestone brought over from Wales. The resulting calcium oxide was then spread on the fields.

An introduction to the physiological roles of calcium

Calcium forms about 2% of the human body, of which 99% is in bones and teeth (Grolier 1998). Calcium concentrations are over a thousand times higher in extracellular space than in the cytosol (Hopkins 1991, p.93). Cellular reserves of calcium are found in the endoplasmic reticulum and brain tissue microsomes (ibid). Cytosolic calcium concentration is also affected by mitocondrial buffering (Nicholls & Ferguson 1992, pp. 209-212).

Calcium is involved in many physiological functions notably:

Calcium shows the importance of bio-inorganic chemistry in metabolism and biology generally. The big six 'organic' elements (hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur) although primary components of nucleic acids, proteins, sugars and fats, are aided in their metabolic pathways by sodium, magnesium, chlorine, potassium, calcium, iron, copper, and molybdenum ions, amongst others. Other metal ions are important toxins; cadmium, mercury and lead. Selenium and iodine are essential trace elements but are toxic at higher levels.

Symbolic meanings of calcium

The importance of bio-inorganic chemistry in biology makes it difficult order some sub-sciences in a countable sequence of complexity. One attempt might be:

This however gives an ambiguous position to bio-inorganic chemistry; it's best ordering at this level being perhaps: Yet bio-inorganic chemistry is (by definition) not organic chemistry. This would suggest that a linear ordering of sciences is insufficient to show some important connections between disciplines. Other methods of showing connections are trees and webs. Investigating the various roles of calcium in physiology would show some of these connections. Analysis of the structures of these connections (through similarities and differences) may then help us to a greater understanding of human physiology and ecology.

This relates back to sociology in the following ways:

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Created 22/5/99
Modified 26/5/99