Calcification (mineralisation), is when calcium phosphate, calcium hydroxide and other mineral salts combine to form crystals, known as hydroxyapatite within bone tissue. They are then deposited into the structural framework of the extracellular matrix, where they solidify. For this process to occur, the presence of collagen fibres are required. The salts crystallise within the spaces of collagen fibres and when these spaces become full, the crystals then assemble themselves amongst these collagen fibres (Tortora et al., 2019).

Bones generally have a substantial blood supply, but healing can take months to repair as minerals such as calcium and phosphorus are distributed gradually through the process. Also, bone cells grow and reproduce slowly as well resulting in a gradual healing process (Tortora et al., 2019).

 

Gender is another contributing factor. For women, bone loss increases quickly after menopause when oestrogen levels decrease. Oestrogen perseveres bone; therefore, a fall in oestrogen levels typically results in bone loss. 

Other risk factors for developing osteoporosis include an inactive lifestyle (Tortora et al., 2019).

How does Botulinum Neurotoxin A prevent the initiation of a muscle action potential at the structure identified in Q. 1? (3 marks) (75 words) 

Botox affects the Neuromuscular junction which is the site for the communication of an action potential by preventing the initiation of a muscle action potential by blocking exocytosis of synaptic vesicles in the neuromuscular junction. As a result, Botox binds and blocks acetylcholine receptors so that it can’t be realised, and ion channels do not open resulting to muscle paralysis (Tortora et al., 2019).

Thyroid hormones are produced from iodine and tyrosine inside thyroglobulin (TGB). 

T3 and T4 are both lipid soluble, so they diffuse through the plasma membrane and into the interstitial fluid the hormones are then transported in the blood bound to plasma proteins, through thyroxine-binding globulin (TGB). T4 is secreted in larger amounts than T3 but T3 is a lot more potent than T4. Additionally, when T4 enters a body cell most of it is converted into T3 via subsequent removal of one iodine (Tortora et al., 2019).