HomeostatisCalcium levels in the blood mustbe maintained within a certainrange or it can be dangerous to thebody.Normal Range: 9.0–10.5 milligramsof Ca+ per deciliter (mg/dL)
HomeostasisCalcium levels in the blood arecontrolled by the endocrinesystem.Two organs located in the neckresponsible for calcium regulationare the thyroid and parathyroid.
HomeostasisCa+ regulation is controlled bynegative feedback systems.
HomeostasisWhen blood calcium levels are toolow the parathyroid will releaseparathyroid hormone (PTH) resultingin:1. Increased osteoclast activityreleasing Ca+ from the bone intothe blood(major way).
Homeostasis2. kidneys will decrease theamount of Ca+ released in theurine.3. Increased vitamin Dproduction in the skin whichwill increase absorption of Ca+from food.
HomeostasisWhen levels of calcium haveincreased or are too high osteoclastactivity is slowed by:1. Less PTH being released2. The thyroid secreting calcitoninwhich decreases osteoclast activityas well.
HomeostasisBone growth:Regulated by Human GrowthHormone (HGH) secreted byanterior pituitary gland at thebase of the brain.
HomeostasisBone growth:Dwarfism – a condition in which aperson is much smaller than anaverage human due to too little HGHproduction by pituitary gland as achild.
Homeostasis Bone growth:Gigantisms – a condition in which aperson is much larger than anaverage human due to too muchHGH production by pituitary gland asa child.
HomeostasisBone growth:GigantismAs an adult overproduction of HGHwill cause the epiphyseal line tothicken, thicken the bones. Seen inthe eyebrows being very thick.
Homeostasis Bone growth:Estrogen and testosterone are twoother hormones affecting bonegrowth:a. They will stimulate bone growthresulting in a growth spurt at puberty.b. Then they will stimulate theepiphyseal plate to ossify stoppingbone growth after puberty.