Calcium Homeostasis | Parathyroid Hormone and Vitamin D

hi I'm dr. Mike here calcium is extremely important in our body for the excitable tissue such as our heart and our skeletal muscles the amount of calcium determines how well that muscle contracts if the amount of calcium in our blood drops then it can change the contractile ability of our heart and our skeletal muscles it can also affect the way our nerves work as well so it's very important that we maintain a very tightly regulated amount of calcium in our bloodstream in order to control this we have something called calcium homeostasis and a number of hormones are involved in this process so let's take a quick look at it first thing is this there is a gland or a number of glands called the parathyroid gland you have your thyroid which is a butterfly-shaped gland that hugs your trachea so here's the head and the neck and you can see the tricky here with the thyroid hugging it if you turn that around and have a look behind the thyroid you'll see there's a couple of glands embedded in the thyroid they're called the power by Roy glands remember power means near or close to now these parathyroid glands release something called parathyroid hormone we'll just call it PTH from now on now what happens is if your blood calcium levels go too low so you can see low blood calcium if they go too low this is going to be a stimulus to trigger your parathyroid glands which are the receptors in this scenario to release their parathyroid hormone PTH now I want you think about this at the same time what's happening is that UV light coming from the Sun is going to interact with our skin and inner skin we've got a cholesterol derivative which is called 7d hydro cholesterol okay now this 7d hydro cholesterol is turned into Coley Kelsey Farrell also known as d3 but from that UV light collie Kelsey Farrell can also not just get be taken from the UV light changing the cholesterol in our skin we can also get it from fish for example so we've got this d3 collie Calcifer ol which is now in our bloodstream and goes to our liver now we can also get another type of vitamin D from other foods such as eggs and that's called agar Kelsey Farah so we get colleague Elsa Farrow from the Sun and from fish and we get a go kalsi Ferrell from eggs and so now I've got d3 indeed to both going to the liver now the liver turns them both into Kelsey deal Kelsey Darragh deal again via bloodstream goes to the kidneys and the kidneys turn it into Kelsey trail this is the functional vitamin D Kelsey trail together with parathyroid hormone have a synergistic relationship so together they do something very special three important things together they one increase the activity of osteoclasts osteo means bone class in this scenario is talking about crushing so parathyroid hormone Kelsey trail triggered osteoclasts to break bone down if they break bone down they release calcium into the blood perfect the trigger or stimulus was a drop of calcium in the blood now we've just released calcium to bring that blood calcium back up second thing they do is they decrease the amount of calcium that we're paying out so they go the kidneys and say don't pay out that calcium keep it in the blood again raising up calcium levels in our blood plasma the last thing they do is they go to our intestines and tell our intestines to increase their absorption of calcium into the blood so the stimulus was a decrease in blood calcium and the effect was an increase in blood calcium that negates the stimulus stopping the release of parathyroid hormone and then this whole homeostatic chain is inhibited this is called negative feedback and this is calcium homeostasis

Channel: Dr Matt & Dr Mike

Views: 84,929

Keywords: calcium, calcium homeostasis, parathyroid, parathyroid hormone, calcitriol, calcidiol, vitamin d, vitamin d3, homeostasis, negative feedback, bone, bone remodelling, osteoporosis, osteopathy, physiotherapy, nursing, medicine, usmle, osteoclast

Id: JYQL7JEsF_4

Length: 3min 56sec (236 seconds)

Published: Sun Mar 24 2019