Physiologic Mechanism of the Hypothalamus and Pituitary Gland (Nursing)

00:01 So now let's look at the concept of the hypothalamus pituitary axis and how things relate when we talk about endocrine function.

00:11 So we can think of things as starting in the hypothalamus.

00:15 And some sort of releasing hormone getting into that short portal system to stimulate the anterior pituitary, and in will in turn then secrete some sort of pituitary hormone that will flow out in the bloodstream to reach its target gland.

00:32 Now, as the anterior pituitary is secreting all this hormone, there's something called feedback that will feed back on to the hypothalamus and tell, "Hey, we have a lot of pituitary hormone out." You can stop secreting the releasing hormone, and thus sort of close the loop and maintain homeostasis.

00:53 And then the target gland itself can go on and do whatever it needs to do, largely, for example, like the thyroid gland that would be making more hormones.

01:05 That also can help, in turn, turn off stimulation in the anterior pituitary and hypothalamus also through feedback.

01:14 As there's more target gland hormone, for example, the thyroid hormone, it would be sent by the pituitary and hypothalamus as being sufficient and turn off the stimulating hormones and maintaining homeostasis.

01:30 So what are some of these hormones being produced by the pituitary gland? Well, the anterior lobe has more than the posterior lobe and they are the growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, prolactin, gonadotropic hormones, and they come in two varieties, follicle stimulating hormone and luteinizing hormone.

01:58 The posterior lobe, on the other hand, only has vasopressin also called antidiuretic hormone and oxytocin.

02:09 The anterior pituitary hormones, such as growth hormone have a wide effect on the body.

02:16 So growth hormone affects many things, liver, muscle, bone, cartilage, other tissues and the name gives you some general idea of what they do.

02:27 They're basically promoting growth of these tissues.

02:33 Thyroid stimulating hormone or TSH tells you what it's doing.

02:38 It's going to act to stimulate the thyroid gland to in turn produce thyroid hormones.

02:46 Thyroid hormones are then going to go on to have a wide array of effects on metabolism.

02:55 Adrenocorticotropic hormone or ACTH actually tells you what it's doing even though it seems like a mouthful.

03:03 But adrenocorticotropic means it has a tropism or tendency to go towards the adrenal cortex.

03:11 So adrenocorticotropic tells you what it's acting on.

03:15 It's acting on the adrenal cortex.

03:19 And that's going to stimulate things like glucocorticoids and androgens.

03:27 The gonadotropic ones the follicle stimulating hormone or FSH will have an effect on the gonads.

03:37 So in the case of the testes that will be sperm production or in the ovaries, ovarian follicle maturation and estrogen production.

03:46 The other one would be luteinizing hormone.

03:50 And that would have an effect on the testes in producing testosterone itself a hormone and also in the ovary with triggering ovulation.

04:02 Prolactin actually tells you what it's doing as well.

04:07 It's going to act on the secretory breast tissue to produce lactation.

04:13 So prolactin is essentially promotion of lactation.

04:19 Moving to the posterior pituitary, we have oxytocin which has an effect on the uterus during contractions.

04:29 So this is actually what's going to stimulate contraction of the uterus during childbirth.

04:34 And it's also going to be what stimulates a type of modified smooth muscle cell in the breast.

04:40 That helps with the milk ejection reflex.

04:43 So while prolactin will help stimulate production of milk, oxytocin has a role in the actual ejection of milk out through the ducts that lead into the nipple.

04:55 Then finally, antidiuretic hormone is also very descriptive.

05:00 If you know that diuretic means to lose water.

05:04 So antidiuretic is going to have an effect that prevents the losing of water.

05:09 So antidiuretic hormone or ADH is going to act on the kidneys, in particular an area called the collecting dock.

05:18 And what that's going to do is help stimulate reabsorption from the filtrate that was filtered out of the blood and get it back into the bloodstream.

05:29 And that's the sort of thing that would be secreted when you're very hot or you're very thirsty or in a dry hot area and you want to hold on to as much water as possible.

05:38 That's where the posterior lobe of the pituitary will help preserve water as much as possible.