fri, April 6, 2006: hypothalamus, pituitary gland

This is the second day of class.... I make /no/ guarantee about the completeness of this information. :)

Today is the pituitary gland and the hypothalimus (sorry for spelling errors).

Basic nomenclature: (warning: terminology is god-awful, practice until second nature)
Pituitary=hypophysis (hypophyseal *adj*) (hypophysecotomy for removal)


The hypothalimus is in the brain, and the pituitary is beneath it. If you draw a line between your ears, and straight through your mouth, the intersection is where the pituitary is located.

Fig 3-35
The pink are ventricles, and contain cerbral spinal fluid which acts as a shock absorber. The most important is the third ventricle. At the base of the 3rd is the hypothalumus.

Fig 5-17
Sagitally (sideways), the region in green is the hypothalamus, and the surrounding area is filled with CSF. The pit gland is below that. The rest of the brain we don't need to worry about.


fig 6-39 (slided face off)
The 3rd vent is a green lind down the middle. The pink is the hypo, and the pit gland is the small ball hanging off the bottom. The pind dots are illustrating individual hypothalmic nuclei. In the central nervous system a neuclius is a collection of neuron cell bodies. Each one has a specific name. Paraventricular nucleus, is one of them and you might encounter that name in your reading. (para means close to the ventricle) Supra-optic nucleus refers to the fact that it sits above the optic chiasm (above and in front of the pit gland).

off slide:
pituitary= 2 major lobes. 1) Anterior lobe (front) 2) posterior love (back)

Fig 2-4
Shows how they originate during dev. This is the 6th week after conception. The brain which becomes the hypoth starts growing downward towards what will become the mouth. The infundibulum betcome the post. pit gland. It is connected to the hypoth, and contains axons that secret hormones. the anterior comes from the roof of the mouth, and has NO neural connection with the hypoth, but is close to it, and controlled by hypoth, but is not controlled through a neuronal connection. The fully formed (pict 4) sit in a depression in bone called sella turcica. (turc's saddle). The fact that the pit gland is surrounded on three sides by bone, if a there is a tumor it can only go up towards the hypoth. When it does that it compresses the optic ciasm (cross over of optic nerves), that is usually how it is diagnosed due to problems with sight.

fig 3-1 ( you will need to be able to put all of these names on every slide, including spelling)
The post lob contains different anitomical regions (infundibular process or pars nervosa), the staulk, is the infundibular stem or neural stalk). Above that is the median eminence. Neurohypophysis (posterior lobe)
hormones secreted::
ADH: anti-diuretic hormone (aka vasopressin)
Oxytocin

Now to move on to the Anterior pit gland (fig 2-1) Ther eis an ant love, and its componect parts have different names. pars distalis hangs down. pars tuberalis wraps around the infidubular stem, and makes up the hypophseal stalk. the pars intermedia is aka intermediate lobe, it is very under deveopled in humans unless you are a preg woman, or an infant. It is more dev in other animals. key point: you can see that the post lob and the hypoth are the same gray because they are connect, but the ant lob is not. but the ant lobe is totally dependent on the hypoth through a vascular connection.

flow chart (general scheme for the control and function of ant pit hormones)
prolactin works only on breasts of preg women to make lactation.
get from this diagram a basic overview and an appreciation that the this system can influence bone growth, etc.

specifically fig 14-8b
all the neuclii have nerurons which secrete ..hypophysiotropic... which create an action potential. The hypophysiotropic hormones don'tw work on other neurons, they go tinot a capilary bed that goes into a median eminence, at the base of the hypoth. the blood flows from that bed to the pit glad is the hypothalamo-hypopheseal portal vessels. once the portal vessels reach the anterior pit gland, it splits up and they diffuse out of the cap bed into the extracellular fliud. they then bind to the ant pit cells to regulate the production of hormones in the cells of the ant pit gland. the target cells are within the ant lobe. The venous outflow exit through the bone. The key point is that the blood flow goes down through and then into the systemic system. There are very few cells that make the hypothalmic neuclui to produce a particular hypophysical hormone, and has to effect a small area like the pit. if it were put into the entire body's flow, it would do nothing because of dilution. and is so low it is difficult to detect in the main blood. If there were a barrier at the portal vessels, there would be no way for it to be controlled.

table: (anterior pit homones) (mem this, including TLAs and real names)
ACTH is a hormone that acts on the adrenal cortex. stands for adrenocoroticotropic hormone or adrenocorticotropin, or corticotropin. you must know all the names.
FSH and LH are both gonadotropin (tropin means it nourishes something, and without them the target glands shrivel up and no longer work)(they regulate the secretion of specific hormone of their targets, and also maintaining the integrity of the target itself).
Know the names and the cell types. we will use this all quarter.
The third column is what types of hormones are released by the hypoth which acts on whatever is in the second column, to produce the first column, and the result is the fourth column.
Anything with an asterix is a primary regulator, and items without are not.

net table: (structure and mechanism of action of hypophysioteropic hormones)
You don't need to mem how many aa there are but you need to know if they are a peptide/etc, and what their major mechanism of action is.

fig 11-17
is another way to presnt the same materiial. The other table has more information, but if you start with this fig it might be easier to conceptualize, and then fill in the other information after you get this.

off-slide:
if you plot growth hormone levels throughout the day, growth hormones are generally higher right after someone goes to sleep. And most are in a circadian rhythm that is released episodically. It you took blood every 15 mins, it would never be flat. the pulsatile release would mean that at some times it would be barely detectable, and then a quick pulse of hormones released, and then back to negligible levels. The amplitude, and frequency can change, but teh pulsitility is fairly constant. This pulsing protects against resistence from over-stimulation.