in this set of hour in this part of the MOOC we're going to discuss the endocrine system so the
endocrine system is very important in maintaining homeostasis in homeostasis is by definition the
maintenance of a dynamically stable state so you are dynamically stable you're not static
in that you're not frozen in time and all of your systems aren't frozen your dynamic and that you're
changing from moment to moment but overall you're stable your blood pressure isn't going way up or
way down your temperatures not going away up and way down so that's what we're talking about when
we're talking about homeostasis dynamically stable State in the neuro MOOC if you if you looked at
that we talked about the autonomic nervous system and how it is part of your nervous system and it
contributes to homeostasis in this MOOC we're gonna speak about the endocrine system and the
endocrine system is slow it doesn't work very fast at all because it's humoral ie blood-borne
so endocrine system is hormones they're secreted into your blood supply that takes those hormones
to other parts of your body where they may act on those cells and then those cells respond and so
it has an effect on your internal environment but it is definitely not fast it is slow so
there are several different types of secretion when we're talking about the whole body and the
endocrine system specifically so you have exocrine secretions and exocrine is systems with ducts so
your salivary glands sweat glands little glands that make a product like saliva or sweat secreted
into a duct and then that duct leads to the surface of your skin or the lumen of your gut or
something like that we have autocrine secretion which is when a single cell makes a product that
it secretes into its surround and then that comes back and finds on that cell that same cell we have
paracrine secretion and peregrin means nearby or local and so cells will secrete peptide or a
hormone that will then act cells nearby the cell that created the substance and then of course we
have endocrine now endocrine is then no ducts it secretes into the vasculature and those products
or hormones are going to act at a distance so here's my little drawings of autocrine we have a
cell at the top that is the little red diamonds are the secretory product the cell secretes it
it comes back around binds to the receptor on that same cell so Auto meaning self it drives
the peptide comes out and binds to the same cell that made it paracrine again acting locally so
the little green cells are making some sort of a peptide or hormone and it's secreted and it
binds to the little blue cells on their receptors so it's a local interaction exocrine again are
things that secrete into ducts so you'll have some sort of a cuboidal epithelium that's been
modified to create a secretory product and some of the best examples easiest ones to talk about
our salivary glands that create saliva and obviously they have ducts that secrete into
your oral cavity sweat glands secrete via adopt onto the surface of your skin help you to sweat
and help reduce temperature body temperature the exocrine pancreas that is reviewed in this part
of the MOOC within the GI system the digestive enzymes of the pancreas are also secreted into
ducts that then dump into your duodenum and your liver is another part of your GI system that makes
bile and secretes that into the GI system via a system of ducts the endocrine system endocrine
glands consists of a cuboidal epithelium that's kind of you know in these guys these cells that
secretes into capillaries so endocrine glands have tons and tons of capillaries within them
they secrete into these capillaries which is kind of labeled here this is a capillary and they have
what are called finestra they're fenestrated capillaries which means little windows that make
them more open so that the hormones can get in and then these capillary beds of course are going to
join the greater system that you learned about in dr. Fox's MOOC on the cardiovascular system
and then those the vascular system distributes those hormone products throughout the entire body
but then they only bind where they're where is appropriate but they do go absolutely everywhere
hormones can either be proteins or small peptides that usually will then bind somewhere in the body
to a surface receptor and we have steroid hormones when you think of steroid hormones you're thinking
about the sex steroids testosterone estrogen progesterone that we'll talk about later these
act via nuclear receptors so they go into the cell and bind to a nucleotide to a receptor
that's already in the nucleus so to summarize I know this is kind of a lot of information for
the first for the first introduction but what I want you to know and what will get you ready for
the the assessment is what are the different types of secretion so think ducts no ducts
think about the individual cell and whether it's local or or at a distance then what are the big
differences between exocrine glands and endocrine glands and be able to define homeostasis once
you have all of these concepts in your head you're going to be ready for the assessment