Endocrine System
First slide
Exocrine vs Endocrine. Want to distinguish the two. Prefix endo means in, internal or
inside. Do not employee the use of ducts. There will be a space between the secreting cell
and the blood stream, but no ducts. The chemical signals the endocrine glands are secreting
are called hormone.
Exocrine, exo means external. Exocrine secrete hormones that go to external environment.
Sweat glands for instance, will secrete into a duct which will empty onto skin. GI tract is
apart of the external environment, and uses ducts. The pancreas both an endocrine and
exocrine gland. The pancreas will function in an exocrine way by secreting digestive
enzymes that travel through the pancreatic ducts and empty into the duodenum of the
small intestine. Technically apart of the external environment.
Hormones and exocrine secretions are both specific. With hormones, they are going to act
on specific cells called target cells. The cell has to have a receptor for that hormone. If it
doesn’t have a receptor, then its not a target cell and won’t be affected by the hormone.
There are a couple of other secretions called paracrine and autocrine secretions. Paracrine
means near to or nearby, so paracrine will affect the cells next to it. Autocrine will affect the
cell that secretes it.
Third slide
Endocrine vs Exocrine continued
4th slide Table 13.1
Endocrine system vs Nervous System table
Both systems function in communication. The nervous system uses neurotransmitters as
their chemical messenger, where as the endocrine system uses hormones. In the endocrine
system, you have hormones that are being secreted into the blood stream. Both
neurotransmitters and hormones will both bind to receptors, thus they have that specificity
in common.
I will make mention that both receptors on and in should be mentioned. Depends on if you
are talking about a hormone that can enter a cell. If a hormone can’t enter the cell, the
receptor will be external. Neurons will release neurotransmitters, and glandular epithelial
cells/tissue will secrete hormones.
Speed of onset of NT is very quick. Just takes a brief moment to get started. Endocrine
system can take a second or can take several hours to days. NT will also stop quickly unless
continued impulses. Endocrine system is variable. Could be short lived or could be days
depending on the hormone.
Slide 5-Diagram of neuron transmission vs hormones
Slide 6 This slide names some of the endocrine organs, not all. Shows locations. Fig. 13.3 In
lecture, will sometime put pictures on quizzes and tests, but we need to be responsible for
location of these organs. Should know for instance, thymus is located in the mediastinum.
Remember thyroid is in the cervical region. Notice something about this picture that is
unique for this organ system. The hypothalamus and pituitary glands are connected
through the infundibulum. The lack of connection makes this system unique.
The hormones pass through the extracellular space and then gets into the blood stream.
Isn’t directly deposited into the blood stream.
Slide 7 and slide 8 Table 13.2 Hormone Names and Abbreviations.
This table is going to tell you the hormone names, abbreviations, and tell you where they
are coming from. Synonyms are not required, but you can use them. ADH can be called
vasopressin. Do need to know everything other than synonyms. Make note of difference
between organ and a region of the organ. The hypothalamus is an organ that will secrete
everything in this list. Sometimes abbrv will be used or whole name can be used. Some
abbrev will be used such as ACTH. Be comfortable with both. Can use abbreviations that
are used in this slide for answers to a question. GnRH vs GHRH make note of.
The pituitary gland has two regions: The anterior lobe and the posterior lobe. They are
very different. The anterior pituitary produces and secretes what is listed on the table. The
posterior pituitary do not produce ADH and oxytocin, they only release them. The
hypothalamus makes them. The hypothalamus has neurons that are making ADH and
Oxytocin, and they send ADH and oxytocin down through their axons which terminate in
the posterior lobe of the pituitary gland. The hormones hang out in the posterior pituitary
until they receive get an impulse that comes along that tells them its time to be released
into the blood stream. So, ADH and oxytocin are produced by the Hypothalamus and
released by the posterior pituitary gland.
The thyroid gland has three hormones coming out of it. Normally, T4 which is thyroxine,
and T3 which is triiodothyronine, but calcitonin is also produced by the thyroid gland, just
a different cell in the same organ. The parathyroid gland only makes one thing. It makes
parathyroid Hormone. PTH.
The adrenal gland: Take note that the adrenal cortex and adrenal medulla are regions of
the adrenal gland. Two adrenal glands. The medulla is the middle, and the cortex is the
more superficial region. The Adrenal Medulla makes epinephrine and norepinephrine. The
adrenal cortex makes aldosterone and cortisol. The adrenal cortex is also a minor producer
of sex hormones. (Androgens) Sex hormones predominantly come from sex organs
however.
Pancreas secretes insulin and glucagon according to this table. There are more.
Pineal gland secretes makes melatonin.
Ovaries make estrogen. Testes make testosterone. Ovaries also make progesterone.
Make note: TRH is released from hypothalamus which causes TSH to be released from
anterior pituitary. TSH travels to the thyroid and causes T3 and T4 to be released. This is a
tropic process.
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Still on TABLE 13.2
The pancreas secretes insulin, glucagon, and somatostatin.
Slide 9 Chemistry of Hormones
There are a couple of categories we can put these hormones into. First are steroid
hormones. Steroids are lipids, which are non-polar substances that have four fused rings of
carbon. It makes their appearance distinctive. Should be able to distinguish because of
rings. All steroid hormones are derived from cholesterol. Can’t produce Estrogen,
testosterone, progesterone and cortisol, aldosterone without cholesterol. All types of
steroid hormones.
Non steroid hormones-Amines, which sounds like amino acid. Amine hormones are coming
from a single amino acid. Usually tyrosine, but sometimes tryptophan.