Physiology 3120 Lecture Notes - Lecture 2: Gametogenesis, Osteoporosis, Glut4
9 May 2018
School
Department
Course
Professor
Physiology 3120
Dr. Hardy
Neuroendocrinology (2)
Pituitary and Hypothalamus
- If you have a disruption in the pituitary, this can lead to widespread endocrine disorders
- Hypothalamus is the sensor – senses changes in glucose, temperature etc and relays that info to
the pituitary to release hormones to deal with those changes
Functional Anatomy
- Ant and post pituitary target a different set of hormones
- Both ant pituitary and post pituitary are innervated by the hypothalamus in a different manner
- Anterior pituitary
o it receives signals from the hypothalamus via the parvicellular neurons
o parvicellular neurons are in the hypothalamus and they are short
o in response to whatever particular stress the hypothalamus is sensing, these short
axons will go on to trigger the release of a hypothalamic hormone
o this hormone travels through the hypophyseal portal system
o bc these axons are short (not long enough to get right into the ant pituitary), these
neuroendocrine cells have short axons which secrete a hormone that travels through
the hypophyseal portal system that targets the anterior pituitary
o in the ant pituitary, the hormones act on a ant pituitary cell (a tropic cell) that can
release an ant pituitary target hormone and secrete that into the blood stream to target
another endocrine gland in the body or a metabolic organ (ex: liver)
o SO if you are talking about the ant pituitary, you are talking about parvicellular neurons
that target the ant pituitary from the hypothalamus and they use hypophyseal portal
system to carry those hormones from the hypothalamus to the target
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- Posterior pituitary
o Hypothalamus targets the post pituitary through magnocellular cells (which have longer
axons and don’t require the hypophyseal portal system)
o In response to some change in metabolism or fear, you can have magnocellular cells
directly secrete a hormone into the post pituitary
o This is then put into the circulation to act on a particular endocrine gland or metabolic
organ of interest
Hypothalamic Neurons and Factors
- 2 major hormones of the magnocellular neuron via the post pituitary:
o vasopressin
o oxytocin
o these target organs such as:
▪ kidney
▪ uterus
▪ mammary gland
- major hormones of the parvicellular hypophyseotropic neuron via ant pituitary:
o trophic hormones: (ACTH,TSH,GH, LH, FSH, prolactin)
o these target organs such as:
▪ adrenal
▪ thyroid
▪ liver
▪ ovary
- SO hypothalamus has neuroendocrine cells
(magnocellular neurons or parvicellular
hypophyseotropic neurons) which secrete
hormones or regular hypothalamic
neurons
o so the neurons in the
hypothalamus can have nervous
system targets as well
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find more resources at oneclass.com
Paraventricular Nucleus:
- there are many hormones produced by magnocellular and parvicellular neurons and the arcuate
nucleus
- some of the hormoens in the artcuate nucleus overlap with hormones that are secreted by
magnocellular or parvicellular cells (Ex: neuropeptide Y) but just know that these are kind of
like 3 diff hot spots in the hypothalamus that can produce hormones that are peptides bt
Episodic Endocrine Secretion
- many hormones in the body are regulated short term (on a min basis) and others on a long term
basis (on a daily basis)
- many of the hypothalamic and pituitary hormones are regulated by circadian rhythm (once a
day) or a diurnal rhythm (exactly 24 hours) but these are both interchangeable terms
- ex of hormones that are released once a day:
o GHRH
o CRH
o Cortisol
- On a daily basis, we have an increase in cortisol production, unless we have a stress activation in
which case we would activate CRH and GHRH production
- Ex: cortisol is produced in a circadian manner once a day (around 4am – just as daylight is
starting to come)
- We can also have hypothalamic and pituitary hormones which are secreted in a ultradian
manner (minute to minute basis)
o Ex: GnRH
o Ex: LH
- This is important so that we prevent receptor desensitization
find more resources at oneclass.com
find more resources at oneclass.com
