Physiology 3120 Lecture Notes - Lecture 52: Hypophyseal Portal System, Growth Hormone–Releasing Hormone, Anterior Pituitary
2 May 2018
School
Department
Course
Professor
Human Physiology Lecture 52
Neuroendocrinology
Pituitary and Hypothalamus
- Pituitary – master endocrine organ that regulates other endocrine organs throughout the body
- Disruption in pituitary and hypothalamus function = endocrine organs
o Widespread physiological impairments
- Acromegaly = too much growth hormone (GH)
o Bone deficiency occurs with too much GH
o Large stature
o EX. Andre the giant
- Hypothalamus, superior to the pituitary, is the sensor
o Changes in fear, glucose, temperature
o Relays information to the pituitary to release hormones to deal with the stress or situation
Functional Anatomy
- Anterior pituitary + posterior pituitary target different set of hormones
o Innervated by the hypothalamus in a different manner
Anterior pituitary
- Receives signals from the hypothalamus via Parvicellular neurons
- Parvicellular neurons are in the hypothalamus
o Short
o In response to stress the hypothalamus is sensing, these short axons go on and trigger a
release of a hypothalamic hormone, which travels the hypopyseal portal system
o Since the axons are short, not long enough to get into the anterior pituitary, the
neuroendocrine cells secrete a hormone that travels through the hypophyseal portal system
and targets the anterior pituitary
- In the anterior pituitary, these hypothalamic hormones act on anterior pituitary cell (tropic cell) that
produces anterior pituitary target hormone, which is secreted in the blood stream to target another
endocrine gland or metabolic organ (e.g. liver)
- Anterior pituitary: Parvicellular neurons that target the anterior pituitary from the hypothalamus.
Use hypophyseal portal system to carry those hormones from the hypothalamus to the anterior
pituitary
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find more resources at oneclass.com
Posterior Pituitary
- Hypothalamus targets the posterior pituitary through Magnocellular cells
- Magnocellular cells
o Longer axons, therefore do not require the hypophyseal portal system
o In response to some change in metabolism or fear, you can have these cells directly secrete
the hormone into the posterior pituitary, which is then secreted into circulation to act on a
particular endocrine gland or metabolic organ
o Protrude from axons to hormone secretory cells in the posterior pituitary, which then
secretes another hormone into the blood stream
o DONT USE HYPOPHYSEAL PORTAL SYSTEM –have direct release into the posterior pituitary
Hypothalamic Neurons and Factors
- Vasopressin and oxytocin
o Target organs such as the kidney, uterus and the mammary glands collectively
- Parvicellular nerves will influence anterior pituitary to produce trophic hormones
o Trophic hormones: ACTH, TSH, GH, LH+ FSH (reproduction and prolactin)
o Target multiple organs – adrenal, thyroid, liver, ovary, etc.
- Hypothalamus has neuroendocrine cells & regular neurons
o Regular neurons in nervous system function (have nervous system targets as well)
o NOT JUST ENDOCRINE GLAND!
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find more resources at oneclass.com
Paraventricular Nucleus:
- There are multiple hormones and peptides produced by mangocellular neurons, Parvicellular
neurons
- Arcuate nucleus – some hormones overlap with magnocellular and Parvicellular cells
- 3 different hot spots in the hypothalamus that can produce hormones and peptides
Episodic Endocrine Secretion
- Many hormones in the body are regulated short term – minute to minute basis, or long term – day to
day basis
- Many hypothalamic and pituitary hormones are regulated by Circadian rhythm – once a day
o AROUND 24 hours
- Diurnal rhythm – EXACTLY 24 hours
- Hormones that are secreted once a day:
o Growth hormone releasing hormone – GHRH
o Corticoid releasing hormone – CRH
▪ Role in activating stress system
o Cortisol
▪ On a daily basis, we have an increase in cortisol production UNLESS we encounter
stress, which would activate CRH and cortisol secretion
- Cortisol – produced in Circadian manner, once a day
o Everyday around 4am, there is a peak in cortisol production
o Just as day light comes in – increase in cortisol secretion
o NAPS DON’T )NFLUENCE T(E C)RCAD)AN R(YT(M
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pituitary master endocrine organ that regulates other endocrine organs throughout the body. Disruption in pituitary and hypothalamus function = endocrine organs: widespread physiological impairments. Acromegaly = too much growth hormone (gh: bone deficiency occurs with too much gh, large stature, ex. Hypothalamus, superior to the pituitary, is the sensor: changes in fear, glucose, temperature, relays information to the pituitary to release hormones to deal with the stress or situation. Anterior pituitary + posterior pituitary target different set of hormones. Innervated by the hypothalamus in a different manner. Receives signals from the hypothalamus via parvicellular neurons. Parvicellular neurons are in the hypothalamus: short. In the anterior pituitary, these hypothalamic hormones act on anterior pituitary cell (tropic cell) that produces anterior pituitary target hormone, which is secreted in the blood stream to target another endocrine gland or metabolic organ (e. g. liver) Anterior pituitary: parvicellular neurons that target the anterior pituitary from the hypothalamus.
