BMS2031 Lecture 14: Week 5. Endocrinology 1&2 Hypothalamus, Pituitary gland and Thyroid gland
31 May 2018
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Week 5. Endocrinology 1&2 Hypothalamus, Pituitary
gland and Thyroid gland
HYPOTHALAMUS AND PITUITARY GLAND
• Anatomy of the hypothalamus and pituitary gland:
• Oxytocin and vasopressin are made in cell bodies of the magnocellular body: supraoptic nuclei
(SON) and paraventricular nuclei (PVN)
• A neuron will only make one hormone
• Stimuli/input -> osmoreceptors in hypothalamus -> detect osmolarity -> increase firing ->
stimulate SON/PVN -> vasopressin
• Stimuli/input -> stretch from uterus/suckling on mammary glands -> impulse travels up spinal
cord -> SON /PVN -> oxytocin
• ADH/Vasopressin:
o 9aa peptide
o Water retaining hormone
o Small changes in osmolarity produce a linear response in linear plasma ADH
Regulated by two factors:
1. Most sensitive factor is plasma osmolarity (changes of 1%)
-detected by osmoreceptors in hypothalamus
2. Blood pressure (changes of 10-15%)
-detected and monitored by pressure baroreceptors present in aortic arch and carotid
bodies
find more resources at oneclass.com
find more resources at oneclass.com
• Oxytocin:
o 9aa peptide
o Hormone essential for lactation
o Stimulates milk letdown whereas prolactin stimulate milk production
o Suckling stimulates mechanoreceptors that ascend through spinal cord and eventually to
SON and PVN to trigger release of oxytocin
o Also released in response to stretch receptors in cervix that sends signals to brain and
hypothalamus
o Analogues are often injected to induce and support difficult labour
o Causes contractions/dilations during child birth and helps uterus go back to normal size
o Involves positive feedback
o Also stimulated during orgasm
o Pathway of lactation and uterine contraction are not independent - Suckling by baby can
also cause contractions of the uterine
o Do’t ko hy e hae it
• Anterior pituitary gland:
o Derived from mesoderm
o In communication with the hypothalamus – PVN sends axon terminals to the median
eminence where they secrete a number of different releasing hormones into the
hypothalamo-hypophyseal portal vessels that travel and act on anterior pituitary
o Secretes a number of different hormones that are made by specific groups of cells:
ACTH related proteins – stimulates adrenal gland
Somatomammotrophin proteins – GH and PRL
Glycoproteins – LH, FSH, TSH
find more resources at oneclass.com
find more resources at oneclass.com
• Proof of releasing hormones between the hypothalamus and anterior pituitary:
Pulsatile secretions of GnRH from hypothalamus -> median eminence -> portal blood system ->
anterior pituitary -> LH and FSH
• Negative feedback: there is a short loop and a long loop
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Endocrinology 1&2 hypothalamus, pituitary gland and thyroid gland. Regulated by two factors: most sensitive factor is plasma osmolarity (changes of 1%) Detected by osmoreceptors in hypothalamus: blood pressure (changes of 10-15%) Acth related proteins stimulates adrenal gland. Somatomammotrophin proteins gh and prl: proof of releasing hormones between the hypothalamus and anterior pituitary: Intracellular mechanism involves: tyrosine kinase jak2 signal transduction system: negative feedbac, secretion is stimulated by: Aging: levels are unrelated to glucose, insulin or cortisol, cortisol peaks just before awakening, effects: Stimulates liver to produce insulin like growth factor igf-1 which then acts on osteoblasts to increase bone growth. After long bones have sealed can get growth in other bones i. e. skull, hands, jaw. Iodination of thyroglobulin: conjugation of iodinated tyrosines, endocytosis of iodinated thyroglobulin, proteolysis of iodinated thyroglobulin, secretion of t3 and t4 into the circulation, hyperplasia (growth) of the thyroid gland, only 1% of thyroglobulin per day is secreted.
