Complete and revised notes from lectures original lecture notes that have been made more concise and descriptive, according to the learning objectives described for exams.
Objectives:
1. Overview of hypothalamus-anterior pituitary axis + their main target organs
2. Effects of aging on production and metabolism of growth hormone, IGF-1,
adrenocortical hormones + thyroid hormones
3. Effects and symptoms associated with age-related changes in neuroendocrine
hormone levels
4. Changes in hormone levels that are from aging + age-related diseases in men and
women
OVERVIEW OF HPA AXIS:
- System of feedback loops that organise the production and
secretion of hormones throughout the brain and body
- Hypothalamus initially controls endocrine system
- Mediates to the anterior + posterior pituitary that pass out
signals to a range of endocrine systems
o Ex. Water retention in the kidney, lactation and
female reproductive cycle
- Hypothalamus and pituitary have neuronal populations
that regulate the systems
- Pituitary has two main lobes: anterior (glandular) + posterior (neuronal)
o Some other animals have an intermediate lobe as well
Posterior Pituitary –
- Posterior pituitary consists of axons connecting to the hypothalamus + form bundle
o Forms a pituitary stalk that suspends the pituitary gland from the
hypothalamus
- Cell bodies in hypothalamus send projections through the pituitary stalk into the
posterior pituitary + form axon terminals with the capillaries of the pituitary vein
Antidiuretic Hormone + Oxytocin –
- Both hormones are made in cell bodies in the hypothalamus
(supraoptic nucleus + PVN)
- ADH + oxytocin are transported down axon stalk + stored in
nerve terminal
- Posterior pituitary secretes ADH + oxytocin into the blood via the
pituitary vein
Anterior Pituitary –
- No neuronal connections from brain to anterior pituitary (AP)
- Hormones are released from hypothalamus + carried to pituitary
through blood vessels
- Neuronal cell bodies in hypothalamus have projections to median
eminence/pituitary portal system at the base of hypothalamus
- Significantly more hormones go through the AP (hence why no specific example)
o Such as prolactin, growth hormone, FSH, LH, thyroid-stimulating hormone
- Hormone is synthesised in cell bodies in hypothalamus (supraoptic nucleus + PVN)
- Hormone is released into the median eminence + travels down through pituitary
portal system into AP
- Hormone acts on endocrine cells in AP to initiate or inhibit release of downstream AP
hormones
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