lecture 26 - pituitary, hypothalamus & growth hormone Flashcards
Where is the pituitary gland located?
At the base of the brain, attached to the hypothalamus.
How is the pituitary gland stimulated to produce hormones?
Activated by the hypothalamus by neural and hormonal imput.
What are the 2 key parts of the pituitary gland?
Anterior lobe and Posterior lobe
How is the posterior lobe of the pituitary connected to the hypothalamus?
By neurons, which have their cell bodies in the hypothalamus, and axon terminals in the posterior lobe
Where are posterior pituitary hormones made?
In the cell body of neurons that connect the hypothalamus to the posterior lobe
Where are posterior pituitary hormones stored?
At the axon endings of the neurons that connect the hypothalamus and posterior pituitary.
What type of hormone are posterior pituitary hormones, and in what medium are they soluble?
Peptide hormones (water soluble)
What are the hormones released by the posterior pituitary?
(ADH) Antidiuretic hormone, oxytocin
What is the rate of the release of posterior pituitary hormones dependent on?
The rate of action potentials fired by the hypothalamus.
What is ADH (hormone)?
Antidiuretic hormone
What is the function of ADH?
Antidiuretic - stimulates the kidneys to reabsorb and conserve water, rather than releasing it as urine
What hormone acts on the kidneys, causing them to reabsorb water?
ADH - antidiuretic hormone
What are the key functions of oxytocin?
Stimulate the contraction of uterine muscles during childbirth and stimulate the milk ejection reflex during breast feeding
How is the anterior pituitary connect to the hypothalamus?
Via a portal vessel network
How does the hypothalamus signal to the anterior pituitary?
Via releasing hormones, released from neurosecretory neurons in the hypothalamus and transported via portal vessels to the anterior lobe.
What type of hormone are releasing hormones released by the hypothalamus?
peptide hormones
How do releasing hormones trigger the release of anterior pituitary hormones?
The peptide hormones bind to target cell membrane receptors, which triggers the secretion of a specific anterior pituitary hormone into the bloodstream.
Where is growth hormone secreted from?
The anterior pituitary
What triggers the release of growth hormone from the anterior pituitary?
GH-RH - growth hormone releasing hormone
What inhibits the release of growth hormone from the anterior pituitary?
GH-IH - growth hormone inhibiting hormone
What is the target gland of growth hormone?
The liver
What is PIH (hormone)?
Prolactin inhibiting hormone
What is PRH (hormone)?
Prolactin releasing hormone.
What does prolactin inhibiting hormone (PIH) inhibit?
Prolactin release and TSH release from the anterior pituitary
What does the anterior pituitary hormone prolactin (PRL) do?
Stimulates the mammary gland to secrete breast milk
What are the direct, long term effects of growth hormone on muscles?
Stimulates protein synthesis
What are the direct, short term effects of growth hormone on muscles?
Inhibits cellular uptake of glucose
What are the short term effects of growth hormone on the liver?
Stimulates glucose synthesis (gluconeogenesis)
What are the short term effects of growth hormone on fat/adipose tissue?
Increase triglyceride/fat breakdown
What are the indirect effects of growth hormone on the body?
Promotes cell division in bones, muscles and other tissues, by releasing Somatomedin C
What is the other name for Somatomedin C?
IGF -1 (insulin growth factor 1)
What is the function of Somatosedin C?
Promotes cell division for growth in the long term
When are GH concentrations in the body highest?
During the night/when asleep
In a negative feedback loop, the increase of what hormones will lead to the release of GH-IH and therefore a decrease in the release of growth hormone from the anterior pituitary?
Somatomedins
Where are somatomedins released from, and in response to what stimulus?
The liver - in response to growth hormone acting on target tissue
Where are the axon terminals of hypothalamus neurons that secrete anterior pituitary releasing hormones found?
Median eminence
