Feedback mechanisms, tropic hormones and neuronal control (also cicadian release and pulsatile release)
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Describe the feedback control of glucose
There is an increase in glucose which leads to an increase in the secretion of insulin. This causes a decrease in glucose which feeds back and the amount of insulin is decreased
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What are tropic hormones?
They stimulate the release of another hormone from other endocrine glands
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What are trophic hormones?
Hormones that have a growth effect on cells/tissues causing hyperplasia and hypertrophy
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Describe the composition of the posterior lobe of the pituitary gland
It is comprised of neuronal tissue with cell bodies of neurones found in the hypothalmus
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Describe the composition of the anterior lobe of the pituitary gland
It is comprised of glandular tissue which are hormone producing. The lobe also has the hypophyseal portal circulation which is a direct route to the anterior lobe
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Where do neuroendocrine cells side?
In the nuclei of the hypothalmus
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Describe the hormone release pathway for the anterior lobe
The arcuate periventricular nucleus releases hypothalmic hormone into the hypophyseal portal circulation which then goes to the anterior lobe which then releases the anterior lobe hormone towards the target tissue
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Why does the hypophyseal portal circulation exist?
So that hormones can get to the anterior lobe as quickly and as concentrated as possible
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Describe the hormone release pathway for the posterior lobe
Hormone is manufactured in the neuroendocrine cell body in the hypothalmus as is sent to the posterior lobe by axonal transport where it is then released into the blood stream
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What does the hypothalmus nuclei monitor?
Levels of circulating hormones, metabolites, nutrients and electrolytes. Stress, cold, trauma, hunger, pain and neural reflexs also affect the nuclei of the hypothalmus
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Depending on which hormone is manufacted by the hypothalmus depends on .......?
Which cells in the anterior pituitary gland are stimulated and therefore which hormones are stimulated
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What types of cells are in the anterior pituitary?
Gonadotroph, somatotroph, thyrotroph, lactotroph and corticotroph
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Describe thyroid hormone production in the pituitary gland.
The neuroendocrine cells release thyrotropin releasing hormone into the hypophyseal portal circulation to the thyroptroph cells. They bind with these cells causing the release of thyroid stimulating hormone being transported to the thyroid gland
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How are cells distinguished in the anterior pituitary lobe?
By what they produce
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What hormones are released from the posterior lobe?
Oxytocin and ADH/vasopressin
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How is oxytocin released?
Activation of stretch sensitive sensory cells feeds back to hypothalmus via the spinal cord which then travels to the hypothalmus and posterior lobe which releases oxytocin which goes to the mammary glands/uterus to cause milk let down or contraction
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Which hypothalmic nuclei are used in the release of oxytocin?
Paraventricular nucleus and supraoptic nucleus
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What action does vasopressin have?
Increased water reabsorption, decreased water excretion, constriction of arterioles and increased arterial pressure
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How is ADH regulated?
Secretory stimulus is in increased plasma osmolarity and decreased plasma volume
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What clinical abnormalities are here with ADH secretion?
Diabetes insipidus- chronic excretion of dilute urine, thirst and disruption of ADH production (caused by pituitary tumours/traumatic injury to skull)
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Other cards in this set
Card 2
Front
Describe the feedback control of glucose
Back
There is an increase in glucose which leads to an increase in the secretion of insulin. This causes a decrease in glucose which feeds back and the amount of insulin is decreased
Card 3
Front
What are tropic hormones?
Back
Card 4
Front
What are trophic hormones?
Back
Card 5
Front
Describe the composition of the posterior lobe of the pituitary gland
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