Lecture 34 Flashcards
What is the general feedback regulation system of the anterior pituitary gland?
The hypothalamus releases releasing hormone to the pituitary gland, this releasing hormone will inhibit release of more of it and stimulate the anterior pituitary gland to release a pituitary hormone, this pituitary hormone will inhibit the hypothalamus further but not the anterior pituitary gland. The target organ will then release the required hormone which will inhibit both the hypothalamus and the anterior pituitary gland.
How does negative feedback regulation of prolactin work?
Prolactin stimulates dopamine neurons in the hypothalamus, dopamine is the prolactin inhibitory hormone and as such the prolactin secretion becomes inhibited as more prolactin is released.
Whare is the different role that prolactin plays in milk release to oxytocin?
Oxytocin causes milk ejection, prolactin causes the actual synthesis of the milk.
What cell types are found in the anterior pituitary gland? Which hormone(s) do they release and what relative percentage do they make up?
Somatotroph cells release growth hormone and make up 50% of the anterior pituitary
Mammotrophs release prolactin and make up 20%
corticotrops release adrenocorticotrophic hormone and make up 20%
Thyrotrophs release thyroid stimulating hormone and make up 5%
Gonadotrophs release luteinizing hormone and follicle-stimulating hormone and make up 5%.
How is growth hormone secretion regulated?
Growth hormone release hormone neurons (hypothalamus) trigger the release of growth hormone, once this growth hormone reaches the liver the liver releases insulin like growth factor-1 (IGF-1) which among other effects stimulates the somatostatin neurons (hypothalamus) and inhibits the growth hormone release hormone neurons, the somatostatin neurons inhibit release of the growth hormone and the inhibition of the GHRH neurons also inhibits the further release of growth hormone.
What are the main parts of a graph of growth hormone secretion based on gender.
Both genders experience a peak during night time (when they sleep), they also experience some smaller pulsatile peaks during the day. Females experience more and longer peaks than males but smaller ones, males only experience 3 or so peaks in a day, with the largest being the one at night by a huge margin.
When is growth hormone secretion at its peak and when is it at its lowest?
growth hormone secretion peaks during puberty and is at its lowest during old age.
Why do girls experience puberty before boys?
Girls reach their highest point of growth hormone secretion earlier than boys (1-3 years on average) hence they hit puberty earlier.
What are the growth effects(long term) of growth hormone? Are they direct effects or indirect?
The growth hormone indirectly stimulates bone, muscle and other tissue growth by stimulating cell division via the insulin like growth factor 1 produced by the liver (IGF-1) and also directly stimulats protein synthesis in muscle tissue.
What are the metabolic effects (short term) of growth hormone? Are they direct or indirect effects?
Growth hormone directly increases blood glucose levels by stimulating glucose synthesis within the liver and stopping cells from up-taking unnecessary glucose.
It also directly increase the breakdown of triglyceride and helps cause free fatty acid mobilisation within adipose tissue.
What disorders are associated with growth hormone problems?
Hyposecretion from childhood causes dwarfism, hypersecretion from childhood causes gigantism. These can also be caused by hyposensitivity or hypersensitivity of the receptors respectively.
In adulthood excess growth hormone leads to thickening of bones, and the soft tissues of the hands, feet and face.
What are some hormones beside growth hormone which are important for growth? What are their functions?
Thyroid hormone: increases the basal metabolic rate and essential for developing the nervous system.
Insulin: glucose metabolism
Cortisol: glucose metabolism
Testosterone/estrogen: essential for puberty.
