Endocrine I Flashcards
What happens when a hormone arrives at a cell?
It binds to the receptor, where it influences reactions within a cell
What is negative feedback?
When a hormone is released in response to a specific stimulus & usually its action reverses the stimulus
What is positive feedback?
Positive feedback amplifies the stimulus & increases the release of a hormone until a particular process is complete
What is the different name for the pituitary gland?
Hypophysis
Where is the pituitary gland situated?
In the hypophyseal fossa (sella turcica)
What is the composition of the hypothalamus?
Hypothalamus is composed of groups of nerve cells involved with the control of the autonomic nervous sytem
What is the function of the hypothalamus
Releases factors which in turn, stimulate the release of pituitary hormones
How do the pituitary gland and the hypothalamus work together?
They act as a unit regulating the activity of most endocrine glands
How many main regions does the hypophysis have?
2
What is the name given to the anterior pituitary?
Adenohypophysis
What is the name given to the posterior pituitary region?
Neurohypophysis
What are the hormones which are released from the adenohypophysis?
- growth hormone
- thyroid stimulating hormone
- adrenocorticotrophic hormone
- prolactin
- FSH & LH
What is the most abundant hormone from the adenohypopyhsis?
Growth hormone
What is the function of Growth Hormone?
- stimulates growth and division of cells especially bone & skeletal
- regulates aspect of metabolism
What hormones stimulate and inhibit growth hormone?
GH is stimulated by growth hormone releasing hormone and is suppressed by GH release inhibiting hormone
What is the function of thyroid stimulating hormone?
Stimulates growth and activity of the thyroid gland
Which hormone stimulates the thyroid?
Thyroid releasing hormone
What is the function of adrenocorticotrophic hormone (ACTH)?
ACTH acts on cells of the adrenal cortex, stimulating them to produce cortisol
When are ACTH levels high and low?
ACTH levels are high around 8am and their lowest at 12am, although high levels sometimes occur around midday and 6pm
How is the secretion of ACTH regulated?
Via negative feedback
What is ACTH associated with?
Sleeping patterns and adjustments can take several days (jet lag)
What are some factors which stimulate secretion of ACTH
- Hypoglycaemia
- exercise
- other stressors
What is the function of prolactin?
Stimulates lactation and has a direct effect immediately after child birth
How large is the neurohypophysis?
It takes up 25% of the hypophysis
What hormones are released from the neurohypophysis?
- antidiuretic hormone (vasopressin)
- oxytocin
What is the function of antidiuretic hormone?
ADH acts on the kidneys to allow reabsorption of water into blood, this reduces the volume of urine formed
What is the function of oxytocin?
- stimulated 2 target tissues during and after childbirth
- contraction of uterine muscles for childbirth and breast cells in lactation
What causes a growth hormone deficiency?
Underproduction of growth hormone
What causes diabetes insipidus?
Underproduction of anti diuretic hormone/ vasopressin
What causes pituitary adenoma?
Over production of any pituitary hormone
What causes hypopituitarism?
Underproduction of any pituitary hormone
