Adrenal And Pituitary Glands Flashcards
What hormones are secreted from the anterior pituitary gland and in which cells?
TSH - thyrotrophs ACTH - corticotrophs Growth hormone - somatotrophs LH and FSH - gonadotrophs Prolactin - lactotrophs
Where is the pituitary gland located?
From the base of the brain suspended from a stalk.
Lies in a deep recess of the sphenoid bone.
Where are the adrenal glands found?
Cap the upper poles of the kidneys and lie against the diaphragm
What is produced in the cortex?
Mineralocorticoids eg aldosterone
Glucocorticoids eg cortisol and corticosterone
Androgens
What is produced in the medulla of the adrenal glands?
Adrenaline
What are the three zones of the cortex in the adrenal glands called and what do the hormones they secrete regulate?
Zona glomerulosa - mineralocorticoids regulate sodium and potassium levels
Zona fasciculata - glucocorticoids regulate carbohydrate metabolism
Zona reticularis - androgens
Which family is cortisol a member of?
C21 steroid family
How are the steroids synthesised?
From cholesterol via progesterone in a series of enzyme catalysed reactions
How is cortisol secretion controlled?
CRF (corticotrophin releasing factor) is released from the hypothalamus
This stimulates the release of ACTH in the anterior pituitary gland
This stimulates the release of cortisol
How is CRF secretion regulated?
Negative feedback by glucocorticoids
Response to stressors
- physical (temperature, pain)
- chemical (hypoglycaemia)
- emotional
From which protein is ACTH derived?
POMC
What can be produced from POMC?
ACTH
Alpha-MSH
Endorphins
When is the peak plasma level of ACTH?
Early morning
What enzyme does ACTH activate and how?
Cholesterol esterase
Binds to receptors on the surface of the zona fasciculata and reticularis
What does cholesterol esterase do?
Increases the conversion of cholesterol esters to cholesterol
What effects does over secretion of ACTH have?
Increased pigmentation due to partial MSH activity
Adrenal hyperplasia and over production of cortisol
What type of symptoms does under secretion of ACTH cause?
Those related to a lack of glucocorticoids only
What is the type of receptor for ACTH?
Melanocortin or corticotrophin receptor
What is the major transport protein of cortisol?
Transcortin/CBG
What is the mechanism of action of cortisol upon its target cells?
Crosses plasma membrane
Binds to cytoplasmic receptors
Hormone/receptor complex enters the nucleus
Interacts with specific regions of DNA which alters the rate of transcription of specific genes
What effects does cortisol have?
Decreased amino acid up take and protein synthesis Increased proteolysis (except in the liver)
Increased hepatic gluconeogenesis and glycogenolysis
Increased lipolysis, high levels of cortisol increase lipogenesis
Decreased peripheral uptake of glucose (anti-insulin)
What does the adrenal medulla synthesise?
Catechol amines including adrenaline and the neurotransmitters noradrenaline and dopamine
How are catecholamines synthesised?
Enzyme catalysed steps
Tyrosine -> dopamine -> noradrenaline -> adrenaline
What effects does adrenaline have?
Cardiovascular system - increased cardiac output and blood supply to muscle
CNS - increased mental alertness
Carbohydrate metabolism - increased glycogenolysis in muscle and liver
Increased lipolysis
