Endocrine Control Systems Flashcards
What are the three types of hormones?
Protein/peptide hormones:
- Hydrophilic
Steroid hormones:
- HYdrophobic
- Testosterone, estrogen, progsterone, cortisol, aldosterone
Tyrosine derived hormones:
- Variable
- Epinephrine, dopamine, thyroid hormone
What type of receptors do protein, steroid and tyrosine hormones bind?
Protein - cell surface receptors
Steroid - cytoplasmic and nuclear receptors
Tyrosine - nuclear receptors
How are protein, steroid and tyrosine hormones inactivated?
Protein - endocytosed by cells, excreted by kidney.
Steroids - excreted in bile by liver
Tyrosine - degraded by enzymes
What type of hormone is dopamine?
Tyrosine derived
Give two examples of each type of hormone
Protein - insulin, glucagon
Steroid - testosterone, cortisol
Tyrosine-derived - adrenaline, thyroxine
Can non-metabolic tissues secrete hormones?
Give examples.
Yeah.
Kidneys - EPO
Cardiac cells - ANP
Adipose tissue - leptin
What three points determine sensitivity and response to a hormone?
- Number of receptors
- Affinity of receptors
- Downstream signalling of molecules
What is the concent of overload desensitisation
Prolonged exposure to a stimulus decreases cell respones to that level of exposure. Allows receptors to respond to changes in concentration of a signal rather than absolute concentration.
What are tropic hormones vs physiological hormones?
Hormone that produce the effect = physiological hormones
Hormone that regulate the physiological hormone = tropic
What is the most important endocrine control axis?
Hypothalamus-Pituitary related axes (e.g. H-P-A adrenal)
What is the main difference between the anterior pituitary and the posterior pituitary?
Anterior pituitary = glandular, produces/secretes hormones AKA adenohypophysis
Posterior pituitary = neural, DOESN’T produce hormones, AKA neurohypophysis.
How does the hypothalamus control the anterior pituitary?
The hypothalamus releases tropic hormones into the hypothalamic-hypophyseal portal vessels, which travel to the AP. The AP then produces and secretes hormones.
The anterior pituitary is well vascularised to pick up the hormones.
What are the majority of cells of the AP?
What are some (4) minor ones?
Majority = Somatotropes - produce growth hormone
Minors = corticotropes (ACTH), thyrotropes (TSH) , gonadotropes (FSH, LH), lactotrope (prolactin)
How does the hypothalamus control the posterior pituitary?
Neurons directly supply the blood supply of the posterior pituitary.
Paraventricular and supraoptic nuclei produce hormones, which travel down the hypothalamic-hypophyseal tract to the PP.
What are the main hormones of the posterior pituitary?
Oxytocin - control of lactation and uterine contraction
ADH - H2O reabsorption in kidney
What are the 5 hypothalamic releasing hormones and their effect on the pituitary?
- Corticotropin releasing hormone (CRH) - stimulates ACTH secretion
- Gonadotropin releasing hormone (GnRH) - stimulates LH and FSH secretion
- Thyrotropin releasing hormone (TRH) - stimulates TSH secretion
- Growth hormone releasing hormone (GHRH) - stimulates GH secretion
- Somatostatin - inhibits GH secretion
Broad function of: FSH/LH, GH, TSH, Prolactin, ACTH
FSH/LH - Act on gonads to produce oestrogen/progestogen + testosterone
GH - Act on Liver and body to produce IGF-1 (growth factor)
TSH - Act on thyroid to produce T3/T4
Prolactin - Breast lactation
ACTH - Act on adrenal cortex to stimulate mineralocorticoid, glucocorticoid and androgen secretion
How is cholesterol brought in mitochondria?
Through cleavage of side chain from cholesterol to form pregnenolone
Which two enzymes are required to create all steroids?
P450SCC enzyme - P450 side chain cleavage
StAR protein - steroidogenic acute regulatory protein (brings pregnenolone int mitochondria)
What two enzyme types are involved in transformation pregnenolone into all other steroids?
Cytochrome P450s (redox)
Hydroxysteroid dehydrogenases (HSDs)
What enzyme (and substrate) is required in making testosterone?
Androstenedione → Testosterone
17β-HSD
What enzymes are required to make androstenedione?
CYP17a1 + 3β-HSD
What enzyme (and substrate) is required to make aldosterone?
Corticosterone + aldosterone synthase
What enzyme (and substrate) is required to make progesteron?
3β-HSD on pregnenolone
What enzymes (and substrate) are required to make oestrogen?
Aromatase converts testosterone to oestradiol.
Also require 17β-HSD to convert androstenedione to testosterone
What is meant by rate limiting transport and rate limiting catalytic steps?
Rate limiting transport step = StAR
Rate limiting catalytic step = P450 SCC
What are the 3 types of corticosteroids and their general function?
- Mineralocorticoids - Regulate minerals (sodium)
- Glucocorticoids - Regluate glucose
- Sex hormones - Low activity precursors to sex hormones
What are the two parts of the adrenal gland and their function?
Adrenal cortex (outer) - produces corticosteroids
Adrenal medulla (inner) - produces catecholamines (Adrenaline, NA)
What adrenal gland layers are dfiferent types of corticosteroids/catecholamines produced?
Give example for each
Zona glomerulosa - mineralocorticoids (aldosterone)
Zona fasciculata - glucocorticoids (cortisol)
Zona reticularis - sex hormones (DHEA, androstenedione)
Medulla - catecholamines (adrenaline, NA)
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