Introduction to Endocrines Flashcards
(27 cards)
What are the 3 major groups of hormones?
- peptide or protein
- steroid
- amines, tyrosine based
what are the steps of peptide hormone synthesis?
- DNA to mRNA in the nucleus
- mRNA to preprohormone in a ribosome
- preprohormone to prohormone in ER
- prohormone to hormone in golgi
- stored in vesicles
What are all steroid hormones derivatives of?
cholesterol
What are all amine hormones derived from and what is the rate limiting step?
tyrosine
tyrosine hydroxylate
What are the examples of Steroid, Amine and Peptide Hormones?
- steriod: aldosterone, cortisol, sex hormones
- peptide: PTH, ACTH, insulin
- amine: T3, T4, catecholamines
What is the more common feedback look and how does it work?
- negative feedback
- the hormone released directly or indirectly inhibits further secretion
What is Long- loop Negative Feedback?
hormone released will feedback to the hypothalamic pituitary axis
What is Short- loop Negative Feedback?
anterior pituitary inhibits the release of hypothalamic hormones
What is Ultrashort- loop Negative Feedback?
the hormone released by the hypothalamus will inhibit itself
What is an example of a hormone that does not use the hypothalamic-pituitary axis for negative feedback?
insulin
What is an example of positive feedback loop?
- estrogen released during ovulation
- oxytocin released during childbirth
How are cyclic variations of hormone release mainly influenced?
changes in neural pathways
How does the response speed vary by the hormone secreted (give examples)?
some are fast acting and some are slow
- norepinephrine/epinephrine cause action within seconds to minutes
- T4 and GH may take days to months
Hormones can elicit a signal at very low concentrations, why?
hormones bind to specific receptors on or in target cells that activate signal amplification pathways
How are steroid and thyroid hormones circulated in the blood?
bound to plasma proteins to create a “reservoir”
- but can also decrease a hormones clearance
How are hormones mainly cleared from the body and why is this imporant?
- excreted by the liver (into bile) and kidneys (into urine)
- important when giving exogenous hormone (ex; hormonal birthcontrol)
What is important to consider since hormones are released into systemic circulation?
blood supply to the target tissue
- decrease blood supply = decreased response time
Hormonal effect depends on amount of hormone present and ?
the presence and number of receptors present
Down-regulation = fewer receptors
→ Leads to reduced sensitivity to a hormone.
What is Down-regulation of receptors?
fewer receptors → leads to reduced sensitivity to a hormone
** this may occur if a hormone is chronically elevated → cell tries to tune out hormone
What is Up-regulation of receptors?
more receptors → leads to increased sensitivity to a hormone
** cell will make more receptors in response to low hormone levels
What are the signals that can occur after hormone binding?
- Changes in membrane permeability
- Activation of intracellular enzymes
- Activation of mRNA transcription due to hormone/receptor complex on response elements of DNA (long onset of effect)
What are the two messenger systems that hormones use for signal amplification?
- adenylyl cyclase-cAMP
- Phospholipase C
What are the hormones that use the Cyclic AMP messenger system?
- ACTH
- AngII (epithelial cells)
- Calcitonin
- Catecholamines (B receptors)
- FSH
- Glucagon
- Vasopressin (V2)
- TSH
- GHRH
- PTH
What are the hormones that use the Phospholipase C messenger system?
- AngII (vascular smooth muscle)
- Catecholamines (alpha receptors)
- GnRH
- Oxytocin
- Vasopressin (V1)
