Intro to Endocrinology Flashcards
What are the 6 types of chemical messengers?
- Neural
- Endocrine
- Neuroendocrine
- Paracrine
- Autocrine
- Cytokine
What’s the site of release and site of action for each of the 6 chemical messengers?
- Neural: released at synaptic cleft, acts locally
- Endocrine: hormone released @ cell or specialized glands, acts some distance away
- Neuroendocrine: released from neurons, acts come distance away
- Paracrine: released by cell, acts on neighboring cells of different type
- Autocrine: released by cell, acts on the same cell
- Cytokine: released into the blood stream, acts on broad-spectrum of target cells
How is the hormone released controlled between the hypothalamus and pituitary gland?
Hypothalamus –> axons terminates in the posterior pituitary –> neurohormones released: ADH, oxytocin, and hypophysiotropic hormone, which controls secretion of anterior pituitary hormones
What are the 3 classes of hormone/ neurohormones?
- Protein & Peptide
- Steroid hormone
- Tyrosine derivatives
What is the derivative of steroid hormones?
cholesterol
Name examples of the steroids hormones
adrenocortical (cortisol, aldosterone) and gonadal (testosterone, estrogen, progesterone) hormones
What hormones are made from the amino acid tyrosine?
thyroid gland (thyroxine, triiodothyronine)
adrenal medulla (epinephrine and norepinephrine)
How are protein/peptide hormones synthesized and where are they stored?
- synthesized in rER: large protein made by rER (prehormone) –> cleaved by ER to form prohormone –> packed in secretion granules by Golgi apparatus, along with some proteolytic enzymes –> can cleave the prohormone into active hormone + other fragments –> when stimulated, the granule is exocytosed out into the extracellular fluid
- stored in vesicles
How are steroid hormones synthesized and where are they stored?
- synthesized from cholesterol
- little hormone storage
- cholesterol is stored in cytoplasmic vacuoles
- can be rapidly mobilized to make hormones
- once made, will diffuse out of the cell into the extracellular fluid
How are thyroid & catecholamine hormones synthesized and where are they stored?
- synthesized from tyrosine
- no storage of thyroid hormones
- thyroxine and tri-iodothyronine exist as part of a large iodinated protein –> thyroglobulin –> stored in lumen of thyroid follicle
- epinephrine and norepinephrine stored in vesicles until needed –> exocytosis
Where are the hormone receptors located? What’s their specificity?
- Membrane: on the surface or in the membrane
peptide/ protein & catecholamine - Cytoplasm or Nucleus: steroid and thyroid hormones
What are the 3 types of 2nd messenger systems?
- Adenylyl-cAMP
- Cell membrane phospholipids
- Calcium-calmodulin
Describe the Adenylyl-cAMP 2nd messenger mechanism.
hormone/ receptor interaction –> stimulate/inhibit adenylyl cyclase (membrane bound) –> stimulation leads to production of cAMP –> activation of protein kinase A –> phosphorylation of target organ
Describe the cell membrane phospholipids 2nd messenger mechanism.
hormone/ receptor interaction –> activation of phospholipase C (membrane bound) –> split into 2nd messengers diacylglycerol & inositol triphosphate
- inositol triphosphate mobilizes Ca2+ from internal store
- Ca2+ activates protein kinase C –<> phosphorylation of target enzymes
- action of protein kinase C is enhanced by diacylglycerol
- diacylglycerol is hydrolyzed to arachidonic acid, precursor to prostaglandin
Describe the calcium-calmodulin 2nd messenger mechanism.
hormone/receptor interaction –> opens Ca2+ channels
- Ca2+ also mobilized from internal site (ex. ER)
- Ca2+ binds to calmodulin –> alters activity of Ca2+ dependent enzymes
