Endocrinology Flashcards
Name five different types of intercellular communication
Direct, autocrine, paracrine, endocrine, synaptic
Direct communication is possible because of the presence of
Connexons/Gap Junctions
When a cell secretes a chemical messenger that binds to receptors on the same cell leading to changes in the cell
autocrine communication
What is the difference between a hormone and a factor
The chemical structure of hormones is known, unknown for factors
Pathway of hormone or paracrine
Hormone goes from interstitial fluid to circulatory. Paracrine stays in interstitial fluid
Define Hormone
Chemical messenger that is released in one tissue and transported into the bloodstream to alter the activity of specific cells in other tissues
Three ways hormones can affect function
1) act as a TF and stimulate synthesis of enzyme or protein 2) Regulate the rate of synthesis (increase/decrease) 3) Turn an existing enzyme of membrane channel on or off
4 similarities between nervous and endocrine system
1) Both rely on release and binding of chemicals 2) Both systems share many chemical messengers (NE/E are hormone when in bloodstream, nT when released across synapse) 3) Both regulated by negative feedback 4) Share common goal, maintain homeostasis
2 differences between nervous and endocrine system
1) NS for crisis management, short term homeostasis 2) NT release is in a very specific area
Difference between endocrine and exocrine cells
endocrine cells release secretions into extracellular fluid and exocrine release onto epithelial surface
Four classes of hormones
peptide, amino acid, lipid
What two main amino acids are hormones are derived from
tyrosine- thyroid hormone, E, NE, dopamine (catcaholamines)
tryptophan- melatonin
What makes peptide hormones unique?
they are synthesized as inactive prohormones and then converted to their active form before or after secretion
What are the subclasses of peptide hormones
glycoproteins- FSH, LH, TSH (FLAT)
short polypeptides- OXT, ADH (posterior pituitary)
small proteins- GH, Prolactin (PIG)
Where are most steroid hormones released from?
1) reproductive organs. androgens by testes in makes, prostaglandin by ovary in females
2) adrenal cortex- corticosteroid
3) kidney- calcitrol
Do peptide hormones and catecholamines bind on the inner or outer surface of the plasma membrane? Which type of response is more rapid?
outer. they are not lipid soluble and this cannot cross the plasma membrane. Binding extracellular is faster
What is the difference between a first and second messenger? What are examples of each?
First messenger (hormone) does something that leads to the appearence of the second messenger Second Messenger (cAMP, cGMP, Ca2+)
Explain mechanism of G protein and cAMP (5 steps)
1) hormone binds 2) G protein activated 3) G protein activates adynlate cyclase 4) adylnate cyclase turns ATP into cAMP 5)cAMP is a second messenger and activates a kinase 6)kinase phosphorylates proteins
How is the level of cAMP lowered?
1) Hormone binds 2) G protein activated 3) G protein activated phosphodiesterase (PDE) 4) PDE inhibits adynlate cyclase activity and converts cAMP to AMP
Explain the relationship between G proteins and Ca2+ ions
1) Hormone binds 2) G protein activated 3) G protein activates phospholipase C (PLC) 4) PLC triggers a cascade that produces DAG and IP3 from membrane phosplipid 5) IP3 diffuses to the cytoplasm and triggers the releae of calcium from intracellular reserves 6) DAG and Ca2+ together, activate protein kinase C (PKC) 7) PKC phosphorlates Ca2+ channel and extracellular calcium can enter cell 8) Ca2+ can act as a second messenger or with calmodulin
E, NE, OXT binding to alpha 1 receptors leads to what kind of activation?
G protein and Ca2+ ion
E and NE binding to alpha 2 receptors leads to what kind of response?
G protein and cAMP
Explain how Thyroid hormones activate
Receptor intracellular 1) TH crosses PM by transport mechanism 2) When in cytoplasm, binds receptors in mitochondria or nucleus 3) complex binds to DNA 4) gene activated 5) transcription and mRNA production 6) translation and protein synthesis
Three mechanisms of Hypothalamic Control over Endocrine function
1) Produces ADH and OXT
2) secretes regulatory hormones to control activity of anterior pituitary
3) control of sympathetic output to adrenal medullae
