2 week 7 Flashcards
diff bw direct and indirect cell-to-cell communication?
direct: physical link via connexons
indirect: use chemical messengers
whats a neurohormone?
chemicals released by neurons into the blood
diff bw primary and secondary endocrine organs?
primary: main function = hormone secretion
secondary: main function = something else
what are the 6 secondary endocrine organs?
heart
stomach
liver
kidney
small intestine
skin
what is hormone secretion regulated by? (5)
neurotransmitters
other hormones
metabolites
ions
hormonal feedback
diff bw hydrophilic and hydrophobic hormones?
hydrophilic (“lipophobic”)
- water/plasma soluble
- NOT lipid soluble, cannot cross plasma membrane
- examples: peptide hormones, protein hormones, catecholamines
hydrophobic (“lipophilic”)
- NOT water/plasma soluble
- lipid soluble, readily cross plasma membrane
- examples: steroid and thyroid hormones
how are hydrophilic and hydrophobic hormones synthesized, released, and transported in blood?
hydrophilic vs hydrophobic
- synthesized: in advance/stored vs on demand
- released: exocytosis vs diffusion
- transported: dissolve vs bind to carrier proteins
describe intracellular receptors (4)
- cytoplasmic/cytosolic or nuclear
- bind hydrophobic hormones
- directly alter gene transcription
- slow responses
describe membrane-bound receptors (4)
- g-protein linked receptors
- ligand-gated ion channels or alter enzyme activity
- bind hydrophilic hormones
- rapid responses
describe the steps of intracellular receptors binding to hormones (5)
- if receptor located in nucleus, hormone diffuses into nucleus and binds (hormone-receptor complex). if receptor located in cytosol, forms hormone-receptor complex that then enters the nucleus.
- in nucleus, hormone-receptor complex binds to hormone response element (HRE), located at the beginning of a specific gene.
- activates or deactivates gene, ultimately increases or decreases synthesis of mRNA.
- mRNA moves into the cytosol.
- mRNA translated by ribosomes to yield proteins.
describe the steps of membrane-bound receptors binding to hormones (6)
- 1st messenger binds to receptor, activating g-protein.
- g-protein releases alpha subunit, which binds to and activates enzyme adenylate cyclase.
- adenylate cyclase converts ATP to cAMP (the 2nd messenger).
- cAMP binds to and activates PKA.
- PKA phosphorylates certain proteins in cell.
- change in cell occurs.
what is amplification?
- single activated receptor can activate several g-proteins, each of which can activate an adenylate cyclase molecule.
- ex the action of one first messenger can lead to the phosphorylation of 2,500,000 proteins.
T or F: hormones carry out a target effect in a cell.
false! hormones simply relay information to cells through receptors.
T or F: cells can have receptors for more than one hormone.
true!
how does the posterior pituitary work?
neurosecretory cells project into posterior pituitary which release hormones into bloodstream