Hormones & Receptors - Vocabulary flashcards

Vocabulary flashcards covering key terms and definitions from the lecture notes on neural-endocrine control, hormone action, steroidogenesis, and receptor signaling.

hypothalamus

Neural control center of the endocrine system that integrates nervous signals to regulate pituitary hormone release.

neuroendocrinology

Study of interactions between the nervous and endocrine systems and how neural signals regulate hormonal secretion.

endocrine system

System that releases mediators (hormones) into the bloodstream to affect distant targets.

hormone

Secreted chemical messenger, produced in small amounts, carried in blood, and acting on specific receptors to elicit a response.

receptor

Protein on or in a target cell that binds a hormone, determining the specificity of the response.

affinity

Strength of the interaction between a hormone and its receptor; higher affinity means tighter binding.

specificity

Property by which receptors respond only to particular hormones due to binding site complementarity.

intracellular receptor

Receptor located inside the cell that often mediates genomic actions of lipophilic hormones.

plasma membrane receptor

Cell-surface receptor (e.g., GPCR, RTK) that transmits signals into the cell upon ligand binding.

saturation

Maximum occupancy of receptors by ligand at a given concentration.

signal transduction

intracellular signaling cascades triggered by receptor activation to elicit cellular responses.

binding reversibility

Many hormone-receptor interactions are reversible, allowing dynamic regulation.

Law of Mass Action

Principle describing rates of association/dissociation of ligands with receptors based on concentrations.

association rate constant (Ka)

Rate at which a hormone binds to its receptor.

dissociation rate constant (Kd)

Rate at which a hormone dissociates from its receptor; lower Kd indicates higher affinity.

Protein hormones (peptide hormones)

Amino-acid based hormones (e.g., insulin, oxytocin) that typically act on cell-surface receptors.

Biogenic amines

Derivatives of amino acids (e.g., norepinephrine, dopamine, serotonin) acting as hormones or neurotransmitters.

Prostaglandins

Lipid mediators derived from arachidonic acid; include PGE2 and PGF2α with diverse physiological roles.

PGE2

A common prostaglandin involved in inflammation and various tissue responses.

PGF2α

A prostaglandin involved in regulating smooth muscle function and other processes.

Cholesterol

Steroid synthesis precursor produced mainly by the liver; lipophilic and converted into steroids.

LDL

Low-density lipoprotein; carries cholesterol to tissues.

HDL

High-density lipoprotein; collects cholesterol from tissues for transport to the liver.

Steroidogenesis

Synthesis of steroids from cholesterol; involves transport into mitochondria and enzymatic steps.

STAR

Steroidogenic Acute Regulatory Protein; mediates transport of cholesterol into mitochondria for steroid synthesis.

TSPO

Translocator Protein; assists cholesterol transport across mitochondrial membranes during steroidogenesis.

Cytochrome P450 side-chain cleavage (P450scc, CYP11A1)

Enzyme that cleaves cholesterol's side chain to pregnenolone, a key step in steroidogenesis.

HMG-CoA reductase

Rate-limiting enzyme in cholesterol synthesis; inhibited by statins.

Statins

Drugs that inhibit HMG-CoA reductase to reduce cholesterol synthesis.

Liver

Organ where cholesterol is synthesized and steroidogenesis begins.

GPCR (G-protein coupled receptor)

Largest family of cell-surface receptors with seven transmembrane domains that signal via G-proteins.

seven-transmembrane domains

Characteristic structural feature of GPCRs spanning the cell membrane seven times.

G-protein

Heterotrimeric protein (α, β, γ) that transmits signals from GPCRs to effectors.

GTP/GDP cycle (α subunit)

Gα subunit binds GDP in inactive state and GTP in active state to propagate signals; intrinsic GTPase activity terminates signal.

RGS proteins

Regulators of G-protein signaling; accelerate GTP hydrolysis to turn off G-protein signaling.

Arrestin

Proteins that desensitize GPCR signaling and promote receptor internalization/recycling.

GnRH

Gonadotropin-releasing hormone; stimulates LH and FSH release from the pituitary.

Phospholipase C (PLC)

Enzyme that cleaves PIP2 to DAG and IP3, activating Ca2+-dependent signaling pathways.

DAG

Diacylglycerol; second messenger that activates protein kinase C (PKC).

IP3

Inositol trisphosphate; releases Ca2+ from intracellular stores, elevating cytosolic Ca2+.

PKC

Protein kinase C; activated by DAG and Ca2+ to phosphorylate target proteins.

SHBG

Sex hormone-binding globulin; binds testosterone and DHT in blood, modulating bioavailability.

Corticosteroid-binding globulin (CBG)

Carrier protein that binds cortisol and other corticosteroids in the blood.

Nuclear/cytoplasmic receptors

Intracellular receptors for lipophilic hormones that regulate gene transcription.

Receptor tyrosine kinases (RTKs)

Cell-surface receptors with intrinsic tyrosine kinase activity that trigger signaling cascades upon ligand binding.