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Questions and Answers
What type of hormones bind to receptors located on the cell membrane?
Which intracellular substance degrades cAMP, thus inactivating the response to a hormone?
phosphodiesterase
Growth factor hormones, such as insulin, bind to which type of receptor?
tyrosine kinase receptors
Which is the correct order of events for hormones activating Gs proteins?
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Which second messenger causes the release of calcium from the endoplasmic reticulum?
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Which of the following adrenergic receptors increase cAMP levels?
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Which of the following hormones has intracellular receptors?
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What is the mechanism of action of lipid-soluble hormones?
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After a lipid-soluble hormone is bound to its intracellular receptor, what does the hormone complex do?
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Which hormone's receptor is always bound to DNA, even when the receptor is empty?
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What keeps intracellular receptors from binding to DNA before a hormone binds to the receptor?
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What tropic hormone stimulates cortisol from the adrenal gland?
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What is the function of the ventral hypothalamic neurons?
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Insulin-like growth factors (IGFs) are intermediary hormones stimulated by which of the following hormones?
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Which of the following hormones is regulated by a neuroendocrine ('letdown') reflex?
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Where is antidiuretic hormone (ADH), also known as vasopressin, synthesized?
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What is the most important regulatory factor controlling the circulating levels of thyroid hormone?
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Study Notes
Hormone Receptors and Mechanisms
- Water-soluble hormones, including insulin and epinephrine, bind to receptors on the cell membrane and cannot diffuse through the plasma membrane.
- Phosphodiesterase is an enzyme that breaks down cyclic AMP (cAMP), thereby inactivating hormone responses.
- Growth factor hormones, like insulin, associate with tyrosine kinase receptors, acting without a second messenger.
- The sequence for hormone activation of Gs proteins involves G protein activation, GTP binding, adenylate cyclase activation, and conversion of ATP to cAMP.
Second Messengers and Effects
- Inositol trisphosphate (IP3) functions as a second messenger that triggers the release of calcium from the endoplasmic reticulum.
- β adrenergic receptors are responsible for increasing cAMP levels through their coupling to adenylate cyclase via Gs proteins.
Lipid-Soluble Hormones
- Cortisol and thyroid hormones, both lipid-soluble, utilize intracellular receptors.
- The mechanism of action for lipid-soluble hormones involves gene activation that leads to increased protein synthesis.
- Once a lipid-soluble hormone binds to its receptor, the hormone-receptor complex acts as a transcription factor, engaging with DNA to activate specific genes.
Thyroid Hormones and Regulation
- Thyroid hormones maintain a constant binding to DNA, even in the absence of ligands, to ensure readiness for action.
- Chaperone proteins prevent intracellular receptors from binding to DNA until the hormone is attached, maintaining regulatory control.
- Adrenocorticotropic hormone (ACTH) stimulates cortisol production from the adrenal gland, with stress and ACTH acting as primary stimuli.
Hypothalamic Function and Growth Hormones
- Ventral hypothalamic neurons regulate thyroid-stimulating hormone (TSH) secretion through releasing and inhibiting hormones.
- Insulin-like growth factors (IGFs) are stimulated by growth hormone (GH) and are crucial for GH’s growth-promoting effects on bone and skin.
Neuroendocrine Reflex and ADH
- Oxytocin release is regulated by a neuroendocrine "letdown" reflex, prompted by suckling or uterine stretching, which enhances milk ejection and uterine contractions.
- Antidiuretic hormone (ADH), also termed vasopressin, is synthesized in the hypothalamus, primarily in the supraoptic nucleus, and stored in the posterior pituitary.
Feedback Mechanisms
- Negative feedback is essential in regulating thyroid hormone circulation; high hormone levels lead to decreased secretion of thyroid-stimulating hormone (TSH), which in turn lowers thyroid hormone production.
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Description
Test your knowledge on hormones and their signaling mechanisms with these flashcards. This quiz covers important concepts such as water-soluble hormones and the role of phosphodiesterase in cellular responses. Perfect for students studying anatomy and physiology.
