Hormones: Chemical Signals and Their Mechanisms

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Questions and Answers

Which of the following is NOT a criterion for a chemical signal to be considered a hormone?

Secreted into the blood

Effects only at high concentrations (correct)

Transported to a distant target

Affects growth or metabolism

Steroid hormones are stored in secretory vesicles before release.

False

Where are the receptors for peptide hormones located?

On the cell surface

Catecholamines are derived from the amino acid ______.

tyrosine Signup and view all the answers

Match the type of hormone with its source or characteristics:

Peptide Hormones = Synthesized as preprohormones Steroid Hormones = Derived from cholesterol Thyroid Hormones = Derived from two tyrosine molecules Melatonin = Derived from tryptophan Signup and view all the answers

Which hormone acts by regulating gene expression?

Cortisol Signup and view all the answers

All amine hormones act similarly to steroid hormones.

False Signup and view all the answers

What is the role of the hypothalamus in endocrine reflexes?

Produces neurohormones that regulate the pituitary gland Signup and view all the answers

Peptide hormones are released by ______ when triggered.

exocytosis Signup and view all the answers

Which of the following is an example of a catecholamine?

Epinephrine Signup and view all the answers

Which hormone primarily targets the mammary glands?

Prolactin (PRL) Signup and view all the answers

Adrenocorticotropic Hormone (ACTH) is controlled by gonadotropin-releasing hormone (GnRH).

False Signup and view all the answers

What hormone does the thyroid gland primarily respond to?

Thyroid-Stimulating Hormone (TSH) Signup and view all the answers

The hormone that stimulates the adrenal cortex is called ______.

Adrenocorticotropic Hormone (ACTH) Signup and view all the answers

Match the anterior pituitary hormones with their controlling factors:

Prolactin (PRL) = Prolactin-releasing factors and dopamine Thyroid-Stimulating Hormone (TSH) = Thyrotropin-releasing hormone (TRH) Growth Hormone (GH) = Growth hormone-releasing hormone (GHRH) and somatostatin Follicle-Stimulating Hormone (FSH) = Gonadotropin-releasing hormone (GnRH) Signup and view all the answers

What is the primary action of insulin following high blood glucose levels?

Stimulates glucose uptake by cells Signup and view all the answers

Short-loop negative feedback involves the suppression of anterior pituitary hormones directly by the target endocrine gland.

False Signup and view all the answers

What feedback mechanism is described as the most dominant and involves peripheral endocrine glands?

Long-loop negative feedback Signup and view all the answers

Low levels of calcium in the blood stimulate the release of ______.

Parathyroid Hormone (PTH) Signup and view all the answers

Which hormone targets the liver and promotes growth and metabolism?

Growth Hormone (GH) Signup and view all the answers

Study Notes

Chemical Signals and Hormones

Chemicals secreted into the blood by a cell travel to distant targets
The hormone affects growth, development, homeostasis, or metabolism at very low concentrations

Peptide and Steroid Hormone Comparison

Peptide Hormones:
- Synthesized in advance as preprohormones, then cleaved into active hormones
- Stored in secretory vesicles
- Released via exocytosis (e.g., insulin)
Steroid Hormones:
- Synthesized on demand from cholesterol
- Not stored, released immediately after synthesis
- Diffuse through the cell membrane (e.g., cortisol)

Hormone Receptor Location and Mechanism

Peptide Hormones:
- Receptors located on the cell surface
- Activate second messenger pathways, leading to rapid responses (e.g., insulin)
Steroid Hormones:
- Receptors located within the cytoplasm or nucleus
- Regulate gene expression, leading to slower but longer-lasting effects (e.g., testosterone)

Amine Hormone Groups

Catecholamines:
- Derived from tyrosine
- Act like peptide hormones (e.g., epinephrine, norepinephrine)
Thyroid Hormones:
- Derived from two tyrosine molecules
- Act like steroid hormones (e.g., thyroxine [T4], triiodothyronine [T3])
Melatonin:
- Derived from tryptophan
- Regulates circadian rhythms

Nervous System and Endocrine Reflexes

The nervous system integrates with the endocrine system through neurohormones and control pathways
Hypothalamus: Produces neurohormones regulating the pituitary gland
Neuroendocrine Reflexes: Electrical signals trigger hormone release (e.g., oxytocin)
Feedback Loops: Coordinate hormonal and neural responses for homeostasis

Anterior Pituitary Hormones

Prolactin (PRL): Controlled by prolactin-releasing factors and dopamine. Targets mammary glands.
Thyroid-Stimulating Hormone (TSH): Controlled by thyrotropin-releasing hormone (TRH). Targets thyroid gland.
Adrenocorticotropic Hormone (ACTH): Controlled by corticotropin-releasing hormone (CRH). Targets adrenal cortex.
Growth Hormone (GH): Controlled by growth hormone-releasing hormone (GHRH) and somatostatin. Targets liver and other tissues.
Follicle-Stimulating Hormone (FSH): Controlled by gonadotropin-releasing hormone (GnRH). Targets gonads.
Luteinizing Hormone (LH): Controlled by gonadotropin-releasing hormone (GnRH). Targets gonads.

Negative Feedback Loops

Long-Loop Negative Feedback: Hormones from target endocrine glands inhibit the anterior pituitary and hypothalamus (e.g., cortisol).
- Examples: Insulin (blood glucose), Parathyroid Hormone (calcium)
Other: Short-loop, Ultra-short-loop

Hormone Interactions

Permissiveness: One hormone enables another's full effect (e.g., thyroid hormone and epinephrine)
Synergism: Two hormones together produce a greater effect than their individual effects (e.g., glucagon and epinephrine on blood glucose)
Functional Antagonism: Two hormones have opposing effects (e.g., insulin and glucagon on blood glucose)

Endocrine Pathologies

Hypersecretion: Excess hormone production (e.g., hyperthyroidism)
Hyposecretion: Deficient hormone production (e.g., hypothyroidism)
Abnormal Target Response: Target cells fail to respond appropriately (e.g., type 2 diabetes)

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Description

This quiz explores the fascinating world of hormones, focusing on their chemical signals, types, and mechanisms of action. You'll learn about the differences between peptide and steroid hormones, their synthesis, and how they interact with cell receptors. Test your knowledge on how these essential substances regulate various physiological processes.