Hormonal Regulation in the Body

Questions and Answers

What is the role of the signal sequence in peptide hormone synthesis?

It prevents the hormone from being cleaved into active forms.

It activates the hormone immediately.

It directs the preprohormone into the endoplasmic reticulum. (correct)

It helps transport the hormone into the target cell.

Where do enzymes chop the prohormone to create active peptides?

In the plasma membrane

In the Golgi complex (correct)

In the endoplasmic reticulum

In the cytoplasm

Which of the following statement is true regarding peptide hormones?

They can easily cross the plasma membrane of target cells.

They are synthesized directly in the secretory vesicles.

They require surface membrane receptors to exert their effects. (correct)

They are always in an active form when released into circulation.

Which structure contains the preprohormone after it is synthesized on ribosomes?

Endoplasmic reticulum Signup and view all the answers

What happens to the contents of secretory vesicles during hormone release?

They are released into the extracellular space by exocytosis. Signup and view all the answers

What triggers the secretion of insulin from pancreatic beta cells?

Increased blood glucose concentration Signup and view all the answers

What does insulin do to target tissues?

Promotes glucose uptake and metabolism Signup and view all the answers

Which feedback mechanism ends the release of insulin?

Negative feedback from decreased blood glucose Signup and view all the answers

What is one source of signals that can also trigger insulin secretion?

Signals from the nervous system or the digestive tract Signup and view all the answers

What size is the pituitary gland in relation to a common object?

The size of a lima bean Signup and view all the answers

What is the primary reason steroid hormones are usually bound to carrier proteins in the blood?

To protect them from enzymatic degradation Signup and view all the answers

Which of the following hormones is derived from tryptophan?

Melatonin Signup and view all the answers

Why are steroid hormones considered to be made on demand?

They are synthesized directly from cholesterol as needed. Signup and view all the answers

From which parent compound are all steroid hormones derived?

Cholesterol Signup and view all the answers

How do catecholamines relate to tyrosine in terms of their chemical structure?

They are a modification of a single tyrosine molecule. Signup and view all the answers

What is the main reason steroid hormones are not stored in endocrine cells?

They have a lipophilic nature which allows for easy diffusion. Signup and view all the answers

What role do carrier proteins play for steroid hormones in the bloodstream?

They allow steroid hormones to travel long distances without degradation. Signup and view all the answers

Which hormones are classified as amino acid-derived or amine hormones?

Melatonin and thyroid hormones Signup and view all the answers

What term describes the substances that influence cell growth and division currently being studied as potential hormones?

Growth factors Signup and view all the answers

How do many growth factors primarily act in the body?

As autocrine or paracrine signals Signup and view all the answers

Why is it important for hormone activity to be of limited duration?

To allow a rapid and adaptable response to internal changes Signup and view all the answers

What was the historical significance of cholecystokinin (CCK) after its discovery?

It was only recognized as an intestinal hormone. Signup and view all the answers

In what two contexts can a single molecule act as both a hormone and a paracrine signal?

When released from one location and influencing nearby cells from another Signup and view all the answers

What is the role of insulin in glucose metabolism?

It facilitates the entry of glucose into cells. Signup and view all the answers

Which of the following does NOT describe a function of CCK?

Regulating glucose levels in the liver Signup and view all the answers

What complicates the classification of signal molecules in the body?

Their ability to act differently depending on the location of secretion Signup and view all the answers

What is the role of aromatase in hormone synthesis?

Converts Testosterone to Estradiol Signup and view all the answers

Which hormone is directly derived from dehydroepiandrosterone (DHEA)?

Testosterone Signup and view all the answers

What is the function of 21-hydroxylase in steroid synthesis?

Convert Progesterone to Cortisol Signup and view all the answers

Which of the following compounds is derived from Cholesterol?

Aldosterone Signup and view all the answers

Which hormone is considered an intermediate compound in the steroidogenesis pathway?

Estrone Signup and view all the answers

In the steroid synthesis pathway, which enzyme is responsible for converting Androstenedione to Estrone?

Aromatase Signup and view all the answers

What type of compound is DHT in relation to Testosterone?

A metabolite Signup and view all the answers

Which of the following is NOT a direct product of cholesterol metabolism?

Androstenedione Signup and view all the answers

Which pathway is regulated by the enzyme aromatase?

Conversion of Testosterone to Estradiol Signup and view all the answers

Which of these hormones is primarily produced in the adrenal cortex?

Cortisol Signup and view all the answers

Study Notes

Hypothalamic Hormones and Growth Factors

In the 1970s, hypothalamic hormones were referred to as "releasing factors" and "inhibiting factors," distinguishing them from traditional hormones.
Growth factors are being researched to determine if they qualify as hormones; these substances influence cell growth and division.
Many growth factors operate locally, exhibiting autocrine or paracrine signaling, as opposed to widespread hormonal circulation.
Eicosanoids are lipid-derived signaling molecules with a classification that can vary based on secretion location (hormone vs. autocrine/paracrine).

Cholecystokinin (CCK)

CCK was initially identified as an intestinal hormone responsible for gallbladder contraction in the 1920s.
Discovered in the mid-1970s, CCK was also found in the brain, where it functions as a neurotransmitter or neuromodulator.

Cellular Mechanisms of Peptide Hormone Action

Peptide hormones are lipophobic and bind to cell surface membrane receptors, preventing their entry into target cells.
Peptide hormones are synthesized as inactive preprohormones and undergo processing in the endoplasmic reticulum (ER) and Golgi complex.
Active hormones are released through exocytosis once cleaved from prohormones within secretory vesicles.

Transport and Half-Life of Steroid Hormones

Steroid hormones, derived from cholesterol, are lipophilic and mostly bound to protein carriers in plasma, enhancing their stability.
Binding protects steroid hormones from degradation and extends their half-life; for example, cortisol is transported this way.
Most steroid hormones are synthesized in the adrenal cortex or gonads and released upon demand, not stored in cells.

Amino Acid-Derived Hormones

Amine hormones are derived from tryptophan or tyrosine; notable examples include melatonin (from tryptophan) and catecholamines/thyroid hormones (from tyrosine).
Catecholamines are modified from a single tyrosine molecule, while thyroid hormones consist of two tyrosine molecules bonded with iodine.

Insulin Secretion and Blood Glucose Regulation

Pancreatic beta cells monitor blood glucose concentrations; insulin is secreted when levels rise after a meal.
Insulin promotes glucose uptake and metabolism in target tissues, decreasing blood glucose levels and providing negative feedback to regulate further insulin secretion.
Insulin secretion can also be stimulated by neural signals or hormones from the digestive tract in response to food.

The Pituitary Gland

The pituitary gland is composed of two fused glands, functioning as a major endocrine center that integrates signals for hormone release.
Its size is comparable to a lima bean, and it plays a crucial role in regulating hormones connected to several physiological processes.

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Description

Explore the intricate roles of hypothalamic hormones and their influence on enzyme activity in the liver and other tissues. This quiz delves into the historical context and physiological functions of releasing and inhibiting factors, highlighting their significance in regulating bodily functions.