Hormone Half-Life

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Questions and Answers

What determines the rate of removal of a hormone from the circulation?

The amount of hormone in the circulation

The rate of synthesis of the hormone

The type of hormone, whether water-soluble or lipid-soluble

It is fairly constant for a given hormone (correct)

What is the main difference in half-lives between water-soluble and lipid-soluble hormones?

There is no significant difference in half-lives

Water-soluble hormones have longer half-lives

Lipid-soluble hormones have shorter half-lives

Water-soluble hormones have shorter half-lives (correct)

What type of hormone interaction occurs when one hormone cannot exert its effects without another hormone being present?

Synergism

Permissiveness (correct)

Antagonism

Negative feedback

What is the main mechanism by which blood levels of hormones are controlled?

Negative feedback systems Signup and view all the answers

What type of stimulus causes the parathyroid glands to secrete parathyroid hormone (PTH)?

Humoral stimuli Signup and view all the answers

What type of nervous system fibers stimulate the adrenal medulla to secrete catecholamines?

Preganglionic sympathetic nervous system fibers Signup and view all the answers

What is the main function of hormones in the body?

To maintain the internal environment in the body Signup and view all the answers

What type of hormone interaction occurs when more than one hormone produces the same effects on a target cell?

Synergism Signup and view all the answers

Which of the following is NOT directly controlled or influenced by the Endocrine System?

Digestive enzyme production Signup and view all the answers

How does the endocrine system maintain homeostasis in the body?

By coordinating and regulating the activities of cells, tissues, organs, and systems. Signup and view all the answers

Which of the following is an example of a negative feedback mechanism within the endocrine system?

Increased blood sugar triggers the release of insulin, which lowers blood sugar. Signup and view all the answers

Which of the following is NOT a function of the endocrine system related to reproduction?

Milk production in the mammary glands Signup and view all the answers

What is the primary function of homeostasis in the body?

To maintain a stable internal environment despite external changes. Signup and view all the answers

What can happen if homeostasis is disrupted?

The body becomes more vulnerable to disease and illness. Signup and view all the answers

What is the effect of ADH on the distal nephron tubule and collecting duct?

Increasing their permeability to water Signup and view all the answers

What is the term for the condition resulting from inadequate ADH production and release?

Diabetes insipidus Signup and view all the answers

Which of the following hormones is produced by the hypothalamus?

ADH Signup and view all the answers

What is the primary function of ADH in the body?

Conservation of water Signup and view all the answers

Which of the following is an example of a nonsteroidal hormone?

ADH Signup and view all the answers

What is the term for the condition resulting from hypersecretion of GH in children?

Gigantism Signup and view all the answers

Which of the following hormones cannot cross cell membranes easily?

Nonsteroidal hormone Signup and view all the answers

What is the term for the condition resulting from hypersecretion of GH in adults?

Acromegaly Signup and view all the answers

Which of the following is NOT a characteristic of positive feedback mechanisms?

They involve a control center that monitors and regulates a variable. Signup and view all the answers

In the example provided for positive feedback, what is the role of oxytocin?

It acts as an effector, stimulating uterine contractions. Signup and view all the answers

Which of the following statements accurately describes the role of calcitonin in the regulation of blood calcium levels?

Calcitonin is released by the thyroid gland and inhibits osteoclasts, decreasing blood calcium levels. Signup and view all the answers

Which of the following scenarios is most likely to be regulated by a negative feedback mechanism?

A drop in blood calcium levels leading to the release of parathyroid hormone. Signup and view all the answers

What is the primary function of the parathyroid hormone in the regulation of blood calcium levels?

To stimulate osteoclasts, increasing bone resorption and increasing blood calcium levels. Signup and view all the answers

What is the key difference between positive and negative feedback mechanisms?

Positive feedback mechanisms amplify the initial change, while negative feedback mechanisms oppose it. Signup and view all the answers

Study Notes

Hormone Removal and Interaction

The rate of removal from the circulation is fairly constant for a given hormone.
The length of time it takes to remove half of the amount of hormone from the circulation is the half-life of that hormone.
Water-soluble hormones have shorter half-lives than lipid-soluble hormones due to rapid degradation in the kidney, liver, and lungs.
Hormones with short half-lives exhibit rapid changes in hormone levels.

Types of Hormone Interaction

Permissiveness: one hormone cannot exert its effects without another hormone being present.
Synergism: more than one hormone produces the same effects on a target cell.
Antagonism: one or more hormones opposes the action of another hormone.

Blood Levels of Hormones

Blood levels of hormones are controlled by negative feedback systems.
Hormone levels vary only within a narrow desirable range.
Hormones are synthesized and released in response to humoral stimuli, neural stimuli, and hormonal stimuli.

Humoral Stimuli

Humoral stimuli are the simplest of endocrine control mechanisms.
Hormone secretion occurs in direct response to changing blood levels of ions and nutrients.
Example: declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH, which causes Ca2+ concentrations to rise and the stimulus is removed.

Neural Stimuli

Neural stimuli involve nerve fibers that stimulate hormone release.
Example: the preganglionic sympathetic nervous system (SNS) fibers stimulate the adrenal medulla to secrete catecholamines.

Hormonal Stimuli

Hormonal stimuli involve the release of hormones in response to hormones produced by other endocrine organs.
Example: the hypothalamic hormones stimulate the anterior pituitary, which in turn stimulates target cells to secrete hormones.

Functions of the Endocrine System

Maintenance of the internal environment in the body (maintaining the optimum biochemical environment).
Integration and regulation of growth and development.
Control, maintenance, and instigation of sexual reproduction, including gametogenesis, coitus, fertilization, fetal growth and development, and nourishment of the newborn.

Homeostasis

Homeostasis is the ability of the human body to maintain relatively stable internal conditions despite changes in the outside world.
A good homeostasis is indispensable to maintain the organism in good health.
Most diseases can be regarded as a result of disturbance of homeostasis.

Feedback Systems

Negative feedback mechanisms cause the variable to change in a direction opposite to that of the initial change.
Positive feedback mechanisms cause the variable to accelerate the change in the same direction as the initial disturbance.

Endocrine System in Feedback Mechanisms

Negative feedback mechanisms: Parathyroid hormone is released in response to declining blood Ca2+ concentration, which stimulates osteoclasts to resorb bone, releasing calcium to the blood, and calcitonin hormone is released to inhibit osteoclasts and encourage calcium salt deposit in bone matrix.
Positive feedback mechanisms: Oxytocin stimulates milk letdown and contraction of the uterus, and prolactin stimulates milk production.

Pituitary Gland: Parts and Hormones

Posterior lobe: stores hormones oxytocin and antidiuretic hormone (ADH).
Anterior lobe: makes and releases hormones such as thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), melanocyte-stimulating hormone (MSH), and prolactin (PRL).
Hormones produced by the hypothalamus and released by the posterior pituitary: oxytocin and antidiuretic hormone (ADH).

Hormonal Control of Water Retention in the Body

The body controls water retention through the hormone antidiuretic hormone (ADH), released by the posterior pituitary gland.
ADH increases permeability to water in the distal nephron tubule and collecting duct, leading to more water moving out of the nephron tubule and collecting duct and back into circulation.

Disorders

Gigantism: hypersecretion of GH in children.
Acromegaly: hypersecretion of GH in adults.
Pituitary dwarfism: hyposecretion of GH.
Diabetes insipidus: inadequate ADH produced and released.

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Description

Learn about the rate of removal of hormones from circulation, half-life of hormones, and the difference in half-lives between water-soluble and lipid-soluble hormones. Test your understanding of hormone regulation.