Chapter 16 Learning Outcomes

Define hormone receptor.

A protein molecule, located either on the plasma membrane (extracellular receptor) or inside the cell (intracellular receptor), that binds with a specific hormone.

Define synergistic effect.

A synergist effect occurs when two hormones have an additive effect so that the net result is greater than the effect each would produce alone.

What effect would increased cortisol levels have on blood glucose level?

Increased cortisol levels would result in elevated blood glucose levels, because cortisol reduces the use of glucose by cells while increasing both the available glucose (by promoting glycogen breakdown) and the conversion of amino acids to carbohydrates.

What is the effect of increased glucagon levels on the amount of glycogen stored in the liver?

Increased levels of glucagon stimulate the conversion of glycogen to glucose in the liver, which in turn reduces the amount of glycogen stored in the liver.

The secretion of which hormone lowers blood glucose concentration?

Insulin

Which type of hormone diffuses across the plasma membrane and binds to receptors in the cytoplasm?

Steroid hormones.

Define endocrine system.

The endocrine system includes organs whose primary function is the production of hormones or paracrine, which are chemical secretions that are transported by the extracellular fluid or bloodstream to target cells in other sites within the body.

Name the organs of the endocrine system.

The hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas (pancreatic islets), pineal gland, and parathyroid glands. Organs of other systems that have secondary endocrine functions are the heart, thymus, digestive tract, kidneys, and gonads.

Define the prefixes hyper- and hypo- in the context of endocrine disorders.

The prefix hyper- refers to excessive hormone production, whereas hypo-refers to inadequate hormone production.

Name the regions and zones of an adrenal gland from superficial to deep.

The regions are the adrenal capsule, adrenal cortex, and adrenal medulla. The zones are the zona glomerulosa, zona fasciculata, and zona reticularis.

Describe the resistance phase.

The resistance phase is characterized by long-term metabolic adjustments, including mobilization of remaining energy reserves (lipids from adipose tissue and amino acids from skeletal muscle), conservation of glucose, elevation of blood glucose concentration, and conservation of salts and water coupled with the loss of K+ and H+.

Identify three common causes of hormone hyposecretion.

Three common causes of hormone hypo secretion are metabolic favors, physical damage, and congenital disorders.

Name the hormones of the thyroid gland.

Thyroxine (T4), or tetraiodothyronine; triiodothyronine (T3); and calcitonin.

Describe the structural classification of hormones.

(1) amino acid derivatives (thyroid hormones, catecholamines, and tryptophan derivatives); (2) peptide hormones (glycoproteins or short polypeptide chains), which are chains of amino acids that are synthesized as prohormones; and (3) lipid derivatives (eicosanoids and steroid hormones), which contain carbon rings and side chains that are built from fatty acids or cholesterol.

Identify the three mechanisms by which the hypothalamus integrates neural and endocrine function.

(1) secretion of antidiuretic hormone (ADH) and oxytocin (OXT), (2) secretion of regulatory hormones that control activity of the anterior lobe of the ptuitary gland, and (3) neural (sympathetic) control over the endocrine cells of the adrenal medullae.

What condition is characterized by increased body weight due to Na+ and water retention and a low blood K+ concentration?

Aldosteronism.

What thyroid hormone aids in calcium regulation?

Calcitonin.

What kind of effect do hormones have if they produce different but complementary effects?

Hormones producing different, but complementary, effects are described as having integrative effects.

List three functions suggested for melatonin in humans.

In humans, melatonin may maintain circadian rhythms, affect the timing of sexual maturation, and protect against damage by free radicals.

What effects would increased circulating levels of glucocorticoids have on the pituitary secretion of ACTH?

Increased circulating levels of glucocorticoids inhibit the release of CRH by the hypothalamus. The lack of CRH reduces the secretion of ACTH from the pituitary gland, so ACTH levels would decrease.

Increased amounts of light would inhibit the production of which hormone?

Melatonin secretion is influenced by day/night patterns. Increased amounts of light would inhibit the production (and release) of melatonin from the pineal gland, which receives inout concerning the presence of light or darkness from visual pathway collaterals.

Why do signs and symptoms of decreased thyroxine concentration not appear until about a week after a thyroidectomy (surgical removal of the thyroid gland)?

Most of the body's reserves of thyroid hormone, thyroxine (T4), are bound to transport proteins in the bloodstream including thyroid-binding globulin, transthyretin, or albumin (a plasma protein). Because these compounds represent such a large reserve of thyroxine, it takes several days after removal of the thyroid gland for blood levels of thyroxine to decline.

Decreased blood calcium level would result in increased secretion of which hormone?

PTH

Explain how parathyroid hormone increases blood calcium level.

Parathyroid hormone (PTH) increases blood calcium levels by increasing calcium release from bones, increasing reabsorption of calcium from the blood by the kidneys, and increasing the production of calciferol by the kidneys, which increases absorption of calcium from the digestive tract.

Identify the hormone-secreting cells of the pineal gland.

Pinealocytes

The release of which pituitary hormone would lead to an increased level of somatomedins in the blood?

Somatomedins mediate the action of growth hormone (GH). Increased levels of GH typically accompany increased levels of somatomedins.

List the three phases of the stress response.

The alarm phase, the resistance phase, and the exhaustion phase.

Name and describe the characteristics and functions of the blood vessels that link the hypothalamus with the anterior lobe of the pituitary gland.

The blood vessels of the hypophyseal portal system link the hypothalamus and anterior lobe of the pituitary gland. Unusually permeable fenestrated capillary beds in each structure are connected by portal vessels. This arrangement ensures that hypothalamic regulatory hormones reach the "downstream" endocrine cells of the anterior lobe directly, before mixing with, and being diluted by, the general circulation.

During which phase of the general adaptation syndrome is there a collapse of vital systems?

The collapse of vital systems occurs during the exhaustion phase of the general adaptation syndrome.

What is the common goal of the nervous and endocrine systems?

The common goal of both the nervous and endocrine systems is to preserve homeostasis by coordinating and regulating the activities of other cells, tissues, organs, and organ systems.

Which of the four hormonal effects are involved in a negative feedback response?

The hormones in a negative feedback mechanism have antagonistic effects.

Describe the locations of the parathyroid glands.

The parathyroid glands are embedded in the posterior surfaces of the lateral lobes of the thyroid gland.

Cite the hormones secreted by each region of an adrenal gland.

The two hormone-secreting regions of an adrenal gland are the adrenal cortex and adrenal medulla. The cortex secretes mineralocorticoids, primarily aldosterone; glucocorticoids, mainly cortisol (or hydrocortisone) and corticosterone; and androgens. The medulla secretes epinephrine and norepinephrine.

Identify the types of cells in the pancreatic islets and the hormones produced by each.

The types of cells in the pancreatic islets (and their hormones) are alpha cells (glucagon), beta cells (insulin), delta cells (GH-IH), and pancreatic polypeptide cells, or PP cells (pancreatic polypeptide hormone).

Define regulatory hormone.

A hormone secreted by the hypothalamus that controls endocrine cells in the anterior lobe of the pituitary gland.

Differentiate between a first messenger and a second messenger.

A first messenger is a hormone whose binding to a protein receptor in the plasma membrane gives rise to a second messenger in the cytoplasm. A second messenger changes the rate of various metabolic reactions by acting as an enzyme activator, an enzyme inhibitor, or a cofactor.

List the hypothalamic releasing hormones.

Corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GH-RH), prolactin-releasing hormone (PRH), and gonadotropin-releasing hormone (GnRH).