Chapter 16: Endocrine System

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).

Identify three main causes of hormone hyposecretion.

Three common causes of hormone hyposecretion are metabolic factors, physical damage, and congenital disorders.

Define hormone receptor.

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

Define regulatory hormone.

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

Define synergistic effect.

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

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.

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

Steroid hormones diffuse across the plasma membrane and bind to intracellular receptors in the cytoplasm or nucleus.

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

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

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

The regions of an adrenal gland from superficial to deep are the adrenal capsule, adrenal cortex, and adrenal medulla. The zones are the zona glomerulosa, zona fasciculata, and zona reticularis.

What hormones are necessary for normal growth and development?

include GH, thyroid hormones, insulin, PTH, calcitriol, and reproductive hormones.

Differentiate between a first and second messenger.

A first messenger is a hormone who's 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

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

Aldosteronism is characterized by increased body weight due to Na+ and water retention and a low blood Concentration.

Decreased blood calcium levels would result in increased secretion of what hormone?

Decreased blood calcium levels result in increased secretion of PTH.

What is Diabetes mellitus?

Diabetes mellitus is an endocrine disorder characterized by elevated blood glucose levels high enough to overwhelm the reabsorption capabilities of the kidneys.

In a dehydrated person, how would the amount of ADH released by the posterior lobe of the pituitary change?

In a person who is dehydrated, the amount of ADH released by the posterior lobe of the pituitary gland increases in response to increased blood osmotic pressure resulting from a rise in solute concentration

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 increase 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.

What effect would increase cortisol levels on blood glucose levels?

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 concentrations?

Insulin secretion lowers blood glucose concentration.

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 input concerning the presence of light or darkness from visual pathway collaterals.

Why do signs and symptoms of 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 globulins, 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.

Explain how the parathyroid hormone increases blood calcium levels.

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 calcitriol by the kidneys, which increases absorption of calcium from the digestive tract.

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.

Identify some clinical problems associated with diabetes mellitus.

Some clinical problems associated with diabetes mellitus are diabetic retinopathy, blockages in heart circulation and increased risk for heart attack, diabetic nephropathy, diabetic neuropathy, and decreased blood flow to the distal limbs.

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

Identify the organs and tissues of the endocrine system and the key functions of the hormones they secrete.

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. Organs of the endocrine system are 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.

Identify the hormone-secreting cells of the pineal gland.

The hormone-secreting cells of the pineal gland are pinealocytes.

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

The hormones in a negative feedback mechanism have antagonistic effects

Name the hormones of the thyroid gland.

The hormones of the thyroid gland are thyroxine (T4), or tetraiodothyronine; triiodothyronine (T3); and calcitonin.

Identify 9 pituitary hormones and their target tissues.

The hormones produced and released by the anterior lobe of the pituitary gland are (1) thyroid-stimulating hormone (TSH), which targets the thyroid gland. (2) adrenocorticotropic hormone (ACTH), which targets the adrenal cortex. (3) follicle-stimulating hormone (FSH) and (4) luteinizing hormone (LH), which target the testes in males and the ovaries in females; (5) growth hormone (GH), which targets liver cells (which respond by synthesizing somatomedins); (6) prolactin (PRL), which targets mammary glands in females. (7) melanocyte-stimulating hormone (MSH), which targets melanocytes in the skin. Hormones released by the posterior lobe of the pituitary gland are. (8) oxytocin (OXT), which targets the uterus and mammary glands. (9) antidiuretic hormone (ADH), which targets the kidneys.

List the hypothalamic releasing hormones.

The hypothalamic releasing hormones are corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GH-RH), prolactin-releasing hormone (PRH), and gonadotropin-releasing hormone (GnRH).

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.

Describe the resistance response.

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+.

Describe the structural classification of hormones.

The structural classes of hormones are (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.

The three mechanisms of hypothalamic integration of neural and endocrine function are (1) secretion of antidiuretic hormone (ADH) and oxytocin (OXT), (2) secretion of regulatory hormones that control activity of the anterior lobe of the pituitary gland, and (3) neural (sympathetic) control over the endocrine cells of the adrenal medullae.

List the three phases of the stress response.

The three phases of the stress response are the alarm phase, the resistance phase, and the exhaustion phase.

Cite the hormones secreted by each region of the 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.

Describe the two types of diabetes mellitus.

The two types of diabetes mellitus are type 1, characterized by inadequate insulin production by the pancreatic beta cells, and type 2, characterized by insulin resistance (failure of the body to use insulin properly)