Chapter 16

Front 1

Define endocrine system.

Back 1

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

Front 2

Name the organs of the endocrine system.

Back 2

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 endocrine functions are the heart, thymus, digestive tract, kidneys, and gonads.

Front 3

Describe the structural classification of hormones.

Back 3

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.

Front 4

Define hormone receptor.

Back 4

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

Front 5

Differentiate between a first messenger and a second messenger.

Back 5

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

Front 6

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

Back 6

Hormones that diffuse across the plasma membrane and bind to receptors in the cytoplasm are steroid hormones.

Front 7

Define regulatory hormone.

Back 7

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

Front 8

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

Back 8

The three mechanisms of hypothalamic integration of neural and endocrine function are (1) secretion of antidiuretic hormone and oxytocin, (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 fo the adrenal medullae.

Front 9

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

Back 9

The blood vessels of the hypophyseal portal system link the hypothalamus and anterior lobe. 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.

Front 10

Name the two lobes of the pituitary gland.

Back 10

The two lobes of the pituitary gland are the anterior lobe and the posterior lobe.

Front 11

Identify the nine pituitary hormones and their target tissues.

Back 11

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; Growth hormone (GH), which targets liver cells (whcih respond by synthesizing somatomedins); (6) prolactin (PRL), which targets mammary glands in females; and (7) melanocyte-stimulating hormone (MSH), which targets melanocytes in the skin. Hormones released by the posterior lobe of the pituitary gland are (1) oxytocin (OXT), which targets the mammary glands, and (2) antidiuretic hormone (ADH), which targets the kidneys.

Front 12

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

Back 12

In a dehydrated individual, the amount of ADH released by the posterior pituitary increases in response to increased blood osmotic pressure resulting from a rise in solute concentration.

Front 13

List the hypothalamic releasing hormones.

Back 13

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

Front 14

If a blood sample contained elevated levels of somatomedins, which pituitary hormone would you expect to be elevated?

Back 14

Somatomedins mediate the action of growth hormone. Elevated levels of growth hormone typically accompany elevated levels of somatomedins.

Front 15

What effect would elevated circulating levels of glucocorticoids have on the pituitary secretion of ACTH?

Back 15

Elevated 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. This is an example of negative feedback.

Front 16

Name the hormones of the thyroid gland.

Back 16

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

Front 17

What thyroid hormone aids in the regulation of calcium?

Back 17

Calcitonin aids in calcium regulation.

Front 18

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

Back 18

Most of the body's reserves of thyroid hormone, thyroxine, are bound to transport proteins in the bloodstream called thyroid-binding globulins. Because these compounds represent such a large reservoir of thyroxine, it takes several days after removal of the thyroid gland for blood levels of thyroxine to decline.

Front 19

Describe the locations of the parathyroid glands.

Back 19

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

Front 20

Explain how parathyroid hormone raises the blood calcium levels.

Back 20

Parathyroid hormone (PTH) raises blood calcium levels by reducing calcium deposition in reducing calcium deposition in bones, by increasing reabsorption of calcium from the blood by the kidneys, and by increasing the production of calcitriol by the kidneys

Front 21

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

Back 21

Decreased blood calcium levels result in increased secretion of parathyroid hormone (PTH).

Front 22

Identify the two regions of an adrenal gland, and cite the hormones secreted by each.

Back 22

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

Front 23

List the three zones of the adrenal cortex.

Back 23

The three zones of the adrenal cortex are the zona glomerulosa, zona fasciculata, and zona reticularis.

Front 24

What effect would elevated cortisol levels have on blood glucose levels?

Back 24

Elevated 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 the breakdown of glycogen) and the conversion of amino acids to carbohydrates.

Front 25

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

Back 25

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

Front 26

The secretion of which hormone lowers blood glucose concentrations?

Back 26

The secretion of insulin lowers blood glucose concentrations.

Front 27

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

Back 27

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

Front 28

Identify the hormone-secreting cells of the pineal gland.

Back 28

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

Front 29

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

Back 29

Melatonin secretion is influenced by light-dark cycles. Increased amounts of light would inhibit the production (and release) of melatonin from the pineal gland, which receives neural input concerning the presence of light of darkness from visual pathway collaterals.

Front 30

List three functions of melatonin.

Back 30

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

Front 31

Define diabetes mellitus.

Back 31

Diabetes mellitus is a condition characterized by elevated blood glucose levels resulting from inadequate insulin production or diminished sensitivity to insulin by cells.

Front 32

Identify and describe the two types of diabetes mellitus.

Back 32

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).

Front 33

Why does a person with diabetes mellitus urinate frequently?

Back 33

An individual with type 1 or type 2 diabetes has such high blood glucose levels that the kidneys cannot reabsorb all the glucose; some glucose is lost in the urine. Because the urine contains high concentrations of glucose, less water can be reclaimed by osmosis, so the volume of urine production increases, and the individual needs to urinate more often.

Front 34

Name a peptide by the heart and a hormone released by the kidneys.

Back 34

The heart secretes natriuretic peptide, and the kidneys release erythropoietin.

Front 35

Identify several hormones necessary for normal growth and development.

Back 35

Hormones necessary for normal growth and development include GH, thyroid hormones, insulin, PTH, calcitriol, and reproductive hormones.

Front 36

Explain the action of renin in the bloodstream.

Back 36

Upon its release into the bloodstream, renin functions as an enzyme that activates the renin-angiotensin system, which ultimately causes blood pressure to rise.

Front 37

List the three phases of the stress response.

Back 37

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

Front 38

Describe the resistance phase.

Back 38

The resistence phase is characterized by long-term metabolic adjustments, including mobilization of remaining energy reserves, conservation of glucose, elevation of blood glucose concentrations, and conservation of salts and water coupled with the loss of potassium and hydrogen.

Front 39

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

Back 39

The collapse of vital systems occurs during the exhaustion phase of the GAS.

Front 40

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

Back 40

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

Front 41

Identify three common causes of hormone hyposecretion.

Back 41

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

Front 42

What condition is characterized by increased body weight due to sodium and water retention and a low blood potassium concentration?

Back 42

Aldosteronism is characterized by increased body weight due to sodium and water retention and low blood potassium concentration.