The Endocrine System

Question 1

Peptide hormones

Answer 1

Made of amino acids, must bind to extracellular receptor, effects are rapid and short-lived, water-soluble and can travel freely through bloodstream without carriers

Question 2

First messenger

Answer 2

The peptide hormone itself, binding to receptor and triggering transmission of second signal, known as second messenger

Question 3

Signal cascade

Answer 3

Connection between hormone at surface and effect brought about by second messengers in cell, with possibility of amplification (increase in signal intensity)

Question 4

G-protein coupled receptor activation sample pathway

Answer 4

Binding of peptide hormone leads to activation or inhibition of adenylate cyclase, raising or lowering cyclic adenosine monophosphate (cAMP) levels accordingly, which can bind to protein kinase A, phosphorylating cAMP response element-binding protein (CREB) to exert ultimate effect of hormone

Question 5

Steroid hormones

Answer 5

Derived from cholesterol, produced by gonads and adrenal cortex, easily cross cell membrane, lipid-soluble and require carrier to travel in bloodstream, slower and longer-lasting effects, have intracellular or intranuclear receptors, which can then bind DNA directly in complex with hormone to increase or decrease transcription of genes

Question 6

Amino acid-derivative hormones

Answer 6

Derived from one or two amino acids, include catecholamines (epinephrine and norepinephrine) and thyroid hormones (triiodothyronine and thyroxine), catecholamines bind to G protein-coupled receptors like peptide hormones and thyroid hormones bind intracellularly like steroid hormones

Question 7

Direct hormones

Answer 7

Secreted and then act directly on a target tissue

Question 8

Tropic hormones

Answer 8

Require an intermediary to act, usually originate in brain and anterior pituiary gland

Question 9

Hypothalamus

Answer 9

Bridge between nervous and endocrine systems, regulates pituitary gland through tropic hormone paracrine release into a portal system

Question 10

Negative feedback

Answer 10

When a hormone or product later in the pathway inhibits hormones or enzymes earlier in the pathway

Question 11

Hypophyseal portal system

Answer 11

Blood vessel system that directly connects hypothalamus with anterior pituitary (hypophysis is alternative term for pituitary), then stimulating the release of other hormones from anterior pituitary

Question 12

List of hormones secreted by hypothalamus

Answer 12

Gonadotropin-releasing hormone (GnRH): releases tropic follicle-stimulating hormone (FSH) and tropic luteinizing hormone (LH)
Growth hormone-releasing hormone (GHRH): releases direct growth hormone (GH)
Thyroid-releasing hormone (TRH): releases tropic thyroid-stimulating hormone (TSH)
Corticotropin-releasing factor (CRF): releases tropic adrenocorticotropic hormone (ACTH)

Question 13

Exception to tropic pattern from hypothalamus to anterior pituitary

Answer 13

Prolactin-inhibiting factor (PIF), or dopamine, that is released by hypothalamus actually causes decrease in prolactin secretion, as the absence of PIF is what allows direct prolactin hormone to be released

Question 14

Cortisol

Answer 14

ACTH released by anterior pituitary causes adrenal cortex to increase the level of this hormone secreted into blood

Question 15

Posterior pituitary

Answer 15

Does not receive tropic hormones through hypophyseal portal system, rather through neurons from the hypothalamus, releases oxytocin and antidiuretic hormone (ADH), does not synthesize any hormones itself

Question 16

Oxytocin

Answer 16

Synthesized in hypothalamus and released from posterior pituitary, stimulates uterine contractions during labor, and milk letdown during lactation promoted by suckling, secreted during childbirth, has a positive feedback loop

Question 17

Antidiuretic hormone

Answer 17

Synthesized in hypothalamus and released from posterior pituitary, also called vasopressin, increases reabsorption of water in collecting ducts of kidneys, secreted in response to increased plasma osmolarity or increased solute concentration in blood, leading to increased blood volume and higher blood pressure

Question 18

Prolactin

Answer 18

Stimulates milk production in mammary glands, decreased secretion by dopamine

Question 19

Endorphins

Answer 19

Direct hormones released by anterior pituitary, decrease perception of pain

Question 20

Growth hormone

Answer 20

Promotes growth of bone and muscle, requires large amounts of glucose and so prevents large glucose uptake in non-growing tissues and stimulates breakdown of fatty acids, stimulated by GHRH

Question 21

Gigantism and dwarfism

Answer 21

Excess and deficit of GH released in childhood before closure of epiphyseal plates during puberty, respectively

Question 22

Acromegaly

Answer 22

Excess of GH released in adulthood, effect in smaller bones as epiphyseal plates in long bones are sealed

Question 23

Thyroid

Answer 23

Controlled by TSH from the anterior pituitary, has two major functions: setting basal metabolic rate (through release of T3 and T4) and promoting calcium homeostasis (through release of calcitonin)

Question 24

Triiodothyronine (T3) and thyroxine (T4)

Answer 24

Produced by iodination of tyrosine in follicular cells of thyroid, numbers 3 and 4 refer to number of iodine atoms attached to the tyrosine, can reset basal metabolic rate of body by making energy production more or less efficient, as well as altering utilization of glucose and fatty acids, increased amounts lead to increased cell respiration and increased protein and fatty acid turnover

Question 25

Hypothyroidism

Answer 25

Results from deficiency of iodine or inflammation of the thyroid, thyroid hormones are secreted in insufficient amounts or not at all, lethargy, decreased body temp, slowed respiratory and heart rate, cold intolerance, weight gain

Question 26

Cretinism

Answer 26

Intellectual disability and developmental delay in children as a result of hypothyroidism

Question 27

Hyperthyroidism

Answer 27

Excess of thyroid hormone, resulting from tumor or thyroid overstimulation, heightened activity level, increased body temp, increased respiratory and heart rate, heat intolerance, weight loss

Question 28

Calcitonin

Answer 28

Produced by C-cells (or parafollicular cells), decreases plasma calcium levels by increasing calcium excretion from kidneys, decreasing calcium absorption from gut, and increased storage of calcium in bone, stimulated by high levels of calcium in blood

Question 29

Parathyroid hormone (PTH)

Answer 29

Produced by parathyroid glands, antagonistic hormone to calcitonin, raises blood calcium levels, decreases excretion of calcium by kidneys, increases absorption of calcium in gut via vitamin D, increases bone resorption Also promotes phosphorus homeostasis by increasing resoprtion of phosphate from bone and reducing reabsorption of phosphate in kidney

Question 30

Vitamin D

Answer 30

Required for absorption of calcium and phosphate in the gut, activated by PTH

Question 31

Adrenal cortex

Answer 31

One segment of the adrenal glands located on top of the kidneys, secretes corticosteroids (glucocorticoids, mineralocorticoids, cortical sex hormones)

Question 32

Glucocorticoids

Answer 32

Corticosteroids secreted by adrenal cortex that regulate glucose levels and affect protein metabolism

Question 33

Cortisol and cortisone

Answer 33

Glucocorticoids that raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis, can decrease infammation and immunologic responses (cortisol is known as stress hormone as it is released in times of stress)

Question 34

Mineralocorticoids

Answer 34

Corticosteroids used in salt and water homeostasis

Question 35

Aldosterone

Answer 35

Most noteworthy mineralocorticoid, increases sodium reabsorption in disal convoluted tubule and collecting duct of nephron, leading to increase in blood volume and pressure, keeping plasma osmolarity constant, also decreases reabsorption of potassium and hydrogen ions to promote their excretion

Question 36

Renin-angiotensin-aldosterone system

Answer 36

Decreased blood pressure causes juxtaglomerular cells of kidney to secrete renin, which cleaves inactive angiotensinogen to active form angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme (ACE) in the lungs, stimulating the adrenal cortex to secrete aldosterone

Question 37

Cortical sex hormones

Answer 37

Androgens and estrogens that can also be synthesized in adrenal cortex, but at a smaller amount that in gonads

Question 38

Adrenal medulla

Answer 38

Derivative of nervous system, produces sympathetic hormones epinephrine and norepinephrine and secretes them into bloodstream

Question 39

Islets of Langerhans

Answer 39

Hormone-producing cells in pancreas that contains alpha, beta, and delta cells, which secrete glucagon, insulin, and somatostatin, respectively

Question 40

Glucagon

Answer 40

Secreted by alpha cells in pancreas during times of fasting when glucose levels are low in blood, triggering glycogenolysis, gluconeogenesis, and degrading protein and fat

Question 41

Insulin

Answer 41

Antagonistic to glucagon, secreted by beta cells in pancreas when blood glucose levels are high, induces muscle and liver cells to take up glucose and store it as glycogen for later use, stimulates anabolic process such as fat and protein synthesis

Question 42

Hypoglycemia

Answer 42

Caused by excess of insulin, low blood glucose concentration

Question 43

Hyperglycemia

Answer 43

Excess glucose in the blood as a result of underproduction, insufficient secretion, or insensitivity to insulin (diabetes mellitus)

Question 44

Polyuria and polydipsia

Answer 44

Increased frequency of urination and increased thirst, respectively, often in diabetics as a result of excess excretion of water due to excess presence of glucose in fitrate

Question 45

Type I diabetes

Answer 45

Insulin-dependent diabetes, caused by autoimmune destruction of beta cells of the pancreas, resulting in low or absent insulin production, requiring regular injections of insulin to prevent hyperglycemia and permit glucose uptake into cells

Question 46

Type II diabetes

Answer 46

Non-insulin-dependent diabetes, caused by receptor-level resistance to effects of insulin, partially inherited and due to environmental factors (high carb diets and obesity), insulin required only when diabetic bodies can no longer control glucose levels

Question 47

Somatostatin

Answer 47

Secreted by delta cells in pancreas, inhibitor of both insulin and glucagon secretion, stimulated by high blood glucose and amino acid concentrations, also produced by hypothalamus (also decreases growth hormone secretion)

Question 48

Testes

Answer 48

Secrete testosterone in response to stimulation by FSH and LH, causing sexual differentiation of male during gestation and promotes development and maintenance of secondary sexual characteristics in males

Question 49

Ovaies

Answer 49

Secrete estrogen and progesterone in response to FSH and LH, respectively, estrogen is involved in development of female reproductive system during gestation and secondary sexual characteristics in females, both hormones govern menstrual cycle and pregnancy

Question 50

Pineal gland

Answer 50

Secretes melatonin, demonstrated to be involved in circadian rhythms, sensation of sleepiness, responds to decreases in light intensity

Question 51

Erythropoietin

Answer 51

Produced by kidneys, stimulating bone marrow to increase production of erythrocytes (red blood cells) in response to low oxygen levels in the blood

Question 52

Atrial natriuretic peptide (ANP)

Answer 52

Released by heart to help regulate salt and water balance, promotes excretion of sodium and increases urine volume, antagonistic to aldosterone as it lowers blood volume and pressure, with no effect on blood osmolarity

Question 53

Thymosin

Answer 53

Released by thymus, important for proper T-cell development and differentiation, with thymus atrophying by adulthood and thymosin levels dropping accordingly