Endocrine System

Front 1

What is the function of endocrine glands?

Back 1

Synthesize and secrete chemical substances called hormones directly into the circulatory system

Front 2

What is the function of exocrine glands?

Back 2

Secrete substances that are transported by ducts

EX: gall bladder

Front 3

What is the function of hormones?

Back 3

Regulate the function of target organs or tissues

Front 4

What is the specificity of hormonal action depend on?

Back 4

It is determined by the presence of specific receptors on or in the target cells.

Front 5

What is the pituitary gland?
What is another name for it?

Back 5

The pituitary (hypophysis) is a small, tri-lobed gland lying at the base of the brain.

Front 6

What are the three lobes of the pituitary gland?

Back 6

1. Anterior
2. Posterior
3. Intermediate (no function)

Front 7

What is the function of the anterior pituitary?

Back 7

Synthesizes both direct hormones, which directly stimulate their target organs, and tropic hormones, which stimulate other endocrine glands to release hormones.

Front 8

What regulates the hormonal secretions of the anterior pituitary?

Back 8

Hypothalamic secretions called releasing/inhibiting hormones or factors

Front 9

What are the three direct hormones of the anterior pituitary?

Back 9

1. Growth Hormone (GH, somatotropin)
2. Prolactin
3. Endorphins

Front 10

What is the function of Growth Hormone (GH)?

Back 10

Promotes bone and muscle growth, inhibits the uptake of glucose by certain cells, and stimulates the breakdown of fatty acid, thus conserving glucose.

Front 11

How is GH secretion controlled?

Back 11

Stimulated by the hypothalamic releasing hormone (GHRH) and inhibited by somatostatin

Secretion is also under neural and metabolic control

Front 12

1. In children, what does a GH deficiency result in?
2. In children, what does an overproduction of GH result in?

Back 12

1. Dwarfism
2. Gigantism

Front 13

In adults, what does an overproduction of GH result in?

Back 13

Acromegaly, a disorder characterized by a disproportionate overgrowth of bone, localized especially in the skull, jaw, feet, and hands

Front 14

What is the function of prolactin?

Back 14

Stimulates milk production and secretion in female mammary glands

Front 15

What is the function of endorphins? What is another name ?

Back 15

Endorphins (enkephalins)inhibit the perception of pain.

Front 16

What are the four tropic hormones?

Back 16

1. Adrenocorticotropic hormone (ACTH)
2. Thyroid-stimulating hormone (TSH)
3. Luteinizing hormone (LH)
4. Follicle-stimulating hormone (FSH)

Front 17

What is the function of adrenocorticotropic hormone (ACTH)?

Back 17

Stimulates the adrenal cortex to synthesize and secrete glucocorticoids; regulated by the releasing hormone corticotropin releasing factor (CRF)

Front 18

What is the function of the thyroid-stimulating hormone (TSH)?

Back 18

Stimulates the thyroid gland to absorb iodine and then synthesize and release thyroid hormone; regulated by the releasing hormone TRH

Front 19

What is the function of the luteinizing hormone?

Back 19

In females, LH stimulates ovulation and formation of the corpus luteum.
In males, LH stimulates the interstitial cells of the testes to synthesize testosterone.

Front 20

What regulates LH?

Back 20

Estrogen, progesterone, and gonadotropin releasing hormone (GnRH)

Front 21

What is the function of the follicle-stimulating hormone (FSH)?

Back 21

In females, FSH causes maturation of ovarian follicles.
In males, FSH stimulates maturation of the seminiferous tubules and sperm production.

Front 22

What regulates FSH?

Back 22

Estrogen and GnRH

Front 23

What is the function of the posterior pituitary?

Back 23

It does not synthesize hormones; it stores and releases the hormones oxytocin and ADH, which are produced by the neurosecretory cells of the hypothalamus.

Front 24

How is hormone secretion in the posterior pituitary regulated?

Back 24

Stimulated by action potentials descending from the hypothalamus.

Front 25

What are the two hormones secreted by the posterior pituitary?

Back 25

1. Oxytocin
2. Antidiuretic Hormone (ADH)

Front 26

What is the function of oxytocin?

Back 26

Secreted during childbirth, oxytocin increases the strength and frequency of uterine muscle contractions.
Oxytocin stimulates milk secretion in the mammary glands since oxytocin secretion is also induced by suckling.

Front 27

What is the function of ADH?

Back 27

Increases the permeability of the nephron's collecting duct to water, thereby promoting water reabsorption and increasing blood volume.

Front 28

When is ADH secreted?

Back 28

When plasma osmolarity increases, as sensed by osmoreceptors in the hypothalamus, OR when blood volume decreases, as sensed by baroreceptors in the circulatory system

Front 29

What is the hypothalamus?

Back 29

Part of the forebrain; located directly above the pituitary gland; receives neural transmissions from other part of the brain and from peripheral nerves that trigger specific responses from its neurosecretory cells

Front 30

How does the hypothalamus interact with the anterior pituitary?

Back 30

Hypothalamic releasing hormones are hormones that stimulate/inhibit the secretions of the anterior pituitary

Front 31

Where are releasing hormones secreted?

Back 31

Into the hypothalamic-hypophyseal portal system

Front 32

What is the hypothalamic-hypophyseal portal system?

Back 32

A circulatory pathway in which blood from the capillary bed in the hypothalamus flows through a portal vein into the anterior pituitary, where it diverges into a second capillary network

Front 33

What is the purpose of the hypothalamic-hypophyseal portal system?

Back 33

Serves as a way for releasing hormones to immediately reach the anterior pituitary

Front 34

Since overproduction of hormones is potentially harmful to an organism, what is a preventative mechanism used?

Back 34

Negative feedback

Front 35

How does the hypothalamus interact with the posterior pituitary?

Back 35

Neurosecretory cells in the hypothalamus synthesize both oxytocin and ADH and transport them via their axons into the posterior pituitary for storage and secretion

Front 36

What is the thyroid gland?

Back 36

A bi-lobed structure located on the ventral surface of the trachea

Front 37

What is the function of the thyroid gland?

Back 37

Produces and secretes throxine, triiodothyronine, and calcitonin

Front 38

What are the two thyroid hormones? How are they produced?

Back 38

1. Thyroxine (T4)
2. Triiodothyronine (T3)
Both are derived from the iodination of the amino acid tyrosine

Front 39

Why are thyroid hormones necessary for growth and neurological development in children?

Back 39

They increase the rate of cellular respiration and the rate of protein and fatty acid synthesis and degradation in many tissues

Front 40

What is the cause of hypothyroidism?

Back 40

inflammation of the thyroid or iodine deficiency; thyroid hormones are undersecreted or not secreted at all

Front 41

What are common symptoms of hypothyroidism?

Back 41

Slowed heart rate and respiratory rate, fatigue, cold intolerance, and weight gain

Front 42

What is cretinism?

Back 42

Hypothyroidism in newborn infants; characterized by mental retardation and short stature

Front 43

What are the symptoms of hyperthyroidism?

Back 43

Increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, and protruding eyes

Front 44

What is the function of calcitonin?

Back 44

Decreases plasma Ca+2 concentration by inhibiting the release of Ca+2 from bones

Front 45

What are the parathyroid glands?

Back 45

4 small pea-shaped structures embedded in the posterior surface of the thyroid

Front 46

What is the function of the parathyroid glands?

Back 46

Synthesize and secrete parathyroid hormone (PTH), which, together with calcitonin and Vitamin D, regulates plasma Ca+2 concentration

Front 47

How does Parathyroid hormone (PTH) stimulate intestinal calcium absorption?

Back 47

Converting Vitamin D into its active form

Front 48

How does PTH raise Ca+2 concentration in the blood?

Back 48

By stimulating Ca+2 release from bone and decreasing Ca+2 excretion in the kidneys

Front 49

What are the adrenal glands?

Back 49

Situated on top of the kidneys and consist of the adrenal cortex and the adrenal medulla

Front 50

How is the adrenal cortex stimulated?

Back 50

In response to stress, ACTH stimulates the adrenal cortex to synthesize and secrete the steroid hormones, which are collectively known as corticosteroids

Front 51

What are the corticosteroids?

Back 51

Derived from cholesterol; include:
glucocorticoids, mineralocorticoids, and cortical sex hormones

Front 52

What is the function of the glucocorticoids?

ex: cortisol, cortisone

Back 52

Involved in glucose regulation and protein metabolism: raise blood glucose levels by promoting gluconeogenesis and decrease protein synthesis; also reduce body's immunological and inflammatory responses

Front 53

What is the function of mineralocorticoids?

ex: aldosterone

Back 53

Regulate plasma levels of sodium and potassium, and consequently, the total extracellular water volume; stimulates the secretion of potassium ion and hydrogen ion into the nephron and their subsequent excretion in urine

Front 54

What is the function of aldosterone?

Back 54

Causes active reabsorption of sodium and passive reabsorption of water in the nephron

Front 55

How is aldosterone secretion regulated?

Back 55

The renin-angiotensin system

Front 56

What is the renin-angiotensin system?

Back 56

When blood volume falls, the juxtaglomerular cells of the kidney produce renin (enzyme that converts the plasma protein angiotensinogen to angiotensin I; Angtiotensin I is converted to angiotensin II, which stimulates the adrenal cortex to secrete aldosterone

Front 57

What is the function of the cortical sex hormones?

Back 57

Androgens (male sex hormones) secreted by adrenal cortex have small effect in men. Overproduction of the adrenal androgens may have masculinizing effects on women.

Front 58

What is the function of the adrenal medulla?

Back 58

The secretory cells of the adrenal medulla can be viewed as specialized sympathetic nerve cells that secrete hormones into the circulatory system; produces epinephrine and norepinephrine

Front 59

Epinephrine and norepinephrine both belong to which class of amino acid-derived compounds?

Back 59

Catecholamines

Front 60

What is the function of epinephrine?

Back 60

Increases the conversion of glycogen to glucose in liver and muscle tissue, causing a rise in blood glucose levels and increase in the basal metabolic rate

Front 61

What is the "fight or flight response"?

Back 61

Effects elicited by the sympathetic nervous stimulation in response to stress

ex: increase the rate and strength of heartbeat, dilate and constrict blood vessels in such a way as to increase the blood supply to skeletal muscle, the heart, and brain, while decreasing the blood supply to kidneys, skin, and digestive tract

Front 62

How is the endocrine function of the pancreas performed?

Back 62

Performed by small glandular structures called islets of Langerhans, which are composed of alpha, beta, and delta cells

Front 63

How is the exocrine function of the pancreas performed?

Back 63

Performed by cells that secrete digestive enzymes into the small intestine via a series of ducts

Front 64

What do alpha cells produce and secrete?

Back 64

Glucagon

Front 65

What is the function of glucagon?

Back 65

Stimulates protein and fat degradation, the conversion of glycogen to glucose, and gluconeogenesis - all of which serve to increase blood glucose levels

Front 66

How is glucagon secretion regulated?

Back 66

Stimulated by a decrease in blood glucose and by gastrointestinal hormones; inhibited by high plasma glucose levels; works antagonistically to insulin

Front 67

What is insulin?

Back 67

Protein hormone secreted in response to high blood glucose concentration; stimulates the update of glucose by muscle and adipose cells and the storage of glucose as glycogen, thus lowering blood glucose levels; stimulates the synthesis of fats from glucose and the uptake of amino acids

Front 68

What is the result of an overproduction of insulin?

Back 68

Hypoglycemia (low blood glucose levels)

Front 69

What is the result of an underproduction of insulin?

Back 69

Hyperglycemia (high blood glucose levels); insensitivity to insulin leads to diabetes mellitus

Front 70

What is the result of high blood glucose levels?

Back 70

Excretion of glucose and water loss

Front 71

What is ketoacidosis?

Back 71

Dangerous lowering of blood pH due to excess keto acids and fatty acids in the plasma; characteristic of diabetes

Front 72

What do beta cells produce and secrete?

Back 72

Insulin

Front 73

What do delta cells produce and secrete?

Back 73

Somatostatin

Front 74

What is somatostatin secretion regulated by?

Back 74

Increased by high blood glucose levels or high amino acid levels, leading to both decreased insulin and glucagon secretion; also regulated by CCK and GH levels

Front 75

What is the function of somatostatin?

Back 75

Inhibition...regardless of where it acts

Front 76

What is testosterone?

Back 76

Induces embryonic sexual differentiation and male sexual development at puberty; maintains secondary sex characteristics

Front 77

What is the function of the testes?

Back 77

Interstitial cells of testes produce and secrete androgens like testosterone

Front 78

How is the secretion of testosterone regulated?

Back 78

Negative feedback mechanism involving FSH and LH

Front 79

What is testicular feminization?

Back 79

Insensitivity to testosterone; genetic male (XY) has female secondary sexual characteristics

Front 80

What is the function of the ovaries?

Back 80

Synthesize and secrete estrogens and progesterone

Front 81

What is estrogen?

Back 81

Steroid hormones necessary for normal female maturation; stimulate development of female reproductive tract, contribute to development of secondary sexual characteristics, and responsible for thickening of endometrium

Front 82

How is estrogen secreted?

Back 82

Ovarian follicles and corpus luteum

Front 83

What is progesterone?

Back 83

Steroid hormone secreted by the corpus luteum during the luteal phase of the menstrual cycle; stimulates the development and maintenance of the endometrial walls in preparation for implantation

Front 84

What is the menstrual cycle?

Back 84

From puberty through menopause, the interactions between hormones secreted by ovaries, hypothalamus, and pituitary gland result in a monthly cyclical pattern

Front 85

What are the 4 phases of the menstrual cycle?

Back 85

1. Follicular phase
2. Ovulation
3. Luteal phase
4. Menstruation

Front 86

What is the Follicular Phase?

Back 86

Follicles mature as FSH and LH act together

Front 87

What is Ovulation?

Back 87

A surge in LH at midcycle triggers ovulation; mature ovarian follicle bursts and releases an ovum

Front 88

What is the Luteal Phase?

Back 88

Ruptured follicle becomes corpus luteum and secretes estrogen and progesterone to build up uterine lining in preparation for implantation; progesterone + estrogen inhibit FSH and LH

Front 89

What occurs during menstruation?

Back 89

If the ovum isn't fertilized, corpus luteum atrophies, progesterone and estrogen levels decrease, menses occurs, and LH and FSH levels begin to rise again

Front 90

What occurs during the first trimester of pregnancy?

Back 90

Corpus luteum is preserved by human chorionic gonadotropin (HCG)--> hormone produced by the blastocyst and the developing placenta; progesterone and estrogen secretion by corpus luteum is maintained

Front 91

What occurs during the second trimester of pregnancy?

Back 91

HCG levels decline, progesterone + estrogen levels increase which in turn inhibit GnRH secretion, preventing FSH and LH secretion and the onset of a new menstrual cycle

Front 92

What do urine pregnancy tests look for?

Back 92

Presence of HCG in the urine; can be detected in the urine 1-2 weeks after conception

Front 93

What is menopause?

Back 93

Result of a progressive decline in functioning of ovaries with advancing age

Front 94

What is the pineal gland?

Back 94

Tiny structure at the base of the brain that secretes the hormone melatonin

Front 95

What is the role of melatonin?

Back 95

Not clear, but believed to play a role in regulation of circadian rhythms

Front 96

What is renin?

Back 96

Enzyme secreted by kidney; involved in regulation of aldosterone secretion

Front 97

What is erythropoietin?

Back 97

Secreted by the kidney in response to decreased renal oxygen levels; stimulates bone marrow to produce red blood cells

Front 98

What is atrial natriuretic hormone?

Back 98

Heart is an endocrine organ; releases this hormone which is involved in the regulation of salt and water balance

Front 99

What is thymosin?

Back 99

Secreted by thymus; stimulates T lymphocyte development and differentiation

Front 100

What are the three classifications of hormones?

Back 100

1. Peptides
2. Steroids
3. Amino acid derivatives

Front 101

What are the 2 ways in which hormones affect the activities of their target cells?

Back 101

1. Extracellular receptors
2. Intracellular responses

Front 102

Peptide hormones act as:

Back 102

First messengers: their binding to specific receptors on the surface of their target cells triggers a series of enzymatic reactions within each cell --> cascade effect = with each step, the hormone's effects are amplified

Front 103

What are the enzymes responsible for the production and destruction of cyclic AMP?

Back 103

Synthesized by adenylate cyclase (plasma membrane enzyme)
Destroyed/hydrolyzed by phosphodiesterase = cytoplasmic enzyme

Front 104

How are steroid hormones synthesized?

Back 104

Precursors already present in the cell undergo enzymatic reactions that convert them into active hormones; steroid hormones are not stored, but secreted at a rate determined by rate of synthesis

Front 105

What is th mechanism of steroid hormones?

Back 105

Enter their target cells directly and bind to specific receptor proteins in the cytoplasm; receptor-hormone complex enters the nucleus and directly activates the expression of specific genes by binding to receptors on the chromatin; this induces a change in mRNA transcription and protein synthesis

Front 106

What are amino acid derivatives?

Back 106

Hormones composed of one or two modified amino acids; synthesized in the cytoplasm of glandular cells

Front 107

What is the mechanism of amino acid derivatives?

Back 107

Activate target cells via secondary messengers (in most cases)

Front 108

What is the function of the hormone secretin?

Back 108

Secreted by duodenum when acidic chyme enters the small intestine; secretin stimulates the secretion of pancreatic juice, which contains a high concentration of bicarbonate ion and is therefore alkaline enough to neutralize the chyme

Front 109

Steroid hormones bind to receptors in the nucleus and directly regulate:

Back 109

the transcription of mRNA

Front 110

T/F: Hormones must be present in large quantities to have an effect.

Back 110

FALSE; hormones are capable of being effective at picomolar concentrations

Front 111

T/F: K+ is reabsorbed from the glomerular filtrate.

Back 111

FALSE: K+ is considered a waste product and is secreted into the distal convoluted tubule

Front 112

Where is glucose reabsorbed?

Back 112

Proximal convoluted tubule

Front 113

What is acetycholine?

Back 113

Primary neurotransmitter in a parasympathetic nervous response

Front 114

At which end is hydrostatic pressure greater?

Back 114

Arteriolar end - forcing fluids out of vessels

Front 115

At which end is osmotic pressure greater?

Back 115

Venule end - drives fluids back into the vessels

Front 116

T/F: ACh diffuses through the presynaptic membrane after its synthesis.

Back 116

FALSE: AChE degrades ACh very quickly after release in order to prevent constant stimulation of the synapse

Front 117

What is the pathway of estrogen?

Back 117

Since estrogen is derived from cholesterol, it is lipid soluble. Thus, it crosses membranes via simple diffusion - does not require channels

Front 118

T/F: Insulin would require a second messenger to relay its signal.

Back 118

TRUE: Insulin is a peptide hormone. Peptide hormones are unable to cross the plasma membrane and a second messenger is activated to relay the signal to the interior of the cell.