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nrp511 > Mechanism of Hormone Regulation > Flashcards

Mechanism of Hormone Regulation Flashcards

1
Q

Five Functions of the Endocrine System

A
  1. Differentiate reproductive and CNS during fetus development
  2. Coordinate male and female reproductive systems
  3. Stimulate growth and development during children and teens
  4. Maintained optimal internal environment
  5. Initiate corrective responses when emergency demand occurs
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2
Q

Hypothalamic-pituitary- target glands axis

A

forms the structural and functional basis for central integration of the neurologic and endocrine systems, creating what is called the neuroendocrine system

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3
Q

Hormone release is regulated by one or more of the following mechanism

A

(1) chemical factors (i.e., blood glucose or calcium levels)

(2) endocrine factors (a hormone from one endocrine gland controlling another endocrine gland)

(3) neural control.

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4
Q

An example of chemical regulation

A

insulin is secreted following chemical stimulation by increased plasma glucose levels

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5
Q

An example of endocrine regulation

A

Cortisol from the adrenal cortex regulates and stimulates insulin secretion from beta cells within the pancreas.

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6
Q

An example of neural control

A

The autonomic nervous system directly stimulates the insulin-secreting cells of the pancreas

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7
Q

Negative feedback

A

most common
a decrease in the production of hormones as s result of a signal from another hormone

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8
Q

Positive Feedback

A

occurs when a neural, chemical, or endocrine response increases the synthesis and secretion of a hormone

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9
Q

The protein (peptide) hormones

A

are water soluble

generally circulate in free (unbound) forms

have a short half-life of seconds to minutes because they are catabolized by circulating enzymes.
e.g. insulin

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10
Q

Lipid-soluble hormones

A

are transported bound to a carrier protein and can remain in the blood for hours to days.
e.g. cortisol

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11
Q

Hormone receptors of the target cell have two main functions:

A

(1) to recognize and bind with high affinity to their particular hormones

(2) to initiate a signal to appropriate intracellular effectors

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12
Q

upregulation

A

Low concentrations of hormone increase the number of receptors per cell

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13
Q

downregulation

A

high concentrations of hormone decrease the number or affinity of receptors

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14
Q

Water-soluble hormones

A

are proteins that are polarized with a high molecular weight

cannot diffuse across the lipid layer of the cell (plasma) membrane

interact or bind with receptors in or on the cell membrane and activate a second messenger to mediate short-acting responses

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15
Q

lipid-soluble steroids

A

diffuse freely across the plasma and nuclear membranes and bind the cytosolic or nuclear receptors

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16
Q

first messenger

A

Water-soluble hormone binding with the plasma membrane receptor initiates a complex cascade of intracellular effects

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17
Q

second messenger

A

conveys the signal from the receptor to the cytoplasm and nucleus of the cell and mediates the effect of the hormone on the target cell

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18
Q

Second messengers include

A

1) cyclic adenosine monophosphate (cAMP)

(2) cyclic guanosine monophosphate (cGMP), calcium

(3) inositol triphosphate (IP3) and membrane-associated diacylglycerol (DAG)

(4) the tyrosine kinase system

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19
Q

lipid-soluble hormones

A

synthesized from cholesterol

include glucocorticoids, androgens, estrogens, progestins, mineralocorticoids, vitamin D, and retinoid

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20
Q

steroid hormones can cross the plasma and nuclear membranes by simple diffusion because

A

they are relatively small, nonpolar, lipophilic, hydrophobic molecules

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21
Q

The binding of hormones with their receptors stimulates three general types of effects by:

A
  1. Acting on preexisting channel-forming proteins to alter membrane channel permeability
  2. Activating preexisting proteins through a second-messenger system
  3. Activating genes to cause protein synthesis
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22
Q

Direct effects

A

obvious changes in cell function that specifically result from stimulation by a particular hormone
e.g. insulin has a direct effect on skeletal muscle cells, causing increased glucose transport into these cells

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23
Q

Permissive effects

A

less obvious hormone-induced changes that facilitate the maximal response or functioning of a cell
e.g. insulin has a permissive effect on mammary cells, facilitating their response to the direct effects of prolactin

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24
Q

hypothalamic-pituitary axis (HPA)

A

forms the structural and functional basis for the central integration of the neurologic and endocrine systems

produces a number of releasing/inhibitory hormones and tropic hormones that affect a number of diverse body functions

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25
Q

Hypothalamus

A

contains special neurosecretory cells that can synthesize and secrete the hypothalamic-releasing hormones that regulate the release of hormones from the anterior pituitary

synthesize the hormones ADH and oxytocin that are then stored and released from the posterior pituitary gland.

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26
Q

HYPOTHALAMIC HORMONES (HYPOPHYSIOTROPIC HORMONES)

A
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27
Q

The Anterior Pituitary

A

accounts for 75% of the total weight of the pituitary gland

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28
Q

Name the three parts of the anterior pituitary gland

A

(1) the pars distalis: major component of the anterior pituitary and the source of the anterior pituitary hormones

(2) the pars tuberalis: a thin layer of cells on the anterior and lateral portions of the pituitary stalk.

(3) the pars intermedia: lies between the two

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29
Q

The anterior pituitary is composed of two main cell types:

A

(1) the chromophobes, which appear to be nonsecretory

(2) the chromophils, which are considered the secretory cells of the adenohypophysis.

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30
Q

Tropic hormones

A

affect the the physiologic function of specific target organs

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31
Q

What are the 3 categories of tropic hormones

A
  1. corticotropin-related hormones (adrenocorticotropic hormone [ACTH] and melanocyte-stimulating hormone [MSH])
  2. glycoproteins (luteinizing hormone [LH], follicle-stimulating hormone [FSH], and thyroid-stimulating hormone [TSH])
  3. somatotropins (growth hormone [GH] and prolactin)
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32
Q

Melanocyte-stimulating hormone (MSH)

A

promotes the pituitary secretion of melanin, which darkens skin color

Corticotropin related hormone

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33
Q

follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

A

influence reproductive function

are glycoproteins

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34
Q

Adrenocorticotropic hormone (ACTH)

A

regulates the release of cortisol from the adrenal cortex

Corticotropin related hormone

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35
Q

Growth hormone (GH)

A

GH is essential to normal tissue growth and maturation

peaks during adolescence

GH also impacts aging, sleep, nutritional status, stress, and reproductive hormones

In the bone, GH stimulates epiphyseal growth and increases osteoclast and osteoblast activity, resulting in increased bone mass

GH also increases amino acid transport in muscles.

Other functions of GH include lipolysis and enhancement of hepatic protein synthesis.

36
Q

Prolactin

A

functions to induce milk production during pregnancy and lactation

It has immune stimulatory effects and modulates immune and inflammatory responses with both physiologic and pathologic reactions.

37
Q

posterior pituitary (neurohypophysis)

A

secretes two polypeptide hormones: (1) ADH, also called arginine-vasopressin; and (2) oxytocin

38
Q

Name the three parts of the posterior pituitary

A

(1) median eminence -contains at least 10 biologically active hypothalamic-releasing hormones, as well as the neurotransmitters dopamine, norepinephrine, serotonin, acetylcholine, and histamine

(2) pituitary stalk - secretes the hormones of the posterior pituitary

(3) the infundibular process, also known as the pars nervosa or neural lobe.

39
Q

ADH

A

Antidiuretic Hormone- acts on the vasopressin 2 (V2) receptors of the renal tubular cells to increase their permeability.

Increased permeability leads to increased water reabsorption into the blood, thus concentrating the urine and reducing serum osmolality.

These effects may be inhibited by hypercalcemia, prostaglandin E, and hypokalemia.

40
Q

Oxytocin

A

contraction of the uterus and milk ejection in lactating women

may affect sperm motility in men

functions near the end of labor to enhance the effectiveness of contractions, promote the delivery of the placenta, and stimulate postpartum uterine contractions, thereby preventing excessive bleeding

41
Q

Pineal Gland

A

secretes melatonin

42
Q

Melatonin

A

is stimulated by exposure to dark and inhibited by light exposure

regulates circadian rhythms and reproductive systems, including the secretion of gonadotropin-releasing hormones and the onset of puberty

increases nitric oxide release from blood vessels, removing toxic oxygen free radicals, and decreasing insulin secretion

Melatonin has been used therapeutically in humans to help with sleep disturbances, jet lag, and inflammatory and psychological disorders.

43
Q

Thyroid Gland

A

produces hormones that control the rates of metabolic processes throughout the body

consists of follicles that contain follicular cells surrounding a viscous substance called colloid

normally produces 90% T4 and 10% T3

a 2 month’s supply of thyroid hormone is stored in this gland

44
Q

follicular cells

A

synthesize and secrete thyroid hormone

45
Q

Thyroid hormone (TH)

A

is regulated through a negative-feedback loop involving the hypothalamus, the anterior pituitary, and the thyroid gland

46
Q

Thyroid-stimulating hormone (TSH)

A

glycoprotein hormone synthesized and stored within the anterior pituitary.

47
Q

Effects of TSH

A

(1) an immediate increase in the release of stored thyroid hormones
(2) an increase in iodide uptake and oxidation,
(3) an increase in thyroid hormone synthesis
(4) an increase in the synthesis and secretion of prostaglandins by the thyroid.

48
Q

Effects of TH

A

essential for normal growth and neurologic development in the fetus and infant and affects metabolic, neurologic, cardiovascular, and respiratory functioning across the lifespan

is required for the metabolism and function of blood cells, as well as normal muscle functioning and the integrity of skin, nails, and hair

affect cell metabolism by altering protein, fat, and glucose metabolism, and, as a result, heat production and oxygen consumption are increased.

49
Q

Parathyroid Glands

A

produce parathyroid hormone (PTH), which is the single most important factor in the regulation of serum calcium concentration

50
Q

Parathyroid Hormone (PTH)

A

increases serum calcium concentration and decreases the concentration of serum phosphate by stimulating the mechanism of breaking down bone to increase serum calcium

at a low dose, it stimulates bone formation

acts on the kidney to increase calcium reabsorption while phosphate reabsorption is decreased

51
Q

Pancreas

A

the endocrine gland that produces hormones and an exocrine gland that produces digestive enzymes

houses the islets of Langerhans

52
Q

What 4 hormone-secreting cells are found in the islets of Langerhans?

A

alpha cells, which secrete glucagon

beta cells, which secrete insulin and amylin

delta cells, which secrete gastrin and somatostatin

F (or PP) cells, which secrete pancreatic polypeptide that stimulates gastric secretion and antagonizes cholecystokinin.

53
Q

Insulin

A

an anabolic hormone that promotes glucose uptake primarily in the liver, muscle, and adipose tissue

54
Q

Secretion of insulin is regulated by

A

chemical, hormonal, and neural control.

55
Q

Factors influencing insulin secretion

A

when the beta cells are stimulated by the parasympathetic nervous system, usually before eating a meal

increased blood levels of glucose, amino acids (leucine, arginine, and lysine), and gastrointestinal hormones (glucagon, gastrin, cholecystokinin, secretin)

56
Q

Insulin secretion decreases

A

in response to low blood levels of glucose (hypoglycemia)

in response to high levels of insulin (through negative feedback to the beta cells)

in response to sympathetic stimulation of the beta cells in the islets

in the presence of prostaglandins

57
Q

Insulin sensitivity

A

is affected by age, weight, abdominal fat, and physical activity

58
Q

Amylin

A

peptide hormone cosecreted with insulin by beta cells in response to nutrient stimuli

It regulates blood glucose concentration by delaying gastric emptying and suppressing glucagon secretion after meals.

Amylin also has a satiety effect which reduces food intake

59
Q

Glucagon

A

is an antagonist to insulin and acts to increase blood glucose during fasting, exercise, and hypoglycemia

acts primarily in the liver to increase blood glucose concentration by stimulating glycogenolysis

60
Q

How does glucagon work

A

High glucose levels cause glucagon release to be inhibited

low glucose levels and sympathetic stimulation promote glucagon release

61
Q

Pancreatic Somatostatin

A

a hormone essential in carbohydrate, fat, and protein metabolism

is involved in regulating alpha-cell and beta-cell function within the islets by inhibiting the secretion of insulin, glucagon, and pancreatic polypeptide.

62
Q

Incretins

A

control post meal glucose levels by promoting glucose-dependent insulin secretion, inhibiting glucagon synthesis, promoting hepatic glucose secretion, and delaying gastric emptying

63
Q

Gastrin

A

stimulates the secretion of gastric acid.

64
Q

Ghrelin

A

intestinal hormone

stimulates GH secretion, controls appetite, and plays a role in obesity and the regulation of insulin sensitivity and glucose tolerance

65
Q

Pancreatic polypeptide

A

promotes gastric secretion, antagonizes cholecystokinin, and is frequently increased in pancreatic tumors and in diabetes.

66
Q

The adrenal cortex is made up of

A
  1. The zona glomerulosa, the outer layer, constitutes about 15% of the cortex and primarily produces the mineralocorticoid aldosterone
  2. The zona fasciculata, the middle layer, constitutes 78% of the cortex and secretes the glucocorticoids cortisol, cortisone, and corticosterone.
  3. The zona reticularis, the inner layer, constitutes 7% of the cortex and secretes mineralocorticoids (aldosterone), adrenal androgens and estrogens, and glucocorticoids.
67
Q

glucocorticoids

A

have metabolic, neurologic, anti-inflammatory, immunosuppressive, and growth-suppressing effects

are released under stress

68
Q

how do glucocorticoids work

A

increase blood glucose concentration by promoting gluconeogenesis in the liver

conserving glucose by decreasing the uptake of glucose into muscle cells, adipose cells, and lymphatic cells by antagonizing insulin

results in increased glucose for the brain during stress.

69
Q

effects of glucocorticoids

A

depression of cellular immunity than humoral immunity

decrease immune and inflammatory responses by decreasing natural killer cell activity

suppress the synthesis, secretion, and actions of chemical mediators involved in inflammatory and immune responses, including histamine

70
Q

glucocorticoids cause poor wound healing and increase chances for infection by

A

suppression of innate and adaptive immunity

71
Q

Name 3 additional effects of glucocorticoids

A

inhibition of bone formation

inhibition of ADH secretion

stimulation of gastric acid secretion

72
Q

cortisol

A

most potent of the naturally occurring glucocorticoids

main secretory product of the adrenal cortex

is needed to maintain life and regulate the body during both positive and negative stress

73
Q

cortisol secretion is regulated primarily by

A

the hypothalamus and the anterior pituitary gland

74
Q

3 factors that regulate ACTH

A

(1) negative feedback effects of high circulating levels of cortisol and synthetic glucocorticoids suppress both CRH and ACTH, whereas low cortisol levels stimulate their secretion

(2) diurnal rhythms affect ACTH and cortisol levels (ACTH peaks 3 to 5 hours after sleep begins and declines throughout the day. Cortisol levels peak just before awakening)

(3) psychologic and physiologic stress increases ACTH secretion, leading to increased cortisol levels

75
Q

Mineralocorticoid

A

directly affect ion transport by epithelial cells, causing sodium retention and potassium and hydrogen loss

76
Q

Aldosterone

A

most potent of the naturally occurring mineralocorticoids

acts to conserve sodium by increasing the activity of the sodium pump of the epithelial cells in the nephron

is degraded in the liver and is excreted by the kidney.

77
Q

renin-angiotensin-aldosterone system

A

regulates synthesis and secretion of aldosterone

activated by sodium and water depletion, increased potassium levels, and a diminished effective blood volume

78
Q

Adrenal Medulla

A

store and secrete the catecholamines epinephrine (adrenaline) and norepinephrine

79
Q

Catecholamines

A

epinephrine (adrenaline) and norepinephrine

Their release and the body’s response is the “fight or flight” response

80
Q

Radioimmunoassay (RIA),

A

uses antibodies and radiolabeled hormones to determine the quantity of hormone in the plasma.

81
Q

Enzyme-linked immunosorbent assay (ELISA)

A

used to determine circulating hormone levels

82
Q

bioassay

A

involves the use of graded doses of hormone in a reference preparation and then comparison of the results with an unknown sample

83
Q

Endocrine changes that may be associated with aging include

A

altered biologic activity of hormones

altered circulating levels of hormones

altered secretory responses of endocrine glands

altered metabolism of hormones

loss of circadian control of hormone release

changes in the secretion of hypothalamic regulatory hormones.

84
Q

atrophy of the thyroid gland

A

is associated with infiltrative glandular changes

secretion of thyroid hormones may diminish with age

85
Q

Klotho proteins

A

The kidney, choroid plexus, and parathyroid gland secrete this, which has antiaging effects

86
Q

These decrease with aging, leading to decreased bone and muscle mass.

A

Growth hormone levels

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