Chapter 18 Flashcards Preview

Biology 235 > Chapter 18 > Flashcards

Flashcards in Chapter 18 Deck (127):
1

hormone

a mediator molecule that is released in one part of the body but regulates the activity of cells in other parts of the body; most enter the bloodstream; bind to receptors on or in the target cells

2

exocrine gland

secrete products into ducts that carry the secretions into body cavities, into the lumen of an organ, or to the outer surface of the body; i.e. sudoriferous (sweat), sebaceous (oil), mucous and digestive glands

3

endocrine glands

secrete their products (hormones) into interstitial fluid surrounding the secretory cells rather than into ducts, from the interstitial fluid, hormones diffuse into the blood which carries the hormones to the target cells

4

receptors

protein that only specifically recognize and bind to one hormone

5

down regulation

if a hormone is present in excess, the number of target cell receptors may decrease; makes target cell less sensitive to the hormone

6

up regulation

when a hormone is deficient, the number of target cell receptors may increase; makes target cell more sensitive to a hormone

7

circulating hormones

most endocrine hormones; pass from secretory cells that make them into interstitial fluid and into the blood

8

local hormone

act locally on neighbouring cells or on the same cell that secreted them without first entering the blood stream

9

paracrine

local hormones that act on neighbouring cells

10

autocrine

local hormones that act on the same cell that secreted them

11

lipid soluble hormones

soluble in lipids; include steroid hormones, thyroid hormones and nitric oxide

12

steroid hormone

derived from cholesterol; each is unique due to the presence of different chemical groups attached at various sites on the four rings at the core of its structure (allows for different function)

13

thyroid hormones

synthesized by attaching iodine to the amino acid tyrosine

14

nitric oxide

gas; both a hormone and a neurotransmitter

15

water soluble hormones

soluble in water; include amine hormones, peptide and protein hormones and eicosanoid hormones

16

amine hormones

synthesized by removing a molecule of CO2

17

peptide and protein hormones

amino acid polymers

18

glycoprotein hormones

protein hormones with attached carbohydrate groups ; i.e. thyroid stimulating hormone

19

eicosanoid hormones

derived from arachidonic acid (20 C fatty acid)

20

prostaglandins and leukotrienes

two types of eicosanoid hormones

21

3 functions of transport proteins

1. make lipid soluble hormones temporarily water soluble (increasing solubility in blood)
2. they retard passage of small hormone molecules through the filtering mechanism in the kidneys (slowing the rate of hormone loss in the urine)
3. provide a ready reserve of hormone (already ready in the bloodstream)

22

free fraction

0.1-10% of the molecules of a lipid soluble hormone are not bound to a transport protein

23

Action of Lipid-Soluble Hormones

1. A free lipid-soluble hormone molecule diffuses from the blood, through interstitial fluid, and through the lipid bilayer of the plasma membrane into a cell.
2. If the cell is a target cell, the hormone binds to and activates receptors located within the cytosol or nucleus. The activated receptor–hormone complex then alters gene expression: It turns specific genes of the nuclear DNA on or off.
3. As the DNA is transcribed, new messenger RNA (mRNA) forms, leaves the nucleus, and enters the cytosol. There, it directs synthesis of a new protein, often an enzyme, on the ribosomes.
4. The new proteins alter the cell’s activity and cause the responses typical of that hormone.

24

Action of Water Soluble Hormones

1. A water-soluble hormone (the first messenger) diffuses from the blood through interstitial fluid and then binds to its receptor at the exterior surface of a target cell’s plasma membrane. The hormone–receptor complex activates a membrane protein called a G protein. The activated G protein in turn activates adenylate cyclase.
2. Adenylate cyclase converts ATP into cyclic AMP (cAMP). Because the enzyme’s active site is on the inner surface of the plasma membrane, this reaction occurs in the cytosol of the cell.
3. Cyclic AMP (the second messenger) activates one or more protein kinases, which may be free in the cytosol or bound to the plasma membrane. A protein kinase is an enzyme that phosphorylates (adds a phosphate group to) other cellular proteins (such as enzymes). The donor of the phosphate group is ATP, which is converted to ADP.
4. Activated protein kinases phosphorylate one or more cellular proteins. Phosphorylation activates some of these proteins and inactivates others, rather like turning a switch on or off.
5. Phosphorylated proteins in turn cause reactions that produce physiological responses. Different protein kinases exist within different target cells and within different organelles of the same target cell. Thus, one protein kinase might trigger glycogen synthesis, a second might cause the breakdown of triglyceride, a third may promote protein synthesis, and so forth. As noted in step 4 , phosphorylation by a protein kinase can also inhibit certain proteins. For example, some of the kinases unleashed when epinephrine binds to liver cells inactivate an enzyme needed for glycogen synthesis.
6. After a brief period, an enzyme called phosphodiesterase inactivates cAMP. Thus, the cell’s re- sponse is turned off unless new hormone molecules continue to bind to their receptors in the plasma membrane

25

first messenger

when a water soluble hormone binds to its receptor at the outer surface of the plasma membrane, it acts as the first messenger

26

second messenger

the first messenger (the hormone) then causes the production of a second messenger inside the cell, where hormone specific stimulated responses take place

27

cyclic AMP (cAMP)

common second messenger

28

G protein

a membrane protein that activates edentate cyclase

29

adenylate cyclase

converts ATP into cyclic AMP

30

permissive effect

the actions of some hormones on target cells require a simultaneous or recent exposure to a second hormone (second hormone is said to have a permissive effect)

31

synergistic effect

when the effect f two hormones acting together is greater or more extensive than the effect of each hormone acting alone, the two hormones are said to have a synergistic effect

32

antagonistic effect

when one hormone opposes the actions of another hormone, the two hormones are said to have antagonistic effects

33

3 factors that affect responsiveness of a target cell to a hormone

1. the hormone's concentration in the blood
2. the abundance of target cell's hormone receptors
3. influences exerted by other hormones

34

control of hormone secretion (3 factors)

1. signals from the nervous system
2. chemical changes in the blood
3. other hormones

35

pituitary gland (hypophysis)

"master" endocrine gland since it secretes several hormones that control other endocrine glands

36

hypothalamus

master of the pituitary gland

37

infundibulum

a stalk that attaches the hypothalamus to the pituitary gland

38

anterior pituitary or anterior lobe or adenohypophysis

composed of epitelial tissue; consists of 2 parts: the pars distalis (larger portion) and the pars tuberalis (forms a sheath around the infundibulum)

39

releasing hormones

stimulates release of anterior pituitary hormones

40

inhibiting hormones

suppresses release of anterior pituitary hormones; from the hypothalamus

41

hypophyseal portal system

blood flows from capillaries int he hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary

42

neurosecretory cells

clusters of specialized neurons above the optic chiasm

43

human growth hormone (hGH) or somatotropin

stimulates several tissues to secrete insulinlike growth factors (hormones that stimulate general body growth and regulate aspects of the metabolism

44

thyroid-stimulating hormone (TSH) or thyrotropin

controls the secretions and other activities of the thyroid gland

45

follicle-stimulating hormone (FSH)

secreted by gonadotrophs; stimulate secretion of estrogens and progesterone and the maturation of oocytes in the ovaries and they stimulate sperm production and secretion of testosterone in the testes

46

Luteinizing hormone (LH)

secreted by gonadotrophs; stimulate secretion of estrogens and progesterone and the maturation of oocytes in the ovaries and they stimulate sperm production and secretion of testosterone in the testes

47

Growth Hormone Releasing Hormone (GHRH)

promotes secretion of human growth hormone

48

Growth Hormone Inhibiting Hormone (GHIH)

suppresses secretion of human growth hormone

49

Thyrotropin Releasing Hormone (TRH)

from the hypothalamus; controls TSH secretion

50

gonadotropins

secreted by gonadotrophs; FSH and LH

51

Gonadotropin Releasing Hormone (GnRH)

controls secretion of LH and FSH

52

Prolactin (PRL)

initiates and maintains milk production by the mammary glands; by itself only has a weak effect

53

Prolactin Inhibiting Hormone (PIH)

dopamine in females; inhibits the release of prolactin from the anterior pituitary most of the time

54

Prolactin Releasing Hormone (PRH)

promotes release of prolactin

55

adrenocorticotropic hormone (ACTH) or corticotropin

controls production and secretion of cortisol and other glucocorticoids by the cortex of the adrenal glands

56

Corticotropin Releasing Hormone (CRH)

stimulates secretion of ACTH by corticotrophs

57

Melanocyte Stimulating Hormone (MSH)

increases skin pigmentation in amphibians by stimulating the dispersion of melanin granules in melanocytes; Exact role in humans is unknown but may influence brain activity; when present in excess, can cause darkening of skin.

58

posterior pituitary or neurohypophysis

does not synthesize hormones; it does store and release 2 hormones

59

pituicytes

specialized neuroglia that are associated with the axon terminals in the posterior pituitary

60

hypothalamohypophyseal tract

this tract begins in the hypothalamus and ends near blood capillaries in the posterior pituitary

61

oxytocin (OT)

two target tissues: mother's uterus and breasts; stretching of cervix of uterus stimulates the release of OT which enhances contraction of smooth muscle cells in the wall of the uterus; after delivery: stimulates mammary glands to release milk in response to the sucking by an infant

62

Antidiuretic (ADH)

substance that decreases urine production; causes kidneys to return more water to the blood, decreasing urine volume

63

thyroid gland

butterfly shaped

64

lateral lobes

2 sides of the thyroid gland (either side of the trachea)

65

isthmus

narrow passage anterior to the trachea that connects the lateral lobes

66

thyroid follicles

microscopic spherical sacs that make up most of the thyroid gland

67

follicular cells

secrete thyroid hormones;

68

thyroxine or tetraiodothyronine or T4 and Triiodothyronine T3

secretion is increased by TRH which stimulates TSH; high iodine levels suppresses T4; Increase basal metabolic rate; stimulate synthesis of proteins; increase use of glucose and fatty acids for ATP production; increase lipolysis; enhance cholesterol excretion; accelerate body growth; contribute to development of nervous system

69

parafollicular cells or C cells

produce calcitonin (CT)

70

Calcitonin

decrease the calcium level in the blood by inhibiting the action of osteoclasts (the cells that break down bone EM); controlled by negative feedback system

71

thyroglobulin (TGB)

T3 and T4 combine with transport proteins in the blood (mainly TGB)

72

Basal Metabolic Rate (BMR)

increased by thyroid hormone; the rate of oxygen consumption under standard (basal) conditions by stimulating the use of cellular oxygen to produce ATP

73

calorigenic effect

As cells produce and use more ATP, more heat is given off and body temperature rises

74

Control of Thyroid Hormone Secretion

1. Low blood levels of T3 and T4 or low metabolic rate stimulates the hypothalamus to secrete TRH.
2. TRH enters the hypophyseal portal veins and flows to the ante- rior pituitary, where it stimulates thyrotrophs to secrete TSH.
3. TSH stimulates virtually all aspects of thyroid follicular cell activity, including iodide trapping (1 in Figure 18.11), hormone synthesis and secretion (2 and 7 in Figure 18.11), and growth of the follicular cells.
4. The thyroid follicular cells release T3 and T4 into the blood until the metabolic rate returns to normal.
5. An elevated level of T3 inhibits release of TRH and TSH (negative feedback inhibition).

75

parathyroid glands

round masses of tissue partially embedded in the posterior surface of the lateral lobes of the thyroid gland

76

chief (principal) cells

most numerous cells in the parathyroid hormones; produce PTH

77

parathyroid hormone (PTH) or parathormone

major regulator of levels of calcium, magnesium and phosphate; increase the number and activity of osteoclasts; result: elevated bone resorption which releases ionic calcium and phosphates

78

calcitrol

stimulates increased absorption of Ca2+ from foods in the GI tract which helps increase the blood level of Ca2+

79

adrenal glands or suprarenal glands

superior to each kidney

80

adrenal cortex (3 zones)

zona glomerulosa, zona fasciculata and zona reticularis

81

mineralocorticoids

hormone that affects bone homeostasis; secreted by the zone glomerulosa

82

aldosterone

major mineralcorticoid; regulates homeostasis of 2 mineral ions (sodium and potassium ions); helps adjust blood pressure and volume; promotes excretion of H+ in urine and removal of acids from the body

83

renin-angiotensin-aldosterone (RAA) pathway

controls secretion of aldosterone

84

renin

enzyme that is secreted by certain cells of the kidneys when stimulated by lowered BP

85

angiotensinogen

plasma protein produced by the liver; renin converts angiotensinogen into angiotensin I

86

glucocorticoids

regulate metabolism and resistance to stress: includes cortisol, corticosterone and cortisone; control of glucocorticoid secretion involves corticotropin releasing hormone (CRH)

87

androgens

secreted by adrenal cortex; includes DHEA, testosterone and estrogen

88

adrenal medulla

the inner region of the adrenal gland; modified sympathetic ganglion of the autonomic nervous system

89

chrommaffin cells

hormone producing cells int he adrenal medulla

90

epinephrine and norepinephrine (NE)

synthesized by adrenal medulla; adrenaline and noradrenaline; fight or flight response

91

pancreas

both an endocrine and exocrine gland

92

acini

clusters of exocrine cells of the pancreas

93

pancreatic islets or islets of Langerhans

clusters of endocrine tissue; 4 types: A cells, B cells, D cells and F cells

94

alpha or A cells

17% of pancreatic islet cells and secrete glucagon

95

Beta or B cells

constitue 70% of pancreatic islet cells; secrete insulin

96

Delta or D cells

constitute about 7% of pancreatic islet cells; secrete somatostatin

97

F cells

remainder of pancreatic islet cells; secrete pancreatic polypeptide

98

regulation of insulin and glucagon secretion

The principal action of glucagon is to increase blood glucose level when it falls below normal. Insulin, on the other hand, helps lower blood glucose level when it is too high. The level of blood glucose controls secretion of glucagon and insulin via negative feedback

99

ovaries

paired oval bodies located int he female pelvic cavity; produce steroid hormones: estrogens and progesterone

100

estrogen and progesterone

Together with gonadotropic hormones of anterior pituitary, regulate female reproductive cycle and oogenesis, maintain pregnancy, prepare mammary glands for lactation, and promote development and maintenance of female secondary sex characteristics

101

inhibin

Inhibits secretion of FSH from anterior pituitary.

102

relaxin

Increases flexibility of pubic symphysis during pregnancy; helps dilate uterine cervix during labor and delivery.

103

testosterone

Stimulates descent of testes before birth; regulates spermatogenesis; promotes development and maintenance of male secondary sex characteristics

104

inhibin

Inhibits secretion of FSH from anterior pituitary.

105

pineal gland

small endocrine gland attached to the roof of the third ventricle of the brain at the midline; consists of neuroglia and secretory cells called pinealocytes

106

pinealocytes

secretory cells of the pineal gland; secretes melatonin

107

thymus

located behind the sternum between the lungs

108

thymosin, thymic humoral factor, thymic factor and thymopoietin

hormones produced by the thymus; promote maturation of T cells (a type of white blood cell that destroys microbes and foreign substances) and may retard the aging process

109

eicosanoids

2 families: prostaglandins (PG) and leukotrienes (LT); found in virtually all body cells except RBC, where they act as local hormones

110

growth factors

play important roles in tissue development, growth and repair

111

stress and the general adaptation syndrome

sequence of bodily changes resulting from a variety of stressful situations

112

resistance reaction

second stage of stress response

113

exhaustion

Prolonged exposure to high levels of cortisol and other hormones involved in the resistance reaction causes wasting of muscle, suppression of the immune system, ulceration of the gas- trointestinal tract, and failure of pancreatic beta cells.

114

stress and disease

Although the exact role of stress in human diseases is not known, it is clear that stress can lead to particular diseases by temporarily inhibiting certain components of the immune system. Stress related disorders include gastritis, ulcerative colitis, irritable bowel syndrome, hypertension, asthma, rheumatoid arthritis (RA), migraine headaches, anxiety, and depression. People under stress are at a greater risk of developing chronic disease or dying prematurely.

115

pituitary dwarfism

hypo secretion of hGH during growth years slows bone growth and the epiphyseal plate close before normal height is reached

116

giantism

hyper secretion of hGH during childhood; an abnormal increase in the length of long bones

117

acromegaly

hyper secretion of hGH during adulthood; Although hGH cannot produce further lengthening of the long bones because the epiphyseal plates are already closed, the bones of the hands, feet, cheeks, and jaws thicken and other tissues enlarge. In addition, the eyelids, lips, tongue, and nose enlarge, and the skin thickens and develops furrows, especially on the forehead and soles

118

diabetes insipidus

disfunction of posterior pituitary; due to defects in ADH receptors or an inability to secrete ADH

119

congenital hypothyroidism

hypo secretion of the thyroid hormones that is present at birth; causes severe mental retardation and stunted bone growth

120

myxedema

hypothyroidism during the adult years; symptom: is edema (accumulation of interstitial fluid) that makes the facial tissues swell and look puffy

121

graves disease

most common hyperthyroidism; occurs more in females than males; autoimmune disorder in which the person produces antibodies that mimic the action of TSH, so the antibodies continually stimulate the thyroid; symptom: enlarged thyroid

122

goiter

an enlarged thyroid; associated with hyperothyrodism, hypothyroidism and eurothyroidism (normal secretion of thyroid hormone)

123

cushing's syndrome

hyper secretion of cortisol by the adrenal cortex; can be caused a tutor; causes breakdown of muscle proteins and redistribution of body fat resulting in spindly arms and legs, a round face and a hump on the back

124

Addison's disease

cause: hypo secretion of glucocorticoid and aldosterone
symptoms: mental lethargy, anorexia, nausea and vomiting, weight loss

125

diabetes mellitus

most common endocrine disorder
cause: an inability to produce or use insulin
symptom: excessive urine production, excessive thirst and excessive eating

126

hypoglycemia

decreased blood glucose level because the excess insulin stimulates too much uptake of glucose by body cells (symptom of hyperinsulism- too much insulin injected)

127

hyperglycemia

increased blood glucose levels