Cobine: The Pituitary and Hypothalamus Flashcards Preview

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Flashcards in Cobine: The Pituitary and Hypothalamus Deck (98):
1

The (blank) is a portion of the brain located just inferior to the thalamus

hypothalamus

2

The pituitary measures ~1 cm in diameter and is located in the (blank)

sella turcica

3

How is the hypothalamus connected to the pituitary?

via the pituitary stalk (infundibulum)

4

The hypothalamus serves many neural functions and plays an important role in connecting the nervous system to the (blank) and regulating (blank)

endocrine system; regulating pituitary function

5

Six hormones released by the hypothalamus

GRHR, GnRH, SS, TRH, DA, CRH

6

Two lobes of the pituitary gland

anterior lobe (adenohypophysis)
posterior lobe (neurohypophysis)

7

During embryo development, the two lobes of the pituitary gland originate from different sources. What does the anterior lobe originate from? The posterior lobe?

anterior: an invagination of the pharyngeal apithelium (Rathke's pouch)
posterior: from a neural tissue outgrowth from the hypothalamus

8

Secretion by the anterior pituitary is controlled by hormones secreted by neurons within the (blank)

hypothalamus

9

Secretion from the posterior pituitary is from (blank) which originate in the hypothalamus and terminate in the posterior lobe.

magnocellular neurons

10

2 major cell types of the anterior pituitary gland

1. acidophils
2. basophils

11

2 major acidophils in the anterior pituitary gland. Which is more abundant, and what do they secrete?

somatotropes (40%) - secrete growth hormone; lactotropes (20%) - secrete prolactin

12

3 major basophils in the anterior pituitary gland. Which is most abundant, and what do they secrete?

1. corticotropes (20%) - secrete adrenocorticotropic hormone (ACTH)
2. thyrotropes (5%) - secrete thyroid stimulating hormone (TSH)
3. gonadotropes (5%) - secrete FSH and LH

13

Three hormone types

1. peptide and protein
2. tyrosine-derived
3. steroid

14

Ex. of peptide/protein hormones

ACTH, ADH, oxytocin

15

Ex. of tyrosine-derived hormones

thyroid hormones, catecholamine hormones

16

Ex. of steroid hormones

glucocorticoids, mineralocorticoids, sex hormones

17

Which type of hormone makes up the majority of hormones?

peptide/protein hormones

18

Peptide and protein hormones are synthesized as (blank) and require (blank)

preprohormones; post-translational processing

19

What is the half life of a typical peptide hormone?

4-170 minutes

20

Steps in protein hormone synthesis

1. formation of preprohormone- chain directed to ER lumen by a signal sequence
2. enzymes chop off signal sequence to generate prohormone
3. prohormones from ER to golgi
4. secretory vesicles with enzymes chop the prohormone into active peptides
5. contents released into extracellular space
6. hormone free in circulation to reach its target

21

What does post-translational modification of AA do to them? Where does it occur?

alters their function and structure; occurs in the ER, Golgi, and secretory vesicles

22

Some examples of post-translational modification

cleavage - removal of AA's, or generating multiple copies of the same hormone
attachment of other biochemical groups (ex: carbohydrates)
changing the chemical nature of the AA
changing the structure (removal of disulfide bridges)
protein folding

23

3 families of anterior pituitary hormones

1. glycoprotein family
2. growth hormone/prolactin family
3. pro-opiomelanocortin family (POMC)

24

3 hormones in the glycoprotein family

1. Thyroid stimulating hormone (TSH)
2. Lutenizing hormone (LH)
3. Follice-stimulating hormone (FH)

25

Glycoproteins have two subunits - what are they? Which is common to all? Which is unique?

alpha and beta; alpha common to all; beta unique

26

What determines the hormone half life of the glycoprotein family hormones?

greater degree of glycosylation

27

3 hormones in the glycoprotein family. What is their target and their major action?
1. Thyroid stimulating hormone
2. Follicle stimulating hormone
3. Lutenizing hormone

1. thyroid gland - increases synthesis of thyroid hormones
2. ovary/testes - increases folliculogenesis and estrogen synthesis in ovaries and sperm maturation in testes
3. ovary/testes - increases ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries and increases testosterone in testes

28

Growth hormone and prolactin are (blank) hormones

polypeptide (190AA's)

29

There are three different forms of prolactin; Which is biologically active?

little, big, and bigbig; little

30

2 hormones in growth hormone/prolactin family. What is their target and their major action?
1. growth hormone
2. prolactin

1. most tissues - growth, IGF-1 production, protein synthesis, decreased glucose utilization, and increased fat utilization
2. mammary glands and hypothalamus - increase milk secretion, growth of mammary glands, decreased GnRH

31

What is unique about growth hormone that sets it apart from other anterior pituitary hormones?

Growth hormone does not function through a target gland - it exerts its effect directly on almost all tissues of the body

32

Growth hormone causes growth of body organs, skeletal grown and increased metabolism. Discuss each.

1. increased size/number of cells in organs
2. increased growth of epiphyseal cartilage, conversion of cartilage to new bone, bone thickening, bone remodeling
3. increased protein synthesis, fat utilization, and glucose production by liver; decreaed protein breakdown, glucose uptake and utilization

33

Some growth effects of GH are mediated by (blank)

insulin-like growth factors (IGFs)

34

Where are IGFs produced? What is their indirect effect? What is the most important IGF?

in liver and at site of action; bone elongation through stimulation of osteoclasts/chondrocytes; somatomedin C

35

How is GH regulated?

Hypothalamus secreted growth hormone releasing hormone (GHRH) and GHIH or somatostatin to inhibit its release. Also IGFs provide feedback regulation and inhibit GHRH and stimulate GHIH

36

Growth hormone releasing hormone (GHRH)
Ghrelin
starvation, protein deficiency
decreased blood glucose or fatty acids
Exercise/Excitement/Trauma
Estrogen & androgens
Sleep

Stimulate GH secretion

37

Somatostatin
obesity
increased blood glucose or blood fatty acids
Aging
Somatomedins (IGFs)
Growth hormone (-ve feedback)

Inhibit GH secretion

38

What is panhypopituitarism?

global underactivity of the pituitary gland - under secretion of growth hormone

39

What are some causes for panhypopituitarism?

pituitary tumors, thrombosis of pituitary vessels, trauma

40

What is the effect of panhypopituitarism?

lethargy, weight gain, loss of sexual function

41

Treatment for panhypopituitarism?

thyroxine, cortisol

42

What are some causes of dwarfism?

congenital defect, pituitary tumor, trauma causing panhypopituitarism, or just GH deficiency

43

Effect of dwarfism?

reduced growth

44

Treatment of dwarfism?

administer human GH, thyroxine, cortisol

45

GH hypersecretion during childhood.

gigantism

46

Cause of gigantism? Effect? Treatment?

hyperactivity of otherwise normal cells, pituitary tumor; rapid growth, hyperglycemia (can lead to Diabetes Mellitus); somatostatin, surgery

47

Two things that excessive growth (gigantism) can cause?

ketosis; insulin resistance

48

Over-secretion of GH

acromegaly

49

Cause of acromegaly?

pituitary tumor AFTER puberty

50

Effect of acromegaly? Treatment?

bones grow in thickness, kyphosis, enlarged organs, diabetes; somatostatin, surgery

51

Members of the POMC family are polypeptide hormone products of the (blank) gene. They are generated as a result of cleavage of POMC by (blank)

POMC; endopeptidases

52

2 hormones in the POMC family. What is their target? What is their major action?
1. ACTH
2. B-lipotropin

1. adrenal cortex - increase synth and secretion of adrenal cortical steroids
2. fat - increase fat mobilization

53

ACTH and β-LPH can be further cleaved into β-endorphins and α-MSH. Under conditions where ACTH levels are increased, α-MSH can be produced and may lead to (blank) of the skin

hyperpigmentation

54

Six hormones released by the hypothalamus? Which are releasing? Which are inhibitory?

CRH
DA - inhibitory
GnRH
GHRH
SS - inhibitory
TRH

55

↑ Synthesis & secretion of thyroid-stimulating hormone (TSH) & prolactin (PRL)

thyrotropin-releasing hormone (TRH)

56

↑ Synthesis & secretion of luteinizing hormone (LH) & follicle-stimulating hormone (FSH)

Gonadotropin-releasing hormone (GnRH)

57

↑ Synthesis & secretion of adrenocorticotrophic hormone (ACTH)

Corticotropin-releasing hormone (CRH)

58

↑ Synthesis & secretion of growth hormone (GH)

Growth hormone-releasing hormone (GHRH)

59

↓ GH secretion

Growth hormone-inhibitory hormone (PHIH; somatostatin)

60

↓ Synthesis & secretion of prolactin (PRL)

Prolactin-inhibiting hormone (PIH)
Also known as dopamine

61

What is unique about the hypothalamic hormone dopamine compared to the other five?

it has an amine structure, instead of a peptide structure

62

Hypothalamic releasing/inhibitory hormones are secreted in the hypothalamus and collect in the (blank); enter the portal system and are conducted to the (blank) where they influence secretion from glandular cells. This is an example of...

median eminence; anterior pituitary
NEUROENDOCRINE REGULATION

63

Several hypothalamic hormones are released in a pulsatile fashion but only pulsatile (blank) release is critical for pituitary (gonadotropin) secretion

GnRH

64

The pulsatile release of GnRH in pituitary portal blood can be measured in the peripheral blood as (blank)

LH

65

Hypothalamus is a (blank) for environmental and sensory information

"collecting center"

66

Three types of feedback loops

1. long loop negative feedback
2. short loop negative feedback
3. ultra-short loop negative feedback

67

Example:
CRH secreted from hypothalmus→
ACTH secreted from anterior pituitary→
Cortisol secreted from adrenal cortex;
Cortisol inhibits ACTH release and CRH release.

long loop negative feedback

68

Example:
CRH secreted from hypothalmus→
ACTH secreted from anterior pituitary;
THEN
ACTH inhibits CRH release.

short loop negative feedback

69

Hypothalamic or pituitary hormones directly regulating the cells that secrete the hormone.
Example:
CRH secreted from hypothalmus;
THEN CRH inhibits further CRH release.

ultra-short loop negative feedback

70

Endocrinopathies are classified as primary, secondary, or tertiary
Primary - at level of (blank)
Secondary - at level of (blank)
Tertiary - at level of (blank)

target organ; pituitary; hypothalamus

71

Hormones of the posterior pituitary are secreted by (blank). The bodies of these neurons are located in the (blank). The hormones are synthesized in the cell bodies and transported down the nerve axons into the posterior pituitary.

neurons; hypothalamus

72

Two hormones of the posterior pituitary

1. ADH
2. oxytocin

73

Origin of oxytocin: magnocellular neurons in the (blank) nuclei

paraventricular

74

Half life of oxytocin? Functions?

2 mins; milk ejection, hastens delivery

75

Origin of ADH: magnocellular neurons in the (blank) nuclei

supraoptic

76

Half life of ADH? When is it secreted?

2 minutes; in response to low blood volume or increased plasma osmolality

77

2 functions of ADH

1. reabsorption of water in collecting tubules (V2 receptor --> cAMP --> increased aquaporins)
2. vascular smooth muscle contraction (V1 receptor --> IP3, DAG --> [Ca+])

78

Two pathophysiologies of ADH secretion

1. diabetes insipidus
2. SIADH

79

Problem: Unable to conserve water due to ↓ADH synthesis (central DI) or insensitivity to ADH at the collecting ducts (nephrogenic DI)
Causes: trauma, tumors, infection (e.g. meningitis)
Principle symptoms: ↑water loss from kidneys (polyuria) triggers ↑ thirst (polydipsia)

diabetes insipidus

80

Increased water retention, atria of heart stretched, increased ANF, sodium loss, hyponatremia, concentrated urine

SIADH

81

ADH secreted from lung cancer
Stroke, infection

Causes of SIADH

82

asymptomatic during early stages especially if serum sodium falls slowly. Rapid fall associated with confusion, drowsiness, convulsions, coma and death.

symptoms of SIADH

83

Damage from malnutrition (e.g. anorexia, bulimia),
Genetic disorders,
Radiation,
Surgery,
Head trauma,
Lesion,
Tumor,
Other physical injury to the hypothalamus.

causes of hypothalamic disease

84

disruptions in:
Body temperature regulation,
Growth,
Weight,
Sodium and water balance,
Milk production,
Emotions,
Sleep cycles.

effects of hypothalamic disease

85

Usually benign adenomas
May produce excess hormone or restrict activity of the pituitary to lessen hormone production

pituitary gland tumors

86

Most common pituitary gland tumor

prolactinomas

87

What causes this?
Polyuria and polydipsia

ADH deficiency

88

What causes this?
Hypogonadism

gonadotropin deficiency

89

What causes this?
Adrenal insufficiency

ACTH deficiency

90

What causes this?
hypothyroidism

TSH deficiency

91

What causes this?
Failure to thrive, short stature, fatigue, weakness, decreased QOL

GH deficiency

92

Increased prolactin, increased milk production, decreased reproductive function

prolactinomas

93

increased GH, increased bone growth, acromegaly or gigantism

somatotrophic adenomas

94

increased ACTH and cortisol

corticotrophic adenomas

95

decreased LH/FSH

gonadotrophic adenomas

96

rarest adenomas

thyrotrophic adenomas

97

Hormones of the posterior pituitary are not synthesized there, they are stored there, and they are NOT secreted by the pituicytes, but by NEURONS.

Yep

98

Oxytocin is NOT the physiological trigger for parturition

Nope, it's not