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chapter 18 endocrine system > 18.6 hypothalamus & pituitary gland > Flashcards

18.6 hypothalamus & pituitary gland Flashcards

1
Q

What is the endocrine gland that secretes several hormones that control other endocrine glands? (the “master”)

A

pituitary gland (also known as hypophysis)

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2
Q

What is the pituitary gland’s master?

A

the hypothalumus

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3
Q

Cells in the hypothalamus synthesize at least how many hormones? How many in the pituitary gland?

A

Hypothalamus - 9
Pituitary gland - 7

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4
Q

Where is the pituitary gland located?

A

in the hypophyseal fossa of the sella trice of the sphenoid bone

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5
Q

How does the pituitary gland attach to the hypothalamus?

A

by a stalk, the infundibulum

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6
Q

The infundibulum has 2 anatomically separate portions which are?

A

anterior pituitary (also called anenohyphosis) & posterior pituitary (also called neurohypophysis)

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7
Q

Wheich portion of the pituitary gland accounts for 75% of the total weight of the gland? (anterior or posterior)

A

Anterior

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8
Q

What kind of tissue is the anterior pituitary composed of?

A

epithelial tissue

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9
Q

What are the 2 parts of the anterior pituitary ?

A

pars distils - larger portion
pars tubercles - from sheath around the infundibulum

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10
Q

What tissue is the posterior pituitary composed of?

A

neural tissue

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11
Q

What are the 2 parts of the posterior pituitary ?

A

pars nervosa - larger bulbar portion
Infundibulum

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12
Q

The 3rd region of the pituitary gland is called the pars intermedia which is what?

A

atrophies during fetal development & ceases to exist as a separate lobe in adults, however some of its cells migrate to adjacent parts of the anterior pituitary where they persist

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13
Q

What are the 5 types of anterior pituitary cells?

A
  1. somatotrophs
  2. thyrotrrophs
  3. gonadotrophs
  4. lactotrophs
  5. corticotrophins
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14
Q

How many hormones to the 5 anterior pituitary glands secrete?

A

7

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15
Q

Somatotrophs secrete what hormone?

A

growth hormone (GH)
(also known as smatotopin)

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16
Q

What does the growth hormone stimulate in the body?

A

general body growth & regulate aspects of metabolism

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17
Q

What hormone does thyrotrophs secrete?

A

thyroid-stimulating hormone (TSH) (also known as thryotropin)

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18
Q

What does TSH control in the body?

A

controls the secretions & other activities of the thyroid gland

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19
Q

What hormones do gonadotrophs secrete? (2)

A

Gonadotropins:
1. follicle-stimulating hormone (FSH)
2. Luteinizing hormone (LH)

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20
Q

What do the FSH & LH hormones act on in the body?

A

FSH & LH act on the gonads (testes & ovaries)
produce sperm and secrete testosterone in men and stimulate the ovaries to mature oocytes and secrete estrogen and progesterone

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21
Q

the lactotrophs secrete what hormone?

A

prolactin (PRL)

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22
Q

What does prolactin (PRL) initiate?

A

milk production in the mammary glands

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23
Q

What hormones do the coricotrophs secrete? (2)

A
  1. Adrenocorticotropic hormone (ACTH)
  2. Melanocytestimulating hormone (MSH) -> remnants of the pars intermedia
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24
Q

What does the adrenocorticotropic hormone (ACTH) stimulate to secrete glucocorticoids such as cortisol?

A

the adrenal cortex

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25
Q

hypothalamus releases hormones which stimulates secretion of anterior pituitary hormones. What are the 5 hormones related by the hypothalamus?

A
  1. Growth hormone-releasing hormone (GHRH)
    2.Thyrotropin-releasing hormone (TRH)
  2. corticotropin-relaying hormone (CRH)
  3. Prolactin releasing hormone (PRH)
  4. Gonadotropin releasing hormone (GnRH)
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26
Q

Growth hormone-releasing hormone (GHRH) also known as somatocrinin stimulates secretion of what hormone?

A

growth hormone

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27
Q

Thyrotropin-releasing hormone (TRH) stimulates secretion of what hormone?

A

thyroid-stimulating hormone

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28
Q

Corticotropin-Relaying hormone (CRH) stimulates secretion of what hormone?

A

adrenocorticotropic hormone

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29
Q

Prolactin-relasing hormone (PRH) stimulates secretion of what hormone?

A

prolactin

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30
Q

Gonadotropin-relasing hormone stimulates secretion of which hormones?

A

FSH and LH

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31
Q

How do hypothalamic hormones that release or inhibit anterior pituitary hormones reach the anterior pituitary?

A

through a portal system

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32
Q

Hypothalamus produces 2 inhibiting hormones? What do these do and what are the 2?

A

suppress secretion of anterior pituitary hormones
1.growth hormone inhibiting hormone (GHIH)
2.Prolactin-inhibiting hormone (PIH)

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33
Q

In the hypophyseal portal system how does blood flow?

A

From capillaries in hypothalamus –> portal veins that carry blood to capillaries of the anterior pituitary

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34
Q

How is blood brought into the hypothalamus?

A

the superior hypophyseal arteries (branches of the internal carotid arteries)

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35
Q

At the junction of the median eminence of the hypothalamus & the infundibulum, the arteries divide into a capillary network called what?

A

primary plexus of the hypophyseal portal system

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36
Q

From the primary plexus, blood drains into the hypophyseal portal veins which pass down where?

A

outside the infundibulum

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37
Q

In the anterior pituitary the hypophyseal portal veins divide again and form another capillary network called what?

A

secondary plexus of the hypophyseal portal system.

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38
Q

Hypophyseal veins drain blood from where? so that the hormones can travel to target tissues in the body

A

anterior pituitary

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39
Q

The anterior pituitary hormones that act on other endocrine glands are called what?

A

tropic hormones (or tropins)

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40
Q

release of anterior pituitary hormones is regulated by hypothalamus & _____ _______

A

negative feedback

41
Q

The secretory activity of what 3 types of anterior pituitary cells decreases when blood levels of their target gland hormones rise?

A

thyrotrophs, corticotrophins and gonadotrophs

42
Q

adrenocorticotropic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete glucocorticoids, mainly cortisol, in turn the elevated blood level of cortisol does what

A

decreases secretion of both ACTH and CRH by suppressing the activity of the anterior pituitary corticotrophins & hypothalamic neurosecretory cells

43
Q

What are the most numerous cells in the anterior pituitary?

A

somatotrophs –> which secrete growth hormone = most plentiful anterior pituitary hormone

44
Q

What does growth hormone promote in the body?

A

growth of bones & skeletal muscles and regulates certain aspects of metabolism

45
Q

How does GH exert its growth promoting effects indirectly?

A

through small protein hormones called insulin-like growth factors (IGFs) or somatomedins

46
Q

In response to the growth hormone cells in which parts of the body secrete IGFs? (4)

A

-Liver
-Skeletal muscle
-Cartilage
-Bone

47
Q

IGFs synthesized in the liver enter the bloodstream as what?

A

hormones that circulate to target cells throughout the body to cause growth

48
Q

IGFs produced in skeletal muscle, cartilage & bone act as what?

A

autocrines or pancrines to cause growth of those tissues

49
Q

effects of GH indirect & direct?

A

indirect- body growth
direct- metabolism

50
Q

functions of IGFs and GH ? (3)

A

increase growth of bones & soft tissues
enhance lipolysis
decrease glucose uptake

51
Q

How do IGFs cause growth of bones?

A

in bones IGFs stimulate osteoblasts, promote cell devision at epiphyseal plate & enhance synthesis of proteins needed to build more bone matrix

52
Q

How do IGFs help to grow soft tissues such as skeletal muscle, kidneys and intestines?

A

IGFs cause cells to grow by increasing uptake of amino acids into cells & accelerating protein synthesis
Also decrease breakdown of proteins & use amino acids for ATP production

53
Q

Due to effects of GH (acting with IGFs as mediators) what happens in childhood & teenage years?

A

increases growth of skeleton and soft tissues

54
Q

Due to effects of GH (acting with IGFs as mediators) what happens in adults?

A

helps maintain mass of bones & soft tissues & promotes healing of injuries and tissue repair

55
Q

what results from GH enhance lipolysis in adipose tissue?

A

increased use of the released fatty acids for ATP production by body cells

56
Q

GH influences carbohydrate metabolism by?

A

decreasing glucose uptake –> which decreases the use of glucose for ATP production in most body cells

57
Q

The action of decreasing glucose uptake spares glucose for what?

A

so that its available to neutrons for ATP production in times of glucose scarcity

58
Q

GH stimulates liver cells to release what into the blood

A

glucose

59
Q

somatotrophs release bursts of growth hormone how often?

A

every few hours (especially in sleep)

60
Q

secretory activity of somatotrophs is controlled by which 2 hypothalamic hormones?

A
  1. growth hormone-releasing hormone (GHRH)
  2. growth hormone-inhibiting hormone (GHIH)
61
Q

Which factors would promote GHRH secretion from the hypothalamus?

A

-hypoglycemia
-decreased blood levels of fatty acids
-increased blood levels of amino acids
deep sleep
-increased activity of the sympathetic nervous system (stress or vigorous exercise)
-other hormones (testosterone, estrogens, thyroid hormones & gherkin)

62
Q

Which factors would promote GHIH secretion

A

-hyperglycemia
-increased blood levels of fatty acids
-decreased blood levels of amino acids
-obesity
-aging
-high levels of GH and IGFs

63
Q

Which is an example of negative feedback inhabitation? GHIH or GHRH?

A

GHRH - because the GH will be able to secrete IGFs

64
Q

After being secreted due to factors that would secrete GHIH , GHIH enters the hypophyseal portal system & flows into the anterior pituitary,, what happens after that?

A

it prevents the somatotrophs from secreting GH by interfering with the singling pathway used by GHRH

65
Q

Release of TRH (thyroid releasing hormone depends on blood levels of T3 & T4. High levels of thyroid hormones (T3 & T4) inhibit secretion of TRH via what feedback?

A

negative -> there is no inhibiting hormone

66
Q

prolactin works with other hormones & initiates and maintains milk production by mammary glands. By itself it has a ___ effect

A

weak

67
Q

ejection of milk from the mammary glands depends on the hormone ______

A

oxytocin

68
Q

Milk production and ejection consitute ?

A

lactation

69
Q

breast tenderness just before menstruation may be caused by elevated ______

A

prolactin

70
Q

in females what hormone inhibits the release of prolactin from the anterior pituitary ?

A

prolactin inhibiting hormone (PIH) which is dopamine

71
Q

just before menstruation begins what happens to the secretion and blood level of prolactin

A

secretion - diminishes
blood level - rises
(but not enough to stimulate milk production)

72
Q

As the menstrual cycle begins what happens to Prolactin levels

A

PIH is again secreted and prolactin level drops

73
Q

during pregnancy what happens to the prolactin level

A

prolactin level rises stimulated by prolactin-releasing hormone (PRH) from the hypothalamus

74
Q

sucking of a nursing infant causes a ____ in hypothalamic secretion of PIH?

A

reduction

75
Q

hyper secretion of prolactin in mails causes what?

A

erectile dysfunction

76
Q

hyper secretion of prolactin in females causes what?

A

galactorrhea (inappropriate lactation)
amenorrhea (absence of menstrual cycles)

77
Q

What is the role of the posterior pituitary?

A

does not synthesize hormones
it stores and releases 2 hormones

78
Q

What does the posterior pituitary consist of

A

axons and axon terminals of more than 10,000 hypothalamic nerurosecretory cells

79
Q

The cell bodies of the hypothalamic neurosecretory cells are in which nuclei of the hypothalamus?

A

paraventricular & supraoptic nuclei

80
Q

the axons of the neurosecretory cells from which tract?

A

the hypothalamichypophyseal tract

81
Q

Where does the hypothalamichypophyseal tract begin and end

A

begins in the hypothalamus & ends near blood capillaries in the posterior pituitary

82
Q

The neuronal cell bodies of both paraventricular and supraoptic nuclei synthesize with which 2 hormones?

A

oxytocin (OT) and antidiuretic hormone (ADH)

83
Q

the axon terminals in the posterior pituitary are associated with specialized neuroglia called?

A

pituicytes

84
Q

Blood is supplied to the posterior pituitary by

A

inferior hypophyseal arteries (which branch from internal coroitid arteries

85
Q

the inferior hypophyseal arteries drain into a capillary network called what? that receives secreted oxytocin and antidiuretic hormones called

A

capillary plexus of the infundibular process

86
Q

From the plexus hormones pass into where for distribution to target cells in other tissues

A

they pass into the hypophyseal veins

87
Q

antidiuretic

A

substance that decreases urine production

88
Q

ADH decreases urine volumes by?

A

returning more water to the blood

89
Q

in absence of ADH urine output would

A

increase more than a tenfold from the normal 1-2L per day to about 20L per day

90
Q

why does drinking alcohol often cause frequent urination

A

because alcohol inhibits the secretion of ADH

91
Q

ADH also decreases the water lost through sweated and causes contraction of arterioles –> this does what to BP

A

increases BP (other name for ADH is vasopressin)

92
Q

what 2 major stimuli promote ADH secretion?

A
  1. rise in blood osmolarity
  2. decrease in blood volume
93
Q

high blood osmolarity is detected by what neurons in the hypothalamus ?

A

osmoreceptors (monitor changes in blood osmolarity)

94
Q

decreased blood volume is detected by volume receptors in ?

A

in the atria of the heart and by baroreceptors in the walls of certain blood vessels

95
Q

blood carries ADH to which 2 target tissues?

A

the kidneys and smooth muscle in blood vessel walls

96
Q

how do the kidneys respond to ADH?

A

retain more water –> decreases urine output

97
Q

How do the smooth muscle in the walls of arterioles (small arteries) respond to high levels of ADH?

A

they contract which constrict (narrows) the lumen of these blood vessels –> increase BP

98
Q
A

chapter 18 endocrine system (11 decks)

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