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Bio 432 > Topic 8 - Hypothalamus and Anterior Pituitary > Flashcards

Topic 8 - Hypothalamus and Anterior Pituitary Flashcards

1
Q

What is the hypothalamus connected to?!

A

Between the brain and the endocrine system (pituitary)

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2
Q

What does the hypothalamus do?

A

Migrates many signals in order to keep homeostasis

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3
Q

What does the specialized region around the hypothalamus lack, and what does this allow?

A
  • A blood brain barrier

- This allows the brain to interact directly with hormones in the blood

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4
Q

What does the BBB do?

A

It protects the brain from diseases

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5
Q

Portal hypophoysial

A

System of blood vessels in the brain that connects the hypothalamus with the anterior pituitary

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6
Q

What is the main function of the portal hypophoysial?

A

Transports and exchanges hormones to allow a fast communication between the hypothalamus and the anterior pituitary

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7
Q

Pituitary

A

The major endocrine gland, that is a pea-sized body attached to the base of the brain

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8
Q

What is the main function of the pituitary?

A

It is important for controlling growth and development and the functioning of the other endocrine glands.

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9
Q

Anterior pituitary

A

Hypothalamic hormones secreted by neurons through particle hypophoysial vessel; then anterior pituitary releases hormones into the blood

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10
Q

How are both the hypothalamus and the pituitary hormones released?

A

In pulses

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11
Q

Posterior pituitary

A

Neurons originate in the hypothalamus and project into the posterior pituitary; neurons deliver hormones then released directly from the post pituitary into the blood

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12
Q

What 4 endocrine glands does the hypothalamus stimulate?

A
  1. Thyroid
  2. Adrenals
  3. Gonads
  4. Pituitary
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13
Q

What does the hypothalamus control? (7)

A
  1. Temp
  2. Appetite
  3. Thirst
  4. Fatigue
  5. Behaviour
  6. Defense against carcadian
  7. Blood pressure
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14
Q

What are 7 inputs (both internal and external) for the hypothalamus?

A
  1. Light
  2. Smell
  3. Neural inputs
  4. Hormones
  5. Blood borne inputs
  6. Stress
  7. Immune stimuli
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15
Q

What are 2 outputs of the hypothalamus?

A
  1. Direct innervation to adrenal medulla, kidney, parathyroid gland and pancreatic islets
  2. Neurosecretion —> causes other cells to release hormones
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16
Q

What is the main function of thyrotropin releasing hormone?

A

Regulates thyroid stimulating hormone

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17
Q

What is the main function of gonadotropin releasing hormone?

A

Regulates the pituitary gonadotropins LH and FSH

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18
Q

What is the main function of somatostatin?

A

Inhibits GH, TSH, insulin, glucagon and others

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19
Q

What is the main function for growth-hormone releasing hormone?

A
  • Stimulation of GH (GHRH tropic effect on GH

- GHRH is tropHic for somatotrophs (helps them grow)

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20
Q

What is the main function for prolactin-inhibiting hormone?

A

Inhibits PRL

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21
Q

What is the main function for corticotropin-releasing hormone?

A

Regulates the adrenalcortical function, ACTH release, regulates appetite, sympathetic NS and adrenal medulla

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22
Q

Tropic

A

Is a hormone that stimulates an endocrine gland to grow and secrete it hormone
–> 1 hormone causes another hormone to do something

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23
Q

Where are tropic hormones secreted and what are 2 examples of tropic hormones?

A
  • Secreted by the anterior pituitary
    1. Thyroid stimulating hormone
    2. Thyrotropin
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24
Q

Trophic

A

Are hormones of the anterior pituitary that effects the growth, nutrition or function of other endocrine glands

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25
Q

What are 3 examples of trophic hormones?

A
  1. Thyroid releasing hormone
  2. Adrenocorticotropic hormone (ACTH)
  3. Corticotropin
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26
Q

What are 5 hormones of the anterior pituitary?

A
  1. Somatotrophs
  2. Lactotrophs
  3. Thyrotrophs
  4. Corticotrophs
  5. Gonadotrophs
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27
Q

What do somatotrophs secrete?

A

GH

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28
Q

What do Lactotrophs secrete?

A

PRL

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29
Q

What do Thryotrophs secrete?

A

TSH

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30
Q

What do cortocotrophs secrete?

A

Adrenocorticotrophic hormone

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31
Q

What do gonadotrophs secrete?

A

LH and FSH

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32
Q

What is the receptor type for GnRH?

A

GPCR

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33
Q

Where is GnRH found? (5)

A
  1. Pituitary
  2. Brain
  3. Placenta
  4. Ovaries
  5. Testis
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34
Q

What does G alpha q stimulate and whats its main effect?

A
  • It stimulates PRL

- Its main effect is in pituitary release of LH and FSH

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35
Q

What are the main functions of GnRH? (2)

A
  1. Stimulates the release and synthesis of hormones from gonadotroph cells (eg. LH and FSH)
  2. Effects emotions (limbic system)
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36
Q

What to organs make GnRH?

A
  1. Placenta

2. Ovaries

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37
Q

What do gonadotrophs promote?

A

Sex steroid production and gametogenesis

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38
Q

What are gonadotrophs stimulated by?

A

GnRH

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39
Q

How do hormones downregulate themselves?

A

By using negative feedback loops

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40
Q

What sex does LH belong to?

A

Male (testis)

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41
Q

What sex does FSH belong to?

A

Female (ovary)

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42
Q

What is the receptor type for cortocotropin releasing hormone?

A

GPRC

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43
Q

What is the main function of corticotropin releasing hormone and using what?

A

Regulates stress via adrenocortocotrophic hormone

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44
Q

POMC

A

Proopiomelanocortin

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45
Q

VP

A

Vasopressin

46
Q

OT

A

Oxytocin

47
Q

What do CRH stimulate the secretion from?

A

Products derived from proopiomelanocortin

Eg) ACTH

48
Q

What 2 factors mediate ACTH release?

A
  1. Vasopressin

2. Corticotropin releasing hormone

49
Q

What kind of regulator is VP?

A

Positive

50
Q

What kind of regulator is OT?

A

Negative

51
Q

What 2 factors inhibit ACTH release?

A
  1. OT

2. CRH

52
Q

Where is CRH secreted from?

A

Placenta

53
Q

What stimulates corticotrophs?

A

Corticotropin releasing hormone

54
Q

What does cortisol help the respond to?

A

Stress

55
Q

How does cortisol respond to stress? (5)

A
  1. It maintains blood pressure and cardiovascular function
  2. Reduces immune responses
  3. Maintains blood glucose levels
  4. Regulates the metabolism of proteins, carbs and fats
56
Q

How is cortisol regulated? (3)

A
  1. Mainly by the circadian rhythm (ACTH release)
  2. Feedback
  3. Stress
57
Q

What is short feedback?

A

ACTH inhibits its own secretion (fast)

58
Q

What is long feedback?

A

Cortisol acts on pituitary or hypothalamus to decrease ACTH synthesis (fast or slow)

59
Q

What does fast (non-nuclear) depend on?

A

Depends on the rate of change of cortisol levels

- Doesnt involve the nucleus

60
Q

What does slow (nuclear) depend on?

A

Depends on the absolute levels of cortisol and involves transcription (nuclear effects)

61
Q

What time of the day does cortisol peak?

A

Before waking up

- And decreases as the day goes on

62
Q

What is the receptor type for thyrotropin releasing hormone?

A

GPCR

63
Q

What does TRH regulate?

A

Thyroid axis from thyrotroph cells of the anterior pituitary

64
Q

How does TRH regulate thyroid axis?

A

Via TSH

65
Q

What are 2 possible effects TSH causes?

A
  1. Increase in thyroid gland size

2. Vascularization

66
Q

What stimulates and inhibits thyrotrophs?

A
  • Simulated by TRH

- Inhibited by somatostatin

67
Q

TH axis/ regulation steps (5)

A
  1. Neurons from the hypothalamus secretes TRH into portal veins that provide a direct route for TRH to the anterior pituitary
  2. Thyrotropes are stimulated by TRH and secrete TSH into the pituitary venous system (inhibited by somatotrophs)
  3. Cells in the tyroid are stimulated by TSH and secrete TH into the capillaries for transport to target tissues or via blood stream back to the hypothalamus and pituitary
  4. TH transported into cells of the target tissues
    5a. Negative feedback: serum T3 and T4 levels regulate TRH and TSH
    5b. Negative feedback: excess iodide inhibits
68
Q

What does somatostatin inhibit?

A

Secretion of TSH for the pituitary

69
Q

What is the main active nuclear TF?

A

T3

70
Q

What happens if you have too much iodide?

A

You will inhibit it

71
Q

What happens if you have to little iodide?

A

You would get an increase in TH

72
Q

What does PRL help with?

A

In the preparation of the mammary glands for future milk production

73
Q

PIH

A

Prolactin inhibiting hormone

74
Q

What does dopamine (aka PIH) do?

A

It inhibits PRL

75
Q

What stimulated PRL? (3)

A
  1. Sleep
  2. Stress
  3. Suckling stimulation by baby nursing at breast
76
Q

What does PRL do for women who are not pregnant?

A

Helps to regulate the menstrual cycle

77
Q

What does PRL do for men?

A

Affects sperm production

78
Q

What type of receptor do dopamine have?

A

G alpha 1

- They inhibit AC and decreases cAMP levels

79
Q

What is the role of PIH?

A

Inhibits dopamine which leads to increase in PRL (milk)

80
Q

What does PRL inhibit?

A

GnRH synthesis

  • -> thus inhibiting ovulation in females and spermatogenesis in males
  • Decreases LH and FSH
  • Increases dopamine
81
Q

DA

A

Dopamine

82
Q

How does somatostatin regulate growth, thyroid and insulin axes?

A

By inhibiting them

83
Q

What is the receptor type for somatostatin?

A

GPCR G alpha i

–> inhibits AC, decreases cAMP and decreases GH secretion

84
Q

Where is somatostatin made? (3)

A

Pancreas

  1. Gut
  2. Thyroid
85
Q

Where are the 2 different types of somatostatin found?

A
  1. Hypothalamus

2. Gut

86
Q

What does GHRH regulate?

A

GH

87
Q

What receptor type is GHRH?

A

GRCP G alpha s

–> activates AC which produces cAMP and increases GH secretion

88
Q

What doe gets stimulated when GH increases?

A

Somatotoph cells of the anterior pituitary

89
Q

What do somatotrophs produce, and how?

A

GH by increasing cAMP levels

90
Q

What stimulates somatotrophs what does this stimulation produce?

A
  • GHRH stimulates somatotrophs

- Stimulates the production of IGF-1

91
Q

What does somatostain inhibit and how?

A

GH but decreasing cAMP levels

92
Q

MSH

A

Melanocyte

93
Q

PC

A

Prohormone convertase

94
Q

How is POMC processed?

A

In a tissue specific manner

95
Q

What kind of modifications occur for for POMC

A

Post-translational modifications

96
Q

What cleaves POMC in the anterior pituitary, and what does this generate?

A
  • PC1 at dibasic AA sites

- This generates ACTH

97
Q

What is present in the intermediate pituitary? (2)

A
  1. PC1

2. PC2

98
Q

How many melanocortin GPCRs are there?

A

5

99
Q

Where does ACTH bind to MCR?

A

Adrenal cortex

100
Q

What does G alpha s activate?

A

AC which stimulates PKA

101
Q

What is crucial for the development of the adrenal cortex (trophic effect)?

A

The binding of ACTH to MCR

102
Q

What does MSH stimulate in mammals?

A

Melanocytes

103
Q

What do melanocytes do?

A

They produce a pigment melanin which protects the skin cells from UV radiation damage

  • in fish, frogs and octopuses they act like camouflage
  • Protect microbes against damage from high temp and chemical stresses
104
Q

What is the production of MSH increased in frogs?

A

When the animal is in a dark location (camouflage)

105
Q

How is MSH produced?

A

Produced when sun exposure and makes melanin

106
Q

What properties make melanin an excellent photoprotectant?

A

Photochemicals properties

107
Q

What do photoprotectant do?

A

They absorb harmful UV radiation and transforms the energy into harmless heat

108
Q

What is 1 benefit of having photoprotectant?

A

Prevents the indirect DNA damage that is responsible for the formation of malignant melanoma and other skin cancers

109
Q

What inhibits ACTH as part of the stress axis? (3)

A
  1. CRH
  2. VP
  3. OT
110
Q

What is MSH involved in?

A

Stimulation

111
Q

Where is POMC expressed?

A

Intermediate pituitary gland

Bio 432 (19 decks)

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