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Chapter 18: The Endocrine system > 18.2 Hypothalamus and pituitary > Flashcards

18.2 Hypothalamus and pituitary Flashcards

1
Q

What is the other name for the pituitary gland?

A

hypophysis

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2
Q

Discuss the structure, location and connection to the hypothalamus of the pituitary gland

A

It is a small but critical endocrine gland at the base of the brain, just below the hypothalamus, in a bony cavity. It is connected to the hypothalamus via a thin stalk.

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3
Q

What are the two lobes that the pituitary gland is divided into?

A

The anterior pituitary gland and posterior pituitary gland

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4
Q

What is the anterior pituitary made up of (adenohypophysis)

A

It is made up of glandular epithelial tissue, functioning as a major hormone-secreting gland

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5
Q

What is the posterior pituitary made up of (neurohypophysis)

A

It is composed of nervous tissue and makes up part of the neuroendocrine system

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6
Q

In what 3 ways do the two lobes of the pituitary differ

A
  1. functions
  2. control mechanisms
  3. embryonic origins
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7
Q

What gland regulates the two lobes in different ways?

A

The hypothalamus

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8
Q

In what way is the anterior pituitary connected to the hypothalamus

A

Through a specialised vascular link

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9
Q

In what way is the posterior pituitary connected to the hypothalamus

A

via a neural pathway

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10
Q

The hypothalamus and the posterior pituitary work together as a unit to release which two essential hormones?

A

vasopressin and oxytocin

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11
Q

Where are the two posterior pituitary hormones stored and released from

A

the posterior pituitary gland

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12
Q

Where are the two posterior pituitary hormones synthesized

A

The hypothalamus (the posterior pituitary does not synthesize hormones)

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13
Q

In which two regions does the hypothalamus house neurosecretory neurons

A

The supraoptic nucleus and the paraventricular nucleus

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14
Q

These neurosecretory neurons extend their axons down to the __________, where their _________ are located

A

Posterior pituitary, terminals

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15
Q

The posterior pituitary itself is an extension of the hypothalamus and contains the terminals of the neurosecretory neurons along with?

A

glial-like cells called pituicytes

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16
Q

What type of hormones are vasopressin and oxytocin classified as?

A

They are peptide hormones

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17
Q

What kind of granules are the two posterior pituitary hormones packaged into after being synthesised by the hypothalamus so they can be transported to the posterior pituitary via the axons?

A

secretory granules

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18
Q

True or false: each neuron produces and stores only one of the hormones

A

true

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19
Q

Explain the process of how vasopressin and oxytocin are released into the bloodstream via exocytosis

A

Synaptic input triggers action potentials to travel down the axons. They cause the release of vasopressin/oxytocin from the neuronal terminals within the posterior pituitary and into the bloodstream (systemic blood) via exocytosis

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20
Q

Explain the two functions of vasopressin

A
  1. Water conservation- it conserves water by promoting reabsorption in the kidneys, particularly in response to high plasma osmolarity, which is detected by the hypothalamic osmoreceptors (primary role)
  2. Vasoconstriction- It causes contraction of arteriolar smooth muscle (but this effect is less significant under normal conditions)
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21
Q

Explain the three functions of oxytocin

A
  1. Uterine contractions- It stimulates uterine muscle contractions during childbirth, adding to the delivery process
  2. Milk ejection- it promotes the ejection of milk from the mammary glands during breastfeeding, triggered by the infant’s suckling.
  3. Behavioural effects- plays a role in maternal bonding and attachment earning its nickname “love/cuddling hormone”. It is also thought to contribute to bonding between romantic partners
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22
Q

True or false: The paraventricular and supraoptic nuclei both contain neurons that produce vasopressin and oxytocin

A

true

23
Q

Where is the exact location where the posterior pituitary hormones are synthesised

A

in the neuronal cell body in the hypothalamus

24
Q

What kind of 6 hormones does the anterior pituitary secrete

A

peptide hormones

25
Q

What is the primary function of all 6 of the anterior pituitary hormones

A

They function as tropic hormones

26
Q

List the six hormones produced by the anterior pituitary
(G-FLAT-P)

A
  1. Growth hormone
  2. Thyroid-stimulating hormone
  3. Follicle -stimulating hormone
  4. Luitenizing hormone
  5. Prolactin
  6. Adrenocorticotropic hormone
27
Q

_________ is the only anterior pituitary hormone that is not tropic

A

prolactin

28
Q

How many cell types within the anterior pituitary secrete the 6 hormones

A

5

29
Q

Give the following from Growth hormone: secreted by, primary function and mechanism

A

secreted by: Somatotropes
Primary function: Regulates overall body growth and influences metabolism
mechanism: GH exerts its effects through the JAK/STAT pathway

30
Q

Give the following from Thyroid-stimulating hormone (TSH): secreted by, primary function and mechanism

A

Secreted by: Thyroptropes
primary function: Stimulates the thyroid gland to secrete thyroid hormone and it promotes the growth of the thyroid gland
mechanism: TSH binds to G-protein coupled receptors and activates the cAMP pathway

31
Q

Give the following from Adrenocorticotropic hormone (ACTH): secreted by, primary function and mechanism as well as the precursor

A

Secreted by: Corticotropes
Primary function: Stimulates the secretion of cortisol from the adrenal cortex and promotes adrenal gland growth
mechanism: ACTH also binds to G-protein coupled receptors and activates the cAMP pathway
Precursor: Synthesised as part of pro-opiomelanocortin (POMC), which also give rise to melanocyte-stimulating hormone (MSH) and endorphin in other tissue.

32
Q

Give the following from FSH: secreted by, primary function and mechanism

A

screted by: gonadotropes
Primary function: Regulates gamete production (ova and sperm). In females, FSH stimulates the growth of ovarian follicles and estrogen secretion.
Mechanism: acts through the cAMp pathway

33
Q

Give the following from LH: secreted by, primary function and mechanism

A

Secreted by: gonadotropes
Primary function: In females, it triggers ovulation by regulating the secretion of estrogen and progesterone, and helps form the corpus luteum. In males, it stimulates testosterone secretion by the testes.
Mechanism: Acts through the cAMP pathway

34
Q

Give the following from Prolactin: secreted by, primary function and mechanism

A

secreted by: lactotropes
Primary function: It enhances breast development and promotes milk production in females (lactation). Its role in males is less understood, but it may enhance the immune system in both sexes.
Mechanism: PRl acts through the JAK/STAT pathway

35
Q

Why are FSH and LH as well as TSH known as gonadotropins

A

Because they regulate the gonads

36
Q

What kind of hypothalamic hormones are key regulators of the anterior pituitary hormone secretion?

A

Releasing and Inhibiting hormones

37
Q

What do hypothalamic releasing hormones do

A

They stimulate the anterior pituitary to secrete specific hormones

38
Q

What do hypothalamic inhibiting hormones do?

A

They prevent or reduce the secretion of specific anterior pituitary hormones

39
Q

These regulatory hormones are small peptides collectively known as

A

hypophysiotropic hormones

40
Q

Hypophysiotropic hormones play a crucial role in a three-hormone sequence, often referred to as?

A

An endocrine axis

41
Q

What are the 4 steps in which the three hormone sequence operates in

A
  1. Hypothalamic hormone is released (hormone 1)
  2. This hormone stimulates/inhibits the release of a tropic hormone from the anterior pituitary (hormone 2)
  3. The tropic hormone then regulates the secretion of a hormone from the target endocrine gland (hormone 3)
  4. The hormone from the target endocrine gland then brings about a physiological response
42
Q

What are the 7 hypophysiotropic hormones

A
  1. Thyrotropin-releasing hormone(TRH): Stimulates the release of TSH
  2. Corticotropin-releasing hormone(CRH): Stimulates the release of ACTH
  3. Gonadotropin-releasing hormone (GnRH): stimulates the release of FSH and LH
  4. Growth Hormone-Inhibiting hormone (GHIH)/ somatostatin: Inhibits the release of GH
  5. Growth hormone-Releasing hormone (GHRH): Stimulates the release of GH
  6. Prolactin-inhibiting hormone (PIH)/ dopamine: Inhibits the release of prolactin
  7. Prolactin-releasing hormone (PRH): Stimulates the release of prolactin
43
Q

Besides the hypothalamus, what regulates the anterior pituitary?

A

by the negative feedback loop: the hormone released due to the influence of the tropic hormone of the anterior pituitary

44
Q

What is the hypothalamic-hypophyseal portal system

A

It is a unique vascular connection that allows hypothalamic regulatory hormones to reach the anterior pituitary directly at high concentrations. (capillary-to-capillary connection)

45
Q

What would happen if the hypothalamc-hypophyseal portal system did not exist

A

The blood containing the hypothalamic regulatory hormones would first have to go through the general circulation of the body and after that to go the anterior pituitary. This would dilute the hormones and cause the body to respond slowly.

46
Q

Explain the pathway of the hypothalamic-hypophyseal portal system, i.e where it starts and ends

A

It begins at the base of the hypothalamus with a group of capillaries that recombine into small portal vessels, which descend through the connecting stalk into the anterior pituitary. The portal vessels then branch into another capillary network in the anterior pituitary, which drains into the systemic venous system.

47
Q

Where are the axon terminals of the hypothalamic-hypophyseal portal system located

A

on the capillaries at the portal system’s origin.

48
Q

Where are the hormones stored before they are stimulated to be released and delivered to the anterior pitutiary

A

Axon terminals of the neurons in the hypothalamus

49
Q

What are the two complex inputs that regulate hypophysiotropic hormones

A

Neural input and chemical input

50
Q

Explain neural input

A

Hypothalamic neurons integrate signals from various brain regions, those involved in emotions, such as the limbic system. Emotional states can greatly influence hormone release, as seen in menstrual irregularities during stress

51
Q

Explain chemical input

A

The hypothalamus is not fully protected by the blood-brain barrier, which allows it to monitor blood-borne chemicals. This feature makes it particularly responsive to negative feedback from target-gland hormones.

52
Q

Via what mechanism do target-gland hormones inhibit hormones from the anterior pituitary and the hypothalamus

A

negative feedback

53
Q

What does it mean when it is said that diurnal rhythms are superimposed on the negative feedback regulation?

A

This means that the set point for hormone secretion changes based on the time of day.

Chapter 18: The Endocrine system (4 decks)

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