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Bio regulatory systems 2 > Pituitary Gland > Flashcards

Pituitary Gland Flashcards

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1
Q

What are the 2 main groups of Hormones?

A

Peptide and Steroid

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2
Q

How are peptide hormones made?

A

synthesised as PRO-HORMONES which are really long, these then need to be cleaved to yield the smaller active hormone

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3
Q

How are Steroid hormones synthesised?

A

In a series of reactions from CHOLESTEROL

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4
Q

How are peptide hormones stored?

A

In Vesicles (they are then released in response to a signal)

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5
Q

How are steroid hormones stored?

A

Released immediately (not stored)

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6
Q

What receptors do peptide hormones bind and what is the effect ?

A

Receptors on Cell Membrane and transduce signal using 2nd messenger systems?

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7
Q

What receptors do steroid hormones bind to and what is the effect?

A

Intracellular receptors to change gene expression directly

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8
Q

What is above the pituitary gland ?

A

Hyperthalamus which has the Optic Chiasm coming off it (in front of the pituitary gland) and the Mamillary body next to it

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9
Q

What is the name of the stalk that connects the hyperthalamus to the pituitary gland?

A

Infundibulum

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10
Q

Where does the pituitary gland sit?

A

In a depression in the sphenoid bone called the SELLA TURCICA

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11
Q

What does supra sella mean?

A

when the pituitary gland is no longer sitting the sell turcica because it has grown to big and when it grows it grows upwards

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12
Q

What is the median eminence ?

A

Bit of the hyperthalamus immediately adjacent to the pituitary stalk It is very rich in blood vessels

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13
Q

What regulates anterior pituitary function and how?

A

Short PARVOCELLULAR NEURONS in the HYPERTHALAMUS release factors into the median eminence and then these are carried into the anterior pituitary by PORTAL CIRCULATION

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14
Q

What is the alternative name for the Anterior Pituitary?

A

Adenohypophysis

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15
Q

What are the 5 cell types that make up the Anterior pituitary?

A

Made up of endocrine cells (no neural tissue unlike the hypothalamus and posterior pituitary) Somatrophs Lactotrophs Cortciotrophs Thyrotrophs Gonadotrophs

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16
Q

Describe the Hypothalamo-pituitary portal system?

A

1-Short parvocellular neurones release factors into blood vessels in the median eminence

2- These blood vessles have fenestrations(gaps in the cell membrane) which allows the hormones to leak out of the median eminence blood vessels and leak into the the pituitary PORTAL vessles

3-Hormones transported in the blood steam to the anterior pituitary

4-Anterior pituitary is full of hormones, the factors/hormones that arrive from the hypothalamus are either inhibit or stimulate the release of hormones from the anterior pituitary cells

4-Anterior pituitary hormones then leave gland via the blood and are released into circulation

17
Q

Describe the regulation of thyroid hormone production?

A

1- TRH is released from the short hypothalamic paravocellular neurones

2-TRH enters portal circulation and travels down the portal system into the anterior pituitary gland

3-TRH stimulates the release of Thyroid stimulating hormone(TSH) from the anterior pituitary THYROTROPHS

4-TSH leaves the gland via the blood and travels to the thyroid gland to stimulate thyroid hormone release (THYROXINE-T4)

18
Q

Which hormones are made in each of the 5 cell types in the anterior pituitary?

A

Somatotrophs- Growth hormone Lactotrophs-Prolactin (important for breast lactation) Thyrotrophs-Thyroid stimulating hormone Gonadotrophs- Luteinising hormone(LH) and Follicle stimulating hormone(FSH) Corticotrophs- Adenocorticotrophic hormone

19
Q

How are each of the anterior pituitary hormones regulated by the hyperthalamus?

A

Hormone from the hypothalamus regulate the release and inhibition of hormones from anterior pituitary cells

Growth hormone is the only anterior pituitary hormone which is regulated by both and inhibiting and releasing hormone

Prolactin is the only hormone of the anterior pituitary gland that is regulated by only an inhibiting hormone

GROWTH HORMONE RELEASING HORMONE- causes release of growth hormone

SOMATOSTATIN-inhibits the release of growth hormone

DOPAMINE -inhibits the release of prolactin(this is regulated as inhibitory as usually there is not a lot of prolactin in the body so to produce more, less dopamine is produced)

THYROID RELEASING HORMONE-stimulates the release of TSH

GONADOTROPHIN RELEASING HOROMONE- stimulates the release of LH and FSH

CORTICOTROPHIN RELEASING HORMONE- stimulates the release of Adenocorticotrophic hormone

20
Q

Where are the hormones for the Anterior pituitary hormones?

A

Growth Hormone- General Body Tissues (particularly the liver)

Prolactin-Breasts

Thyrophin (same as TSH)- Thyroid

Gonadotrophins(LH and FSH)-Testes(male) and Ovaries(Female)_

Adrenocorticotrophin -Adrenal cortex

21
Q

How can we look top see if someone has a pituitary tumour?

A

Coronal( verical cross section) MRI pictures from front to back of the head

22
Q

What is bitemporal hemianopia

A

When someone has a pituitary tumour it grows upward and out (cant grow down because of the bone beneath it)

This causes it to COMPRESS the OPTIC CHIASM this effects vision as fibres from the nasal retinae (which go to the eye) cross in the optic chiasm and it generally prevents transmission of sensory information from the LATERAL VISUAL FIELDS to the OCCIPITAL LOBES

In bitemporal hemianopia you cant see anything in your temporal fields of your vision

23
Q

How can you assess bitemporal hemianopia?

A

by testing the perimeter of there visual fields

  • patient sits in front of a machine that flashes lights everywhere and the patient has to press a button every time they see a light flash
24
Q

Describe milk production?

A

NEUROENDOCRINE REFLEX ARC

1-Mechanical stimulation of the nipple and surrounding areas (when infant latches onto the nipple) causing afferent pathways to be activated

2- afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones

3-Less dopamine in the hypothalamic pituitary portal system causes LESS inhibiton of the anterior pituitary lactotrophs so more Prolactin in produced

4-increased prolactin increases milk SECRETION in mammary glands

25
Q

Describe mechanisms of growth hormone action?

A

Anterior pituitary produces growth hormone ->this goes to body tissues and the liver-> when it binds to receptors on the liver it causes insulin like growth factor IGF-1 (mainly) and IGF-2 to be made and released

-The skeleton and body tissues also has receptors for IGF-1 causing growth INDIRECTLY(binding of IGF1 from liver) as well as DIRECT binding of growth hormone to skeleton muscles

26
Q

What disorder come from to much growth hormone in adults and kids?

A

ACROMEGALY- adults -you cant grow taller as you have no growth potential so different body part start growing bigger

GIGANTISM- kids- have growth potential so they grow really tall

27
Q

What are the signs and symptoms of acromegaly?

A

coarsening of facial features (macroglossia and prominent nose)

Large Jaw

increased feet and hand size

sweatiness

headache

28
Q

What hormones come from the posterior pituitary gland?

A

ARGENINE VASOPRESSIN-also known as ADH

OXYTOCIN

29
Q

What is the alternative name for the posterior pituitary gland?

A

Neurohypophsis

30
Q

How do signals get from the hypothalamus to the posterior pituitary?

A

Via MAGNOCELLULAR NEURONS - these are very long neurones that go straight from the hypothalamus to the posterior pituitary, they are able to do this because unlike the anterior pituitary the posterior pituitary is continuous with the hypothalamus so contains NEURAL TISSUE

31
Q

Where do the magnocellular neurons originate from?

A

SUPRAOPTIC (AVP) and PARACENTRICULAR hypothalamic nuclei ->stalk->posterior pituitary

32
Q

Describe regulation of the release of posterior pituitary hormones?

A

1-Two sets of hypothalamic neurosecretary cells produce AVP and oxytocin

2- excitation of these hypothalamic magnocellular neurons stimulates release of AVP or oxytocin into the posterior pituitary from cell endings, where they then diffuse into the blood capillaries

3- then leave the posterior pituitary via the blood

33
Q

What are the functions of vasopressin?

A
  • stimulation of water reabsorption in the renal collecting duct which concentrates urine It acts through the V2 RECEPTOR in the kidney to do this
  • vasoconstrictor via the V1 receptor
  • stimulates ACTH (adrenocorticotrophic hormone ) release from the anterior pituitary
34
Q

How does vasopressin concentrate urine?

A

1-AVP in blood binds to the V2 receptor in the collecting duct

2- this stimulates an intracellular cascade which then promotes the movement of AQUAPORIN 2 to the membrane of the collecting duct that is in contact with the urine

3- aquaporins allow the passage of water from the urine through and across the membrane

4- water leaves the cells of the collecting duct via AQUAPORIN 3 channels and enter the blood plasma

35
Q

What is the differenc between the funtion of oxytocin and prolactin?

A

Prolactin-involved in the synthesis of milk Oxytocin -involved in milk ejection as it causes CONTRACTION

36
Q

What are the 2 functions of oxytocin?

A

1-Produced by breast during lactation in MYOEPITHELIAL CELLS and cause contraction and therefore milk is ejected

2-Produced in uterus at paturition in MYOMETRIAL CELLS and causes contraction which results in the delivery of the baby

Bio regulatory systems 2 (15 decks)

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