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B > Pituitary Gland > Flashcards

Pituitary Gland Flashcards

1
Q

What is a hormone

A

A messenger that is carried from the organ where they are produced to the organ where they affected by means of bloodstream

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2
Q

What are the two types of hormone

A

Peptide and steroid

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3
Q

Peptide hormone synthesis

A

Synthesised as pro hormones requiring further processing for example cleavage to activate. So pro hormones are basically long peptide chains for example Insulin

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4
Q

Steroid hormone synthesis

A

Synthesising a series of reactions from cholesterol

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5
Q

Stores with peptide hormones

A

They are stored in vesicles just beneath the membrane of cells and these are only released when the vesicles fuse with the cell membrane

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6
Q

Steroid home storage

A

Released immediately so it’s constitutive secretion

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7
Q

Peptide hormone receptors

A

Find receptors on the cell membrane and transducer signal using second messenger system

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8
Q

Steroid hormone receptors

A

Bind to intracellular receptors to change gene expression directly

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9
Q

What is the name of the neurons that regulate anterior pituitary function

A

Parvocellular neurons

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10
Q

Characteristics of hypothalamic parvocellular neurons

A

Short and terminate on median eminence
Release hypothalamic releasing – factors into capillary plexus and median Eminence
These hypothalamic regulatory factors are carried by portal circulation to anterior pituitary

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11
Q

Name the anterior pituitary

A

Adenohypophysis

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12
Q

Why is the anterior pituitary anatomically distinct from the hypothalamus

A

It’s not neuronal instead it has endocrine cells

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13
Q

Five types of endocrine cells (cells which contain hormones)

A 
Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs 
Gonadotrophs
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14
Q

What are the endocrine cells in the anterior pituitary gland controlled by

A

Regulated by hypothalamic releasing – inhibiting factors via hypophyseal- pituitary portal system

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15
Q

Hypothalamus-pituitary portal system

A

) axon terminals of hypothalamic neurosecretory cells release hormones ( Releasing hormones and inhibitory hormones ) into the hypothalamo-pituitary portal system ( diffuse in as there are lots of fenestrations in the blood vessels)

These travel in the portal system to the anterior pituitary

The releasing hormones and inhibitory hormones stimulate or inhibit the release of hormones from the anterior pituitary cells

The anterior pituitary hormones leave the gland via the blood

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16
Q

Thyroid hormone production

A

Axon terminals of hypothalamic neurosecretory cells release TRH into hypothalamic-hypophysial portal system

TRH travels in the portal system to the anterior pituitary

TRH stimulates the release of the Thyroid Stimulating Hormone ( thyrotrophin) from anterior pituitary thyrotrophs

TSH leaves the gland via the blood to travel to the thyroid gland to stimulate thyroid hormone release ( thyroxine )

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17
Q

Somatotrophs

A

Growth hormone ( somatotrophin )

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18
Q

Lactotrophs

A

Prolactin

19
Q

Thyrotrophs

A

Thyroid stimulating hormone ( TSH) Thyrotrophin

20
Q

Gonadotrophs

A

LH

FSH

21
Q

Corticotrophs

A

Adrenocorticotrophic hormone ( ACTH, corticotrophin )

22
Q

Growth hormone regulators

A

Growth hormone releasing hormone - on switch

Somatostatin - off switch

23
Q

Prolactin

A

Dopamine ( inhibitory )

24
Q

TSH ( thyrotrophin)

A

Thyrotrophin releasing hormone

25
Q

LH , FSH

A

Gonadotropin releasing hormone

26
Q

Adrenocorticotrophic hormone ( ACTH, corriocotrophin )

A

Corticotrophin releasing hormone

27
Q

Target cells of growth hormone

A

General body tissues in particular liver

28
Q

Prolactin target

A

BreastS of lactating women

29
Q

TSH target

A

Thyroid

30
Q

Gonadotrophs ( LH and FSH) target

A

Testes and ovaries

31
Q

Adrenocorticotrophic hormone target

A

Adrenal cortex

32
Q

What may cause a bitemporal hemianopia

A

Cannot see temporal aspects of visual field / outer aspects due to pituitary tumour which has grown out of sella tursica and onto optic chiasm ( supra sella)

Fibres from the nasal ( medial) retinae cross at the optic chiasm and compression of the optic chiasm by a pituitary tumour prevents the transmission of sensory information from lateral visual fields to the occipital lobe

33
Q

Milk production ( reflex arc)

A

Mechanical stimulation of nipple and surrounding area activates afferent sensory pathways

Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones

Less dopamine in the hypothalamic pituitary portal system causes less inhibition of anterior pituitary lactotrophs

Increased plasma prolactin increases milk secretion in mammary glands which travels by blood to nipple

34
Q

Mechanisms of growth hormone action

A

Direct secretion of somatotrophin onto body tissues

Indirectly somatotrophin travels to liver where it stimulates Insulin like Growth factor ( somatomedin )
IGF-1 then binds to receptors on muscle and bone and can also stimulate growth

35
Q

Gigantism

A

Too much growth hormone release before puberty ends leads to gigantism as the femur / epiphyseal plates only fuse together after puberty has finished

But if too much growth hormone happens after puberty has fished once the growth plates have fused , you can’t grow taller and this is called acromegaly. But get other physiological changes

36
Q

Physiological features of acromegaly

A

Coarsening of facial features
Macroglossia ( increased size of tongue )
Prominent nose
Large jaw - prognathism
Increased hand and feet size and spade like hands
Sweatiness
Headache

37
Q

What is the posterior pituitary gland called

A

Neurohypophysis

38
Q

Hormones associated with the posterior pituitary gland

A 
Arginine vasopressin ( AVP)/ ADH 
Oxytocin
39
Q

Why is the posterior pituitary gland anatomically continuous with the hypothalamus

A

Posterior pituitary gland is made of neuronal tissues and has hypothalamic magnocellular neurons

These are long and originate in super optic ( AVP) and paraventricular (oxytocin ) hypothalamic nuclei

Nuclei -> stalk -> posterior pituitary

40
Q

Regulation of the posterior pituitary gland

A

Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to the posterior pituitary

Excitation of these hypothalamic magnocellular neurones stimulates the release of AVP or oxytocin onto the posterior pituitary where they diffuse into blood capillaries and then leave the posterior pituitary via the b
Pod

41
Q

Physiological action of vaspressin

A

Stimulation of water reabsorption in the renal collecting duct

This concentrates the urine

Acts through the V2 receptor in the kidney

Also a vasoconstrictor ( V1)

Stimulates ACTH release from anterior pituitary

42
Q

Actions of oxytocin when delivering baby

A

Acts on uterus at parturition
Causes myometrial cells to contract
Delivery of baby

Can use oxytocin analogue for women who need biological encouragement to contracts

43
Q

Oxytocin and lactation

A

Milk ejection is controlled by the posterior pituitary gland

Oxytocin acts on breast during lactation
Which causes myoepothelial cells to contract
Milk ejection

44
Q

Milk ejection reflect arc

A

Mechanical stimulation of nipple and surrounding area causes afferent pathways
Afferent signals integrated in the hypothalamus and stimulate oxytocin releasing neurone activity
Action potentials travel down oxytocin neurones and oxytocin is secreted into the bloodstream
Incradrf plasma oxytocin increases milk ejection in mammary glands

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