Endocrine System W3 Flashcards by elizabeth burtonshaw-walker

What is the endocrine system

Collection of glands that produce and secrete hormones

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It regulates…

Growth and development, metabolism, maintenance and repair of tissues, reproduction nand sexual function, tissue function and sleep

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Major glands

Hypothalamus, pituitary, thyroid, parathyroid, adrenals, pineal, pancreas, ovaries and testes

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What cells that secrete aren’t part of the e.system

Non-endocrine secretary cells
- Neurons
- Add oppose tissue
- Kidney cells
- Liver cells
- GiT cells

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What are hormones

Chemical messenger that travel in blood stream and sometimes bound to proteins to help transport them to their target cells

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Three classes of hormone

Steroid - lipophyllic ie cortisol

Peptide - hydrophylllic ie insulin

Amino acid derivded - hydrophilic ie thyroid

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Why is the pituitary gland called the master gland

Secretes hormones that control the actions of other endocrine glands nad tissues

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What is the pituitary gland physically

Pea sized and oval struure that is suspended under the brain by the pituitary stalk annd sits with a crevice of the sphenoid bone

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What does th pineal gland secrete

Melatonin which plays part in the role of sleep and circadian rythums

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The posterior consists of…

Nervous tissue

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Anterior consists of…

Glandular epithelial tissue

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Posterior connects by…

Glandular neural pathway

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Anterior connects by …

Unique vascular link

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Posterior releases

Oxytocin and vasoprssin(nit-diuretic)

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Anterior releases…

ACTH, TRH, GH, prolactin, FSh, LH and MSH

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Oxytocin

Produced by the posterior pituitary and has several functions in women:
• Contraction of the uterine muscle to help expel infant during childbirth
- Secretion increased by reflexes originating within birth canal during birth
• Promotes ejection of milk from mammary glands during breast feeding
- Secretion increased by suckling
• Influences social behaviours
- Mating/bonding with infant/relationships
• Injection (Syntocinon) used to induce labour and prevent postpartum haemorrhage

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Vasopressin

also known as antidiuretic hormone (ADH)

Peptide hormone

Increases water reabsorption + Reduces urine volume, making it more concentrated + Helps prevent dehydration

Causes narrowing of blood vessels, which increases blood pressure

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Diabetes insipidus

This is caused by a lack of vasopressin (ADH)
The main symptoms are polyuria (excessive dilute urine >2L/day) and polydipsia
Left untreated, it leads to shock-like symptoms – hypotension, tachycardia, tachypnea etc
and can lead to hypernatremia
Treatment
- Vasopressin injection
- Desmopressin injection/tablet/nasal spray (this is longer acting and has no
effects on V2 receptors so no vasoconstriction)

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Anterior pituitary Synthesises …

hormones and releases them into blood stream

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5 cell types in the anterior pituitary secrete six major hormones:

Somatotropes – GH (growth hormone (somatotropin))
Thyrotropes – TSH (thyroid stimulating hormone)
Corticotropes – ACTH (adrenocorticotrophic hormone)
Gonadotropes – FSH (follicle stimulating hormone) and LH (luteinizing hormone)
Lactotropes – PRL (prolactin)

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three-hormone sequence

Hormones from the hypothalamus cause the release of these hormones and in response
they travel in the blood and cause the release of hormones from other tissues and organs or
directly affect those tissues. . When sufficient
hormone has been released, the increase in blood concentrations has a negative feedback
on the hypothalamus and pituitary to decrease further secretion.

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Control of anterior pituitary hormones

They are not secreted at a constant rate
Secretion of each is independent of each other

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Major factors controlling secretion of anterior pituitary hormones

Hypothalamic hormones (releasing and inhibitory hormones)
◦ Neural or hormonal inputs to stimulate or inhibit secretion
◦ Somatostatin (GHIH) inhibits GH and TSH
◦ Dopamine (PIH) inhibits PRL
Feedback by target-gland hormones

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The hypothalamic pituitary (hypophyseal) portal system

This is a unique vascular link between hypothalamus and anterior pituitary
There is a direct capillary to capillary bed so the hypothalamic hormones just travel locally
within this
Upon arrival to the pituitary, the hypothalamic hormones bind to specific receptors on
specific cells in the anterior pituitary

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GHRH from the hypothalamus binds …

receptors on somatotroph cells in the anterior pituitary, triggering the release of GH

What is GH

protein hormone made by the pituitary gland Key Functions: - Promotes height growth in children by acting on bones and cartilage. - Stimulates protein synthesis and muscle growth. - Increases fat breakdown to provide energy. - Helps regulate blood sugar and insulin levels. - Stimulates the liver to produce IGF-1

GH works by…

stimulating IGF (insulin-like growth factor) Doesn’t directly affect tissues

What else is growth influenced by

genetics, adequate diet, chronic disease, stressful environment, other growth influencing hormones eg thyroid hormone, insulin estrogens, androgens etc

What s GH deficiency due to

congenital (present at birth) - ie due to genetic mutations or acquired (developed later) - ie may be caused by brain tumours

GH in adulthood result in…

GH Excess - Enlarged hands, feet, and facial features (e.g. jaw, nose) - Thickened skin - Joint pain GH Deficiency - Decreased muscle mass and strength - Increased body fat, especially around the waist

Treatment of GH deficiency

ethical considerations around treatment with GH - potential risk of cancer Treatment is somatotropin - synthetic form of GH

Synthetic somatotrophin is given for…

Short stature (pituitary dwarfism), Turner’s syndrome, chronic renal insufficiency in children. It is also used illicitly by athletes to increase muscle mass

Somatorelin

GHRH (growth hormone releasing hormone) stimulates growth hormone release

Mecasermin

is given when there is growth failure in children lacking adequate IGF-1

Treatment for excess GH

Surgery - trans-sphenoidal through the nose to the p.gland Medicines - Somatostatin

Different forms of analogues of somastatin

octreotide lanreotide pasireotide

Other drugs that may be given depending on the cause include

Dopamine agonist or GHRH antagonist

Somatostatin

Given for GH excess produced by hypothalamus inhibits the release of GH, TSH, insulin and glucagon

Where are the adrenal glands located?

Above the left and right kidneys and they have a cortex and a Medalla

The outer cortex and the inner medulla are divided into three zones:

Zona glomerulosa – outermost Zona fasciculata – middle Zona reticularis - inner zone

Where is aldosterone produced in the adrenal gland?

Zona glomerulosa

Where is cortisol and corticosteroids produced in the Adrena gland

Zona fasciculata

Where are androgens produced in the adrenal gland?

Zona reticularis

Where are Epinephrine and norepinephrine produced in the adrenal glands?

Medalla

Three categories of steroid produced in the district zones

Mineralocorticoids - aldosterone Glucocorticoids - cortisol Sex hormones - progestogens

How many steroids are produced from cholesterol?

More than 30

How do steroid hormones act on the cell to increase protein synthesis?

cross the cell membrane binding to intracellular receptors hormone receptor complex enters the nucleus and binds to specific DNA sequences This activates gene transcription leads to increased mRNA production enhances protein synthesis

Aldosterone

Is the major mineralocorticoid and is essential for life and it acts on the distal and collecting tubes of the kidney

Functions of aldosterone

Promotes sodium absorption in the kidney Increases potassium and hydrogen excretion in urine The sodium retention reduces water retention expanding ECF volume This increased blood pressure in the long-term

Cortisol

The major glucocorticoid

Functions of cortisol

Role in metabolism to increase blood glucose concentration at the expense of proteins and fat stores Stimulates hepatic gluconeogenesis Inhibits glucose uptake by several tissues

Control of cortisol secretion

Released in response to ACTH from the pituitary which intern is released in response to CRF from the hypothalamus

Cortisol rhythm

Has a diurnal rhythm as cortisol levels are highest in the morning and lowest at night

Cortisol and stress

Is increased by both physical stress and psychological stress

Aldosterone hypersecretion

due to a hyper secreting adrenal tumour made of aldosterone secreting cells or due to high activity of rennin angiotensin aldosterone system causing narrowing a blood vessels

What does hyper secretion result in?

hypernatraemia, hypokalaemia and high blood pressure (due to sodium & water retention)

Cortisol and aldosterone deficiency

Results in Addison’s disease due to a deficiency in glucocorticoids and mineralocorticoids

Where is the thyroid gland?

Located below the larynx and wrapping around the tracker and looks like a bow tie

What hormones does the thyroid secrete?

Thyroid hormone which contains iodine and calcitonin

Actions of thyroid hormone in the body

Key Actions of Thyroid Hormones - Increases basal metabolic rate (BMR) - Essential for normal growth in children - Increases heart rate and cardiac output - Improves alertness, reflexes, and mood - Increases gut motility (low levels can lead to constipation)

Endocrine System W3 Flashcards

(60 cards)