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Endocrine system Flashcards

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1
Q

What are the main endocrine glands?

A
  • •Kidneys & Liver: Erythropoietin
  • •Heart:Atrial natriuretic peptide
  • •Adipose tissue: is endocrinologically active!
  • •Paracrines: chemical messengers with locally acting effects (within the same tissue)
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2
Q

How are hormones classified?

A
  • Amino acids
  • Steroids
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3
Q

What are the characteristic of aminoacid based hormones?

A
  • Are water-soluble and can not cross the cell membrane of target cells*
  • *Exception: thyroid hormones (T4, T3)
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4
Q

What are the characteristics of steroids?

A

Are lipid-soluble and can diffuse across the cell membrane of target cells

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5
Q

Name some amino acid based hormones

A

Peptide chains & Proteins

  • •ACTH, TSH, ADH
  • •Insulin, Glucagon
  • •Growth Hormone

Amino acid derivatives

  • •Adrenaline, noradrenaline
  • •Thyroid hormones (T4, T3)
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6
Q

Name the five Steroid hormones

A

Adrenal cortex

  • •Referred to as Corticosteroids
  • •Cortisol, Aldosterone

Synthesised from cholesterol

  • •Gonadalhormones:
  • •Progesterone, Androgens, Oestrogens
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7
Q

What are the actions of the hormones?

A

Target cells: influences the activity of only those tissue cells that have receptors for it

** note: some have more than one target cell - EG. noradrenaline at SA node

  1. •Alteration of cell membrane permeability or excitability
  2. •Stimulation of synthetic activity or secretion e.g. enzymes, proteins
  3. •Activation/deactivation of enzymes
  4. •Stimulation of mitosis
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8
Q

How do hormone communicate at target cells?

A
  • second messenger systems
  • •direct gene activation
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9
Q

What is the target cell communication mechanism for second messenger system?

A
  1. Are water-soluble and can not cross the cell membrane of target cells
  2. Act upon receptors embedded in the cell membrane of target cells
  3. Rely on intracellular signaling molecules (second messengers) to mediate their effects
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10
Q

What is the target cell communication mechanism for direct gene activation?

A

Steroids

  1. Are lipid-soluble and can diffuse across the cell membrane of target cells
  2. Are therefore capable of direct gene activation
  3. Bind to receptors within the cytosol of target cells

Thyroid hormones

  1. Are transported intotarget cells by membrane-bound transporter proteins
  2. Are also capable of direct gene activation
  3. Bind to receptors fixed to the DNAof target cells
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11
Q

What are the hormones that use second messenger system?

A

Amino acid based hormones

Example

•Cyclic AMP

  • •E.g. ACTH, FSH, LH, Glucagon, PTH, Calcitonin

•Tyrosine Kinase

  • •E.g.insulin

•PIP2& Calcium

  • •E.g. oxytocin, ADH
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12
Q

What type of hormones use direct gene activation

A

lipid (Thyroid) and steroid-based hormone use direct activation

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13
Q

What type of hormones use second messenger activation ?

A

Amino acid hormones

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14
Q

What are the 3 mechanisms of regulation of hormone release?

A

Humoral stimulus

Neural stimulus

Hormonal stimulus

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15
Q

What is the neural stimulus as a mechanism for regulation of hormone release?

A

Hormone release can be caused by neural input

Example: short term response to stress

  • •Sympathetic nervous stimulation of the adrenal medulla
  • •Adrenal medulla releases adrenaline & noradrenaline
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16
Q

What is humoral stimulus as a mechanism for the regulation of hormone release?

A

•Hormone release can be caused by altered blood levels of certain ions or nutrients

example: •blood concentration of calcium (Ca2+)

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17
Q

What is hormonal stimulus as a mechanism for the regulation of hormone release?

A

Hormone release may be caused by another hormone (trophic) hormone

Example: endocrine glands controlled by the hypothalamic-pituitary axis

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18
Q

How is hormonal release turned off?

A

negative feedback control loop

  • •When hormone levels rise sufficiently to cause target organ effects
  • •Target organ effects “feed back” to the reduce the initial stimulus for hormone release
  • •Results in the inhibition of further hormone release
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19
Q

What is neurophysis hormone and what is its function?

A

The posterior lobe, along with the infundibulum

  • Composed largely of neural tissue
  • •Hasneural connectionsto the hypothalamus – the hypothalamic-hypophyseal tract

FUNCTION

  • •Not a true endocrine gland that manufactures hormones
  • •Stores and releases releases “ready made” hormones received from the hypothalamus
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20
Q

What are the 2 posterior pituitary hormones?

A

Oxytoxcin

ADH

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21
Q

What is oxytocin and its function?

A

•Produced by paraventricularneurons

Stimulus for release from posterior pituitary:

  • •Impulses from hypothalamus in response to cervical/uterine stretching; suckling of infant at breast

Function:

  • •Uterine contractions (labour); milk ejection
  • •Psychoactive effects: promotes nurturing, bonding and trust
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22
Q

What is the ADH hormone and its function?

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A

•Produced by supraventricular neurons

Stimulus for release from posterior pituitary:

  • •Impulses from hypothalamus in response to increased blood osmolarity or decreased blood volume
  • Angiotensin II also stimulates the release of ADH

Function:

  • •Increases the reabsorption of water by acting on the cells of the kidney tubules (DCT & CD)
23
Q

What are the anterior pituitary hormones?

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A
  1. Growth hormone
  2. Prolactin
  3. ADRENOCORTICOTROPHIC HORMONE (ACTH)
  4. THYROID STIMULATING HORMONE (TSH)
  5. FOLLICLE STIMULATING HORMONE (FSH)
  6. LUTEINISING HORMONE (LH)?
24
Q

What is the location and function of the anterior pituitary gland?

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A
  • •The anterior lobe is referred to as the adenohypophysis
  • •Composed largely of glandular tissue
  • •Hasvascular connections to the hypothalamus – the hypophyseal portal system(a network of capillary plexuses connected by veins)
  • •Hypothalamic hormones released into the portal system control the release of anterior pituitary hormones

FUNCTION

  • Synthesises and releases six major hormones
  • TSH, ACTH, FSH & LH are trophic hormones
  • i.e. they regulate the secretions of other endocrine glands
25
What is the stimulus release and function for Growth hormone?
**Stimulus** **for release:** * •GH Releasing Hormone (hypothalamic hormone) – released in response to low levels of GH * •Secondary triggers: low levels of blood sugar and fatty acids, high levels of blood amino acids **Functions:** * •Anabolic hormone that stimulates somatic growth * •Mobilises fats for use as an energy source, in preference over glucose
26
What is the stimulus release and function for Prolactin?
**Stimulus** **for release:** * •Unlike other anterior pituitary hormones, PRL release is controlled by dopamine(also referred to as PRL inhibiting hormone) * •Low levels of dopamine result in PRL release – this is enhanced by factors such as breast-feeding and oestrogens (e.g. use of OCP) **Functions:** * •Promotes mammary gland development and milk production * • Promotion of sexual gratification after orgasm
27
What is the stimulus release and function for ADRENOCORTICOTROPHIC HORMONE (ACTH)?
**Stimulus for release** * •Corticotrophin-releasing hormone (hypothalamic hormone) – in response to stressors e.g. fever, hypoglycaemia **Functions** * •Promotes release of hormones from the adrenalcortex * •Glucocorticoids, androgens, mineralocorticoids * •Thecleavage product of ACTH is alpha-Melanocyte Stimulating Hormone (a-MSH) * •aMSHstimulates the production of melanin (relevant in certain endocrine pathologies)
28
What is the stimulus release and function for THYROID STIMULATING HORMONE (TSH)?
**Stimulus for release** * •Thyrotrophin-releasing hormone (hypothalamic hormone) **Functions** * •Stimulates thyroid gland to release thyroid hormones: thyroxine/tetraiodothyronine (T4) and triiodothyronine (T3)
29
What is the stimulus release and function for FOLLICLE STIMULATING HORMONE (FSH)?
Stimulus for release: * Gonadotrophin Releasing Hormone (GnRH) from the hypothalamus Functions: * •F: Stimulates maturation of ovarian follicle and production of oetrogens * M:Stimulates production of androgen-binding protein by sustentacular cells (supports sperm production
30
What is the stimulus release and function for LUTEINISING HORMONE (LH)?
**Stimulus** **for release:** * Gonadotrophin Releasing Hormone (GnRH) from the hypothalamus **Functions:** * •F: Triggers ovulation and converts the ruptured follicle into the corpus luteum (the corpus luteum secretes progesterone and some oestrogen) * •M: Stimulates production of testosterone by interstitial (Leydig) cells
31
Image of the hypothalamus + hormones
32
Introduce the adrenal glands
LOCATION: Paired glands atop the kidneys STRUCTURE: * •Right adrenal gland– pyramidal in shape * •Left adrenal gland – semilunarin appearance * •Enclosed in a fibrous capsule and a cushion of fat * •Each gland possesses a cortexand a medulla – both regions play an endocrine role FUNCTION: production fo hormones
33
What is the vascular supply to the adrenal glands?
ARTERIAL SUPPLY: Superior, middle, inferior adrenal arteries (50-60 branches) VENOUS DRAINAGE * •Right adrenal vein àIVC * •Left adrenal vein àrenal vein àIVC LYMPHATIC DRAINAGE * •Rich lymphatic drainage via the adrenal lymphatic vessels * •Drainage to the lumbar nodes
34
What is the neurovascular supply to the adrenal glands?
Sympathetic supply: * •Abdominopelvic splanchnic nerves: T10-L2 Parasympathetic supply: * Hypothesised to be branches of Vagus nerve CNX
35
WHat are the 3 zones of the adrenal cortex?
1. outer cortex: Zona glomerulosa 2. Middle Cortex: Zona fasciculata 3. InnerCortex: Zona reticularis
36
What are the functions of the zona glomerulosa?
* produce mineral corticodes: aldosterone •Acts on thedistal aspectsof thenephron: * •Na+ reabsorption * •K+ secretion •Primarily under control of RAAS Otherstimuli for release: * •High plasma levels of K+ * •Stress response – mediated by CRH & ACTH * •Atrial natriuretic peptide inhibits aldosterone release
37
What are the functions of the zona fasciculata?
Produce glucocorticoids 1. Promotes gluconeogenesis (Mobilization fatty acid, increase breakdown protein, maintain blood levels of glucose) 2. Enhances the effect of SNS on vascular smooth muscle (BP regulation) 3. Regulation of the immune response
38
What are the consequences of excess cortisol?
1. •Hyperglycaemia 2. •Negative effects on bone density 3. •Muscle mass, cartilage formation 4. •Hypertension 5. •Immunosuppression
39
What are the functions of the Zona reticularis?
1. Produces androgens to supplement those produced by the gonads 2. DHEA and androstenedione 3. Increase levels during the lead up to puberty 4. Source of oestrogen after menopause
40
by which mechanism do steroid hormones act upon their target cells?
Direct regulation mechanism. Important facts \*\*\*\*All hormones produced by the adrenal cortex are a steroid hormone \*\*\*\*Another name for this group of hormones: “corticosteroids”
41
What are the functions of the adrenal medulla?
* •Features spherical chromaffin cells clustered around blood-filled capillaries and sinusoids * •Chromaffin cells synthesise catecholamines: * •Adrenaline(80%) & Noradrenaline (20%) * •Catecholamines augment the activity of the SNS: * •áHR & cardiac contractility * •Peripheral vessel constriction, áBP * •ábloodglucose, BMR
42
How is the adrenal medulla regulated?
1. •Preganglionic sympathetic fibres leave the cord at T10-L1 2. •Unlike other abdominopelvic splanchnic nerves, these nerves pass through the prevertebral ganglia without synapsing 3. •Instead, these preganglionic nerves terminate at the adrenal medulla, where they synapse directly with chromaffin cells 4. •Chromaffin cells are considered to be modified postganglionic sympathetic neurons
43
What is hypercortisolism?
a range of conditions characterised by an excess of circulating cortisol
44
What is cushins disease vs. cushing's syndrome?
* Cushing’s Disease: hypercortisolism due to increased ACTH secretion from the anterior pituitary - caused by pituitary microadenoma * Cushing syndrome: hypercortisolism has occurred somewhere else - caused by iatrogenic
45
WHat are the clinical features of cushing's syndrome
**Increased glucocorticoid activity** **hyperandrogenism**
46
What is the management of cushings syndrome?
Surgery: remove the tumour modification of glucocorticoid therapy
47
What are the two types of adrenocortical hypofunction?
PRIMARY ADRENOCORTICAL INSUFFICIENCY **Addison’sDisease** decrease cortisol SECONDARY ADRENOCORTICAL INSUFFICIENCY
48
What are the causes of Addison's disease?
Autoimune infection metastatic disease bilateral adrenalectomy
49
What are the clinical features for Addison disease?
**Skin changes** **+ ACTH =** promote melanin production = + melanocyte stimulating hormone
50
What is Phaeochromocytoma?
* A tumour arising from the chromaffin cells of the adrenal medulla * Most common cause of excess catecholamine production
51
What are the clinical features for Phaeochromocytoma?
Hypertension Intermittent catecholamine secretion (systemic)
52
What is the pharamachological management for addison?
Hormone supplement of - cortisol - flurocortisone
53
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