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Lecture 2 Endo I > Endocrine system > Flashcards

Endocrine system Flashcards

1
Q

What does the endocrine system consist of?

A

Ductless endocrine glands that secrete hormones.

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2
Q

What specialised glands are part of the endocrine system?

A

Thyroid gland, adrenal glands, etc.

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3
Q

Which tissues contain endocrine cells?

A

Hypothalamus, adipose tissue, gastrointestinal tract.

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4
Q

What are the types of hormones derived from cholesterol?

A
  • Steroids, which are hydrophobic.
  • Produced by gonads and adrenal cortex; derived by cholesterol.
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5
Q

Classification of hormones

A

Peptides, Amines, Steriods

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6
Q

What are peptide hormones

A
  • Cleaved from larger polypeptides during posttranslational modification.
  • Small peptides: TRH (GluHisPro), vasopressin.
  • Proteins: Insulin, Growth hormone.
  • Glycoproteins: long polypeptides bound to one or more carbohydrate groups (FSH & LH).
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7
Q

Property of peptide hormones

A
  • Water-soluble.
  • Travel in bloodstream without carriers.
  • Rapid but short-lived effect.
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8
Q

How does peptide hormones work?

A

Charged hormone (first messenger) → bind to extracellular receptor → activates second messenger → signalling cascade through amplification.

Example: GPCR

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9
Q

What are hormones?

A

A signalling molecule secreted by glands into bloodstream to distant target tissue → bind to receptor → regulate gene expression/cellular functions.

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10
Q

Property of steroid hormones

A
  • Lipid-soluble.
  • Travel in bloodstream with carriers.
  • Bound hormones are inactive.
  • Slower but long-lived effect.
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11
Q

How does steroid hormones work?

A

Non-polar hormone → bind to intracellular/intranuclear receptors → receptor conformational change (eg. Receptor dimerization) → hormone receptor complex bind directly to DNA → alter gene transcription.

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12
Q

What are amine hormones?

A
  • Derived from modified amino acids (tyrosine).
  • Share traits from both peptide & steroid hormones.
  • Catecholamines (epinephrine & norepinephrine) → GPCR. Adrenaline rush
  • Thyroid hormones (thyroxine) → Intracellular receptors. Metabolic rate.
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13
Q

How are the action of hydrophilic hormones mediated?

A

By membrane receptors.

  • G-protein linked: Activate second messenger pathway.
  • Ion-channel linked: Mostly for neuropeptide hormones.
  • Enzyme-linked: Most are protein kinases (Insulin receptor → Receptor tyrosine kinase).
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14
Q

How are the action of hydrophobic hormones mediated?

A

By nuclear receptors.

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15
Q

Elaboration: Direct hormones

A

Secreted & act directly on target (non-endocrine) tissue.

Example: Insulin

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16
Q

Elaboration: Tropic hormones

A

Stimulate secretion of other hormones to travel to target (endocrine) tissue.

Example: GnRH & LH

17
Q

How is endocrine function regulated?

A
  • Hormone secretion
  • Tissue and sensitivity
  • Hormone binding to plasma proteins, metabolism and activation in organs (liver and kidney).
18
Q

Elaboration: Hormone secretion

A
  • Respond to changes in internal & external environment.
  • Negative and positive feedback; feed forward.
  • Neuroendocrine reflexes (eg. Secretion of oxytocin in response to uterine stretching.)
  • Circadian rhythms (cortisol secretion)
19
Q

Elaborate: Tissue and sensitivity

A
  • Tissue receptors.
  • Transcription cofactors (co-repressors and co-activators).
20
Q

Endocrine disorders: Hyposecretion

A
  • Resulted from heredity, dietary deficiency, immunologic factors.
  • Causes can be primary/secondary (deficiency of another hormone).
  • Can be treated by Hormone Replacement Therapy.
21
Q

Endocrine disorders: Hypersecretion

A
  • Due to tumours of endocrine glands, autoimmune disease.
  • Causes can be primary/secondary.
22
Q

Endocrine disorders: Lack of tissue response

A
  • Endocrine dysfunction can arise from the unresponsiveness of target cells (eg. Testicular feminisation syndrome, type II diabetes).

Lecture 2 Endo I (2 decks)

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