7.1 Main Endocrine Glands and Hormone Types

Question 1

Autocrine signaling?

Answer 1

Chemicals affect same cells that secreted them, eg. white blood cells make growth factor to drive their own proliferation

Question 2

Paracrine signaling?

Answer 2

Chemicals secreted to neighbouring cells.

Question 3

Endocrine signaling?

Answer 3

Chemicals diffuse into and travel through blood stream to target cells long distance

Question 4

Onset and duration of endocrine signals is…

Answer 4

slower (minutes to hours) and lasts longer (hours to days+).

Question 5

List the main endocrine glands:

Answer 5

Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus gland
Adrenal glands
Pancreas
Ovary/testes

Question 6

Exocrine vs endocrine?

Answer 6

Exocrine glands have ducts and the substances they make are not hormones. These substances travel along ducts to the surface.

Endocrine glands are ductless. Instead, they release their products (hormones) into the surrounding fluid.

Question 7

Hormone types

Answer 7

Peptides & proteins - chains of amino acids
Steroids - derived from cholesterol
Amines - derived from tyrosine and tryptophan (amino acids)

Question 8

Peptide hormones

Answer 8

• All hormones from hypothalamus and pituitary gland are peptide
  
  • Most common
  • Short half-life - a few minutes
  • Amino acid chains of different lengths (3-200 AAs)
  • Hydrophilic/lipophobic - free in blood but can’t pass the plasma membrane
  • Stored in vesicles (secretory) and released via exocytosis (most regulated part)
  • Preprohormone (in ER) -> cleaved into prohormone (Golgi body)
  • Stimulus secretion coupling - secreted according to a specific stimulus to the cell

Question 9

Steroid hormones

Answer 9

• Derived from cholesterol - lipophilic
  
  • Synthesised de novo (as needed)
  • Synthesised in smooth ER of gonads, adrenals, and placenta
  • Diffuse directly out of secretory cell
  • High proportions bound to carrier proteins in plasma (probably partly because they’re lipophilic and blood is water-based), which extends the half-life (stops liver metabolising them.
  • Receptors are in the cytoplasm or nucleus of target cells (this means that the hormones have to pass the plasma membrane)
  • Effects from activation of target genes for protein synthesis

Question 10

Amine hormones

Answer 10

• Small size
  
  • Comprised of 1-2 amino acids, a benzene ring, and an OH group.
  • Tyrosine -> catecholamines (dopamine, noradrenaline, adrenaline)
  • Tyrosine -> thyroid hormones (coupled tyrosine with iodine attached)
  • Tryptophan -> melatonin (secreted from pineal gland, regulates sleep-wake cycle)

Question 11

Catecholamines (derived from, soluble, carrier proteins, receptors, activate, half-life)

Answer 11

Derived from tyrosine
Hydrophilic
Half bound to carrier proteins
Receptors on cell surface
Activates 2nd messengers
Half-life of a few minutes
More like peptides

Question 12

Thyroid hormone (derived from, soluble, carrier proteins, receptors, activate, half-life)

Answer 12

Iodinated tyrosine derivative
Hydrophobic
Bound to carrier proteins
Intracellular receptors
Activates genes
Half-life of a few days