Endocrine

Question 1

hormones

Answer 1

chemical messengers carried via the blood stream

Question 2

permissiveness

Answer 2

hormone-hormone interaction

i.e. hormone A requires the presence of hormone B to be fully active

Question 3

endocrine system consists of ___________

Answer 3

glands that secrete hormones

Question 4

Hormone types

Answer 4

1. Peptide hormones (strings of amino acids)
2. Amino-Acid Derivative hormones
3. Steroid hormones
4. Thyroid hormones

Question 5

explain peptide hormones

Answer 5

• > range from 3 amino acid peptides to small proteins and are initially synthesized on the ribosome of endocrine cells as preprohormones
• > cleaved from prohormones by proteolytic enzymes in the granuar ER of the cell

Question 6

what happens to peptide hormones once released

Answer 6

• > the hormone diffuses into the capillaries supplying blood to the secreting endocrine glands
• > these endocrine gland capillaries are “leaky” (discontinuous) resulting in relatively easy diffusion of the hormone into the blood between the enothelial cells of the capillary walls

Question 7

Important things to note about peptide hormone

Answer 7

many circulating peptide hormones are also neurotrnsmitters HOWEVER, circulating hormones do not activate receptors in the brain as the blood-brain barrier prevents transfer.

therefore the neurotransmitter form of the hormone is the only form capable of activating the brain

Question 8

Amino acid derivative hormones

Answer 8

includes:

• > thyroid hormones (produced by thyroid gland)
• > epinephrine, norepinephrine (catecholamines) (produced in the adrenal gland and sympathetic neurons)
• > dopamine (produced in the hypothalamus and posterior pituitary)

Question 9

steroid hormones

Answer 9

• > produced by the adrenal gland, gonads, kidneys and placenta (during pregnancy)

includes:

cortisol, aldosterone, testosterone, estradiol (estrogens)

• > source for production of steroid hormones is cholesterol brought to the endocrine glands via the bloodstream (LDLs)

Question 10

thyroid hormones

Answer 10

• > also classed as amino-acid derivative hormones but considered separately from the majority of the other amino acid derivatives due to the complexity of thyroid hormone storage and importance of the hormone for overall body function
• > hydrophobic, complex storage
• > binds intracellular receptor proteins in target cells
• > complex then binds with DNA and activates transcription

Question 11

explain hormone transport in the blood

Answer 11

1. peptide hormones and the catecholamine = water soluble (easy transport)
2. steroid hormone and thyroid hormones = circulate largely bound to plasma proteins

Question 12

why is the concentration of free hormones in the plasma more important that the total free + bound hormones

Answer 12

• > concentration of a hormone in the plasma is also determined by it’s rate of removal from the blood
• > the liver and kidneys play a major role in the removal or transformation of a circulating hormone
• > generally, free hormones (such as the peptide and catecholamines) have a short half-life in the blood while the protein bound hormones last longer

Question 13

prohormone pathway

Answer 13

• > prohormones are packaged into secretory vesicles of the golgi nad are cleaved during this process resulting in the formation of the active hormone + remainder of the prohormone

* increased cytosolic Ca2+ triggers the packaging and release of the active hormones

* increased cytosolic Ca2+ can be result of either increased extracellular Ca2+ concentrations or increased agranular ER Ca2+ concentrations as a result of direct or indirect stimuli

Question 14

active hormone transport after being cleaved

Answer 14

released into the bloodstream and once released, the hormone diffuses into the capillaries supplying blood to the secreting endocrine glands

• > these endocrine gland capillaries are “leaky” resulting in relatively easy diffusion of the hormone into the blood between the endothelial cells of the capillary walls