Hormones

What are hormones?

Chemical messengers released from group of cells called glands. Transported through bloodstream until they reach target organ. Bind to receptor and cause effect.

Endocrine glands

glands without ducts that secrete substances directly into the blood.

Exocrine glands

Secrete substances into ducts which lead to other tissues

Thyroid gland

Hormone: thyroxine

Target organ: all cells

Effect: controls metabolism

Pancreas

Hormone: insulin

Target organs: liver,muscle

Effect: controls glucose levels

Pituitary gland

Hormone: LH, FSH, ADH

Target organ: muscle, bone, ovaries

Effect: regulates growth, stress

Parathyroid gland

Hormone: parathyroid hormone

Target organ: kidneys, bones

Effect: Controls calcium levels

testes

Hormone: testosterone

Target organ: testes

Effect: regulates sperm production

Ovaries

Hormone: Oestrogen, progesterone

Target organs: ovaries, uterues

Effect: regulates menstrual cycle

Steroid

lipids that can pass through cell memberane. (testosterone/oestrogen)

peptides

charged so can’t pass through cell membranes. (adrenaline)

Steroid hormones mechanism

Steroids can pass into cells and impact cells directly.

• hormone binds to receptor

• hormone-receptor bind together to form a hormone-receptor complex.

• HRC acts as a transcription factor.

• Binds to DNA.

• translated and causes cbanve in cell.

Peptide hormone mechanism

Can’t pass through cell membrane so:

• binds to a receptor on cell membrane.

• binding triggers activation of receptor protein

• series of reactions involving other membranes occur

• formation of secondary messenger (cAMP)

• secondary messenger triggers a response