Endocrine System

hormones

Types of Hormones

• steroids

• peptides

• amino acid derivatives (amine hormones)

Steroids

-made from cholesterol (lipid)

• hydrophobic

-bind to an intracellular receptor, often on the nuclear membrane

-trigger transcription and translation of new proteins

-act slowly, but have longer lasting and sometimes permanent effects

Note: ex. testosterone or progesterone

Peptides

-short amino acid chains

• hydrophilic

-bind to a receptor on the target cell’s surface and trigger a signal transduction cascade

• G-protein

-have rapid, temporary effects on the cells

-typically they activate or deactivate existing enzymes

Amino acid derivatives (amine hormones)

-structurally similar to peptide hormones

-some act like peptide hormones and trigger a signalling cascade

-some act like a steroid hormones (ex. thyroid hormones)

-hydrophilic

Hypothalamic-Pituitary Axis

central control for most hormone activity

-involves hypothalamus, anterior pituitary, and posterior pituitary

Hypothalamus

secretes neurohormones (hormones produced in nerve tissue)

Anterior Pituitary

a gland that is stimulated by those neurohormones(from hypothalamus) to make and secrete other hormones that stimulate other glands

Posterior Pituitary

made up of nerve tissue and it stores hormones made by the hypothalamus that it releases when stimulated by action potentials from the hypothalamus

Hypothalamic-Pituitary Feedback End…

Once production reaches the bottom and has adequate quantity of hormone then hormones tell hypothalamus to stop producing all related hormones on chain

Note: NOT AT HIGH LEVEL OF PRODUCTION ALL OF THE TIME

Endocrine System (glands/organs)

• hypothalamus

• pituitary gland

• thyroid gland

• thymus

• parathyroid gland

• pancreas

• adrenal gland

• ovaries

• testes

Hormone Control of Food Intake

• Anorexic hormones

• Orexic hormones

Anorexic Hormones

satiety (full) signals

-leptin (produced by adipose tissue)

-insulin (produced by pancreas)

Orexic Hormones

hunger signals

-ghrelin (released by stomach in response to lack of food)

Hormone Control of Digestion

-CCK

-Gastrin

• peptide hormone secreted in response to stomach expanding that stimulates the realses of HCI

-Secretion

• peptide hormone that stimulates bicarbonate to neutralize acidic chyme

Low Blood Sugar…

—promotes glucagon release—> pancreas —glucagon—> liver (stimulates glycogen breakdown) —> raises blood sugar

High Blood Sugar…

—promotes insulin release—> pancreas —>

—insulin—stimulates glycogen formation—>liver—>lowers blood sugar

—stimulates glucose uptake from blood—> tissue cells——> lowers blood sugar