lecture ch eighteen: endocrine system

What is the endocrine system?

Controls body processes using hormones released into the blood.

What are the 4 types of cell communication?

Direct, Paracrine, Endocrine, Synaptic.

What is Direct Communication?

Two cells touch and exchange molecules through gap junctions (ex: cardiac cells).

What is Paracrine Communication?

Chemicals affect only nearby cells in the same tissue.

What is Endocrine Communication?

Hormones travel through blood to distant tissues.

What is Synaptic Communication?

Neurotransmitters cross a gap between nerve cells.

What are the 3 hormone classes?

Amino acid derivatives, peptide hormones, and lipid derivatives.

What are amino acid derivatives? (What hormones have a base of an amino acid derivative?)

Tyrosine → thyroid hormones, epinephrine, norepinephrine; Tryptophan → serotonin, melatonin.

What are Peptide Hormones?

Amino acid chains that start inactive then activate (ex: glycoprotein: TSH, LH, FSH).

What are eicosanoids made of? Examples, and what do they do?

Arachidonic acid ( ex: prostaglandin = cell activity, leukotrienes = clotting

What are steroid hormones, and how are they transported?

Made from cholesterol and transported bound to blood transport proteins (ex: estrogen, androgens, progesterone).

Which hormones pass through the cell membrane, and what is the cell membrane made of?

Steroid and thyroid hormones (fat-soluble) ; phospholipid bilayer

Which hormones cannot pass through the cell membrane?

Peptide hormones and catecholamines (dopamine, norepinephrine, and epinephrine) (bind surface receptors).

What is a First Messenger?

The hormone that binds to the surface receptor.

What is a Second Messenger?

Intracellular molecule that amplifies the signal (cAMP, Ca²⁺).

What is a G Protein?

Enzyme between first and second messenger that increase or decrease cAMP & Ca

What is Down-Regulation?

Too much hormone → fewer receptors → less sensitivity.

What is Up-Regulation?

Too little hormone → more receptors → more sensitivity.

How do Steroid Hormones work?

Enter cell → bind cytoplasmic/nuclear receptors → activate genes.

How do Thyroid Hormones work?

Enter cell → bind nuclear/mitochondrial receptors → activate genes or increase ATP.

What triggers hormone secretion?

Humoral, hormonal, or neural stimuli.

What is a Simple Endocrine Reflex?

One hormone fixes one problem then stops (ex: insulin).

What is a Complex Endocrine Reflex?

Multiple hormones and steps coordinated by the hypothalamus.

What does the Hypothalamus do?

Makes ADH and oxytocin; controls the pituitary, secreting hormones that control the anterior lobe and pituitary.

What is the Hypophyseal Portal System?

Blood vessel system carrying releasing/inhibiting hormones to pituitary (AL)

What are the two lobes of the pituitary, and how many hormones are involved?

Anterior (makes 7 hormones); Posterior (releases 2 hypothalamic hormones).

What are the anterior lobe hormones?

TSH, ACTH, [FSH, LH], Prolactin, GH, MSH.

What are the posterior lobe hormones?

ADH and Oxytocin

TSH — trigger and effect? (anterior lobe)

Trigger: TRH (Thyrotropin Releasing Hormone) from hypothalamus

Released by: Anterior pituitary

Target: Thyroid gland

Effect: Thyroid releases T3 and T4

ACTH — trigger and effect? (anterior lobe)

Trigger: CRH (Corticotropin Releasing Hormone) from hypothalamus

Released by: Anterior pituitary

Target: Adrenal cortex

Effect: Releases glucocorticoids (cortisol)

FSH & LH (Gonadotropins) — trigger and effect? (anterior lobe)

Trigger: GnRH (Gonadotropin Releasing Hormone) from hypothalamus

Released by: Anterior pituitary

Target: Testes / ovaries

Effect: Release sex hormones and eggs/sperm

Prolactin — trigger and effect? (anterior lobe)

Trigger: PRH (release) / PIH (inhibit) from hypothalamus

Released by: Anterior pituitary

Target: Mammary glands

Effect: Produces milk

Growth Hormone — trigger and effect? (anterior lobe)

Trigger: GH-RH (release) / GH-IH (inhibit) from hypothalamus

Released by: Anterior pituitary

Target: Liver

Effect: Liver releases somatomedins (growth factors)

MSH — trigger and effect? (anterior lobe)

Trigger: MRF from hypothalamus

Released by: Anterior pituitary

Target: Melanocytes

Effect: Release melanin (skin pigment)

ADH — trigger and effect? (posterior lobe)

Trigger: Dehydration or low blood pressure

Released by: Posterior pituitary (made by hypothalamus)

Target: Kidneys

Effect: Conserve water / reduce water loss

Oxytocin — trigger and effect? (posterior lobe)

Trigger: Suckling response

Released by: Posterior pituitary (made by hypothalamus)

Target: Mammary glands

Effect: Release milk

What is the thyroid gland and what does it produce?

Located at front of trachea. Contains follicles filled with colloid that use iodine to produce T3, T4, and Calcitonin

What do T3 and T4 do?

Increase metabolism, protein synthesis, ATP production.

What does Calcitonin do?

Lowers blood calcium & inhibits osteoclasts.

What does parathyroid hormone do?

Raises blood calcium & stimulates osteoclasts

How do Calcitonin and PTH relate?

Opposites that balance calcium levels.

What are the two layers of the adrenal gland?

Cortex (outer) and medulla (inner).

What are the 3 cortex hormones?

Aldosterone (mineralocorticoids), cortisol (glucocorticoids), and androgens

What does aldosterone do, where is it produced, and what’s the other name for it?

Regulates water and electrolyte balance.

zona glomerulosa

mineralocorticoid

What does cortisol do? Where is it produced, and what’s the other name for it?

Raises blood sugar; reduces inflammation.

zona fasciculata

glucocorticoids

What do androgens do? Where is it produced?

Affect secondary sex characteristics.

zona reticularis

What does the Adrenal Medulla produce?

Epinephrine and norepinephrine → Increases glucose/fat breakdown, heart rate, and blood pressure

What does the Pineal Gland produce?

Melatonin → regulates sleep/wake cycle.

What makes the Pancreas unique?

Has exocrine (enzymes) and endocrine (hormones) functions.

What does Glucagon do?

Made by alpha cells; raises blood sugar.

What does Insulin do?

Made by beta cells; lowers blood sugar.

What is Diabetes Mellitus?

Insulin lack/resistance → high blood sugar.

What does the Kidney produce?

EPO → increases red blood cell production.

What does the Heart produce?

Natriuretic peptides → increase sodium/water secretion.

What does the Thymus produce?

Thymosin → Helps immune cells grow and mature.

What do the Gonads produce?

Testes → Androgens (sperm maturation)

Ovaries → Estrogens (egg follicle maturation)