Monday, 19 SeptemberChapter 11 The Endocrine System

• Classes of hormones• The adrenal gland• Fates of hormones• Renin-Angiotensin-Aldosterone System• Control of hormone secretion• Hormone interactions (permissive effects)

1QQ # 61. Stress leads to the secretion of epinephrine which alters

the metabolism of many cell types. Describe the effects of EPI on two different cell types and explain how these effects are beneficial to the person.

2. Starting with the arrival of carbohydrates in the stomach list the sequence of events, cell types, and hormone(s) that comprise a feedforward mechanism. What is the purpose of this feedforward mechanism?

3. Beginning with the ingestion of a large amount of sugar, list the sequence of events in a reactive hypoglycemic person that ultimately leads to a headache, fast heart rate, and cold, clammy skin.

Endocrine Organs (Table 11-1)

• Pituitary Gland• Thyroid Gland• Pancreas• Gonads• Gastrointestinal Tract• Heart• Kidney• Hypothalamus• Liver• Etc.

Hormone: chemical messengerscarried by blood to target cells

upon which they act.

Only those cells having receptorsCan respond to a given hormone

Analogy: SSNs and receptors

Hormone

Paracrine agent

Autocrine agent

Neurotransmitter

Neuromodulator

3 Chemical Classes of Hormones

• 1: Amine hormones (from amino acid tyrosine)– Thyroid hormones – Adrenal medullary hormones (catecholamines)

• 2: Peptide hormones (peptides & proteins)• 3: Steroid Hormones (derivatives of cholesterol)

Why does the chemical class matter?

Fig. 11.01

Catecholaminessoluble in plasma

ThyroidHormones Not soluble in plasma, bound & free

AmineHormones

Adrenalmedulla

NT

NT

Fig. 11.03Steroid hormones

not soluble in plasma, not storable in vesicles

Target cells have intracellular receptors.Changes is gene expression.

Timecourse?

Bound & Free

Fig. 11.02Peptide Hormones

Examples of Peptide Hormones:Insulin, glucagonprolactin, erythropoietin,parathyroid hormone,gastrin, leptin, growth hormone,oxytocin, vasopressin,FSH, LH, GHRH, andmany more!

Cell surface receptors on target cells

Guess peptide!

Soluble in plasma

e.g.Beta cell

Know Table 11-2 p 323

• Hormone class

• Major form in plasma

• Location of receptors

• Signal transduction mechanisms

• Rate of excretion / metabolism

Questions so far?

Fig. 11.05

Adrenal Gland

Part of Sympathetic Nervous System

Hormones of the Adrenal Cortex

Hormones of the Adrenal Cortex

Glucocorticoids

Mineralicorticoid

Androgens

DHEA

“Andro”

What regulates the secretion of cortisol and aldosterone?

Fig. 11.06Gonadal Steroids(not adrenal cortex)

King DS, Sharp RL, Vukovich MD, Brown GA, Reifenrath TA, Uhl NL, Parsons KA . Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial. JAMA 1999; 281(21):2020-8

Estrogens

Fast if freeSlow if bound

Be able to giveExamples.

T4 to T3 and Testosterone to Estradiol

Ex: Renin

What happens to hormones once released?

Renin-angiotensin-aldosterone

Angiotensinogenfrom liver, anever-present plasma protein

ReninAngiotensin IAngiotensin converting

enzyme (ACE)

Angiotensin II

ThirstArterial smooth muscle … vasoconstriction…increase blood pressure

Zona Glomerulosa of Adrenal Cortex

Aldosterone Promotes Na+ retention in Kidney

Renin is an enzyme released from kidney cells into bloodstream, its “substrate” is a plasma protein called Angiotensinogen.

Aldosterone

Na+ reabsorption in kidney

Plasma volume

Blood pressure

Renin from Juxtaglomerular cells in Kidney

Multi-step process involving Angiotensin I and II

(-)

Angiotensin II

thirst

Drink

vasoconstriction

K+ in plasma

_______

Blood Pressure

Fast if freeSlow if bound

Be able to giveExamples.

T4 to T3 and Testosterone to Estradiol

Ex: Renin

What happens to hormones once released?

Factors that affect hormone secretion

Recall example: beta cells of Islets of Langerhans

Secretion is usually pulsative, may be diurnal.

Integrator!

Fig. 11.08

Thyroid hormone stimulates production of beta-adrenergic receptors

Permissive effect