Practical #1- Chapter 16, 17, and 20

The Endocrine System

• 2nd major control system of the body

How does the endocrine system work

• Slower acting system that uses chemical messengers(hormones) to maintain homeostasis

Endocrine Glands

• The glands that make up the endocrine system produce chemical messengers called hormones that travel through the blood to other parts of the body.

Exocrine Glands

• Exocrine glands release(secrete) substances through openings (ducts) onto your body surfaces. Exocrine glands secrete sweat, tears, saliva, milk, and digestive juices.

Insert endocrine system pics

Pineal gland

• sleep-wake cycle(circadian rhythm)

• melatonin

Hypothalamus

• Control center of autonomic and endocrine functions

Anterior Pituitary

• Hypophyseal portal system

• tropic hormones:

TRH to TSH to thyroid gland to T3 and T4

GnRH to FSH to Gonads

GnRH to LH to Gonads

CRH to ACTH to Adrenal cortex

Not tropic hormones:

GHRH to GH to Liver, muscle, bone

PIH to PRL to mammary glands

Posterior Pituitary

• only stores hormones

• Oxytocin- uterine contractions and milk ejection from hypothalamus target uterus

• ADH- water retain from hypothalamus target kidneys

Thyroid Gland

• Regulates metabolism, heart rate, and body temperature

• Triiodothyronine (T3)

• Thyroxine (T4)

• What stimulates the release of T3 and T4

• target most cells of the body; increases tissue growth and development. T

Parathyroid Gland

• regulates calcium and phosphorus levels

• parathyroid hormone: released when there are low levels of calcium; target the bones and kidneys

Thymus

• helps T lymphocytes (T cells) mature so they can fight infections

• thymosin

• thymopoietin

Adrenal Glands

• stress response and metabolism

• Adrenal cortex: aldosterone, cortisol, gonadocorticoids to testosterone OR some estrogen

• Adrenal Medulla: catecholamines (epinephrine and norepinephrine)

Pancreas

• regulates blood sugar

• insulin (decrease blood glucose)

• glucagon (increase blood glucose)

• Negative Feedback Loops

Testes and Ovaries

• Regulate reproduction and secondary sex characteristics

• Ovaries (females): estrogen, progesterone

• Testes (males): testerone

Negative and Positive Feedback Loops

• negative feeback is the most common

• change in regulated variable to stimulates or triggers a response to affect the same variable

• stimulus occurs to hormone is released to hormone levels rises or falls to target organ responds to homeostasis is restored to hormone levels return to normal

• Ex: pancreas (glucagon and insulin)

• adrenal medulla (response to stress)

• thyroid gland (body temperature)

Aldosterone

• increases blood levels of Na+ and water by increasing Na+ and water reabsorption at kidneys

  • decrease blood levels of K+ by increasing excretion of K+ at kidneys