Endocrine System

Hormones!

The human endocrine system

• The endocrine system consists of ductless glands that produce hormones.

• Hormones are chemical messengers that travel through the blood stream and affect activities throughout the body.

Human Endocrine System Diagram

Hypothalamus andPituitary gland

Thyroid and Parathyroid glands

Thymus

Adrenal gland Pancreas

Ovary

Testes

Main players• Hypothalamus-secretes many hormones that

regulate the pituitary• Pituitary makes hormones that stimulate adrenals,

thyroid, growth, and the production of ova and sperm• Thyroid-regulates metabolism• Parathroid-regulates calcium levels• Thymus-T-cell development• Adrenals-make adrenalin for flight of fight• Pancreas-blood glucose levels

Feedback loops

• How hormones are controlled!

Negative feedback loops-for homeostasis!

• Most common way to keep levels steady-homeostasis

• When gland X releases hormone X, this stimulates target cells to release hormone Y. When there is an excess of hormone Y, gland X "senses" this and inhibits its release of hormone X.

• Example-glucose homeostasis with insulin

Positive Feedback Loops

• Less Common• When gland X releases hormone X, this

stimulates gland X to release more hormone X.

• This causes a HUGE amount of hormone in a short period of time.

Positive feedback loops

• One example is the onset of contractions in childbirth. When a contraction occurs, the hormone oxytocin is released into the body, which stimulates further contractions. This results in contractions increasing in amplitude and frequency causing the release of more oxytocin.

• Lactation also involves positive feedback in that the more the baby suckles, the more milk is produced, via a surge in prolactin secretion.

Challenge!

• Which gland produces hormones for fight or flight?

• Which gland controls and regulates many other glands?

• Which one makes adrenaline?• Which feedback loops contribute to

homeostasis?

Excretory System

• Removes wastes from metabolism• Involves lungs (for CO2)• Involves kidneys (for urea)-Keep needed

water

Human Urinary System Diagram

Nephron

Kidney

Ureter

UrinaryBladder

Urethra

Kidney

How it works•The urinary system: the kidneys, ureters, urinary bladder and urethra• Eliminate majority of metabolic wastes from the body. •nephron is made of a Bowman’s capsule: tubules and capillaries (called the glomerulus) • Fluid (filtrate) enters capsule•As filtrate passes through the tubule of the nephron, materials needed by the body are reabsorbed and the remainder of the filtrate becomes urine.