Endocrine System

Endocrine System

Long term control

Helps maintain homeostasis

Glands

Target Tissues

Hormones

Feedback Loops

Control hormone levels in the body

If the hormone level gets too high, the gland that produces it senses that, and shuts off production for a while.

Works like a bathtub overflow or a thermostat

When the level of thyroid hormones gets high enough, the pituitary gland detects this and shuts off its production of TSH

Pituitary Gland

TSH Hormone

Thyroid Gland

Thyroid Hormone (Thyroxine)

Hormones

Chemicals released by a gland that make a change somewhere else in the body.

They go to a target tissue (TT)

1 stage hormones (single gland releases a hormone that goes directly to a target tissue)

2 stage hormones (a gland releases a hormone that engages another gland that releases a hormone that goes to the target tissue)

Types Of Hormones

Non-steroid hormone: Sits on the cell membrane, does not go in the cell, and is soluble in water. (example: Insulin, growth hormone)

Steroid Hormones: Goes into a cell to make a change, not soluble in water. (example: male and female sex hormones)

Glands

Ductless glands: No tubes, special only to the endocrine system. The hormone gets directly released into the blood stream.

Ducted gland: Gets released only to a small area (example: Oil duct on a hair or sweat glands)

Pituitary Gland

Master gland

Two lobes: Posterior and Anterior

Releases hormones that cause other glands to release their hormones (2 stage hormones)

Ex. TSH, FSH, LH

Lobes Of The Pituitary

Anterior: Growth hormone, ACTH, TSH, FSH, LH, PRL

Posterior: ADH, Oxytocin

Thyroid Gland

Releases thyroxine

Thyroxine regulates metabolism in the body

Pituitary releases thyroid- stimulating hormone (TSH), the TSH goes to the thyroid, then the thyroid releases thyroxine. (2-stage hormone)

Low thyroxine=Low metabolism=High weight

Thyroid and Iodine

Iodine is an important part of your diet

Iodine levels too low=enlargement of thyroid gland

Shows importance of negative feedback loop to shut off thyroxine

No iodine in diet= thyroxine production drops

To compensate, the pituitary makes more TSH

Too much TSH causes the thyroid gland to enarge= goiter

Pancreas

Islets of Langerhans release 2 major hormones: Insulin and Glucagon

Insulin: Released when blood sugar is high, makes cells