Endocrine System

Function of endocrine system

1. To secrete hormones

2. Hormones are chemical messengers that coordinate and direct

target cells and organs

Goal of endocrine system

maintain homeostasis

How is the endocrine system regulated

by feedback mechanisms that function to maintain homeostasis

negative feedback

What is a tropic hormone

A hormone that has an endocrine gland as its target = a hormone that controls the release of other hormones

hormones that have other endocrine glands as their target

ACTH

Produced by: Anterior Pituitary

Target: Adrenal Cortex

Function: Stimulates the adrenal cortex to produce and release cortisol, which helps manage stress and regulate metabolism.

ADH

Produced by: Posterior Pituitary (synthesized by hypothalamus)

Target: Kidneys

Function: Regulates water balance by promoting water reabsorption in the kidneys, reducing urine output, and increasing blood volume.

calcitonin

Produced by: Thyroid Gland (specifically parafollicular cells or C cells)

Target: Bones and Kidneys

Function: Lowers blood calcium levels by inhibiting osteoclast activity in bones and increasing calcium excretion by the kidneys.

epinephrine

Produced by: Adrenal Medulla

Target: Various organs (heart, lungs, muscles, liver)

Function: "Fight or flight" response—prepares the body for quick action by increasing heart rate, dilating airways, and releasing glucose for energy.

prolactin

Produced by: Anterior Pituitary

Target: Mammary Glands

Function: Stimulates milk production in females following childbirth.

thyroxine

Produced by: Thyroid Gland

Target: Most body cells

Function: Regulates metabolism, energy production, and growth by increasing oxygen consumption and heat production in tissues.

insulin

Produced by: Pancreas (specifically beta cells of the Islets of Langerhans)

Target: Liver, Muscle, and Fat Cells

Function: Lowers blood sugar levels by promoting the uptake of glucose into cells for energy or storage as glycogen.

GH

Produced by: Anterior Pituitary

Target: Liver, Muscle, and Bone

Function: Stimulates growth and cell reproduction by promoting the release of IGF-1 (Insulin-like Growth Factor 1), which stimulates bone and muscle growth.

Tropic hormone (long answer)

A tropic hormone is a hormone that stimulates the release of another hormone from another gland. Tropic hormones typically target other endocrine glands.

Positive feedback

Negative feedback: When hormone levels reach a certain threshold, signals are sent to reduce hormone production. A classic example is the regulation of thyroid hormones (T3 and T4). High levels of these hormones inhibit the release of TRH (thyrotropin-releasing hormone) from the hypothalamus, which in turn inhibits TSH (thyroid-stimulating hormone) from the pituitary, lowering thyroid hormone levels.

Negative feedback

Positive feedback: In positive feedback, the release of a hormone is amplified, such as during childbirth when oxytocin stimulates uterine contractions, which in turn stimulate more oxytocin release, continuing the cycle until delivery.

Overall function

The endocrine system is responsible for regulating and coordinating various functions in the body through the secretion of hormones. These hormones act as chemical messengers that travel through the bloodstream to target organs and tissues, where they help maintain homeostasis, regulate metabolism, growth and development, tissue function, sexual function, and mood.

Hyper secretion

overproduction

too much hormone

Hypo secretion

underproduction

too little hormone