BIO Ch3 - Endocrine system

Endocrine system

A system of ductless glands which release chemicals into the bloodstream to regulate body functions and maintain homeostasis

Homeostasis

The body’s ability to maintain a stable internal environment despite changes to the external environment

Protein based hormones

Hydrophilic hormones that bind to extracellular receptors as they cannot diffuse through the hydrophobic phospholipid bilayer

Steroid hormones

Lipid based hydrophobic hormones that can pass through the phospholipid bilayer and bind to intracellular receptors

Hypothalamus

The central control centre that receives signals from other organs and sends hormones to the pituitary gland to regulate various bodily functions

Pituitary gland

The body’s 'master gland’ located at the base of the brain that releases hormones to tell other glands what to do

Pineal gland

Small gland in the brain that produces melatonin that regulates sleep

ADH

Antidiuretic hormone is produced by the hypothalamus and secreted by the pituitary gland. It regulates blood pressure and decreases the urine output by the kidneys

Oxytocin

Oxytocin is produced by the hypothalamus and secreted by the pituitary gland. It is important for reproduction, social bonding, childbirth and breastfeeding

Thyroid gland

A butterfly-shaped gland in the neck that produces thyroxine

Thyroxine

A hormone that regulates metabolism, heart and muscle function, brain development and bone health

Adrenal glands

Two glands located at the top of each kidney that produce adrenaline and cortisol

Adrenaline

A hormone that facilitates the body’s “fight or flight” response, increasing heart rate, breathing rate, strength and alertness

Cortisol

A hormone that regulates the body’s stress response

Pancreas

Produces insulin and glucagon which work together to maintain healthy blood glucose levels

Insulin

A hormone that decreases blood glucose levels by stimulating the movement of glucose from the bloodstream into the liver and the body’s cells where it can be used for energy

Glucagon

A hormone that increases blood glucose levels by stimulating the liver to release stored glucose into the bloodstream

Four stages of a negative feedback loop

Stimulus → Receptor → Effector → Response → Repeat

Examples of negative feedback loops

Blood glucose regulation and thermoregulation

Example of the negative feedback loop for decreasing blood glucose levels

Stimulus - increase in blood glucose level

Receptor - pancreas beta cells and brain glucose receptors

Effector - pancreas beta cells that release insulin

Response - Insulin stimulates the liver and body cells to absorb glucose, decreasing blood glucose levels

Positive feedback loop

A process where the response enhances the initial input, creating a self-amplifying effect

Examples of positive feedback loops

Childbirth and breastfeeding