Find out how the your body uses special cells that are central to the brain (inside the brain) to sense levels of CO2 and pH. Rishi is a pediatric infectious disease physician and works at Khan Academy. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.

The video resource "Central Nervous System: Crash Course A&P #11" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

Learn about compliance (and elastance) of arteries, veins, and lead pipes! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Unfortunately, malnutrition often causes problems that can lead to more malnutrition. Learn how this cycle can develop.

Get a clearer idea of what a "Depolarization Wave" means and how it goes from cell to cell through the entire heart! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Get an overview of three of the key macromolecules of life (proteins, fats, and carbohydrates), and how they get digested and absorbed.

The video resource "Digestive System, Part 1: Crash Course A&P #33" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

The video resource "Digestive System, part 2: Crash Course A&P #34" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

The video resource "Digestive System, part 3: Crash Course A&P #35" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

Learn how there are two distinct Bohr effects happening at the same time in the placenta. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Use the left ventricular pressure and volume information to put together a cool new graph. Rishi is a pediatric infectious disease physician and works at Khan Academy.

See where the pacemaker cells start the electrical wave of depolarization, and how it gets all the way to the ventricles of the heart. Rishi is a pediatric infectious disease physician and works at Khan Academy.

The video resource "Endocrine System, part 1 - Glands & Hormones: Crash Course A&P #23" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

The video resource "Endocrine System, part 2 - Hormone Cascades: Crash Course A&P #24" is included in the "Anatomy & Physiology " course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

Watch how the blood flows through the fetal circulation and compare it to what happens in the baby's body. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Although mom controls the oxygen source, the fetus has a couple of clever tricks to get the most oxygen possible! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Find out what happens to those nifty fetal structures once we get older. Rishi is a pediatric infectious disease physician and works at Khan Academy.