Rachel
About

Khan Academy on a Stick

Healthcare and medicine
  • Meet the heart!
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    Find out exactly where the heart rests in your body and what it does. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Layers of the Heart
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    Take a closer look at the heart, explore some of its interesting features and get to know the three layers that make up the heart. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Flow through the Heart
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    Learn how blood flows through the heart, and understand the difference between systemic and pulmonary blood flow. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Two Circulations in the Body
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    Learn the difference between the pulmonary and systemic circulatory systems in the body. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Lub Dub
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    Ever wonder why the heart sounds the way that it does? Opening and closing of heart valves makes the heart rhythm come alive with its lub dub beats... Rishi is a pediatric infectious disease physician and works at Khan Academy.

Heart introduction

No organ quite symbolizes love like the heart. One reason may be that your heart helps you live, by moving ~5 liters (1.3 gallons) of blood through almost 100,000 kilometers (62,000 miles) of blood vessels every single minute! It has to do this all day, everyday, without ever taking a vacation! Now that is true love. Learn about how the heart works, how blood flows through the heart, where the blood goes after it leaves the heart, and what your heart is doing when it makes the sound “Lub Dub”.

  • Circulatory System and the Heart
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    Introduction to the circulatory system and the heart

  • Arteries vs. Veins - What's the difference?
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    Learn some important differences between arteries (high pressure/low volume) and veins (low pressure/high volume). Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Layers of a blood vessel
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    Remember the 3 key layers of a blood vessel (Tunica intima, Tunica media, and Tunica externa) and how arteries, veins, and capillaries are all different from one another. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Arteries, Arterioles, Venules, and Veins
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    Learn the differences between these blood vessels! 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.

  • Three Types of Capillaries
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    Learn the differences between continuous, fenestrated, and discontinuous capillaries, and how they affect the movement of molecules. 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.

  • Pre-Capillary Sphincters
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    Find out how the body controls how much blood flows through a capillary bed. 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.

Blood vessels

Where does your blood go after it leaves the heart? Your body has a fantastic pipeline system that moves your blood around to drop off oxygen and food to those hungry cells, and removes cell waste. Learn how arteries carry blood away from the heart, how veins bring blood back to the heart, and about the different layers of cells that make up these blood vessels.

  • What is blood pressure?
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    Find out what a systolic and diastolic blood pressure mean. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Learn how a stethoscope can help determine blood pressure
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    Learn how Dr. Korotkoff cleverly used a stethoscope to determine blood pressure, and that we still use his trick today! Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Resistance in a tube
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    Learn how the size of a tube (it's radius) is related to its resistance to something flowing through. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Adding up resistance in series and in parallel

    Learn about how resistance can be added up in series and in parallel (similar to electrical circuits!). Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Adding up resistance problem
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    Here's a chance to see if you can combine what you know to add up resistance in series AND in parallel. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Flow and Perfusion

    Learn the difference between blood flow (Volume/time) and perfusion (Volume/time/amount of tissue). Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Putting it all together: Pressure, flow, and resistance

    See how pressure, flow, and resistance relate to one another and how they each affect the human body. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Blood pressure changes over time

    See how increasing resistance in the blood vessels can cause blood pressure to rise over time. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Blood pressure

Using the stethoscope to check blood pressure is a technique that’s been used for >100 years! Blood pressure is one of the major vital signs frequently measured by health care workers, and it tells us a lot about our blood circulation. Learn what blood pressure is, how it relates to resistance in a tube, why it is necessary to get oxygen to your cells, and how it can change as you age. We’ll finally put it all together by relating pressure, flow, and resistance in one awesome equation!

  • Regulation of blood pressure with baroreceptors
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    Learn about how the arteries use nerve impulses to help regulate blood pressure. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Parts of a nephron
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    Learn about the 5 major parts of the kidney's nephron. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • General overview of the RAAS system - Cells and hormones
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    Learn the important cells and hormones that are working together to control your blood pressure! Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Renin production in the kidneys
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    Learn the three major triggers for Renin production by the Juxtaglomerular cells. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Activating Angiotensin 2
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    See how Renin and ACE work to cut Angiotensinogen down to size! Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Angiotensin 2 raises blood pressure

    See how Angiotensin 2 effects 4 target "organs" to increase blood pressure. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Aldosterone raises blood pressure and lowers potassium

    See how Aldosterone effects the principal cells of the kidney to raise BP and lower potassium. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Aldosterone removes acid from the blood

    See how Aldosterone acts on the alpha-intercalated cell to remove protons (acid) from the blood. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • ADH secretion

    Learn the key triggers for ADH secretion. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • ADH effects on blood pressure

    See how ADH acts on blood vessels and the kidney to raise blood pressure. Rishi is a pediatric infectious disease physician and works at Khan Academy.

  • Aldosterone and ADH
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    Find out how Aldosterone and ADH cause changes in volume and osmolarity. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Blood pressure control

The human body enjoys stability. For example, if your blood pressure changes, the body puts a couple of brilliant systems into motion in order to respond and bring your blood pressure back to normal. There are some quick responses using nerves and some slower responses using hormones. The system using hormones is sometimes called the renin-angiotensin-aldosterone-system (RAAS), which is the main system in the body for controlling blood pressure. When your blood pressure drops too low or gets too high, your kidneys, liver, and pituitary gland (part of your brain) talk to each other to solve the problem. They do this without you even noticing! Learn how the body knows when the blood pressure has changed, and how hormones like angiotensin 2, aldosterone, and ADH help return blood pressure to back to normal.