Heart and Circulation

1. Heart and Circulation Lecture A. Niedzviecki

2. 1. The body's transport system • Blood travels around the body in over 75,000 miles of arteries, veins and capillaries. Stretched end-to-end, that's three times around the world! They transport oxygen from the lungs, remove carbon dioxide from the cells and carry nutrients, hormones and water to all parts of the body.

3. 1. The body's transport system • Arteries and arterioles Carry blood: away from the heart Blood Pressure: high Walls are: thick and muscular with elastic fibres Blood is: oxygenated except pulmonary artery Pulse: strong

4. 1. The body's transport system • Capillaries Carry blood: from arteries to veins Blood Pressure: low Walls are: very thin and leaky - one cell thick Blood is: exchanging nutrients and gases with cells Pulse: none

5. 1. The body's transport system • Veins (and venules) Carry blood: towards the heart Blood Pressure: very low Walls are: thin Blood is: de-oxygenated(except pulmonary vein) Pulse: none

6. 1. The body's transport system • Humans are endothermic and keep a constant body temperature of 37 °C. The circulatory system plays a big part in regulating body temperature and it is self-repairing. • A blood clot quickly forms to seal up a cut before new tissue grows to replace the damaged area.

7. 2.Layout of the circulation • The circulation in humans is a closed loop of tubes that run in a continuous figure of "8" centered on the heart. The heart is the muscle pump that keeps the blood flowing. This is called a "double circulation" system: • One loop carries blood around the lungs . The blood is carried to the lungs in the pulmonary arteries and returns in the pulmonary veins. (Pulmonary circulation) • The other loop supplies blood at high pressure to the head and body. The main artery from the heart is the aorta. It branches to carry blood to the head and body. The blood returns to the heart in the vena cava. (Systemic circulation)

8. 3.Heart structure and action A healthy person's heart runs at about 72 beats per minute when they are resting. That's over 100 thousand beats in a day and over 2 billion in a lifetime.

9. Quick Quiz

10. 3.Heart structure and action

11. 3.Heart structure and action

12. 3.Heart structure and action

13. 3.Heart structure and action

15. 4. Blood pressure Arteries: high pressure, high velocity Capillaries: low pressure, low velocity, large surface area Veins: low pressure, medium velocity

16. 4. Blood pressure • Systolic pressure maximum pressure in an artery at the moment the heart is beating sending blood through the body. • Diastolic pressure lowest pressure in an artery in the moments between beats when the heart rests.

17. 4. Blood pressure • The heart is a muscular pump which generates the blood pressure needed to keep the blood flowing. This can be measured using a piece of equipment called a sphygmomanometer. There are also modern digital blood pressure meters which take the readings automatically.

18. 4. Blood pressure Measuring blood pressure • Doctors always give blood pressure as two readings. A healthy person's normal pressure might be "120 over 80 mm of mercury (mmHg)". • The first number is the higher pressure caused as the left ventricle contracts to push blood out of the heart. Doctors call this the systolic pressure. • The lower value is the pressure in the arteries during the time that the heart is filling with blood. This is the diastolic pressure. • [The standard unit of pressure is the pascal (Pa) and blood pressure can be measured in kilopascals (kPa). A pressure reading of 120 over 80 mmHg is equivalent to 16 over 10 kPa.]

19. 4. Blood pressure • Factors Affecting Blood Pressure • Volume of blood in the body • Heart rate • Diameter of arteries • Elasticity of arteries • Viscosity of the blood

20. 4. Blood pressure • High blood pressure (hypertension) During activity the blood pressure rises to supply blood faster to the hard-working muscles. This is caused by the body producing adrenaline, the so-called “fear, flight or fright” hormone. When relaxed, the pressure drops as the body's demands are normally much lower. • A person has high blood pressure, called hypertension, if their resting blood pressure is higher than about 140/90mmHg. • Hypertension is a problem because it puts great strain on the heart and can also cause tiny blood vessels to break. If this happens in the brain it leads to a stroke. A blood clot forms and deprives a part of the brain of blood. This damages nerve cells and can lead to paralysis or even death. • Medicines called beta-blockers can be given to slow the heart rate and reduce the force of contractions. This helps to reduce the blood pressure. Medicines known as ACE-inhibitors can also help by opening up the arteries and veins to allow the blood to flow more easily.

21. 4. Blood pressure • Low blood pressure (hypotension) : Low blood pressure can be a sign of heart failure and may be due to a dramatic loss of blood due to severe bleeding after something like a road accident. If it is not treated quickly, oxygen is not delivered to the brain and this is fatal. • At the scene of a car accident, fluids may be put in to the blood stream, using an intravenous drip, to help maintain the blood pressure. Adrenaline can be given to stimulate the heart and during a heart attack a defibrillator gives an electric shock to "jump start" the heart to get it beating properly again.

22. 5. Heart Conditions • Coronary Artery Disease • Angina pectoralis • Atherosclerosis • Heart Attack • Heart Failure • Leaking valves etc. • Atherosclerosis (hardening of the arteries) • Embolism of coronary arteries • Arrhythmias • Embolism – blocked artery • Aneurysm – vessel bursts

23. Note: Please READ pgs.26-49 in my Biology notebook It would be a good idea to check out the many links on my web page. December Test is based on page 26-49.