Homeostasis and Blood Flow

1. Homeostasis and Blood Flow The Circulatory System

2. Cardiac Output • Cardiac output is defined as the amount of blood that flows from the heart per minute. • Typically, unless some dysfunction occurs, the blood pump on the right side of the heart will equal the amount pumped on the left side. • Cardiac output is affected by: • Stroke Volume • Heart Rate

3. Stroke Volume • Stroke volume is the quantity of blood pumped with each beat of the heart. • The stronger the heart contractions, the greater the stoke volume. • 70mL of blood per beat leave each ventricle (at rest).

4. Heart Rate • Heart Rate is the number of time the heart beats per minute.

5. Determining Cardiac Output: Cardiac Output = stroke volume X heart rate 70mL/beat X 70 beats/min= 4900ml/min (the cardiac output) • Larger individuals pump more blood per minute; therefore, have a larger cardiac output. • Heart rate increases during exercise; meet demands.

6. Comparing Individual Fitness Levels “Why do two people with the same body mass have different heart rates?”

7. Comparing Individual Fitness Levels • Lee’s lower heart rate indicates a higher stroke volume. Strong heats can pump greater volumes of blood with each beat. • This is why athletes have low heart rates.

8. Lance Armstrong • In all, during those three weeks in July, Armstrong spent eighty-six hours, seventeen minutes, and twenty-eight seconds on the bike. • Lance Armstrong's heart is almost a third larger than that of an average man. During those rare moments when he is at rest, it beats about thirty-two times a minute —slowly enough so that a doctor who knew nothing about him would call a hospital as soon as he heard it. (When Armstrong is exerting himself, his heart rate can edge up above two hundred beats a minute.) • Physically, he was a prodigy.

9. Blood Pressure • Blood Pressure is the force of blood on the walls of the arteries. • Measured with a sphygmomanometer • Measuring blood pressure • Cuff is pumped until it closes off blood flow. A stethoscope is placed below the cuff and air is slowly released until a low-pitch sound is detected. The sound is caused by blood entering the artery. The gauge measures the pressure exerted by blood entering the ventricle during contraction (systolic blood pressure) • Cuff is then deflated more until the sound disappears. This is when the ventricle is in relaxation and the atrium is filling (diastolic blood pressure)

10. Blood Pressure • Normal blood pressure for young adults: • systolic blood pressure: 120mmHg (millimeters of mercury) • Diastolic blood pressure: 80mmHg • It would be reported as: 120/80 • Blood pressure depends on: • Cardiac Output • Arteriolar Resistance • YouTube - Effects of High Blood Pressure on your Body

11. 2 Factors of Blood Pressure • Cardiac Output increase in output will cause an increase in blood pressure. • Arteriolar Resistance the diameter of the arterioles. Constriction of smooth muscles reduces the blood flow, and leaves more blood in the arteries = higher blood pressure. • Muscle can relax and cause the opposite.

12. What Do The Smooth Muscles Of The Arterioles Respond To? • Neural and Hormonal Controls. • Metabolic Products(ex. Products of the breakdown of glucose) • Insufficient Oxygen lactic acid produced. • Sufficient Oxygen CO2 and H2O • Accumulation of CO2 and lactic acid causes the relaxation of smooth muscles (dilation). This results in an increase in blood flow and the delivery of more O2.

13. Homeostasis and Arteriolar Dilation • More metabolic products in most active tissues dilation  more nutrients and oxygen to tissues in need. • Metabolic products minimal in less active tissues  constriction  less nutrients and oxygen.

14. Hypertension • Hypertension (a.k.a. high blood pressure) is caused by an increase resistance to blood flow, which results in a increase in blood pressure. • High blood pressure causes weakening of the blood vessels (may rupture). • The body attempts to compensate by increasing support provided by connective tissues. This leads to hard and less elastic arteries. • Artery rigidity causes an even greater increase in blood pressure and further vessel weakening.

15. Causes of Hypertension • Hereditary • Diet (primary factor) • Susceptible if: • Too much salt can lead to an increase in blood pressure. • “silent killer”; heart attack or stroke are usually your first indications.

16. Regulation of Blood Pressure • There are blood pressure receptors in the walls of the aorta and carotid arteries (in neck)  sensitive to high blood pressures. • When bp exceeds acceptable levels, the receptors respond by sending a message to the medulla oblongata, the bp regulator in the brainstem. • Sympathetic (stress) nerve impulses are decreased and parasympathetic (relaxation) nerve impulses increased.

17. Medulla Oblongata • Decreased Sympathetic Nerve Impulse: • Arterioles dilate • Increasing the outflow of blood from the artery • Stimulated Parasympathetic Nerve Impulse: • Heart rate decreased • Stroke volume decreased • This slows the movement of blood into the arteries, lowering bp.

18. Response to Exercise • In stress, the sympathetic nerves stimulate the adrenal glands. The hormone epinephrine (adrenaline) is released from the adrenal gland and travels in the blood to other organs in the body. • Epinephrine: • stimulate the release of red blood cells from the spleen aids in oxygen delivery. • Increase heart rate (faster oxygen transport). • breathing rate (blood contains higher levels of O2). • Increase removal of waste from tissues.

19. Vigorous Exercise Accelerates the heartbeat in 2 ways: • As cellular respiration increase, so does CO2 levels. This stimulates receptors in the aorta and carotid arteries  medulla oblongata  heart. • As muscle activity increases, the muscle pumps more blood back to the right atrium. Stretch receptors M.O. heart

20. Regulating Body Temperature • Thermoregulation is the maintenance of body temperature within a range that enables cells to function efficiency. • We can maintain temp. regardless of surroundings. • Increases cell respiration to generate heat. • Average body temp: 37 degrees Celsius. • Extremities can vary up to four degrees from core. Human thermoregulation

21. Protecting Against Excessive Heat • When sensors in the brain detect a rise in temp, in coordination with the hypothalamus, a nerve impulse is sent to the sweat glands. • The evaporation of perspiration from the skin causes cooling ( loss of water and salts). • Impulse is also sent to the blood vessels in the skin to dilate blood looses heat to the skin.