Homeostasis and Blood FlowHomeostasis and Blood FlowThe Circulatory SystemThe Circulatory System

Cardiac OutputCardiac Output

Cardiac outputCardiac output is defined as the is defined as the amount of blood that flows from the amount of blood that flows from the heart per minute.heart per minute.

Typically, unless some dysfunction Typically, unless some dysfunction occurs, the blood pump on the right occurs, the blood pump on the right side of the heart will equal the amount side of the heart will equal the amount pumped on the left side.pumped on the left side.

Cardiac output is affected by:Cardiac output is affected by: Stroke Volume Stroke Volume Heart RateHeart Rate

Stroke VolumeStroke Volume

Stroke volumeStroke volume is the quantity is the quantity of blood pumped with each beat of blood pumped with each beat of the heart.of the heart.

The stronger the heart The stronger the heart contractions, the greater the contractions, the greater the stoke volume.stoke volume.

70mL of blood per beat leave 70mL of blood per beat leave each ventricle (at rest).each ventricle (at rest).

Heart RateHeart Rate

Heart RateHeart Rate is is the number of the number of time the heart time the heart beats per beats per minute.minute.

Determining Cardiac Output:Determining Cardiac Output:

Cardiac Output = stroke volume X Cardiac Output = stroke volume X heart rateheart rate

70mL/beat X 70 beats/min= 4900ml/min (the cardiac output)70mL/beat X 70 beats/min= 4900ml/min (the cardiac output)

Larger individuals pump more blood per Larger individuals pump more blood per minute; therefore, have a larger cardiac minute; therefore, have a larger cardiac output.output.

Heart rate increases during exercise; meet Heart rate increases during exercise; meet demands.demands.

Comparing Individual Fitness Comparing Individual Fitness LevelsLevels

““Why do two people Why do two people with the same body with the same body mass have different mass have different heart rates?”heart rates?”

PersonPerson Stroke Stroke VolumVolum

ee

Heart Heart RateRate

CardiaCardiac c

OutputOutput

TomTom 5050 100100 5L5L

LeeLee 100100 5050 5L5L

Comparing Individual Fitness Comparing Individual Fitness LevelsLevels

Lee’s lower heart rate Lee’s lower heart rate indicates a higher indicates a higher stroke volume. Strong stroke volume. Strong heats can pump heats can pump greater volumes of greater volumes of blood with each beat.blood with each beat.

This is why athletes This is why athletes have low heart rates.have low heart rates.

Lance ArmstrongLance Armstrong

In all, during those three weeks in In all, during those three weeks in July, Armstrong spent eighty-six July, Armstrong spent eighty-six hours, seventeen minutes, and hours, seventeen minutes, and twenty-eight seconds on the bike. twenty-eight seconds on the bike.

Lance Armstrong's heart is almost a Lance Armstrong's heart is almost a third largerthird larger than that of an average than that of an average man. During those rare moments man. During those rare moments when he is at rest, it beats about when he is at rest, it beats about thirty-two times a minutethirty-two times a minute —slowly —slowly enough so that a doctor who knew enough so that a doctor who knew nothing about him would call a nothing about him would call a hospital as soon as he heard it. (When hospital as soon as he heard it. (When Armstrong is exerting himself, his Armstrong is exerting himself, his heart rate can edge up above two heart rate can edge up above two hundred beats a minute.) hundred beats a minute.)

Physically, he was a prodigy. Physically, he was a prodigy.

Blood PressureBlood Pressure

Blood Pressure is the force of blood Blood Pressure is the force of blood on the walls of the arteries.on the walls of the arteries.

Measured with a Measured with a sphygmomanometersphygmomanometer

Measuring blood pressure Cuff is pumped until it closes off blood flow. Cuff is pumped until it closes off blood flow.

A stethoscope is placed below the cuff and A stethoscope is placed below the cuff and air is slowly released until a low-pitch sound air is slowly released until a low-pitch sound is detected. The sound is caused by blood is detected. The sound is caused by blood entering the artery. The gauge measures the entering the artery. The gauge measures the pressure exerted by blood entering the pressure exerted by blood entering the ventricle during contraction (ventricle during contraction (systolic blood systolic blood pressurepressure))

Cuff is then deflated more until the sound Cuff is then deflated more until the sound disappears. This is when the ventricle is in disappears. This is when the ventricle is in relaxation and the atrium is filling (relaxation and the atrium is filling (diastolic diastolic blood pressureblood pressure))

Blood PressureBlood Pressure

Normal blood pressure for Normal blood pressure for young adults:young adults: systolic blood pressure: systolic blood pressure:

120mmHg (millimeters of 120mmHg (millimeters of mercury)mercury)

Diastolic blood pressure: Diastolic blood pressure: 80mmHg80mmHg

It would be reported as: It would be reported as: 120/80120/80

Blood pressure depends on:Blood pressure depends on: Cardiac OutputCardiac Output Arteriolar ResistanceArteriolar Resistance

YouTube - Effects of High Blood Pressure on your Body

2 Factors of Blood Pressure2 Factors of Blood Pressure

Cardiac OutputCardiac Output increase in output will increase in output will cause an increase in blood pressure.cause an increase in blood pressure.

Arteriolar ResistanceArteriolar Resistance the diameter of the diameter of the arterioles. Constriction of smooth the arterioles. Constriction of smooth muscles reduces the blood flow, and muscles reduces the blood flow, and leaves more blood in the arteries = leaves more blood in the arteries = higher blood pressure. higher blood pressure.

Muscle can relax and cause the Muscle can relax and cause the opposite. opposite.

What Do The Smooth Muscles Of What Do The Smooth Muscles Of The Arterioles Respond To?The Arterioles Respond To?

Neural and Hormonal Controls.Neural and Hormonal Controls. Metabolic ProductsMetabolic Products (ex. Products of the (ex. Products of the

breakdown of glucose)breakdown of glucose) Insufficient OxygenInsufficient Oxygen lactic acid produced. lactic acid produced. Sufficient OxygenSufficient Oxygen CO2 and H2O CO2 and H2O Accumulation of CO2 and lactic acid Accumulation of CO2 and lactic acid

causes the relaxation of smooth muscles causes the relaxation of smooth muscles (dilation). This results in an increase in (dilation). This results in an increase in blood flow and the delivery of more O2.blood flow and the delivery of more O2.

Homeostasis and Arteriolar Homeostasis and Arteriolar DilationDilation

More metabolic More metabolic products in most active products in most active tissuestissues dilation dilation more nutrients and more nutrients and oxygen to tissues in oxygen to tissues in need.need.

Metabolic products Metabolic products minimal in less active minimal in less active tissues tissues constriction constriction less nutrients and less nutrients and oxygen.oxygen.

HypertensionHypertension

HypertensionHypertension (a.k.a. high blood (a.k.a. high blood pressure) is caused by an pressure) is caused by an increase resistance to blood flow, increase resistance to blood flow, which results in a increase in which results in a increase in blood pressure.blood pressure.

High blood pressure causes High blood pressure causes weakening of the blood vessels weakening of the blood vessels (may rupture).(may rupture).

The body attempts to compensate The body attempts to compensate by increasing support provided by by increasing support provided by connective tissues. This leads to connective tissues. This leads to hard and less elastic arteries. hard and less elastic arteries.

Artery rigidity causes an even Artery rigidity causes an even greater increase in blood pressure greater increase in blood pressure and further vessel weakening.and further vessel weakening.

Causes of HypertensionCauses of Hypertension

HereditaryHereditary Diet (primary factor)Diet (primary factor)

Susceptible if: Susceptible if: Too much salt can lead Too much salt can lead

to an increase in blood to an increase in blood pressure.pressure.

““silent killer”; heart silent killer”; heart attack or stroke are attack or stroke are usually your first usually your first indications.indications.

Regulation of Blood PressureRegulation of Blood Pressure

There are blood pressure There are blood pressure receptors in the walls of the receptors in the walls of the aorta and carotid arteries (in aorta and carotid arteries (in neck) neck) sensitive to high blood sensitive to high blood pressures.pressures.

When bp exceeds acceptable When bp exceeds acceptable levels, the receptors respond by levels, the receptors respond by sending a message to the sending a message to the medulla oblongatamedulla oblongata, the bp , the bp regulator in the brainstem.regulator in the brainstem.

SympatheticSympathetic (stress) nerve (stress) nerve impulses are decreased and impulses are decreased and parasympathetic parasympathetic (relaxation) (relaxation) nerve impulses increasednerve impulses increased ..

Medulla OblongataMedulla Oblongata

Decreased Sympathetic Nerve Decreased Sympathetic Nerve Impulse:Impulse: Arterioles dilateArterioles dilate Increasing the outflow of blood Increasing the outflow of blood

from the arteryfrom the artery

Stimulated Parasympathetic Stimulated Parasympathetic Nerve Impulse:Nerve Impulse: Heart rate decreasedHeart rate decreased Stroke volume decreasedStroke volume decreased This slows the movement of blood This slows the movement of blood

into the arteries, lowering bp.into the arteries, lowering bp.

Response to ExerciseResponse to Exercise

In stress, the sympathetic nerves In stress, the sympathetic nerves stimulate the adrenal glands. The stimulate the adrenal glands. The hormone epinephrine (adrenaline) is hormone epinephrine (adrenaline) is released from the adrenal gland and released from the adrenal gland and travels in the blood to other organs in travels in the blood to other organs in the body.the body.

Epinephrine: Epinephrine: stimulate the release of red blood cells stimulate the release of red blood cells

from the spleenfrom the spleen aids in oxygen delivery. aids in oxygen delivery. Increase heart rate (faster oxygen Increase heart rate (faster oxygen

transport).transport). breathing rate (blood contains higher levels breathing rate (blood contains higher levels

of O2).of O2). Increase removal of waste from tissues.Increase removal of waste from tissues.

Vigorous Exercise Accelerates the Vigorous Exercise Accelerates the heartbeat in 2 ways:heartbeat in 2 ways:

1.1. As cellular respiration As cellular respiration increase, so does CO2 increase, so does CO2 levels. This stimulates levels. This stimulates receptors in the aorta and receptors in the aorta and carotid arteries carotid arteries medulla medulla oblongata oblongata heart. heart.

2.2. As muscle activity As muscle activity increases, the muscle increases, the muscle pumps more blood back to pumps more blood back to the right atrium. Stretch the right atrium. Stretch receptorsreceptors M.O. M.O. heart heart

Regulating Body TemperatureRegulating Body Temperature

ThermoregulationThermoregulation is the is the maintenance of body maintenance of body temperature within a range temperature within a range that enables cells to that enables cells to function efficiency.function efficiency.

We can maintain temp. We can maintain temp. regardless of surroundings.regardless of surroundings.

Increases cell respiration to Increases cell respiration to generate heat.generate heat.

Average body temp: 37 Average body temp: 37 degrees Celsius.degrees Celsius. Extremities can vary up to Extremities can vary up to

four degrees from core.four degrees from core.Human thermoregulation

Protecting Against Excessive HeatProtecting Against Excessive Heat

When sensors in the brain When sensors in the brain detect a rise in temp, in detect a rise in temp, in coordination with the coordination with the hypothalamus, a nerve impulse hypothalamus, a nerve impulse is sent to the sweat glands.is sent to the sweat glands.

The evaporation of perspiration The evaporation of perspiration from the skin causes cooling from the skin causes cooling ( loss of water and salts).( loss of water and salts).

Impulse is also sent to the Impulse is also sent to the blood vessels in the skin to blood vessels in the skin to dilatedilate blood looses heat to blood looses heat to the skin. the skin.