8.11 Measurement of Blood Pressure

The flow through the right ventricle is the same as the flow through the left ventricle.

The pressure in the aorta is six times greater than the pressure in the blood.
Depending on the intensity of the physical activity, the peak power output of the heart is between 1.9 and 14.6 W. We assumed that the systolic blood pressure remained at 120 torr because it rises with increased blood flow.

A person's blood pressure is an indicator of their health.

Some disorders in the body that require medical attention can be seen with both high and low blood pressures.
It is possible that high blood pressure is caused by constrictions in the circulatory system and that the heart is working harder than usual.
Reverend Stephen Hales connected a glass tube to a horse's arteries in 1733 to measure blood pressure.
This method is not satisfactory for routine clinical exams, despite the fact that it is still used in special cases.
The cut-off method is the most common way to measure blood pressure.
Although it is not as accurate as a direct measurement, this method is still adequate.
A cuff containing an inflatable balloon is placed around the upper arm.
The pressure in the balloon is monitored by a pressure gauge.
The flow of blood through the arteries is cut off when the initial pressure in the balloon is greater than the systolic pressure.
The pressure in the balloon is allowed to fall slowly by the observer.
She listens with a stethoscope as the pressure drops.

There is no sound until the balloon's pressure decreases.

The flow of blood below this point is turbulent and accompanied by a characteristic sound.
The systolic blood pressure is recorded at the beginning of sound.
The noise disappears when the balloon's pressure drops further, as the artery expands to its normal size.
The pressure at which the sound begins to fade is taken as the diastolic pressure.

The variation of the blood pressure along the body must be considered in a clinical measurement.

The cuff is placed on the arm to measure the cut-off blood pressure.

The head is 50 cm above the heart.

When the rate of blood flow in the aorta is 5/min, the liter of the blood in the capillaries is about 0.33mm/sec.

The number of capillaries in the circulatory system can be determined by the average diameter of a capillary.

The unconstricted region has an average flow velocity of 50 cm/sec.

When the flow rate is 25 liter/min, use information provided in the text to calculate the power generated by the left ventricle.

The power generated by the right ventricle can be calculated using information provided in the text.

The blood from the heart goes into the aorta and the pulmonary arteries.

The force in the opposite direction is exerted on the rest of the body since the blood is accelerated during this part of the heartbeat.
The reaction force can be measured if a person is placed on a scale.

Discuss the type of information that might be obtained from a ballistocardiograph, and estimate the magnitude of the forces measured by this instrument.

All of us are familiar with the sensation of hotness.

When two bodies are placed in an enclosure, the hotter one will get hotter and the cooler one will get cooler, until the degree of hotness of the two bodies is the same.
Something has been transferred from one body to the other.
It is a form of energy when heat is transformed into work.
The water can turn into steam if it is heated.
The definition of heat is the transfer of energy from a hotter body to a cooler one.

The properties associated with heat will be discussed in this chapter.

We will talk about the motion of atoms and Molecules due to thermal energy and then talk about the functioning of Cells and the Respiratory System.

We need to explain the structure of matter to understand the concept of heat.

Matter is made of atoms and Molecules.
The atoms are not bound together in a gas.
They collide frequently with one another and with the walls of the container as they move in random directions.
In addition to moving linearly, gas molecule vibrates and rotates in random directions.

The atoms are locked up and free to vibrate randomly, about an average position to which they are locked.

The liquids situation is between the two extremes.
The molecule can vibrate, but also have some freedom to move.

The particles in the material have motion.

The hotness of a body is a measure of the internal energy of the body, which is faster in hotter bodies.
The hotter an object is, the greater its internal energy.
The sensation of hotness is caused by random atomic and molecular motion.
The internal energy of matter is related to the temperature.

The equations that describe the behavior of matter as a function of temperature can be derived using these concepts.

Gases are easy to analyze.
The theory considers a gas made of small particles in random motion.
Each particle travels in a straight line until it collides with another particle or with the walls of the container.
The direction and speed of the particle are changed after a collision.
The energy is exchanged among particles.

The particles exchange energy with each other and with the wall of the container.

If the walls of the container are hotter than the gas, the particles colliding with the wall on the average pick up energy from the vibrating molecule in the wall.

The gas is heated until it is as hot as the walls.

There is no net exchange of energy between the walls and the gas after that.

The average amount of energy delivered to the wall by the gas particles is the same as the amount picked up from it.

The individual particles in a gas vary in speed and energy.

It is possible to divide the total number of particles by the total number of individual particles in the container in order to calculate an average kinetic energy for the particles.
If each particle has the same average energy, then many of the properties of a gas can be derived.

The absolute temperature scale is used to measure the temperature in this equation.

38 x 10-23 J/molecule K is the velocity.

When a molecule collides with the wall, the momentum is transferred to the wall.

The change in momentum is a force.
The pressure exerted by a gas on the walls of a container is due to the many collisions of the gas molecule with the container.

The calories are equal to 4.184 J.

1 Cal is equal to 1000 cal and heat is measured in kilocalorie units.

The temperature of 1 g of a substance can be raised by 1 degree with specific heat.

Table 9.1 shows the specific heats of some substances.

The human body is made of water, fat, and minerals.

This composition is reflected by its specific heat.

The heat of the average human body is closer to 0.83 due to its fat and mineral content, which we have not included in the calculation.

The symbol is degree Celsius.

The symbol C* has a Celsius degree.