(Blood Circulation and Pressure)

Domato, Jamaidah E.Ilaji, Fradzne Rheinam A.Rondario, Patricia Joy M.

Toribio, Stephen R.

Fluid

Any substance that cannot maintain its own shape; has no rigidity

Can flow and alter its shape to conform to the outlines of its container

Includes liquids (H₂O), gases (air), very slowly flowing substances (tar and plastics), and even mixtures of liquids and solids (mud)

Liquid Gas Mixed Liquid & Solid

Flowing major feature of a fluid (when acted upon by some force)

makes a fluid different from a solid

SOLID- being incompressible, may be distorted by a force but will not start to flow

Typically, the force is that of gravity, but other forces can also apply.

Gravity Fluids will flow or can be poured (including gases)

Use dry ice to fill a jar with CO₂, then pour it into a jar containing a burning candle. The candle flame will be snuffed out as the invisible CO2 is poured into the jar.

Other forces the acceleration/ deceleration forces or change in direction of a

moving container = cause the fluid to flow or change its shape

force of wind on a body of water = water flows; create surface waves

Pressure force per unit area.

usually more convenient to use than force to describe the influences upon fluid behavior.

Pascal (Newton per square meter)- standard unit for pressure

Also often measured in millimeters of mercury (mm HG), a unit that originated from old-fashioned mercury barometers

CF: 1mm Hg = 133 pascals = 0.02 pounds per square inch

___________________________________________________________

the weight of an object sitting on a surface= the force pressing on its surface

but in different orientations it might have a different area in contact with the surface and therefore exert a different pressure.

Concept(s) of Pressure

Blood pressure readings are a fundamental diagnostic tool for health care professionals. What

is the physics behind blood pressure? PRESSURE

There are many physical situations where pressure is the most important variable.

If you are peeling an apple, then pressure is the key variable:

if the knife is sharp, then the area of contact is small and you can peel with less force exerted on the blade.

If you must get an injection, then pressure is the most important variable in getting the needle through your skin: it is better to have a sharp needle than a dull one since the smaller area of contact implies that less force is required to push the needle through the skin.

----------------------------------------------------------------------------------------------------------

Why does a sharp knife cut more easily than a dull one? A sharp knife blade has a smaller area. Therefore for the same amount of force, the sharp knife blade exerts more pressure and cuts more easily.

A woman wearing spiked high heel shoes can damage a floor more easily than when she is wearing flat shoes. With the spiked heels, the force of her weight is concentrated on a smaller area to exert more pressure.

BP

When visiting a clinic, a patient usually gets a blood pressure reading. High blood pressure, hypertension, can warn of impending cardiovascular disease. Excessively low blood pressure can prevent blood from flowing to higher portions of the body, including the brain. Pressure is a basic physical quantity. How does physics apply to blood pressure?

The blood applies a force of 16,000 newtons to every square meter of artery wall or 2.4 pounds to every square inch.

BP SYS and DIA reading:

Eventually the pressure in the cuff is low enough that blood starts flowing again in the constricted artery. The healthcare worker listening to the artery with a stethoscope hears turbulence as the blood flow resumes, and reads the systolic blood pressure from the sphygmomanometer dial. When the turbulence stops, the pressure reading is the diastolic reading. The blood again flows smoothly because the pressure in the cuff is too low to constrict the blood flow during any part of the pumping cycle.

Blood Pressure force the blood applies to the artery wall divided by the area of the wall.

high bp= the blood applies more force to each m² of artery wall.

Medical personnel measure blood pressure in millimeters of mercury.

a blood pressure reading of 120 mm Hg= 16,000 N/m² or 2.4 lbs/ in²

Diastolic and Systolic Pressure A bp reading is composed of two sets of numbers (e.g 120/80)

systolic pressure- the maximum pressure on the artery walls during

the pumping cycle; when the ♥ is contracted

diastolic pressure- the lowest pressure during the cycle; when the ♥ is relaxed

Blood Pressure BP

HR x SV

PVRCO x

\m/

Cardiac Output

-amt of blood the ♥ pumps

Peripheral Vein Resistance

-resistance of the wall

Heart Rate

-parasympathetic and sympathetic

Peripheral Vein Resistance

-resistance of the wall

Peripheral Vein Resistance

-resistance of the wall

Stroke Volume

-contractility-sec/pump

-blood volume

Blood Pressure

the ♥ pumps blood through the body

With every heartbeat the ventricles (lower heart chambers) contract, squeeze the blood out to the arteries, maximizing the blood pressure, producing the systolic reading.

When the ventricles relax, the blood pressure is minimized, producing the diastolic reading. The heart refills with blood and the cycle repeats.

Effects of High and Low Blood Pressure

if blood pressure is too high (Hypertension):

the extra force on the artery walls eventually leads to increased risk of cardiovascular problems

A weak vessel may burst

If arteries are clogged by fatty deposits from high cholesterol,

the narrow arteries force the ♥ to pump harder, leading to HPN.

Consult physician for health consequences

Pressure in a fluid decreases with height, so there must be enough blood pressure to pump the blood upward to the brain.

if the blood pressure is too low (Hypotension):

the ♥ cannot push the blood up to the brain and the person may faint or pass out

Sphygmomanometer

uses a blood pressure cuff that squeezes the arm to constrict the blood flow in the artery then the pressure in the cuff is slowly decreased ; for blood pressure reading

Blood pressure is taken on the arm at the same level as the ♥ because the pressure in a fluid varies with the height of the fluid.

http://www.school-for-champions.com/science/fluids.htm

http://hyperphysics.phy-astr.gsu.edu/hbase/Precon.html

http://hyperphysics.phy-astr.gsu.edu/hbase/press.html

http://www.suite101.com/content/physics-of-blood-pressure-a63486

http://www.suite101.com/content/understanding-pressure-in-physics-a55694

http://www.cramster.com/answers-sep-10/physics/blood-circulation-blood-transports-substances-required-body_945650.aspx

http://books.google.com.ph/books?id=e9hbt3xisb0C&pg=PA105&lpg=PA105&dq=circulation+of+blood+in+physics&source=bl&ots=MUlqYsze7y&sig=aDon4Yi60-7kzVnUAqnEE3fOFzo&hl=en&ei=-wtITb7_L8jQrQedzMWSBA&sa=X&oi=book_result&ct=result&resnum=9&ved=0CFEQ6AEwCA#v=onepage&q=circulation%20of%20blood%20in%20physics&f=false

http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

http://www.youtube.com/watch?v=ABTvNR59K5Q