Transport of Blood GasesTransport of Blood GasesBlood pressure and Blood pressure and

velocity velocity

Blood PressureBlood Pressure

• Resistance is caused by Resistance is caused by the friction between the the friction between the blood and the vessels blood and the vessels walls. walls.

• Force exerted by the Force exerted by the blood on the inside blood on the inside walls of the blood walls of the blood vesselsvessels

Factors affecting Blood Factors affecting Blood PressurePressure

• Health factor/atherosclerosis/diet/ Health factor/atherosclerosis/diet/ stress/drugs/hereditarystress/drugs/hereditary

Factors affecting Blood Factors affecting Blood PressurePressure

• Age/level of fitness/intensity of Age/level of fitness/intensity of exercise; exercise;

Factors affecting Blood Factors affecting Blood PressurePressure

• Contraction of the heart/stroke Contraction of the heart/stroke volume/ejection fraction/heart ratevolume/ejection fraction/heart rate

• Pressure depends on whether the blood is Pressure depends on whether the blood is forced through the vessel or if blood flow is forced through the vessel or if blood flow is reduced.reduced.

• Blood pressure varies depending on Blood pressure varies depending on whether the heart is contracting or relaxingwhether the heart is contracting or relaxing

• BarorecpetorsBarorecpetors detect change and send detect change and send message to increase or decrease cardiac message to increase or decrease cardiac outputoutput

•Ejection of the blood by the Ejection of the blood by the ventricles contracting creates a ventricles contracting creates a high pressure pulse of blood- high pressure pulse of blood- Systolic pressureSystolic pressure

•The lower pressure as the The lower pressure as the ventricles relax is the ventricles relax is the Diastolic Diastolic pressurepressure

Factors affecting Blood Factors affecting Blood PressurePressure

• Resistance/ Friction/ Elasticity of Resistance/ Friction/ Elasticity of wallswalls

• Blood vessel length/distance from Blood vessel length/distance from the heartthe heart

• Blood vessel diameter/size/ Blood vessel diameter/size/ vasoconstriction/vasodilation/cross vasoconstriction/vasodilation/cross sectional area/lumen sizesectional area/lumen size

Factors affecting Blood Factors affecting Blood PressurePressure

• . Blood viscosity/sweating/loss of . Blood viscosity/sweating/loss of fluidfluid

Lets take your Blood Lets take your Blood Pressure!Pressure!

• Blood pressure is measured at the brachial Blood pressure is measured at the brachial artery in the upper arm using a artery in the upper arm using a sphygmomanometersphygmomanometer

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• Blood pressure is different in the various Blood pressure is different in the various blood vessels and is dependent on the blood vessels and is dependent on the distance of the blood vessel from the heart.distance of the blood vessel from the heart.

Effects of Exercise on BPEffects of Exercise on BP

• During Aerobic exercise systolic pressure During Aerobic exercise systolic pressure increasesincreases due to an increase in cardiac due to an increase in cardiac output, diastolic remains constant. output, diastolic remains constant.

• Isometric work- diastolic also increases Isometric work- diastolic also increases due to an increased resistance on the due to an increased resistance on the blood vessels caused by constant blood vessels caused by constant compression on the blood vessels compression on the blood vessels creating an additional resistance to blood creating an additional resistance to blood flow.flow.

Exam Question

• During a game, the blood pressure of During a game, the blood pressure of a player increases.a player increases.

• What factors determine the ‘blood What factors determine the ‘blood pressure’ in arteries? pressure’ in arteries? (3)(3)

Answers Answers

• A. Contraction of the heart/stroke volume/ejection fraction/heart A. Contraction of the heart/stroke volume/ejection fraction/heart rate; rate;

• B. Increased blood flow/cardiac output/Q; B. Increased blood flow/cardiac output/Q;

• C. (Peripheral) resistance/friction/ elasticity of walls; C. (Peripheral) resistance/friction/ elasticity of walls;

• D. Blood viscosity/sweating/loss of fluid; D. Blood viscosity/sweating/loss of fluid;

• E. Blood vessel length/distance from the heart; E. Blood vessel length/distance from the heart;

• F. Blood vessel diameter/size/ vasoconstriction/vasodilation/cross F. Blood vessel diameter/size/ vasoconstriction/vasodilation/cross sectional area/lumen size; sectional area/lumen size;

• G. Health factor/atherosclerosis/diet/ stress/drugs/hereditary; G. Health factor/atherosclerosis/diet/ stress/drugs/hereditary;

• H. Age/level of fitness/intensity of exercise; H. Age/level of fitness/intensity of exercise;

•

Exam Question

• What are the effects of Exercise on What are the effects of Exercise on BP?BP?

(2)(2)

AnswersAnswers

• During Aerobic exercise systolic pressure During Aerobic exercise systolic pressure increasesincreases due to an increase in cardiac due to an increase in cardiac output, diastolic remains constant. output, diastolic remains constant.

• Isometric work- diastolic also increases Isometric work- diastolic also increases due to an increased resistance on the due to an increased resistance on the blood vessels caused by constant blood vessels caused by constant compression on the blood vessels compression on the blood vessels creating an additional resistance to blood creating an additional resistance to blood flow.flow.

Blood VelocityBlood Velocity

• As blood leaves the heart As blood leaves the heart though the main arteries it has a though the main arteries it has a high systolic high systolic pressure & pressure & VelocityVelocity. .

• What do you think happens to What do you think happens to the blood velocity as it moves the blood velocity as it moves further away from the heart?further away from the heart?

• Can you tell me why?Can you tell me why?

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• Decreases!Decreases!

• Due to; Due to;

1) 1) Increase in cross sectional area Increase in cross sectional area of blood of blood vessels that gets bigger the further away vessels that gets bigger the further away from the heart you travel.from the heart you travel.

2) Vessels get smaller and so 2) Vessels get smaller and so larger total larger total surface areasurface area

Friction reduces, longer the vessel longer Friction reduces, longer the vessel longer the blood is contact with it and the more the blood is contact with it and the more friction affects itfriction affects it

• Velocity of blood is related to the cross Velocity of blood is related to the cross sectional area of the vessels it is passing sectional area of the vessels it is passing through.through.

• Smaller the cross sectional area, the faster Smaller the cross sectional area, the faster the flowthe flow

• Although the capillaries are the smallest Although the capillaries are the smallest vessel, there are some many of them, vessel, there are some many of them, their cross sectional area is much greater their cross sectional area is much greater than that of the arteries. than that of the arteries.

• Flow of blood is slower and more efficient Flow of blood is slower and more efficient for gas exchange for gas exchange

Lets draw it…Lets draw it…• Using graph paper …..Using graph paper …..

• X Axis- Arteries, Arterioles, X Axis- Arteries, Arterioles, capillaries, venules, veins, vena cava.capillaries, venules, veins, vena cava.

• Y Axis- Low, Medium, highY Axis- Low, Medium, high

• Draw a line to represent: Draw a line to represent:

• Blood PressureBlood Pressure

• Cross sectional AreaCross sectional Area

• Blood VelocityBlood Velocity

• Velocity of blood reduces Velocity of blood reduces as it reaches the as it reaches the capillariescapillaries

• However; blood flow However; blood flow does speed up as it does speed up as it enters the Veins and enters the Veins and VenulesVenules

• Can you think why?Can you think why?

•Total cross sectional area Total cross sectional area decreases, causing and increase in decreases, causing and increase in velocity.velocity.

• Blood doesn't flow at constant speeds Blood doesn't flow at constant speeds around the bodyaround the body

• Fastest in arteries, and slows down as it Fastest in arteries, and slows down as it reaches the capillariesreaches the capillaries

• Speed of the blood is related to cross Speed of the blood is related to cross sectional area of blood vesselssectional area of blood vessels

AnswerAnswer

• Venous return Venous return mechanismmechanism

• Veins have one way Veins have one way valuesvalues/ prevent / prevent backflowbackflow

• Muscle contractions compress veins Muscle contractions compress veins and push blood towards the heart- and push blood towards the heart- skeletal muscle pumpskeletal muscle pump

• Breathing movements alter pressure in Breathing movements alter pressure in thorax assist flow back to the heart- thorax assist flow back to the heart- Respiratory PumpRespiratory Pump

Exam Question Exam Question

• A 400 metre hurdler’s blood flows around his A 400 metre hurdler’s blood flows around his body, its pressure and velocity changes, as shown body, its pressure and velocity changes, as shown in in Table 1Table 1. .

Which of the blood vessels in Which of the blood vessels in Table 2Table 2, , AA, , B B or or CC, , represents veins? represents veins?

Pressure Velocity

Blood vessels A High High

Blood vessels B Low Low

Blood vessels C Low Medium

How do we get the blood How do we get the blood back to the heart?back to the heart?

1.1. Read the section called ‘Venous Read the section called ‘Venous Return’ with your partner.Return’ with your partner.

2.2. Read again and make notesRead again and make notes

3.3. Groups of 4- can you now come Groups of 4- can you now come up with an ‘A grade’ answer the up with an ‘A grade’ answer the exam question?exam question?

Exam QuestionExam Question

• Describe the mechanism that Describe the mechanism that assists the return of blood to the assists the return of blood to the heart heart

(3 marks)(3 marks)