Transcript File - twynham a level pe

Transport of Blood Gases
Blood pressure and velocity
Blood Pressure
• Resistance is caused by the
•
friction between the blood
and the vessels walls.
Force exerted by the
blood on the inside walls
of the blood vessels
Factors affecting Blood Pressure
• Health factor/atherosclerosis/diet/
stress/drugs/hereditary
Factors affecting Blood Pressure
• Age/level of fitness/intensity of exercise;
Factors affecting Blood Pressure
• Contraction of the heart/stroke volume/ejection
•
•
•
fraction/heart rate
Pressure depends on whether the blood is
forced through the vessel or if blood flow is
reduced.
Blood pressure varies depending on whether
the heart is contracting or relaxing
Barorecpetors detect change and send message
to increase or decrease cardiac output
• Ejection of the blood by the ventricles
contracting creates a high pressure
pulse of blood- Systolic pressure
• The lower pressure as the ventricles
relax is the Diastolic pressure
Factors affecting Blood Pressure
• Resistance/ Friction/ Elasticity of walls
• Blood vessel length/distance from the
heart
• Blood vessel diameter/size/
vasoconstriction/vasodilation/cross
sectional area/lumen size
Factors affecting Blood Pressure
• . Blood viscosity/sweating/loss of fluid
Lets take your Blood Pressure!
• Blood pressure is measured at the brachial
artery in the upper arm using a
sphygmomanometer
120
__________
80
• Blood pressure is different in the various blood
vessels and is dependent on the distance of the
blood vessel from the heart.
Effects of Exercise on BP
• During Aerobic exercise systolic pressure
increases due to an increase in cardiac
output, diastolic remains constant.
• Isometric work- diastolic also increases
due to an increased resistance on the
blood vessels caused by constant
compression on the blood vessels creating
an additional resistance to blood flow.
Exam Question
• During a game, the blood pressure of a
player increases.
• What factors determine the ‘blood
pressure’ in arteries?
(3)
Answers
• A. Contraction of the heart/stroke volume/ejection fraction/heart
•
•
•
•
•
•
•
•
rate;
B. Increased blood flow/cardiac output/Q;
C. (Peripheral) resistance/friction/ elasticity of walls;
D. Blood viscosity/sweating/loss of fluid;
E. Blood vessel length/distance from the heart;
F. Blood vessel diameter/size/ vasoconstriction/vasodilation/cross
sectional area/lumen size;
G. Health factor/atherosclerosis/diet/ stress/drugs/hereditary;
H. Age/level of fitness/intensity of exercise;
Exam Question
• What are the effects of Exercise on BP?
(2)
Answers
• During Aerobic exercise systolic pressure
increases due to an increase in cardiac
output, diastolic remains constant.
• Isometric work- diastolic also increases
due to an increased resistance on the
blood vessels caused by constant
compression on the blood vessels creating
an additional resistance to blood flow.
Blood Velocity
• As blood leaves the heart though the
•
•
main arteries it has a high systolic
pressure & Velocity.
What do you think happens to the
blood velocity as it moves further
away from the heart?
Can you tell me why?
????
• Decreases!
• Due to;
1) Increase in cross sectional area of blood
vessels that gets bigger the further away
from the heart you travel.
2) Vessels get smaller and so larger total
surface area
Friction reduces, longer the vessel longer
the blood is contact with it and the more
friction affects it
• Velocity of blood is related to the cross sectional
area of the vessels it is passing through.
• Smaller the cross sectional area, the faster the
flow
• Although the capillaries are the smallest vessel,
there are some many of them, their cross
sectional area is much greater than that of the
arteries.
• Flow of blood is slower and more efficient for
gas exchange
Lets draw it…
• Using graph paper …..
• X Axis- Arteries, Arterioles, capillaries,
venules, veins, vena cava.
• Y Axis- Low, Medium, high
• Draw a line to represent:
• Blood Pressure
• Cross sectional Area
• Blood Velocity
• Velocity of blood reduces as
it reaches the capillaries
• However; blood flow does
speed up as it enters the
Veins and Venules
• Can you think why?
• Total cross sectional area decreases,
causing and increase in velocity.
• Blood doesn't flow at constant speeds around
the body
• Fastest in arteries, and slows down as it reaches
the capillaries
• Speed of the blood is related to cross sectional
area of blood vessels
Answer
• Venous return mechanism
• Veins have one way values/ prevent
•
•
backflow
Muscle contractions compress veins and
push blood towards the heart- skeletal
muscle pump
Breathing movements alter pressure in
thorax assist flow back to the heartRespiratory Pump
Exam Question
• A 400 metre hurdler’s blood flows around his body, its
pressure and velocity changes, as shown in Table 1.
Which of the blood vessels in Table 2, A, B or C,
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 back
to the heart?
1. Read the section called ‘Venous
Return’ with your partner.
2. Read again and make notes
3. Groups of 4- can you now come up
with an ‘A grade’ answer the exam
question?
Exam Question
• Describe the mechanism that assists the
return of blood to the heart
(3 marks)