Transcript Physiology, Health & Exercise

Lesson 2
Blood vessels
Cardiac cycle
Heart Sounds
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Blood vessels
There are three types of blood vessels:
Arteries
Capillaries
Veins
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Blood vessels
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Arteries
Carry blood away from the heart
Thick muscular wall to withstand high
pressure of blood
Narrow lumen
Most collagen (tough fibrous protein)tough and durable
Elastic fibres and smooth muscle- allows
stretch & recoil
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Arteries… cont
No valves
Branch into smaller and smaller vesselsarterioles
Contraction of smooth muscle of arterioles
allows blood to be diverted to different
parts of the body
e.g. fight or flight more blood to skeletal
muscles and less to digestive system
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Arteries… cont
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Capillaries
Tiny vessels- 1 cell thick wall 10mm in diameter
Exchange of nutrients and waste with tissues
occurs here
Extensive branching network (capillary bed)
throughout body tissues
Only certain capillary beds open at one time to
allow shunting of blood from one area to
another
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Capillaries… cont
Most numerous type of blood vessel in the
body
Permeable walls
Carry blood at low pressure and low flow
rate
Reduces fluid loss through permeable
capillary walls
Allows sufficient time for exchange of
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materials
Veins
Carry blood back to the heart
Thin muscular wall as blood at low
pressure
Wide lumen- reduces resistance to blood
flow
Less collagen, elastic fibres and smooth
muscle
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Veins… cont
Have valves
Blood at low pressure- return blood
against gravity- so lie close to muscleswhen muscle contract they squeeze the
veins to temporarily increase the blood
pressure
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Veins… cont
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Describe three things that this graph shows.
Major Blood Vessels
NB heart muscle itself
is supplied with blood by
coronary arteries
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Cardiac Cycle
A pattern of contraction (systole) and
relaxation (diastole) by heart in 1 heart
beat
Lasts about 0.8 seconds (based on heart
rate of 75bpm)
Chambers alternately contract and relax
Blood always flows towards low pressure
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Cardiac Cycle…cont
3 phases to the cycle:
1. Atrial systole
2. Ventricular systole
3. Diastole
Decrease in
volume
Increase in
pressure
Blood forced
out
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Atrial systole
 Blood flows into LA and RA under low
pressure
 LA & RA contract simultaneously
 AV (bicuspid & tricuspid) valves open
 Blood forced into LV & RV
 At this point LV & RV in diastole & SL
valves closed
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Ventricular systole
0.1 secs later
AV (bicuspid & tricuspid) valves close
Blood forced into LV & RV which contract
& push blood through open SL valves to
arteries
 High pressure in ventricles




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Diastole
 Atria & ventricles relax
 Elastic recoil of relaxing heart walls
lowers pressure in atria & ventricles
 Blood under high pressure in arteries
drawn back into heart from veins
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Heart Sounds
 Lub dub
 Lub- closing of AV valves
 Dub- closing of SL valves
 Human heart sounds
 Feline heart sounds
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