Cardio vascular system

Cardio vascular system - response single exercise

Anticipatory rise - H.R raised by adrenalin release, highest seen in short sprint events

Increased H. R. - CCC in brain alerted to exercise, stimulates sympathetic nervous system, stimulates AV node, HR is increased to meet O2 demand.

Increased Cardiac Output - Q = HR x SV during exercise SV increases during sub max, HR increases as well. Higher intensity exercise HR increases more, SV very little increase.

Increased Blood Pressure - systolic BP increases during exercise, Diastolic has little change (120/80 mmHg)

Redirection of Blood Flow - vascular shunt, blood redirected away from non vital organs to working muscles. Vasodilation / vasoconstriction of blood vessels.

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Cardio vascular system - long term

Cadiac Hypertrophy - wall left ventricle thicker ,increases strength of contractions, increased SV, Q will increase, more O2 to muscles, delaying fatigue

Increase exercise stroke volume - SV higher at rest trained athletes (Q = SV x HR), lowers resting HR, more blood vessels deliver O2 muscles (increased Q due to increased SV)

Decreased Resting HR - hypertrophy, increased SV results in lower resting HR (less stress on heart)

Reduced resting blood pressure - fitter you are quicker BP returns to normal. Exercise contributes to lowering BP, lower BP = less strain on heart.

Decrease HR recovery - HR returns to resting level quicker (hypertrophy, SV, capillarisation all contribute)

Capillarisation of muscles/alveoli - greater capillary network, greater diffusion area, more O2/CO2 delivered to muscles/lungs

Increase blood volume - training increases blood volume, result of capillarisation (more O2 delivered to muscles/lungs, regulates body temperature).

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Blood Pressure


Force exerted by the blood on the vessel walls 


  • Normal 120/80 mmHg
  • Hypertension - 140/90 - 190/100 mmHg
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Blood Clotting


  • Platelets attach together form plug (blood clot)
  • platelets release fibrin
  • seal the wound / stop any further bleeding
  • fibrin traps red blood cells (rbc) / plasma / white blood cells
  • repair the wound
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Stroke Volume

How does increased Stroke volume Help performance

  • Increased stroke volume is dependent on venous return (Starling’s Law)
  • Increased venous return (VR) stretches atrial wall, due to increased blood volume
  • Excitation of sino-atrial (SA) node which increases heart rate
  • Stretch of ventricle walls / more forceful contraction of heart or ventricle walls
  • Increased stroke volume will increase cardiac output (Cardiac output = stroke volume x heart rate / Q = SV x HR)
  • More blood (oxygen) pumped to working muscles, therefore increases performance
  • Increased performance -  aerobic respiration work for longer / increases the time / intensity for exercise 
  • Delays fatigue, work at a higher intensity for a longer duration
  • Reduced build up or faster removal of lactic acid or carbon dioxide
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Heart Rate response to exercise


  • There is an anticipatory rise (1) caused by adrenaline (1) 


  • rapid / quick / fast increase in heart rate first three minutes
  • due to shortage of oxygen / oxygen deficit
  • Heart rate then plateaus / steady state
  • because oxygen supply has met demand  


  • initially no change for very short period
  • Then rapid decrease
  • O2 demand dropped 
  • steady decrease towards resting HR, removing waste products / repaying O2 debt 
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Cardiac Cycle Control

How is heart rate slowed down?                                               increased?

  • Initiated by parasympathetic nervous system                  sympathetic nervous system
  • message sent down vagus nerve                                    message down accelerator nerve
  • reduces the firing rate / number of impulses                   increase firing rate / number impulse
  • of the sinoatrial node / SA node                                      of SA node
  • Sending impulses to atrioventricular node / AV node      sending impulse to AV node
  • To the bundle of His                                                         To bundle of His
  • and Purkinje fibres                                                           Purkinjie fibres

role of AV node

  • AV node receives increased stimulation of impulses from  SA node
  • AV node slows down impulse allowing complete contraction of atria
  • relays impulse down bundle of His / sends impulse to allow ventricular contraction
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Hypothermia / Hyperthermia

  • Hypothermia reduced core body temperature below 35o  (normal core temperature - 37o)
  • vasoconstriction of blood vessels near skin and extremities (fingers and toes)
  • avoid / reduce further heat loss
  • reduced blood flow to muscles, therefore less oxygen delivered
  • vasodilation of blood vessels near to the vital organs - maintain core temperature (37o )
  • increased heart rate, get blood around body
  • rise in blood pressure to try and get the blood around the body
  • (Severe) hypothermia can cause decreased blood pressure
  • (Severe) can cause a decreased heart rate
  • Leading to cardiac arrhythmias resulting in cardiac arrest / heart attack
  • Hyperthermia increase core body temp above 37o
  • vasodilation blood vessels near skin (sweating)
  • hot conditions make difficult to remove body heat
  • increase in heart rate
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Blood Flow

  • Deoxygenated blood travels in superior / inferior vena cava
  • enters right atrium
  • pushed through tricuspid valve
  • into right ventricle
  • passes through semi-lunar valves / into pulmonary artery
  • lungs - become oxygenated blood
  • pulmonary vein
  • Oxygenated blood enters the left atrium
  • pushed through the bicuspid valve
  • into left ventricle
  • passes through the semi-lunar valves / into aorta
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Cardiac Output

Why does cardiac output increase?

  • As exercise intensity increases, cardiac output increases
  • occurs because stroke volume increases and heart rate increases
  • Q / Cardiac output = SV x HR

Benefits of higher Q following training programme


  • Cardiac output (Q) at rest stays same after training programme
  • this is to maintain body systems - temperature control, energy production, organ function
  • resting stroke volume will increase therefore resting venous return, SO resting heart rate lower and more efficient.


  • Large increase (Q) due to significant rise in exercise intensity
  • Substantial vasodilation and vasoconstriction occurs provide more blood to working muscles, diverting away body functions
  • Increase in venous return, more blood enters the right atrium
  • increases end-diastolic volume (EDV), less blood remains in atria following contraction More blood will enter the ventricle, causes stretch and recoil with greater force
  • Therefore increasing stroke volume / more blood pumped out per beat
  • O2 delivery and CO2 removal is more efficient, exercise at higher intensity for a longer duration crossing the anaerobic threshold at a later point, thus delaying the onset of fatigue/OBLA.
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vascular shunt

Vascular shunt - redirection of blood flow - pre capillary sphincters closed redirecting blood flow


  • Increased blood flow to the muscles / skin
  • allowing exercise intensity maintained / preventing overheating


  • Decreased blood flow to nonessential organs / skin
  • allowing blood redirected to muscles / maintain core body temperature 
  • Vasoconstriction to areas where blood is not required and vasodilation to areas where blood is required, which results in increased blood flow to skeletal muscle
  • More blood is required to supply oxygen and nutrients to working muscles.
  • Increased blood supply to remove waste products.
  • Increased blood flow to skin for thermoregulation cool body via evaporation of sweat.
  • Less blood flow to gut, as the focus during exercise is for increased blood flow to support the body with movement rather than digestion.
  • Same percentage of blood to the heart at rest and during exercise. However, heart is working harder during exercise so receives more blood as cardiac output increases. It requires more blood as it is pumping faster during exercise so will need more oxygen and nutrients than when at rest.
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Blood Vessel Structure


  • Connective blood vessel between arteriole and venule
  • capillaries provide large surface area surrounding muscles / alveoli
  • Ione cell thick / endothelial / semi permeable membrane 


  • carries deoxygenated blood
  • has valves stops back flow
  • large lumen, blood low pressure
  • thin smooth muscle layer


  • oxygenated blood
  • smaller lumen
  • thick smooth muscle layer
  • carries high pressure blood
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Blood cells

Red blood cells / erythrocytes

  • Transport oxygen

White blood cells / leucocytes

  • Fight infection


  • Transport nutrients / red blood cells / white blood cells / maintaining normal blood pressure / maintain homeostasis
  • Transports hormones and proteins
  • Maintains blood volume
  • Balances electrolytes 

Platelets / thrombocytes

  • produced in bone marrow, cell fragments, clots blood
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Sudden arrhythmic death syndrome (SADS)

  • heart condition - sudden death even in seemingly fit athletes
  • hearts normal / natural rythmn disrupted
  • heart stops beating
  • can lead to death
  • ECG screening used to identify those at risk
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