cardiovascular system

• Blood pressure


  Force exerted by the blood against the vessel walls
• Types of blood pressure

  • Diastolic: relaxing
  • Systolic: contracting
• Stroke


  When blood can't reach the brain
• Types of stroke


  • Ischaemic: blood clot + blocked vessel
  • Haemorrhagic: burst vessel
• HDL


  Good cholesterol - breaks down LDL
• LDL


  Bad cholesterol - builds up in vessels
• Atherosclerosis


  When a blood vessel becomes blocked because of an atheroma (build up of LDL)
• Cardiac output


  Q=SVxHR, stroke volume x heart rate
• Trained athlete


  • Reaches 'exercising' cardiac output quicker and higher, quicker recovery
• Bradycardia


  RHR = <60BPM
• Average resting heart rate

  60-80 BPM
• Hypertrophy


  Heart becomes stronger and more elastic, higher end diastolic volume (more blood to be ejected)
• Anticipatory rise


  Release of adrenaline that stimulates the SAN which increases HR before exercise (hormonal control)
• Conduction system


  • SA node
  • AV node
  • Bundle of His
  • Purkinje fibres
• SA node


  Above the right atrium, myogenic structure (pacemaker), emits a signal across the atria, causing atrial systole
• AV node


  Between the right atrium and ventricle, receives the signal to relay it with a delay of 0.1s for atrial diastole
• Bundle of His


  In the septum, separates the signal into left and right for the Purkinje fibres
• Purkinje fibres


  Spread the signal up and out across the ventricles to cause ventricular systole
• Medulla oblongata


  Cardiac control centre
• Nervous control of the heart

  • Sympathetic accelerator nerve
  • Parasympathetic: vagus nerve
• Hormonal control


  Release of adrenaline which acts directly on the SA node to stimulate a greater contraction
• Intrinsic control


  Heart senses changes in temperature, electrolytes and contractility (venous return)
• Neural control receptors


  • Chemoreceptors (decrease in pH/increase in acidity)
  • Baroreceptors (increase in blood pressure)
  • Proprioceptors (increase in muscle and tendon tension)
• Vascular shunt


  Redistribution of blood during exercise
• Vascular changes during exercise

  • Vasodilation: smooth muscle allows more blood to the working skeletal muscles
  • Vasoconstriction: smooth muscle restricts blood to the rest of the body
• Pre-capillary sphincters


  Contract/relax to control the blood flow to accessory muscle/organ tissues
• Red blood cells


  Made in the bone marrow, exact diameter of a capillary, contain millions of haemoglobin
• Haemoglobin


  Iron containing protein that carries oxygen
• Myoglobin


  Stores oxygen in the cells, higher affinity for oxygen than haemoglobin (oxygen will dissociate)
• Venous return


  Blood returning back to the heart
• Skeletal muscle pump


  Muscles contract around blood vessels to push blood around the body back to the heart
• Pocket valves


  Prevents backflow of the blood
• Smooth muscle


  Prevents friction, constricts to push blood
• Respiratory pump


  Pressure changes in the thoracic cavity squeeze blood
• Gravity


  Helps blood to return from above the heart
• Blood pressure


  The force exerted by the blood against the walls of the blood vessel (generated by the heart)
• Normal blood pressure


  120/80 mmHg = systole/diastole
• Exercise


  Temporarily increases blood pressure
• Chronic high blood pressure

  Higher resistance due to atherosclerosis
• Gaseous exchange


  Occurs at 2 sites: alveolus and capillary