Heart

• Blockage to a coronary artery


  -reduction of oxygenated blood flow to cardiac muscle, therefore a reduction on rate of aerobic respiration causing a reduction in energy release, ultimately causing cells to die
• Cardiac muscle


  -cardiac muscle contracts involuntary as part of the autonomic nervous system, contraction is known as myogenic.
• Blockage to a coronary artery results in a reduction o& oxygenated blood flow to cardiac muscle therefore a reduction in the rate of aerobic respiration causing a reduction on energy release ultimately causing cells to die
• Cardiac muscle


  -Cardiac muscle contract on an involuntary basis as part of the autonomic nervous system the contraction is known as myogenic

  -cardiac muscle cells are branched with intercalated discs to create gap Junctions

  -have more mitochondria as they are more reliant on aerobic respiration and skeletal muscles
• SAN(Sinoatrial node)


  -located in the right atrium near the entrance of the superior vena cava.

  -Hearts natural pacemaker.

  -Initiates all heartbeat and determined heart rate.

  -Electrical impulses from the SAN spread throughout both atria and stimulate them to contract
• AVN(atrioventricular node)


  -located near the AV valve.

  -Serves as an electrical gateway to the ventricles.

  -Delays the passage of electrical impulses to the ventricles to ensure that the atria have objected all of the blood into the ventricles before they contract.

  Receives a signal from the SAN and passes them onto the bundle of his
• Bundle of his


  -divided into right and left bundle branches which conduct the impulse towards the apex of the heart.

  -Signals are them passed onto the purkinje fibres turning upwards and spreading throughout the ventricular myocardium
• Purkinje fibres


  -Located in the walls of the ventricle.

  -Conduct the electrical impulse to the individual cells of the ventricles.

  -causes a contraction in a coordinated manner
• Septum

  Insures the deoxygenated blood and oxygenated blood do not mix to efficient oxygenated blood around the body
• Atria


  Collect low pressure blood from the body and lungs continuously
• Ventricles


  Muscular and responsible for pumping blood under pressure pressure to the body and lungs
• Valves


  In short direction, ability of blood flow and prevent backflow
• Summary table 


  Different blood vessels and there properties

  
• Artery adaptations


  -Arteries have a narrow lumen to maintain blood pressure.

  -Lots of elastic tissue which expand with increased blood flow to cope with pressure and recoil to maintain blood pressure.

  -Muscular tissue exerts a force against blood pressure to prevent bursting.

  -endothelium being smooth reduces friction and pressure loss.

  -collagen exerts force against bursting
• Vein adaptations


  -Little elastic and muscle tissue as they carry low pressure blood.

  -Wide lumen to manage a large volume of low pressure blood.

  -Vein valves prevent backflow and pooling of blood towards the feet.

  -Pressure differences between vein compartments and working in tandem with skeletal muscles and shows blood continuously moves back towards the heart
• Capillary adaptations


  -Large surface area due to millions of capillaries

  -one cell thick meaning there is a short diffusion distance.

  -maintains a high concentration gradient with constant blood flow
• parts of the heart showing whether each part is oxygenated or deoxygenated and also high or low pressure

  
• What occurs when pressure in the LV exceeds pressure in the aorta?

  The semi-lunar valve opens
• What is the purpose of the semi-lunar valve opening?

  To let blood flow from the ventricle to the aorta
• What happens when pressure in the aorta exceeds pressure in the LV?

  The semi-lunar valve snaps shut
• What happens when pressure in the LV exceeds pressure in the LA?

  The AV valve snaps shut
• Why does the AV valve snap shut when LV pressure increases?

  To prevent back flow into the atria
• Why does the semi-lunar valve snap shut when aortic pressure increases?

  To prevent back flow into the LV
• What occurs when pressure in the LA exceeds pressure in the LV?

  The AV valve opens
• What is the effect of LA pressure being greater than LV pressure?

  It allows blood into the ventricle
• Chemoreceptors 


  located In the aortic arch, carotid artery and medulla oblongata

  Constantly measuring co2 conc and blood pH

  When co2 increases, blood pH decreases, chemoreceptors then send a signal to the medulla to correct this chrmical imbalance
• Pressure changes 


  On the left side of the heart

  
• risk factors of CHD


  Age- blood vessels become less flexible with advancing age

  Genetics- hypertension predispose individual to developing CHD

  Obesity- places strain on the heart

  Diet- saturated and trans fats

  Diseases

  Exercise-no exercise increases risk

  Sex-males are more likely due to lower oestrogen

  Smoking
• Atherosclerosis


  1. High BP can damage smooth endothelium leading to rough scar tissue
  2. Saturated fats and trans fat are more likely to accumulate on rough scar tissue forming atherosclerotic plaque
  3. The narrowed lumen results in a higher blood pressure in localised region
• chronic problems of atherosclerosis 


  1. severely occluded artery- reduced o2 blood flow down stream, cells will struggle to respire
  2. severely occluded artery- clot is more likely to get stuck resulting in no o2 rich blood flow causing a heart attack or stroke
• atherosclerotic plaque more likely to rupture

  resulting in blood clotting and thrombus
• aneurysm 


  due to chronic wall weakening and the artery eventually bursting causing internal bleeding