Cardiovascular 1

• LOs:

  
• What is homeostasis?

  • State of balance among all body systems needed for body to survive & function correctly
  • A variable actively regulated to remain nearly constant
  • Cardiac cycle plays major role in homeostasis
• What does homeostasis in the body involve?

  Maintenance of internal environment- faced with variation in external environment, activity & intake of nutrients etc.

  Negative feedback loop is core mechanism:

  
• Main functions of the cardiovascular system:

  • Rapid transport & distribution of nutrients (glucose & O2) & removal of waste products (urea & CO2)
  • Distribution of water, electrolytes & hormones using blood
  • Exchange between blood vessels & interstitial fluid
  • Infrastructure of immune system
  • Temperature regulation
• What happens when less oxygen is supplied to the brain?

  Feeling faint
• What varying conditions does the cardiovascular system work under?

  • Exercise
  • Chronic disease (e.g, respiratory disease- COPD)
  • Sickness (e.g, flu)
• Where is pulmonary circulation?

  Lungs- lower resistance & lower pressure as lungs close to heart so requires minimal force to pump blood through them

  
• What are the adaptations of the pulmonary artery?

  Thin elastic walls & a large cross sectional area to allow blood to flow easily without high pressure- allows gas exchange from blood capillaries to alveoli
• What is another name for the cardiovascular system?

  The circulatory system
• What is systemic circulation?

  Circulation of blood from the heart to the rest of the body and back to the heart

  Higher resistance & higher pressure- oxygenated blood needs to be pumped all around body
• Why do systemic arteries have thicker, muscular walls?

  To maintain high pressure & high resistance (blood initially flowing against gravity & through small arterioles with greater resistance)
• Diagram of systemic circulation:

  
• What are the arterial & venous systems?

  Distribution of blood & venous return
• What does systole refer to?

  Contraction of heart during cardiac cycle

  Blood pumped out ventricles & into arteries
• What does diastole refer to?

  Heart relaxed

  Ventricles are filling- assisted by atria contracting
• What does stroke volume refer to?

  Amount of blood pumped into left ventricle per heartbeat (about 70ml)
• What does cardiac output refer to?

  Total volume of blood that heart pumps out per minute

  Stroke volume x Heart rate

  (normally 5-6 litres)
• What does pressure (P) refer to?

  Force per unit area (heart generates a 'head of pressure')
• What does resistance (R) refer to?

  How hard is it for flow (Q) to occur?
• What does 'normal arterial blood pressure' refer to?

  Systolic/diastolic (e.g, 120/80)

  Very variable as every number different as it's a snapshot of that moment
• What does 'mean arterial pressure' refer to?

  Controlled variable in cardiovascular system
• What is the endocardium?

  • Innermost layer of heart
  • Made of smooth endothelial cells which line the heart chambers (atria, ventricles & valves)
  • Prevents blood clotting
• What is the myocardium?

  • Middle & thickest layer of heart
  • Made of cardiac muscle tissue
  • Where action potentials happen to cause heart contractions
• What is the epicardium (visceral pericardium)?

  • Outermost layer of heart
  • Provides heart protection & contains blood vessels that supply blood to heart
• What is the pericardium?

  • Double-layered sack made of fibrous & serous pericardium
  • Surrounds heart reducing friction & anchors it in chest
• What does the right side of the heart do?

  Pumps deoxygenated blood to the lungs
• What does the left side of the heart do?

  Pumps oxygenated blood to the body (left ventricle has thicker muscle)
• What are the different components of the heart?

  • Ventricles
  • Valves
  • Atria
  • Annulus fibrosus
  • Cardiac (striated) muscle
  • Endocardium, myocardium, epicardium & pericardium
• Diagram of the heart:

  
• Describe the atria:

  • Thin-walled compared to ventricles
  • Receive venous blood
  • Right atrium receives systemic venous blood
  • Left atrium receives oxygenated venous blood & sends it to systemic arteries
  • Act as pumps to fill ventricles at low pressures
  • Produce hormone ANP (atrial natriuretic peptide)
• Describe the ventricles:

  • Eject blood into arterial systems including to lungs
  • Left ventricle has thicker wall than right & generates higher pressures- blood to systemic circulation
• Where in the heart does the heartbeat start?

  Sinoatrial node (SAN)

  (Heart's natural/physiological pacemaker located in right atrium)

  • Has excitable cells that generate action potentials- usually through Na & Ca channels which cause depolarisation
  • Ability to generate electrical impulses (spontaneously without external stimuli) that occur at regular consistent rates (heart rate pace)
  • Has dominance over other potential pacemakers as it has fastest rate of spontaneous depolarisation- overrides small other pacemaker cells in heart

  
• What is the outcome of the SAN?

  Causes heart to contract (cardiac muscle contraction) which causes heartbeat
• Diagram of labelled heart layers:

  
• What are the stages of the cardiac cycle?

  1.) Atria contract & ventricles relax

  2.)Atria relax & ventricles contract

  3.) Atria & ventricles relax
• What causes the automaticity of the SAN?

  Unstable resting membrane potential- allows continuous contraction & regular heart beat

  Several ion currents involved

  No 'fast' outward sodium currents