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Clinical Biochemistry: Introduction to Clinical Biochemistry > Heart and Lung Physiology > Flashcards

Heart and Lung Physiology Flashcards

1
Q

What is the function of the Cardiovascular system?

A

Transport mechanism:

  • Oxygen
  • Nutrients - glucose, electrolytes
  • Antibodies / white blood cells to sites of infection
  • Hormones
  • Waste products of metabolism
  • Thermoregulation
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2
Q

What are the cells making up the heart and their function?

A

Conducting Cells​

  • Specialised cells co-ordinate heart beat

Contractile cells​

  • Myocardium (bulk of the heart) which generates pressure to move blood
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3
Q

Describe the electrical activity of the cells of the heart?

A
  • Polarised cell – intracellular negative. Unstimulated-resting potential.
  • Depolarised cell – influx of positive ions, stimulated-action potential. This leads to Ca2+ from ECF and sarcoplasmic reticulum. which causes contraction.
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4
Q

Which particular ions is the heart sensitive to?

A

Very sensitive to changes in:

  • Calcium concentration
  • Potassium concentration.
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5
Q

What determines the End Diastolic Volume?

A

EDV determined by:

  • Filling time – heart rate
  • Venous return – amount of blood returned to heart. Also effects HR – atrial reflex.
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6
Q

How is End Systolic Volume determined?

A
  • Preload – amount of blood present in the heart chamber, i.e. the EDV. More stretch, greater force of contraction.
  • Contractility - the strength of the cardiac contraction.
  • Afterload - the pressure against which the heart must work, the forces that impede the flow of blood out of the heart i.e. vascular resistance. Primarily composed of the pressure in the peripheral vasculature, the compliance of the aorta, and the mass and viscosity of the blood
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7
Q

How is the the heart regulated?

A

Cardiovascular centre located in medulla oblongata regulates the heart through the autonomic nervous system

  • Acts to regulates blood pressure.
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8
Q

Which factors are changed to alter the blood pressure?

A
  1. Heart rate
  2. Stroke volume
    • Contractibility
    • Afterload / Vascular resistance to blood flow through vasodilation / vasoconstriction
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9
Q

How does the Sympathetic nervous system affect BP?

A

Increase BP

  • Increases heart rate (SA, AV nodes)
  • Ventricles contractility
  • Vasoconstriction
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10
Q

How does the parasympathetic affect the blood pressure?

A

Decrease BP

  • Decreases heart rate (SA & AV nodes)
  • Vasodilation
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11
Q

What is the structure for the heart?

A

Inside to Outside

  • Heart Chamber
  • Endocardium
  • Myocardium
  • Epicardium
  • Pericardial Cavity
  • Pericardium (Visceral and Parietal layer)
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12
Q

What is the arterial and venous structure?

A

Arteries and Venous

  • Tunica intima
  • Tunica media
  • Tunica externae
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13
Q

How does electrical activity travel within the heart?

A
  • Sinoatrial Node
  • Atrioventricular node
  • Bundle of His
  • Left and Right bundle branches
  • Apex
  • Purkinje Fibres
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14
Q

What is the sequence of the cardiac cycle?

A
  • Atrial Contraction begins
  • Atria eject blood into the ventricles
  • Atrial systole and AV valves close
  • Isovolumetric ventricular contraction
  • Ventricular ejection occurs
  • Semilunar valves closes
  • Isovolumetric relaxation occurs
  • AV valves open and passive ventricular filling occurs
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15
Q

Which receptors act to regulate the heart?

A

Baroreceptors: They detect arterial BP through the stretch recpetors (carotid sinus / aortic arch / right atrium)

Chemoreceptors: Detect O2 & CO2 levels (carotid bodies and aortic bodies located near the carotid sinus and aortic arch)

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16
Q

Which hormones act to increase the Blood Pressure?

A
  • RAAS: Increased sodium/water retention & angiotensin II to increase Preload and cause vasoconstriction to increase Afterload
  • ADH: Increase water retention to increase Preload
  • Epinephrine / Norepinephrine: increase heart rate, vasoconstriction to increase Afterload
  • Thyroxine
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17
Q

Which hormones act to decrease BP?

A
  • ANP: Causes Vasodilation and Inhibits RAAS.
  • Nitric oxide: Causes Vasodilation
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18
Q

How does potassium affect the heart?

A

Potassium - affects SA node and HR

  • Hyperkalaemia which can cause weak irregular contractions
  • Hypokalaemia which can decrease HR
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19
Q

How does calcium affect the heart?

A

Calcium – affects contractility (SV)

  • Hypocalcaemia which can cause weak contractions and arrhythmias
  • Hypercalcaemia which can cause strong, lengthy contractions and arrhythmias
20
Q

What are the common cardiovascular disorders?

A
  1. Cardiovascular disease
  2. Coronary heart disease
  3. Heart Failure
  4. Hypertension
21
Q

What is Cardiovascular Disease?

A

Atherosclerosis - affects arteries in the heart, brain and peripheral tissues. It involves

  • Deposition of lipid and matrix protein in the arterial wall (medium to large arteries)
  • Narrowing of the vessel lumen
  • Reduced blood supply
  • Heart – causes coronary heart disease
  • Brain – causes stroke
22
Q

What are some risk factors for CVD?

A
  • Age
  • Gender
  • Race
  • Family History
  • Pre existing CVD
  • Smoking
  • Cholesterol
  • Hypertension
  • Obesity
  • Diabetes Mellitus
  • Low physical activity
  • Biochemical (Homocysteine, hsCRP, Fibrinogen, IL-6, MMPs / PAPP-A)
  • Micro RNA (miRNA)
23
Q

What is the Coronary Heart Disease?

A

Also called Ischaemic Heart Disease (IHD)

  • Failure of the coronary circulation to meet the demands of the heart (increased demand/decreased supply)
  • Caused by: cardiovascular disease (coronary arterial disease, CAD), Vasospasm, anaemia, arrhythmias
  • Lack of oxygen leads to Ischaemia
24
Q

What is the Myocardial Infarction?

A
  • End result of Coronary Heart Disease
  • Prolonged ischaemia leads to cell death (necrosis)
  • May also get collagen scarring
25
Q

What is Coronary Artery Disease (CHD)?

A

Atherosclerosis in coronary arteries causing inadequate oxygen supply to the heart.

This leads to

  • Stable angina
  • Acute coronary syndrome (ACS)
26
Q

What is Stable Angina and ACS?

A

Stable Angina

  • Partial occlusion of cardiac artery
  • Unable to supply oxygen if increased demand (exercise, stress)

Acute Coronary Syndrome

  • Due to plaque rupture. This causes a full occlusion of the coronary artery
  • Causing Unstable angina or Myocardial infacrtion
27
Q

How is diagnosis of ACS made?

A
  • ECG changes (ST segment depression or elevation)
  • Biochemical Cardiac Markers (Cardiac enzymes, Myoglobin, Troponins)
28
Q

What are some cardiac enzymes?

A

Troponins

  • Troponin T – binds to tropomyosin
  • Troponin I – inhibitor of ATPase
  • Troponin C – binds calcium

Myoglobin

  • Found in cytoplasm and present in all muscle
  • Haem protein – oxygen transport.

ALT (alanine aminotransferase) and AST (aspartate aminotransferase)

  • Found in cytoplasm of cells in liver, skeletal and cardiac muscle, kidney
  • Increased in plasma following circulatory failure, MI.

LDH (Lactate dehydrogenase)

  • Wide tissue distribution of Five isoforms LDH1 – LDH5. LDH1 – significant in MI
  • Measure total LDH

CK (Creatine Kinase)

  • Found in skeletal and cardiac muscle, brain.
  • Dimer of two subunits M or B. 3 isoforms: MM (skeletal and cardiac), MB (35% of cardiac activity, 5% skeletal), BB (brain)
  • Measure CK and CK-MB (both raised in muscle damage)
29
Q

What are the uses of isoforms of Troponin?

A
  • Troponin T and I used as markers for cardiac damage (cardiac specific isoforms).
  • Troponin I more specific, skeletal troponin T isoforms cross react in cardiac Troponin T assay.

High sensitive assays (hsTnT / hsTnI) – lower detection limits

30
Q

What does detection time depend on?

A
  • Size
  • Cellular location
  • Plasma clearance
31
Q

What are other causes of Raised Troponin?

A
  • Trauma
  • Congestive heart failure–acute and chronic
  • Hypertension
  • Hypotension, often with arrhythmias
  • Renal failure
  • Critically ill patients, esp with diabetes
  • Hypothyroidism
  • Myocarditis
  • Pulmonary embolism
  • Sepsis
  • Burns, esp if total burn surface area > 30%
  • Amyloidosis
  • Acute neurological disease, including CVA
  • Rhabdomyolysis with cardiac injury
  • Vital Exhaustion
  • Polymyositis
  • Shock
32
Q

What is Heart Failure, Symptoms and causes?

A

Failure of heart output to meet demand.

Symptoms:

  • SOB
  • Fatigue
  • Oedema

Causes:

  • Cardiomyopathy
  • Inflammation
  • Valvular heart disease
  • Ischaemic heart disease
33
Q

What is used in the diagnosis of Heart Failure?

A
  • Echocardiogram – gold standard
  • Markers of Heart Failure: Brain natriuretic peptide (BNP)
    • Natriuretic peptide secreted primarily from ventricules as a prohormone (proBNP).
    • Immunoassays available for BNP and NT-proBNP
    • Useful ‘rule-out’ test – echo referral. Negative result excludes heart failure
    • Prognostic indicator in heart failure
34
Q

What increases and decreases BNP?

A

Increased in:

  • Cardiac failure
  • Ventricular hypertrophy, ischaemia, tachycardia, sepsis, COPD, hypoxaemia, renal disease, >70yrs

Reduced levels:

  • Diuretics, ACE inhibitors, Beta-blockers, ARB, Aldosterone antagonists
35
Q

What is Hypertension?

A
  • BP >140/90 mmHg
  • Risk factor CVD – CHD or stroke

Causes

  • Essential hypertension – unknown cause
  • Endocrine hypertension - Conn’s, Cushings,phaeochromocytoma.
36
Q

What are biochemical markers of Hypertension?

A
  • No specific biochemical markers for hypertension
  • Diagnosing endocrine causes

Management/monitoring treatment

  • renal function
  • electrolytes
37
Q

What is the function of the Respiratory System?

A
  • Gas exchange: CO2 exchanged for O2
  • Acid-base regulation
38
Q

How is Respiration regulated?

A
  • Respiratory centre in medulla – controls rate and depth of breathing.
  • Driven by CO2 concentration (PCO2). Maintained within tight limits.
39
Q

What is V/Q mismatching?

A

Ventilation (V) – amount of air reaching the alveoli

Perfusion (Q) – amount of blood reaching the alveoli

V/Q ratio(0.8) is major factor effecting gas exchange in the lung and arterial O2 and CO2 levels

V/Q mismatching

  • ↓V/Q - alveolar ↓pO2 / ↑pCO2
  • ↑V/Q - alveolar ↑pO2 / ↓pCO2
40
Q

What determines pCO2 levels?

A
  • Determined by ventilation in the alveolar
  • Areas of good ventilation in the lung are able to compensate for any alveoli with poor ventilation by hyperventilation
41
Q

What determine pO2 levels?

A

Determined by

  • Ventilation in the alveolar
  • Concentration of O2 in the inspired air
  • Perfusion of the lung
42
Q

What are disorders of Respiration?

A
  • Hypercapnia - ↑PCO2
  • Hypocapnia - ↓PCO2
  • Hypoxaemia – ↓O2 in the blood
43
Q

What is Type 1 respiratory failure and causes?

A

TYPE 1

  • Adequate ventilation
  • Defective oxygenation
  • Hypoxaemia

Causes

  • Pneumonia
  • PE
  • COPD
  • ARDS
44
Q

What is Type 2 respiratory failure and causes?

A

TYPE 2

  • Inadequate ventilation
  • Hypercapnia and hypoxaemia

Causes

  • COPD
  • Exhaustion
  • Opiates
45
Q

What is effect of Hyperventilation and the causes?

A

Hyperventilation

  • Hypocapnia

Causes

  • Anxiety
  • Salicylate
  • Hypoxaemia
46
Q

What are other respiratory disorders and their biochemical tests?

A

Cystic Fibrosis

  • Immuno-Reactive Trypsin (IRT) - part of newborn screening

A1AT deficiency

  • No inhibition of neutrophil elastase - emphysema
  • A1AT

Carbon monoxide poisoning

  • CO has higher affinity for Hb than O2 - hypoxaemia
  • Carboxyhaemoglobin (COHb)

Clinical Biochemistry: Introduction to Clinical Biochemistry (11 decks)

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