Case 11 Flashcards
What is membrane excitability?
The ability of a cell membrane to undergo changes in electric potential in response to stimuli. This allows for generation and spreading of action potentials
Hyperkalemia?
High blood potassium levels
Hypokalemia?
Low blood potassium levels
Symptoms of hyperkalemia?
Irregular heart rhythms (arrhythmia)
Muscle weakness
Nausea
Fatigue
Tingling or numbness
Symptoms of hypokalemia?
Muscle weakness or cramps
Fatigue
Irregular heartbeat (arrhythmia)
Constipation
Numbness or tingling
Increased urination
What is aortic stenosis?
Narrowing of aortic valve opening
What is aortic regurgitation?
Leaking of blood backward from aorta into left ventricle
What is mitral regurgitation?
Backflow of blood from left ventricle into left atrium through mitral valve during contraction
What is mitral stenosis?
Narrowing of mitral valve (which separates left atrium and left ventricle)
What is coronary heart disease?
When coronary arteries (which supply heart) become narrowed or blocked, often due to fatty deposits
What is myocardial infarction?
Heart attack
What is hypertension?
High blood pressure
What are cardiomyopathies?
Group of diseases which lead to structural and functional abnormalities of heart muscle
Describe embryonic cardiac development process?
1) Heart develops from the mesoderm
2) Week 3: Heart tube formed, made of 2 segments, primitive atrium and primitive ventricle
3) Week 4+5: Formation of atria and ventricles
4) Week 5 + 6: Formation of heart valves
5) Week 5 - 8: Development of heart septa and formation of coronary vessels
6) Week 8: Maturation. Heart is complete. It is the first organ to be completed.
Describe fetal circulation?
1) Oxygen and nutrients from mother blood diffuse into placental blood diffuse into fetal blood at placenta
2) Umbilical vein returns the oxygenated blood back to the foetus after placenta
3) Blood distributed around body
4) In heart, foreman ovale and ductus arteriousus are shunts so blood avoids lungs
5) Umbilical arteries return deoxygenated blood to arteries
What is a normal heart beat?
70 per minute
What are cardiomyocytes?
Cells in heart which contract
Explain cardiac cycle?
1) Blood enters atria
2) Atrial contraction and atrioventricular valves open
3) Blood flows into ventricles
4) AV valves close (to prevent backflow) and ventricles contract
5) Pressure in ventricles exceeds pressure in arteries, so semi lunar valves open
6) Blood leaves heart and goes to lungs and body
7) Ventricles relax
Sinoatrial node?
Natural pacemaker in right atrium
Atrioventricular node?
Located between atria and ventricles
Bundle of His?
Divides into bundle branches, transmitting signals to ventricles
Purkinje fibres?
Network of fibres which distribute signals through ventricles
Describe process of conduction of impulses?
1) Sinoatrial node initiates signals, causing atria to contract
2) Signals reach AV node
3) There is a delay, allowing ventricles to fill
4) Bundle of His conducts signals to bundle branches and purkinje fibres
5) Rapid signal transmission through purkinje fibres triggers synchronised ventricular contraction, so loud is pumped effectively
What are natriuretic peptides?
Hormones released by the heart in response to increased blood pressure and volume
Regulate fluid balance, blood pressure and cardiovascular homeostasis
They promote vasodilation and increased urine production
Cardiac output?
Total volume of blood pumped by the heart per minute
Stroke volume?
Volume of blood ejected by left ventricle in one contraction
Venous return?
Blood flow returning to heart from systemic circulation
End Diastolic volume (EDV)?
Maximum amount of blood in heart during cardiac cycle
Blood volume in ventricles just before next contraction
End Systolic volume (ESV)?
Minimum volume of blood in heart during cardiac cycle
Blood volume in ventricles just after contraction
Ejection fraction?
Percentage of blood pumped out of the ventricle with each contraction
Ejection fraction?
Percentage of blood pumped out of the ventricle with each contraction
Describe intracellular fluid?
Found inside cells
Rich in potassium, magnesium and phosphate ions
Contains proteins and nucleic acids
Describe extracellular fluid?
Outside cells
Eg interstitial fluid and plasma
Higher in sodium and chloride ions, contains bicarbonate ions
What is oedema?
Swelling caused by a build up of fluid
Physiological factors which form oedema?
Increased capillary permeability
Changes in osmotic pressure
Lymphatic obstruction
Increased hydrostatic pressure of blood
Sodium and water retention
What is heart failure?
Heart is unable to pump blood effectively
This leads to insufficient oxygen and nutrients reaching tissues
Common causes of heart failure?
Coronary heart disease (blocked blood vessels which supply heart)
Myocardial infarction (heart attack)
Hypertension (high blood pressure)
Valvular heart diseases
Cardiomyopathies (abnormalities of heart)
Signs and symptoms of heart failure?
Dyspnea (shortness of breath) - especially during exercise or when lying down
Fatigue and weakness
Oedema (swelling) in legs, ankles or abdomen due to fluid retention
Persistant coughing
Pink, frothy sputum
Heart arrhythmias
Reduced exercise tolerance
Excessive urination at night
Function of furosemide and why used to treat heart failure?
Inhibits sodium and water re absorption at loop of henle in kidneys
Reduces fluid overload (reducing blood pressure)
Function of glyceryl trinitrotoluene (GTN) and why used to treat heart failure?
Vasodilator
Reducing blood pressure (reduced workload on heart)
Function of carvedilol and why used to treat heart failure?
Blocks beta adrenergic receptors
Reduces heart rate and O2 demand of heart muscle
Dilates blood vessels
Function of rampipril and why used to treat heart failure?
Blocks formation of angiotension II (from angiotension I)
This is a vasoconstrictor
So rampipril acts as a vasodilator
What is atrial fibrillation?
Disorder characterised by irregular and rapid heartbeats
Atria quiver rather than contracting
What are anticoagulants?
Medications which help prevent blood clot formation
Why would an atrial fibrillation patient be given anticoagulants?
Stagnant blood in atria increases risk of clot formation, which could break loose and travel to other parts of body.
What is pericardium?
A double walled sac surrounding the heart
What are the 2 layers of the pericardium?
Fibrous (outer) and Serous (inner)
What are the 3 layers of the heart wall?
Epicardium (outer), Myocardium (middle), Endocardium (inner)
What is tricuspid valve?
Right atrium to right ventricle
What is bicuspid/mitral valve?
Left atrium to left ventricle
What is pulmonary semilunar valve?
Valve linking right ventricle and pulmonary artery
What is aortic semi lunar valve?
Valve linking left ventricle and aorta
What is superior vena cava?
Drains deoxygenated blood from upper body into right atrium
What is inferior vena cava?
Drains deoxygenated blood from lower body into right atrium
What is aorta?
Distributes blood from left ventricle around body
Describe blood flow through heart and lungs?
1) Deoxygenated blood enters right atrium via vena cava
2) It moves through tricuspid valve into right ventricle
3) Contraction sends blood through pulmonary valve into pulmonary artery
4) Blood goes to lungs
5) Blood leaves lungs via pulmonary vein back into left atrium
6) Passes through bicuspid/mitral valve into left ventricle
7) Pumped out of ventricle through aortic valve into aorta, then out into body
