Case 12 Flashcards
What is hypoxia?
Reduced level of oxygen in tissues
What is anoxia?
Severe form of hypoxia
No oxygen supply to tissues
What is ischaemia?
Reduced blood supply to part of the body
This leads to decreased oxygen supply to affected tissues
No removal of substances
What is cardiac metabolism?
The set of reactions in the cells of the heart which converts nutrients into ATP (energy)
What is fatty acid oxidation?
Fatty acids broken down to produce energy
Effect of hypoxia and ischaemia on metabolism?
1) Shifts metabolism toward anaerobic pathways (don’t require oxygen)
2) Increased reliance on glycolysis for ATP production
3) Impaired fatty acid oxidation (less energy produced from fatty acids)
4) Accumulation of lactate and decreased ATP levels
5) Anaerobic metabolism causes cellular acidosis (acidic cells) and compromised organ function
Repurfusion meaning?
Restoration of blood flow after reduced or interrupted supply
What are reactive oxygen species?
Highly reactive molecules containing oxygen
They are natural bi-products of normal cellular metabolism
How can repurfusion damage cellular components?
The blood flow is restored and the sudden influx of oxygen can lead to a burst of reactive oxygen species production.
This can damage cellular components
Glycolysis reaction?
Glucose + ADP + Pi —> ATP + Lactate + H+
ATP production using phosphocreatine reaction?
Phosphocreatine + ADP —> ATP + Creatine
Reaction when ATP is used?
ATP —> ADP + Pi
Infarction meaning?
Death of a tissue due to lack of blood supply
What happens to cells during infarction?
ATP levels are low
Ion pumps have no fuel
Ion levels in cells rise (Na+ and Ca2+)
This causes cells to swell and be damaged
Mitochondria release cell death trigger factors
Cell necrosis meaning?
Cell death caused by external factors
Examples of anoxic and ischaemic damage in organs?
Heart (infarction)
Brain (stroke)
Kidney (acute renal failure)
Pancrease (Pancreatitis)
… it can happen to all organs
3 layers of a blood vessel?
Tunica Intima (inner)
Tunica Media (middle)
Tunica Adventitia (outer)
Tunica - means layer
Describe tunica intima?
Endothelium supported by connective tissue
Describe tunica media?
Smooth muscle cells and elastic fibres
Describe tunica adventitia?
Collagenous connective tissue, nerve endings
Atherosclerosis?
Chronic inflammatory process triggered by accumulation of cholesterol-containing low-density lipoprotein particles in arterial wall.
Lipoproteins?
Contain proteins, phospholipids, cholesterol and triglycerides
Transport lipids in blood stream
Chylomicrons?
Lipoproteins which transport dietary triglycerides from intestines to cells
Very Low Density Lipoprotein?
Transports triglycerides synthesised in liver to various tissues
Intermediate Density Lipoprotein?
Formed from degradation of very low density lipoprotein. Will further degrade in low density lipoprotein.
Transports cholesterol and triglycerides
Low Density Lipoprotein?
Transports cholesterol and triglycerides in blood stream
This is ‘bad cholesterol’
Can contribute to build up of plaque in arteries
High Density Lipoprotein?
Removes excess cholesterol from blood stream by transporting it to liver for excretion or recycling
“Good cholesterol”
High HDL levels help prevent build up of plague, can be achieved by healthy lifestyle
Explain path of blood through the heart?
1)Deoxygenated blood enters right atrium via superior and inferior vena cava
2)Blood moves through tricuspid valve into right ventricle
3)Right ventricle contracts and pumps blood through pulmonary valve into pulmonary artery
4)Blood enters lungs and is oxygenated
5)Pulmonary veins return blood to left atrium
6)Blood passes through mitral valve into left ventricle
7)Left ventricle contracts and oxygenated blood moves into aorta via aortic valve
8)Aorta distributes oxygenated blood around body
What is systole?
Contraction
What is diastole?
Relaxation
What is preload?
Blood which fills heart
What is venous return?
Volume of blood which fills ventricles during each diastole
What is adrenergic stimulation?
Activation of receptors by adrenaline binding
How does adrenergic stimulation increase cardiac output?
Increased heart rate, increased contractility, accelerated relaxation, accelerated conduction
How to calculate ejection fraction?
Stroke volume/ end diastolic volume
How to calculate stroke volume?
End diastolic volume - end systolic volume
What is systolic dysfunction?
When ejection fraction is <55%
What is diastolic dysfunction?
Abnormal relaxation and/or increased ventricular stiffness
What is heart failure?
Heart unable to pump enough blood to meet body’s needs
Caused by structural and/or functional abnormalities of heart
Causes of heart failure?
Coronary heart disease
High blood pressure
Cardiomyopathy
Heart valve disorders
Previous heart attacks
Infections
Arrhythmias
Diabetes - damage to blood vessels and nerves
Obesity
Sleep apnea
What is left heart failure?
Left side of heart unable to pump blood effectively to body
Symptoms of left heart failure?
Shortness of breath
Fatigue and weakness
Persistent coughing or wheezing - white/pink/frothy sputum
Fluid retention
Cardiac arrhythmia
Reduced exercise tolerance
Difficulty concentrating
What is right heart failure?
Right side of heart unable to pump blood effectively to lungs
This can lead to a build up of fluid in body
Symptoms of right heart failure?
Swelling in legs/ankes/feet
Enlargement/tenderness of liver
Abdominal fluid accumulation
Shortness of breath
Fatigue and weakness
Reduced appetite and nausea
Increased heart rate
Cyanosis (blue discolouration of lips or skin) - when severe
How are different heart failures classified?
Class 1 - 4
What are the 2 types of heart failure?
1) Heart failure with reduced ejection fraction/ systolic heart failure
2) Heart failure with preserved ejection fraction/ diastolic heart failure
Describe systolic heart failure?
Hearts left ventricle becomes weak and is unable to pump blood effectively (leading to reduced ejection fraction)
What is chronic beta adrenergic stimulation in heart failure?
Heart is constantly being stimulated meaning it works too hard and can become damaged
What are ICDs - implantable cardioverter defbrillator?
Implantable cardioverter defibrillator
Detects and treats irregular heart rhythms in order to avoid cardiac arrest
Delivers electric shocks
What is CRT - cardiac resynchronisation therapy?
Use of a pacemaker to pace left and right ventricles simultaneously to synchronise contraction - increasing cardiac efficiency
Describe how a heartbeat is generated?
1)Sinoatrial node spontaneously depolarises, generating an electrical impulse which spreads across atria, causing them to contract and push blood into ventricles.
2)Electrical impulses reach atrioventricular nodes located near the bottom of the right atrium. The AV node delays signal slightly to allow ventricles to fill.
3)Electrical impulses travel down to bundle of His, which conduct signal from atria to ventricles
4)Bundle of His divide into Purkinje fibres which spread throughout ventricles and cause them to contract from bottom up and expel blood
5)After contraction, heart depolarises to ‘reset’ ready for next heart beat
Describe process of depolarisation of SA node cells?
1)Slow influx Na+ ions into cell via Na channels depolarises cell
2)Rapid influx of Ca2+ ions through Voltage gated Calcium ion channels further depolarises cell
Describe process of repolarisation of SA node cells?
K+ ions leave cell via K channels, restoring the negative charge inside cell
What is a syncytium?
When cardiac muscle cells are interconnected by intercalated discs, so they function as a single unit during contraction.
What is a gap junction?
They allow for exchange of ions, small molecules and electrical signals between adjacent cells.
Clusters of connexin proteins form channels between cell membranes
Effect of sympathetic autonomic nervous system on heart?
Increase heart rate
Increase atrioventricular node conduction speed
Decreased action potential duration
Effect of parasympathetic autonomic nervous system on heart?
Decreased heart rate
Decreased atrioventricular node conduction speed
What is hypertension?
An increase in peripheral vascular resistance when cardiac output is normal
What is systolic pressure?
Pressure in arteries when heart contracts to pump blood out (maximum pressure value in arteries)
What is diastolic pressure?
Pressure in arteries when heart is relaxed and filling up with blood (minimum pressure value in arteries)
What is diastolic pressure?
Pressure in arteries when heart is relaxed and filling up with blood (minimum pressure value in arteries)
What do the numbers mean in blood pressure readings?
Top number - systolic pressure
Bottom number - diastolic pressure
What is a healthy blood pressure value?
Below 120/80
Above what value is classed as hypertensive?
140/90
Primary vs Secondary hypertension?
PRIMARY - develops gradually over time, no identifiable cause, often genetics, lifestyle and aging contribute
-most common type
SECONDARY - has specific underlying cause and often develops more rapidly
-The underlying cause must be treated
Examples of causes of secondary hypertension?
Drugs and medications, kidney problems, hormonal imbalance, obstructive sleep apnea, adrenal gland tumours, thyroid disorder.