Lecture 10 Part 2 Flashcards
What does endurance training increase?
Heart rate, cardiac output, stroke volume, end systolic residual volume, ejection function and cycle time
What is the fold change from endurance training from normal?
By a 5-fold change
What is one way of measuring the cardiac efficiency?
Buy the pressure-volume loop
What happens when you get an electrical excitation?
Increase in ventricular volume and increased in ventricular pressure (valves opens and blood exists the heart)
What = the total loop area (the mechanical work of the heart)?
Mitral valves open, aortic valve closes, aortic valve opens and mitral valves closes
What increases per ventricle volume?
Ventricle contraction increases per ventricle volume
What does endurance training incorporate?
Combinations of beta-receptor signalling and distension
What happens short term in endurance training?
Chamber distension occurs due to increased venous return - increased preload
What is activated in short term endurance training?
Frank starling and brainbridge mechanisms
What happens to the ventricles in short term in endurance training?
Activates stronger contraction by the frank-starling mechanism
What happens to the atrium short term in endurance training?
Contributes to increased heart rate by the brainbridge reflex
What happens to the heart during longer term endurance training?
There can also be structural remodelling of the heart
What does chamber distension result in?
A larger radius over time
What does laplace’s law mean?
Reduces ventricular pressure. Pressure = wall tension/ radius
What is the stimulus of chamber sustension over a period of time?
It is greater over a period of time
What can ventricular pressure be accommodated by?
By increasing the muscle mass
How chamber distension result into a larger radius?
Increase in preload results in sarcomeres being added in series, cells increase in size, length not width
What is the process of a larger radius called?
Eccentric cardiac hypertrophy
What are some cardiac physiological adaptations in action?
Increased in cardiac output, stroke volume, heart rate and decrease in peripheral vascular resistance
What is the increase in blood volume from a normal person to someone who is pregnant?
35-50% increase in blood volume, 50% up to 9 months
What mechanism is increased in pregnancy?
Preload - as the metabolic demands of the organ systems are increasing all the time
What can happen to the ventricle during pregnancy?
You can have a dilated ventricle - which is responses by eccentric remodelling
What is important to know about dilated ventricles in pregnancy?
That they are reversed 1-3 months post partum
What is increased during strength exercise training?
Increased after load
Describe the changes that occur in strength exercise training?
Increased in wall stress as the force in which the ventricles has to contract is higher, and increase in after load
What is increase wall stress in the cardiac ventricles inversely proportional to?
The thickness of the diameters and radius
What is done to counter the increase in mass due to the induced wall stress?
Sarcomeres are added in parallel - the process Is called concentric cardiac hypertrophy
What happens if the physiological changes are over ridden?
It results in cardiac dysfunction or even heart failure
Define heart failure?
An inability to pump enough blood to meet metabolic demand
What are the symptoms for heart failure?
Decreased SV, CO, Decreased BP, oedema and exercise intolerance
What is the most common cause of heart failure?
Ischaemic heart disease, which is a build up of plaque material that blocks the flow of blood, the block can be complete or it can be partial
What can coronary artery damage result to?
Result to phenotypic alteration of vascular cells
What does alteration vascular cell result in?
Results in the formation of an atherosclerotic and fibrotic plaque restricting blood flow to the myocardium
What does ischaemia cause?
Dysregulation of the cardiomyocytes
What is the process from a heart attack to increased sympathetic drive?
Decrease in cardiac EC coupling, cardiac output, BP, and baroreceptor input
What happens to the feedforward responses from the heart attack?
Increase in circulating catecholamines - overstimulation, more SR ca2+ and leakiness of ca2+ sparks through the RYR2 receptors
How is the there an overload of SR ca2+ ?
From phospholamban phosphorylation
What does beta-signalling overstimulation induce?
Induces ca2+ dysregulation
What does a large increase in ca2+ increase?
Increases the membrane potential of the cell
What happens when the whole membrane potential is increased?
It can start to cause arrhythmias which disrupts the while cell. Different cells can access a ca2+ wave but cardiomyocytes in sarcomeres cannot
What is tissue level EC coupling compounded by? - from a feed forward response
Infarcted tissue leading to fibrosis, loss of contractile tissue again increasing risk of electrical dysregulation (arrhythmias)
What is the treatment for severe heart failure?
Often involves trying to reduce the preload and after load
What are examples of treatment for heart failure?
Diuretics - reduce plasma volume, ACE inhibitors - reduce vasconstriction, beta blockers - inhibit catecholamines overstimulation
What are some potential integrated physiological mechanisms?
Improved respiration, improved skeletal muscle function and improved blood pressure, maintain glucose and homeostasis and reduce sarcopenia
What can sarcomeric protein mutations over time lead to?
Dilated cardiomyopathy or hypertrophic cardiomyopathy
