Fichas
Cardiac Output
Fichas del conjunto (33)
- 1What is the heart? Define cardiac output.*The heart is the pump that moves the blood around the body = its activity is described as the cardiac output
Cardiac Output = Heart rate x Stroke volume
*Heart rate is driven by waves of electrical activity that induce the cardiac muscles to contract. - 2Describe blood flow in the heart.
- 3Outline the components of the conduction system of the heart.Heartbeat is myogenic.
Heartbeat is driven by specialised myocytes composed of the sino-arterial node and the artrioventricular node .
- 4Outline the sequence of cardiac excitation.Spread of action potentials via the purkinje fibres results in coordinated contraction of ventricles.
- 5What causes the sino-atrial node to trigger an action potential?Low resting membrane potential (-60-70v)
Na+ leakage
=Action potential - 6Outline the mechanism underlying spontaeous action potential generation in pacemaker cells.*Sodium ions “leaking” in through the F-type channels and calcium ions moving in through the T-type channels cause a threshold graded depolarization.
*The rapid opening of voltage-gated
calcium L-types channels is responsible
for the rapid depolarization phase.
*Reopening of potassium channels and
closing of calcium channels are responsible for the repolarization phase. - 7Explain the mechanism of contraction of the ventricular cardiomyocytes.*The rapid opening of voltage-gated sodium channels is responsible for the rapid depolarization phase.
*The prolonged “plateau” of depolarization is due to the slow but prolonged opening of voltage-gated calcium channels and closure of potassium channels
*Opening of potassium channels results in the repolarization phase. - 8How does calcium produce contraction of cardiac muscles?*Excitation-Contraction Coupling in Cardiac Muscle
*Calcium ions regulate the contraction of cardiac muscle:
The entry of extracellular calcium ions causes the release of calcium from the sarcoplasmic reticulum.
- 9What is the refractory period? Explain its purpose.*Refractory period = time required before it is possible to re-stimulate muscle contraction > Cardiac muscle (250ms)
*Cardiac muscle has a prolonged refractory period which allows for ventricles to fill with blood prior to pumping. - 10Outline the role of the Autonomic nervous system in regulation of the sino-atrial node.
- 11Outline regulation of heart beat by para/sympathetic nervous system.1. Spontaneous depolarisation of the sino-atrial node is the driver of heart rate
2.Sino-atrial node is regulated by the parasympathetic (reduce) and sympathetic (increase) nerves
3.Electrical activity flows from sino-atrial node – atrioventricular node – purkinje fibres - cardiomyocytes - 12Describe parasympathetic regulation of the depolarisation of the sino-atrial node?
- 13Describe sympathetic regulation of the depolarisation of the sino-atrial node?
- 14What is an electrocardiogram?*ECG is a summation of the spread of action potentials through the various sections of the heart.
*PQRSTU assigned to various deflections - 15Label general electrocardiogram.
- 16Outline electrical events of the cardiac cycle.
- 17Explain how the ECG is used to diagnose disease.*Provides valuable information on the electrical activity of the heart
-Heart rate/ Heart rhythm
-Disturbances of rhythm and conduction
(arrhythmia, pacemaker)
-Conduction velocity
-Anatomical orientation of the heart
-Relative size of chambers
-Condition of tissue within the heart
-Damage to the myocardium
-Influence of certain drugs - 18What is ventricular fibrillation?RESULTS - Random Firing of heart, Fibrillating ventricles cannot pump blood, Fatal after a few minutes
450,000 deaths/year.
CAUSES - Myocardial Infarction (heart attack), Electrical shock, Drug intoxication
Impaired cardiac metabolism - 19Describe structure of the heart.
- 20What are the two phases of the cardiac cycle?SYSTOLE – ventricular contraction and blood ejection
DIASTOLE– ventricular relaxation and blood filling - 21Explain pressure changes in different blood vessels.*Blood pressure is reduced as it passes from arteries to veins since bigger lumen
*Lower artiole pressure in pulmonary system since dont want formation of blood pressure in lungs - 22Explain contractions in one heart beat.*Passive filling of atria
*Atria contact semi lunar valves shut
*When pressure in atria greater than in ventricles AV valves open and blood forced into ventricles
*ventricles begin to contract AV valves shut
*Semi lunar valves only open when pressure in ventricles greater than that of the aorta.
*Diastole - 23Describe the pressure and volume changes that occur during the cardiac cycle.
- 24Explain the heart sounds as heard by a stethoscope.IST SOUND – closure of the atrioventricular (AV) valves ‘lub’
- onset of systole (contraction)
2ND SOUND – closure of pulmonary and aortic valves ‘dub’
- onset of diastole (relaxation) - 25Outline the factors that influence the end diastolic ventricular volume.
- 26What is the frank starling mechanism?*Ventricles contract with more force (i.e. stroke volume ↑) if it contains more blood (i.e. end-diastolic ventricular volume ↑)
*Frank-Starling mechanism determined by length-tension relationship in the muscle i.e. the greater the stretch the more tensioned developed in the cardiac muscle - 27Explain how the frank-starling mechanism maintains balance between the left and right sides of the heart.-If increased venous return to right ventricle then increased contraction = more blood to lungs
- increased venous return to left ventricle then increased contraction = increased stroke volume
*blood doesnt accumulate in lungs - 28Define stroke volume.*Stroke volume (ventricular ejection) is determined by the venous end-diastolic volume (pre-load), arterial (peripheral) resistance (after-load) and sympathetic stimulation.
- 29Describe regulation of stroke volume.SYMPATHETIC NERVOUS SYSTEM REGULATES STOKE VOLUME.
*Sympathetic ganglia
*Sympathetic nerves= b1 adrenergic
receptors
*Increases force and speed of cardiac muscle contraction = Increases ventricular contraction at any given end-diastolic ventricular volume
*Arterial blood pressure opposed ejection of blood. - 30Give an overview of regulation of cardiac output.
- 31What is congestive heart failure?*Congestive Heart Failure (CHF)
-Reduced Cardiac Output/ Tiredness and shortness of breath/ Fluid Retention to increase cardiac output (venous return)
*Chronic Left Ventricular Failure most common
-Coronary artery disease leading to ischaemic heart disease and myocardial infarction( systolic dysfunction)
-Hypertension (high blood pressure) (diastolic dysfunction)
-Cardiomyopathy (viral infection, heavy drinking) - 32Explain what happens during heart failure - systolic dysfunction.*Heart Attack
(myocardial infarction (MI))
*Damage to heart muscle
*Ventricular contractility ↓
*Stroke Volume ↓ - 33Explain what happens during heart failure - diastolic dysfunction.*High Blood Pressure(Hypertension)
*Arterial Pressure increased
*Cardiac resistance (afterload)
*Ventricular Muscle (hypertrophy)
*Stiffening (reduce compliance) of ventricular wall
*End-diastolic ventricular volume
*Stroke Volume ↓
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- (11) Cardiovascular System) Pharmacy Fichas sobre Cardiac Output, creado por Yasmin Beer el 17/04/2018.
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- Yasmin Beer
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