Cardiac output Flashcards
What is cardiac output
volume of blood pumped by each ventricle per minute.
What can effect cardiac output
heat loss, digestion, and localised vasodilation.
How is stroke volume controlled
modified and controlled by
Pre load
contractility
afterload
Define preload
starlings law of the heart. End diastolic volume.
Preload is directly proportional to the force of contraction during systole.
What are two factors that control the end diastolic volume
Duration of ventricular diastole
Volume of blood entering the right ventricle.
Define contractility
Contracitity of cardiac muscle increased by positive inotropic agents and decreased by negative inotropic agents.
What are examples of positive inotropic agents.
Neurotransmitters and hormones of the sympathetic nervous system,
Give examples of negative inotropic agents
parasympathetic neurotransmitters, calcium channel blockers.
Define afterlaod
pressures in the aorta and the pulmonary trunk that needs to be overcome by systole
If after load increases then the preload is constant, then the stroke volume will decrease and more blood will remain In the ventricles.
Afterrload can increases because of narrowing of the arteries and hypertension.
What controls the heart rate and where can this be found
Controlled by cardiovascular centre located in the medulla oblongata
What receptors does the heart receive afferent information
Sensory receptro.
What factored can affect heart rate
Age
gender
physical fitness body temperature
What is congested heart failure
Describes a heart failing to pump.
Associated with valve defects, septal defects
Heart is overstretched and strarts to contract less forcefully
What is left ventricular failure
Blood to back up backing the lungs causing an increase in venue pressure and a build up of fluid in the lungs.
What is right ventricular failure
Blood bak sup into systemic system.
decreased volume of blood returning to the left atrium via the pulmonary vein.
can cause decreased blood flow to the kidneys resulting in activation of the rennin angiotensin aldosterone system which increases the kidneys reuptake of water.
