Lecture 12 - Control of cardiac output Flashcards
What is cardiac output?
The volume of blood ejected by each ventricle per minute
What is heart rate?
Number of heart beats per minute
What is stroke volume?
The volume of blood ejected by each ventricle per beat
What is the formula for cardiac output?
Cardiac output = heart rate x stroke volume
What are some factors that affect heart rate?
Atrial reflex
Hormones
Venous returnW
What are some factors affecting stroke volume?
Filling time
Autonomic innervation
Hormones
Vascular tone
What are chronotropic effects?
Factors that affect the heart rate
What is the process of the innervation of the heart?
Sensory cells detect a change needs to be made and a signal is sent to the medulla oblongata in cardioregulatory centre
What are the two centres within the cardioregulatory centre?
Cardioinhibitory and cardioregulatory centre
Where are chemoreceptors?
In the carotid artery and medulla oblongataW
Where are baroreceptors?
In carotid artery and aorta
What do chemoreceptors detect?
CO2
pH
What do baroreceptors detect?
Pressure
What type of chronotropic effect does parasympathetic have?
Negative
Lowers heart rate
Reduces CO
What type of chronotropic effect does sympathetic have?
Positive
Increases heart rate
Increases cardiac output
What does the parasympathetic division do in control of pacemaker cells?
Opens potassium ion channels
Causes faster repolarization
What is venous return?
Stretches the pacemaker cells which increases heart rate
What is the formula for stroke volume?
End diastolic volume - end systolic volume
What is preload?
The degree to which ventricular muscle cells are stretched at the end of diastole
Directly proportional to end diastolic volume
Dependent on ventricular filling time
What is contractility?
The force produced by ventricular muscle cells during systole at a given period
Has chronotropic and inotropic effects
What is afterload?
The force the ventricle needs to overcome to open the semilunar valve and eject blood
What division are positive inotropic effects?
Sympathetic
What division are negative inotropic effects?
Parasympathetic
What are some factors affecting venous return?
Posture - blood pools in legs, decreases venous return
Skeletal muscle pump - movement of skeletal muscle constricts veins, increases VR
Respiratory pump - increases venous return
What do vaso dilation and constriction do in relation to afterload?
Dilation = reduces afterload
Constriction = increases afterload
What does sympathetic division do in control of pacemaker?
Opens sodium ion channels
Causes depolarisation
