Cardiovascular Regulation Flashcards
Cardiodynamics
The movement and the forces of the heart during contraction
End diastolic volume
the amount of blood within the ventricles after complete relaxation (diastole)
End systolic volume
The amount of blood found within the ventricles (remaining) after a complete contraction
stroke volume
the amount of blood taken away from the heart (pumped) per heartbeat (EDV-ESV)
Ejecton fraction
How much of the blood that is pumped from the heart (precentage) - calculated by SV/ EDV
Preload
the degree of stretching that can be produced by the heart in order to acoomodate the blood during ventricular dialstole. it is directly proportional to the EDV - the higher the preload, the higher the end diastolic volume will be.
Afterload
is the tension created by the ventricular systole - enough to be be able to open the semi lunar valves.
Cardiac output
Stoke volume x heartrate
Stoke volume is dependent on
the end diastolic volume - end systolic volume
What two factors increase the preload? (starlings law)
The venous filling time and the venous return
what does preload do?
increases energy of contraction - more preload, more stronger contraction.
allows stretching of the myocytes to increase the area for the blood to fill the ventricles.
what 3 factors affect the end systolic volume?
The preload - the amount of stretching of the myocytes, allows more volume of blood in which then increases the tension of the myocytes - as more the filling of the ventricles, more myocyte tension generated thus more force of contraction.
The Contractibility - the ability and the force within the left ventricles in order to contract the heart with a certain amount of preload - autonomic intervention and hormones.
The Afterload - the amount of tension created by the contraction, enough to open up the semilunar valves.
what is the pressure in the aorta? what is the pressure in pulmonary artery
Aorta= 80mmHg PA= 20mmHg
what happens if the afterload increases but the preload remains the same?
Stroke volume will decrease as the heart contractions are too rapid to be able to remove all the blood from the atria.
Factors that increase contractility? POSITIVE INOTROPIC AGENTS
Beta adrenergic agonists, neurtotransmitters, sympathetic hormones,
Factors that decrease contractility?
parasymathetic hormones and neurotransmitters, beta blockers, vrampril, calcium channel blockers, muscarininc agonists, increase in pottasium, increase in anoxia or acidosis.
Factors that influence heartrate?
Autonomic regulation, hormones
where is the cardiovasular control centre
medulla oblongata
where does it receive its information from (cardiovascular centre)
the baroreceptors, proprioreceptors, chemoreceptors, which are brought by the glossophyrengeal nerve into the Medulla.
The higher centres of the brain such as the crebral cortex and hypothalumus.
where does the info go from the medulla?
the sympathetic chain which branches off the spinal chord into the throacic region into the cardiacc plexus. (ACCELERATOR)
the parasympathetic branch which goes from the medulla oblongata directly (VAGUS)
What does the vagus nerve do?
decreases depolarisation
decreases heartrate
decreases contractility of the heart
decreases stroke volume.
what does the accelerator nerve do?
opp to vagus
The cardiovasucular centre contains a vasomotive centre and a cardiac centre - what regions are in the cardiac centre and what do they do?
Cardioacceleratory centre - increases heartrate and spontaneous depolarisations of the SA node.
Cardioinhibitory centre - decreases heartrate and spontaneous depolarisations of the SA node,
Why does homestasis control the CVS
in order to maintain enough perfussion into tissues and allow enough blood flow.
