Cardiovascular System Esraa kiwan

Cardiac Output Cardiac Output: is the volume of blood pumped by each ventricle per minute

Cardiac Output Cardiac output = Stroke Volume X Heart Rate CO = SV x HR Stroke Volume: volume of blood pumped by each ventricle per beat or stroke (averages 70 ml/beat) Heart Rate: heart beats/min (averages 70 beats/min)

CO= 70 ml/beat x 70 beats/min Cardiac Output Stroke Volume: volume of blood pumped per beat or stroke (averages 70 ml/beat) Heart Rate: heart beats/min (averages 70 beats/min) CO = SV x HR CO= 70 ml/beat x 70 beats/min = 4,900 ml/min ≈ 5 liters/min

Cardiac Output Resting cardiac output ≈ 5 L/min During exercise cardiac output can increase to 20 to 25 L/min Cardiac reserve: the difference between the cardiac output at rest and the maximum volume of blood the heart can pump per minute

Cardiac Output CO = SV x HR Cardiac output depends on heart rate and the stroke volume ( cardiac output increases or decreases in response to changes in heart rate or stroke volume . i.e. when one of them increase it will increase the cardiac out put) CO = SV x HR

The heart is innervated by both divisions of the autonomic nervous system (sympathetic & parasympathetic), which can modify the rate & strength of contraction. (not initiation of contraction)

Autonomic Regulation of HR

Stroke Volume Control Two types of controls influences stroke volume: Intrinsic control  The extent of venous return Extrinsic control  The extent of sympathetic stimulation of the heart Both factors increase stroke volume by increasing the strength of contraction of the heart

Stroke Volume Control Intrinsic control: Intrinsic ability to regulate SV (output) in response to changes in venous return (input)

Stroke Volume Control

Stroke Volume Control Extrinsic control: (sympathetic nervous system) Arterial muscle: increases contractility Ventricular muscle: increases contractility Adrenal medulla: increase epinephrine (augments the sympathetic actions on the heart) Veins: increase venous return

Effect Of Sympathetic Stimulation On SV

Shift of the frank starling curve to the left by sympathetic stimulation

Cardiac Output Regulation

Blood Pressure Blood pressure is the force exerted by the blood against a vessel wall Depends on: Volume of blood contained within the vessel Compliance or Distensability of the vessel wall

Blood Pressure During each heartbeat, Blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure Systolic pressure: The maximum pressure exerted in the arteries when the blood is ejected into them during ventricular systole  averages 120 mmHg Diastolic pressure: The minimum pressure within the arteries occurs when the blood is draining off into the rest of vessels during ventricular diastole  averages 80 mmHg

Blood Pressure Measurement Directly: inserting a needle (a canula) to blood vessel, which is linked to a device measure the blood pressure Indirectly: through the use of a sphygmomanometer

Blood Pressure Measurement

Blood Pressure Pulse pressure: is the difference between systolic and diastolic pressure (systolic – diastolic) Blood pressure = 120/80 Pulse pressure  40 mmHg Mean arterial pressure: is the average pressure responsible for driving blood forward MAP= diastolic pressure + 1/3 pulse pressure = 80 + (1/3 * 40) = 93 mmHg

Regulation of blood pressure Blood pressure is regulated by controlling: Cardiac output Total peripheral resistance Blood volume Blood pressure= cardiac output X peripheral resistance Cardiac output= HR X SV Total peripheral resistance depends on the radius of all arterioles as well as blood viscosity Resistance 1/r ( r: radius of the vessel)

Regulation of Blood Pressure Cardiac output= HR X SV HR SV

Regulation Of Blood Pressure Total peripheral resistance:

Regulation of Blood Pressure

Regulation of Blood Pressure Baroreceptor:

Regulation of Blood Pressure Baroreceptor:

Regulation of Blood Pressure Baroreceptor:

Regulation of Blood Pressure Blood volume: