Transcript averages 70 beats/min

Esraa kiwan
Cardiac Output
Cardiac Output: is the volume of
blood pumped by each ventricle
per minute
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)
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
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 depends on heart rate and the stroke volume
CO = SV x HR
( 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)
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 
Extrinsic control 
The extent of venous return 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
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
Shift of the frank starling curve to the left by
sympathetic stimulation
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: