Cardiovascular Physiology
@ @ @
ab ab ab
d yL yL yL
tu ud tu
d
NS St N NS
I. Heart as a pump
A) Overview
Superior Venae
Cavae
Aorta
Description
Pulmonary artery
Left atrium The heart is a fist-sized organ that pumps blood
Right atrium
@ @ @
ab ab ab
throughout your body. It’s your circulatory system’s
yL yL main organ. Muscle and tissue make up this
yL
ud ud tu
d
St St
powerhouse organ.
N N Pulmonary vein NS
Your heart contains four muscular sections (chambers)
Pulmonary valve
Mitral valve that briefly hold blood before moving it. Electrical
Aortic valve impulses make your heart beat, moving blood through
Tricuspid valve these chambers.
Your brain and nervous system direct your heart’s
Right ventricle Left ventricle function.
Inferior Venae
Cavae
Blood flow
@ @ @
ab ab ab
yL yL yL
ud Everything start off with Deoxygenated blood from 2 Venae cavae
tu
d
tu
d
N St (superior and inferior) drains to Right atrium
NS NS
→ This blood goes down to Right ventricle, then it will be pumped to
Pulmonary arteries for gas exchange in lung (O2 replace CO2)
Pulmonary artery
Aorta
After exchanging gas, the blood will be oxygenated and flow back
to Left atrium through Pulmonary vein
→ This blood goes down to Left ventricle, then it will be pumped to Venae Cavae
Aorta for gas exchange in tissues (cells need oxygen to function)
=> Finally, after exchanging gas and becoming deoxygentated, the
blood will go back to Right atrium through Venae cavae for the next Pulmonary vein
pump
@ @ @
ab ab ab
d yLFunction d yL d yL
tu tu tu
NS NS NS
It delivers oxygen and nutrients to all your organs and tissues. It also
transport hormones, immune cells, and clotting proteins to specific target
cells.
It removes carbon dioxide and other waste products from those same
places to liver and kidneys
B) Conducting system of heart
does not require stimulation from the brain to beat → it generates its own
b@ b@ b@
-The heart electrical impulses through specialized cardiomyocyte cells
La electrical current originates from a natural ‘pacemaker’ , then spreadsythrough
(pacemaker)
y-The La the heart chambers. Wherever the current passes, the muscle cellsyLa
tud in that area contract tud tu
d
NS NS NS
Electrical current pathway: SA node → AV node → Bundle of His → Purkinje fiber
1.SA node (Sinoatrial node)
Location: Upper wall of the right atrium
Rate: 60-100 bpm
Bundle of His Function: Spontaneously generates electrical action potentials
SA node
→ atria contract to pump blood to ventricles
2.AV node (Atrioventricular node)
Location: Lower back section of the interatrial septum
@ @ @
ab ab
Rate: 40-60 bpm
ab
d yL yL
Function:
d d yL
tu tu + Introduces a delay of about 0.09 to 0.12 seconds tu
NS Purkinje fibersN
S →ensure the atria have completely emptied blood into ventricle NS
+ Acts as an electrical bridge between the atria and the ventricles
AV node →relay impulses to the Bundle of His and Purkinje fibers
3.His-Purkinje system
Location: Bundle of His: within the interventricular septum
→ bifurcates into left and right bundle branches
Purkinje fibers: form a network embedded in ventricular walls
Rate: 20-40 bmp
Function: Rapidly and simultaneously distribute the electrical impulse to all parts
of the ventricular myocardium (fastest conduction velocity)
Note: The structure with the highest intrinsic rate acts as the
primary pacemaker
→ @
If a higher-level center fails, the next one in the hierarchy
@ @
ab ab ab
yL yL yL
automatically takes over to maintain the heartbeat
d d d
tu tu tu
NS NS NS
, a) Electrical conduction cycle b) Cardiac cycle
@ @ @
L ab L ab ab
dy dy d yL
tu tu tu
NS NS NS
@ @ @
ab ab ab
d yL d yL d yL
tu tu tu
NS NS NS
Ventricular filling Atrial systole Ventricular systole Isovolumic relaxation
1 - Ventricular late 2 - SA node initiates an 4 - Electrical impulse passes Ventricular repolarization
diastole action potential through the AV node and His– (not shown in image a) :
→
AV valves open & 3 - The impulse spreads Purkinje system → Ventricles begin to
Semilunar valves close across both atria 5 - Ventricular depolarization: relax
→
No new electrical => Atrial depolarization + Ventricular pressure rises → All valves are closed
impulse has been leads to atrial systole sharply => Ventricular pressure
generated yet → Push the remaining → AV valves close & rapidly decreases, but
=> Blood flows passively blood into the ventricles Isovolumic contraction begins volume remains constant
from the atria into the 6 - Ventricular ejection:
ventricles due to a
a b@ a b@
+ Occurs when ventricular
ab
@
d yL
pressure gradient
d yL pressure exceeds arterial
d yL
tu tu tu
NS NS NS
pressure
=> Semilunar valves open &
Blood is ejected into the
pulmonary artery and aorta
C) Action potentials
(Cellular basis of cardiac electrical activity)
@ @ @
ab ab ab
d yL d yL d yL
tu tu tu
NS NS NS
b@
a potentials in Ventricular muscle ab
@
ab
@
d yL
Action
d yL d yL
tu tu tu
NS NS NS
Phase 0 – Rapid Depolarization Phase 3 – Rapid Repolarization
Rapid opening of fast voltage-gated Na⁺ channels due to an external stimulation Ca²⁺ channels close
A large influx of Na⁺ into the cell Outward K⁺ current increases
Membrane potential rapidly returns to a negative value
Membrane potential rises sharply from approximately –85 mV to +20 mV
Phase 4 – Resting Membrane Potential
Phase 1 – Initial Repolarization Stable membrane potential at approximately –85 mV
Fast Na⁺ channels become inactivated Dominated by K⁺ permeability
Transient outward K⁺ current begins Na⁺ channels are in the resting (closed but activatable) state
Membrane potential briefly decreases from its peak
Phase 2 – Plateau Phase Note:
L-type Ca²⁺ channels open, allowing Ca²⁺ to enter the cell ARP: No AP can occur regardless of stimulus
@ @ RRP: Stronger stimulus needed, reduced response
@
ab ab ab
At the same time, K⁺ continues to leave the cell
yL→ yL yL
Inward Ca²⁺ current and outward K⁺ current are balanced => Plateau phase: prolongs ventricular refractory period
tu
d Membrane potential remains relatively stable, forming the Plateau
tu
d → prevents tetanus, allows proper contraction,
tu
d
NS NS ejection and relaxation NS
Action potentials in Pacemaker cells
Slow Na⁺ entry through funny channels during phase 4 gradually brings
the membrane to threshold, triggering Ca²⁺-mediated depolarization,
followed by K⁺-dependent repolarization
=> Pacemaker cells can spontaneously generate action potentials without
@ @ @
ab
requiring external stimulation
ab ab
d yL d yL d yL
tu tu tu
NS NS NS
@ @ @
ab ab ab
d yL yL yL
tu ud tu
d
NS St N NS
I. Heart as a pump
A) Overview
Superior Venae
Cavae
Aorta
Description
Pulmonary artery
Left atrium The heart is a fist-sized organ that pumps blood
Right atrium
@ @ @
ab ab ab
throughout your body. It’s your circulatory system’s
yL yL main organ. Muscle and tissue make up this
yL
ud ud tu
d
St St
powerhouse organ.
N N Pulmonary vein NS
Your heart contains four muscular sections (chambers)
Pulmonary valve
Mitral valve that briefly hold blood before moving it. Electrical
Aortic valve impulses make your heart beat, moving blood through
Tricuspid valve these chambers.
Your brain and nervous system direct your heart’s
Right ventricle Left ventricle function.
Inferior Venae
Cavae
Blood flow
@ @ @
ab ab ab
yL yL yL
ud Everything start off with Deoxygenated blood from 2 Venae cavae
tu
d
tu
d
N St (superior and inferior) drains to Right atrium
NS NS
→ This blood goes down to Right ventricle, then it will be pumped to
Pulmonary arteries for gas exchange in lung (O2 replace CO2)
Pulmonary artery
Aorta
After exchanging gas, the blood will be oxygenated and flow back
to Left atrium through Pulmonary vein
→ This blood goes down to Left ventricle, then it will be pumped to Venae Cavae
Aorta for gas exchange in tissues (cells need oxygen to function)
=> Finally, after exchanging gas and becoming deoxygentated, the
blood will go back to Right atrium through Venae cavae for the next Pulmonary vein
pump
@ @ @
ab ab ab
d yLFunction d yL d yL
tu tu tu
NS NS NS
It delivers oxygen and nutrients to all your organs and tissues. It also
transport hormones, immune cells, and clotting proteins to specific target
cells.
It removes carbon dioxide and other waste products from those same
places to liver and kidneys
B) Conducting system of heart
does not require stimulation from the brain to beat → it generates its own
b@ b@ b@
-The heart electrical impulses through specialized cardiomyocyte cells
La electrical current originates from a natural ‘pacemaker’ , then spreadsythrough
(pacemaker)
y-The La the heart chambers. Wherever the current passes, the muscle cellsyLa
tud in that area contract tud tu
d
NS NS NS
Electrical current pathway: SA node → AV node → Bundle of His → Purkinje fiber
1.SA node (Sinoatrial node)
Location: Upper wall of the right atrium
Rate: 60-100 bpm
Bundle of His Function: Spontaneously generates electrical action potentials
SA node
→ atria contract to pump blood to ventricles
2.AV node (Atrioventricular node)
Location: Lower back section of the interatrial septum
@ @ @
ab ab
Rate: 40-60 bpm
ab
d yL yL
Function:
d d yL
tu tu + Introduces a delay of about 0.09 to 0.12 seconds tu
NS Purkinje fibersN
S →ensure the atria have completely emptied blood into ventricle NS
+ Acts as an electrical bridge between the atria and the ventricles
AV node →relay impulses to the Bundle of His and Purkinje fibers
3.His-Purkinje system
Location: Bundle of His: within the interventricular septum
→ bifurcates into left and right bundle branches
Purkinje fibers: form a network embedded in ventricular walls
Rate: 20-40 bmp
Function: Rapidly and simultaneously distribute the electrical impulse to all parts
of the ventricular myocardium (fastest conduction velocity)
Note: The structure with the highest intrinsic rate acts as the
primary pacemaker
→ @
If a higher-level center fails, the next one in the hierarchy
@ @
ab ab ab
yL yL yL
automatically takes over to maintain the heartbeat
d d d
tu tu tu
NS NS NS
, a) Electrical conduction cycle b) Cardiac cycle
@ @ @
L ab L ab ab
dy dy d yL
tu tu tu
NS NS NS
@ @ @
ab ab ab
d yL d yL d yL
tu tu tu
NS NS NS
Ventricular filling Atrial systole Ventricular systole Isovolumic relaxation
1 - Ventricular late 2 - SA node initiates an 4 - Electrical impulse passes Ventricular repolarization
diastole action potential through the AV node and His– (not shown in image a) :
→
AV valves open & 3 - The impulse spreads Purkinje system → Ventricles begin to
Semilunar valves close across both atria 5 - Ventricular depolarization: relax
→
No new electrical => Atrial depolarization + Ventricular pressure rises → All valves are closed
impulse has been leads to atrial systole sharply => Ventricular pressure
generated yet → Push the remaining → AV valves close & rapidly decreases, but
=> Blood flows passively blood into the ventricles Isovolumic contraction begins volume remains constant
from the atria into the 6 - Ventricular ejection:
ventricles due to a
a b@ a b@
+ Occurs when ventricular
ab
@
d yL
pressure gradient
d yL pressure exceeds arterial
d yL
tu tu tu
NS NS NS
pressure
=> Semilunar valves open &
Blood is ejected into the
pulmonary artery and aorta
C) Action potentials
(Cellular basis of cardiac electrical activity)
@ @ @
ab ab ab
d yL d yL d yL
tu tu tu
NS NS NS
b@
a potentials in Ventricular muscle ab
@
ab
@
d yL
Action
d yL d yL
tu tu tu
NS NS NS
Phase 0 – Rapid Depolarization Phase 3 – Rapid Repolarization
Rapid opening of fast voltage-gated Na⁺ channels due to an external stimulation Ca²⁺ channels close
A large influx of Na⁺ into the cell Outward K⁺ current increases
Membrane potential rapidly returns to a negative value
Membrane potential rises sharply from approximately –85 mV to +20 mV
Phase 4 – Resting Membrane Potential
Phase 1 – Initial Repolarization Stable membrane potential at approximately –85 mV
Fast Na⁺ channels become inactivated Dominated by K⁺ permeability
Transient outward K⁺ current begins Na⁺ channels are in the resting (closed but activatable) state
Membrane potential briefly decreases from its peak
Phase 2 – Plateau Phase Note:
L-type Ca²⁺ channels open, allowing Ca²⁺ to enter the cell ARP: No AP can occur regardless of stimulus
@ @ RRP: Stronger stimulus needed, reduced response
@
ab ab ab
At the same time, K⁺ continues to leave the cell
yL→ yL yL
Inward Ca²⁺ current and outward K⁺ current are balanced => Plateau phase: prolongs ventricular refractory period
tu
d Membrane potential remains relatively stable, forming the Plateau
tu
d → prevents tetanus, allows proper contraction,
tu
d
NS NS ejection and relaxation NS
Action potentials in Pacemaker cells
Slow Na⁺ entry through funny channels during phase 4 gradually brings
the membrane to threshold, triggering Ca²⁺-mediated depolarization,
followed by K⁺-dependent repolarization
=> Pacemaker cells can spontaneously generate action potentials without
@ @ @
ab
requiring external stimulation
ab ab
d yL d yL d yL
tu tu tu
NS NS NS
