APPLIED ANATOMY & PHYSIOLOGY
THE CARDIOVASCULAR SYSTEM
Structure of the heart
Chambers of the heart
o 2 parts of the heart separated by the septum (muscular wall) & each part contains chambers atrium
& ventricles.
o Atria are smaller as all they do is push blood down into the ventricles
o Ventricles have thicker muscular wall as they need to contract with grater force to push blood out of
the heart.
o Left side of the heart is larger as it needs to pump blood all around the body.
o Right side pumps deoxygenated blood to the lungs.
Blood vessels of the heart
1. Vena cava brings deoxygenated blood to the right atrium
2. Pulmonary vein delivers oxygenated blood to the left atrium
3. Pulmonary artery leaves the right ventricle with deoxygenated blood to lungs
4. Aorta leaves the left ventricle with oxygenated blood leading to the body
Valves of the heart
Regulate blood flow by ensuring it moves in one direction. Open to allow blood to pass through & close to
prevent backflow
1. Tricuspid valve = between right atrium & right ventricle
2. Bicuspid valve = left atrium & left ventricle
3. Semi lunar valves = ventricles & the pulmonary artery & aorta
Cardiac conduction system
o Group of specialized cells in the wall of the heart, send electrical impulses to the cardiac muscle
causing it to contract
o SYSTOLE – heart contracts (forcing blood out), DIASTOLE – heart relaxes (to fill with blood)
o Heart muscle is MYOGENIC (generates its own impulses), the beat starts in the heart muscle itself
in the:
o SINOATRIAL NODE (SAN) – found in the wall of right atrium pacemaker, electrical impulse in SAN
stimulates contraction of the cardiac muscle to generate the heartbeat, impulse spreads through
the heart in a WAVE OF ECITATION
o Impulse through atria
o ATRIAL SYSTOLE – walls of the atria contract forcing blood into the ventricles
o ATRIOVENTRICULAR NODE (AVN) – found in
o BUNDLE OF HIS – specialised fibres found in the septum (separating 2 ventricles), collection of
heart muscle cells that transmit electrical impulses to the AVN via the bundle branches to the
ventricles
o PURKINJE FIBRES – smaller bundles which branch from the bundle of his, these muscle fibres
conduct impulses in the walls of the ventricles
o VENTRICULAR SYSTOLE – ventricles contract and empty so blood can be delivered to the rest of
the body
Supergirl Awaited Asteroids But People Vacated
1
, APPLIED ANATOMY & PHYSIOLOGY
Factors affecting the change in rate of the conduction system
Neural control mechanism
▹ Sympathetic nervous system – stimulates the heart to beat faster (by impulses being sent to the
SAN)
▹ Parasympathetic nervous system – returns heart to resting level
▹ Nervous system is made of 2 parts:
1. CNS = the brain & the spinal cord
2. Peripheral nervous system = Nerve cells (transmit info to & from CNS)
▹ Coordinated by the cardiac control in the medulla oblongata of the brain
▹ Sympathetic nervous impulses are sent to the SAN & there is a decrease in parasympathetic nerve
impulses so that heart rate increases.
▹ The cardiac control centre is stimulated by:
Chemoreceptors
o DETECT CHEMICAL (blood acidity) CHANGES - ↑/↓ in CO2 concentration
o Detect increase in CO2 concentration in the blood → Sympathetic nervous system stimulated →
Increase in HR
Baroreceptors
o Respond to the stretching of the arterial wall caused by changes in blood pressure.
o Increase in blood pressure → Parasympathetic nervous system stimulated → Decrease in HR
Proprioceptors
o Sensory nerve endings located in muscles, tendons & joints.
o Provide information on movement & body position. (detect changes in muscle movement)
o Increase in muscle movement → Sympathetic nervous system stimulated → Increase in HR (SAN)
Hormonal control mechanism
o Adrenaline (stress hormone) is released by the sympathetic nerves & cardiac nerves during
exercise
o Stimulates the SAN which increases the speed (HR) & force of contraction, therefore increasing
cardiac output. Muscles therefore receive more blood & oxygen
o Anticipatory rise – nerves/stress = adrenaline released
Impact of physical activity on stroke volume, heart rate & cardiac output
o Need to transport more oxygen to working muscles so heart has to work harder
o More blood is pumped around the body faster
o Therefore, stroke volume, heart rate & cardiac output change
Stroke volume
Stroke volume = volume of blood pumped out of the heart ventricles in each contraction
(approx. 70ml)
Stroke volume depends on:
1. Venous return: vol of blood returning to the heart via the veins. If venous return increases so does
stroke volume (more blood entering heart = more blood leaving heart)
2. The elasticity of cardiac fibres: the more they can stretch (during diastole) the greater the force of
contraction = increased ejection fraction
3. Greater contractility of the cardiac tissues (myocardium)= greater force of contraction = increased
stroke volume = increased ejection fraction
Ejection fraction: proportion (%) of blood leaving the left ventricle per beat
Starling’s law: Increased venous return → greater diastolic filling of the heart → cardiac muscle
stretched → more force of contraction → increased ejection fraction
2
THE CARDIOVASCULAR SYSTEM
Structure of the heart
Chambers of the heart
o 2 parts of the heart separated by the septum (muscular wall) & each part contains chambers atrium
& ventricles.
o Atria are smaller as all they do is push blood down into the ventricles
o Ventricles have thicker muscular wall as they need to contract with grater force to push blood out of
the heart.
o Left side of the heart is larger as it needs to pump blood all around the body.
o Right side pumps deoxygenated blood to the lungs.
Blood vessels of the heart
1. Vena cava brings deoxygenated blood to the right atrium
2. Pulmonary vein delivers oxygenated blood to the left atrium
3. Pulmonary artery leaves the right ventricle with deoxygenated blood to lungs
4. Aorta leaves the left ventricle with oxygenated blood leading to the body
Valves of the heart
Regulate blood flow by ensuring it moves in one direction. Open to allow blood to pass through & close to
prevent backflow
1. Tricuspid valve = between right atrium & right ventricle
2. Bicuspid valve = left atrium & left ventricle
3. Semi lunar valves = ventricles & the pulmonary artery & aorta
Cardiac conduction system
o Group of specialized cells in the wall of the heart, send electrical impulses to the cardiac muscle
causing it to contract
o SYSTOLE – heart contracts (forcing blood out), DIASTOLE – heart relaxes (to fill with blood)
o Heart muscle is MYOGENIC (generates its own impulses), the beat starts in the heart muscle itself
in the:
o SINOATRIAL NODE (SAN) – found in the wall of right atrium pacemaker, electrical impulse in SAN
stimulates contraction of the cardiac muscle to generate the heartbeat, impulse spreads through
the heart in a WAVE OF ECITATION
o Impulse through atria
o ATRIAL SYSTOLE – walls of the atria contract forcing blood into the ventricles
o ATRIOVENTRICULAR NODE (AVN) – found in
o BUNDLE OF HIS – specialised fibres found in the septum (separating 2 ventricles), collection of
heart muscle cells that transmit electrical impulses to the AVN via the bundle branches to the
ventricles
o PURKINJE FIBRES – smaller bundles which branch from the bundle of his, these muscle fibres
conduct impulses in the walls of the ventricles
o VENTRICULAR SYSTOLE – ventricles contract and empty so blood can be delivered to the rest of
the body
Supergirl Awaited Asteroids But People Vacated
1
, APPLIED ANATOMY & PHYSIOLOGY
Factors affecting the change in rate of the conduction system
Neural control mechanism
▹ Sympathetic nervous system – stimulates the heart to beat faster (by impulses being sent to the
SAN)
▹ Parasympathetic nervous system – returns heart to resting level
▹ Nervous system is made of 2 parts:
1. CNS = the brain & the spinal cord
2. Peripheral nervous system = Nerve cells (transmit info to & from CNS)
▹ Coordinated by the cardiac control in the medulla oblongata of the brain
▹ Sympathetic nervous impulses are sent to the SAN & there is a decrease in parasympathetic nerve
impulses so that heart rate increases.
▹ The cardiac control centre is stimulated by:
Chemoreceptors
o DETECT CHEMICAL (blood acidity) CHANGES - ↑/↓ in CO2 concentration
o Detect increase in CO2 concentration in the blood → Sympathetic nervous system stimulated →
Increase in HR
Baroreceptors
o Respond to the stretching of the arterial wall caused by changes in blood pressure.
o Increase in blood pressure → Parasympathetic nervous system stimulated → Decrease in HR
Proprioceptors
o Sensory nerve endings located in muscles, tendons & joints.
o Provide information on movement & body position. (detect changes in muscle movement)
o Increase in muscle movement → Sympathetic nervous system stimulated → Increase in HR (SAN)
Hormonal control mechanism
o Adrenaline (stress hormone) is released by the sympathetic nerves & cardiac nerves during
exercise
o Stimulates the SAN which increases the speed (HR) & force of contraction, therefore increasing
cardiac output. Muscles therefore receive more blood & oxygen
o Anticipatory rise – nerves/stress = adrenaline released
Impact of physical activity on stroke volume, heart rate & cardiac output
o Need to transport more oxygen to working muscles so heart has to work harder
o More blood is pumped around the body faster
o Therefore, stroke volume, heart rate & cardiac output change
Stroke volume
Stroke volume = volume of blood pumped out of the heart ventricles in each contraction
(approx. 70ml)
Stroke volume depends on:
1. Venous return: vol of blood returning to the heart via the veins. If venous return increases so does
stroke volume (more blood entering heart = more blood leaving heart)
2. The elasticity of cardiac fibres: the more they can stretch (during diastole) the greater the force of
contraction = increased ejection fraction
3. Greater contractility of the cardiac tissues (myocardium)= greater force of contraction = increased
stroke volume = increased ejection fraction
Ejection fraction: proportion (%) of blood leaving the left ventricle per beat
Starling’s law: Increased venous return → greater diastolic filling of the heart → cardiac muscle
stretched → more force of contraction → increased ejection fraction
2
