Cardiovascular System
Biology 2122
Chapter 18
Heart Anatomy
Location: Mediastinum
Coverings (Pericardium)
–
Fibrous and Serous layers
–
Serous (Parietal and Visceral =
epicardium)
Heart Wall (Layers)
–
Epicardium; Myocardium;
Endocardium
Chambers
Atria
–
–
Pectinate muscles; auricles
Superior and Inferior Vena Cava
•
–
Right-side
Deoxygenated Blood
•
Coronary sinus/Pulmonary veins
Ventricles
– Trabeculae carneae/Papillary muscles
– Pulmonary Trunk
– Aorta
Circulation
– Pulmonary vs. Systemic
Coronary Circulation
Arterial – Left Coronary Artery
– Anterior Interventricular
• “Left Anterior Descending”
– Circumflex
Arterial – Right Coronary Artery
– Marginal artery
– Posterior Interventricular artery
Venous
– Cardiac veins
– Coronary sinus
• Great, middle, small cardiac veins
Angina pectoris and Myocardial Infarctions
Heart Valves
• Atrioventricular Valves
– Prevents backflow – chordae tendineae
– Tricuspid (right)
– Mitral (left)
• Semilunar Valves
– Aortic
– Semilunar
• Stenosis
• Heart Animation
Microscopic - Cardiac Tissue Histology
• Cardiac Tissue
– Striated
– Branching
– Uninucleated
– Intercalated discs
• Gap junctions
– Functional
Syncytium
– High in
mitochondria
Cardiac Tissue - Contraction
• Autorhythmic Cells
• Heart Contracts as a unit
– Ion passage through gap junctions
– Steady and rhythmical waves of depolarization
• Depolarization
– Longer absolute refractory periods
– 250 ms
• Similar to depolarization events in skeletal
muscle
– Differs in Ca++ release (SR)
Intrinsic Conduction System
Sets basic or normal rhythm
– Autorhythmic Cells
Sequence of Excitation
1. SA node (right atria)
– “pacemaker”
2.
Atrioventricular node
– Above tricuspid valve
3.
Atrioventrical bundle
– “bundle of his”
– Superior interventricular septum
4.
Bundle branches
5.
Purkinje fibers
– Apex
• Intrinsic Conduction System
Animation
Disorders
1. Arrhythmias
2. Fibrillation
3. Heart Block
Extrinsic Innervation and Control
• Autonomic Nervous System
– Sympathetic Effects
– Parasympathetic Effects
• Cardiac centers
– Medulla Oblongata
– Cardioacceleratory Center
• Sympathetic (T1-T5)
• Innervate SA and AV nodes
– Cardioinhibitory Center
• Vagus Nerve
• To SA and AV nodes
Electrocardiogram
EKG lead placements
Electrocardiography
• The Electrocardiogram (ECG)
• Waves
1. P-Wave
– Depolarization (Atrial contraction)
– SA node
2. QRS
– Ventricular depolarization
– Ventricular contraction
3. T-Wave
– Ventricular repolarization
Electrocardiography
P-Q Interval
S-T Segment
Q-T Interval
Abnormal ECG
Non-functional SA
Node
Heart Block – Some P-waves not conducted
through (see more P-waves)
Heart Sound
• “Lub-Dub”
• Lub
– AV valve closure
• Dub
– SL valves snap shut
– Ventricular relaxation
• Heart Murmer
Cardiac Cycle
 Systole vs diastole
 The cardiac cycle involves all events associated with
blood flow through the heart during one complete
heartbeat
 Ventricular filling: Mid-Late Diastole
◦ EDV (end diastole volume)
 Ventricular Systole
◦ ESV (end systolic volume)
 Isovolumetric Relaxation – Early diastole
Cardiac Cycle
Cardiac Cycle Animation
Cardiac Output
CO is defined as the amount of blood pumped out by each
ventricle in one minute.
 calculated as the product of stroke volume and rate
HR X SV = 5.25 L/min
Stroke volume - volume of blood pumped out by one ventricle
with each beat
CO is variable
 increases in response to special demands like exercise
The difference between resting CO and maximal CO is called
cardiac reserve. In trained athletes it is 7 times that of normal
(35 L/min)
Stroke Volume Regulation
SV is the difference between EDV (blood in ventricle
during diastole) and ESV (blood in ventricle during
systole)
Normal SV = 70 ml/beat
Depends on the following factors
◦ Preload (Frank-Starling Law)
◦ Contractility
◦ Afterload
Regulation of Stroke Volume
1. Preload
– Frank-Starling Law
– Cardiac muscle cells stretched to optimal
length before contraction
2. Contractility
– Independent of stretch
– Greater Ca++ influx
– Increased leads to greater SV
3. Afterload
– Back pressure on aortic and pulmonary
valves
– Overcome pressure for ventricles to be able
to eject blood
Regulation of Heart Rate
1. Autonomic Nervous System
2. Chemical Regulation
– Hormones (Epinephrine and Thyroxine)
– Ions
• Calcium (Hypo- and Hypercalcemia)
• Potassium (Hypo- and Hyperkalemia)
• Disorders/Imbalances
1. Tachycardia and Bradycardia
2. Congestive Heart failure