Cardiovascular System

Biology 2122Chapter 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 CirculationArterial – 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

Heart Block – Some P-waves not conducted through (see more P-waves)

Non-functional SA Node

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 OutputCO 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 variableincreases 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 RegulationSV 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