The Cardiovascular System Chapter 11. Heart is two pumps in one: Right side – pulmonary circulation Left side – systemic circulation Heart→ Arteries →

The Cardiovascular System

Chapter 11

Heart is two pumps in one:

Right side – pulmonary circulation

Left side – systemic circulation

Heart→ Arteries → Arterioles → Capillaries → Venules→ Veins → Heart

Artery – any vessel that carries blood AWAY from the heart.

Vein – any vessel that carries blood TOWARD the heart

Parietal pericardium:

outer fibrous layer

inner serous layer

Pericardial cavity

Visceral pericardium

Pericarditis

Heart WallLayers (superficial to deep):

1. Epicardium – serous membrane

2. Myocardium – muscle layer

3. Endocardium – continuous throughout circulatory

system

Cardiac Muscle:

involuntary, striated

Intercalated discs:

gap junctions

functional syncytium

desmosomes – “spot welds”

Ventricular Geometry

LV

RV

Common Disorders

Ischemia – reduced blood flow

Hypoxia – reduced oxygen supply

Angina pectoris – “strangled chest” referred pain

Myocardial infarction – death of an area of tissue due to interrupted blood flow (“Heart attack”)

Congestive heart failure – heart is unable to supply bloodflow to body

Fibrillation – uncoordinated, unsynchronized beating of heart, no net bloodflow

Cardiac cycle

One complete heart beat:

•Systole (contraction) and

•Diastole (relaxation) of both ventricles

•Remember: Blood pressure = systole/diastole ≈ 120/80 normal average

“Heart beat”• http://www.youtube.com/watch?v=ZlB-915Cf

Cg

• http://www.youtube.com/watch?v=7eFn8Cgcx8g

• http://www.youtube.com/watch?v=NYB-rJZQt4w&feature=fvw

Know sequence of cardiac cycle

Know sequence of cardiac cycle

http://www.youtube.com/watch?v=12_nJamoyTk- Know

understand

Cardiac Muscle Contraction - know

• Heart muscle:– Is stimulated by nerves and is self-excitable

(automaticity)– Contracts as a unit– Has a long (250 ms) absolute refractory period

• Cardiac muscle contraction is similar to skeletal muscle contraction

http://www.youtube.com/watch?v=IjU81a5TjZs;

http://www.dnatube.com/video/317/Beating-Heart-Cell;

http://www.youtube.com/watch?v=55tAIOcBg3w&feature=related;

http://www.youtube.com/watch?v=_gbGA5il4Sg

Heart Physiology: Intrinsic Conduction System - know• Autorhythmic cells:– Initiate action potentials – Have unstable resting potentials called

pacemaker potentials– Use calcium influx (rather than sodium) for rising

phase of the action potential

http://www.youtube.com/watch?v=Lhl897Mz-h8&feature=related; http://www.interactivephysiology.com/demo/systems/buildframes.html?cardio/actnpot/01

Pacemaker and Action Potentials of the Heart - know

Heart Physiology: Sequence of Excitation - know

• Sinoatrial (SA) node generates impulses about 75 times/minute

• Atrioventricular (AV) node delays the impulse approximately 0.1 second

• Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)

http://www.smm.org/heart/heart/pumping.htm; http://depts.washington.edu/physdx/heart/demo.html

Heart Physiology: Sequence of Excitation - know

• AV bundle splits into two pathways in the interventricular septum (bundle branches)– Bundle branches carry the impulse toward the

apex of the heart– Purkinje fibers carry the impulse to the heart

apex and ventricular walls

Heart Physiology: Sequence of Excitation - know

Heart Excitation Related to ECG - know

Extrinsic Innervation of the Heart - know• Heart is

stimulated by the sympathetic cardioacceleratory center

• Heart is inhibited by the parasympathetic cardioinhibitory center

Electrocardiography - know• Electrical activity is recorded by

electrocardiogram (ECG)

• P wave corresponds to depolarization of SA node

• QRS complex corresponds to ventricular depolarization

• T wave corresponds to ventricular repolarization

• Atrial repolarization record is masked by the larger QRS complexhttp://www.youtube.com/watch?v=lYMSkGXFoN4&feature=related

Electrocardiography (EKG)

http://www.youtube.com/watch?v=ew6Jp74vaN4

Heart Murmurs – abnormal sounds caused by the flow of blood.

Mitral stenosis (abnormal narrowing)

Mitral valve prolapse (turns “inside out”)

1.

2.

3.

Conduction system of the heartSinoatrial (SA) node – “pacemaker’ →

Atrioventricular (AV) node →

Atrioventricular (AV) Bundle - Bundle of His→

Purkinje fibers – conduction myofibers

Ectopic pacemaker = implanted device that uses electrical impulses to reproduce or regulate the rhythms of the heart

Ectopic pacemaker

ECG (or EKG)

• An electrocardiogram (ECG / EKG) is an electrical recording of the heart and is used in the investigation of heart disease.

• Normal adult 12-lead ECG:

Abnormally slow heartbeat

Abnormally fast heartbeat

Regulation of Heart Rate

• Sympathetic N.S. increases heart rate and force of contraction through increased epinephrine secretion

• Parasympathetic N.S. decreases heart rate and force of contraction through the vagus nerve. Sends continuous impulses. Secretes acetylcholine

Other factors that influence heart rate

• Temperature• Ion concentration K+ and Ca + +

• Hormones• Hypoxia, acidosis and alkalosis slow

heart• Age• Gender• Physical fitness

Fetal Circulation

• Obtains oxygen and nutrients from maternal circulation

• Two arteries off internal iliac arteries run through umbilical cord

• Umbilical vein returns oxygenated blood

• Several shunts in fetal circulation:

•Ductus venosus – bypasses fetal liver and dumps blood from umbilical vein into inferior vena cava.

•Foramen ovale – hole in atrial septum, blood passes from right atrium to left atrium, bypassing the developing lungs

•Ductus arteriosus – connects pulmonary artery with aorta

•If does not close – patent ductus arteriosus – get mixing of venous and arterial blood.