Circulation

What is the pathway of the blood flow in the body?

Valves of the Heart

• Heart needs to prevent the backflow of blood into other chambers.

• Four valves accomplish this.

• Composed of dense connective tissue covered by endothelium

• Two basic types:

Atrioventricular Valves

• Lie between the atria and ventricles• Right side is the tricuspid valve

– 3 flaps– Tendon-like cords – Connect to papillary muscles (look like nipples)

• Left side is mitral (cone shaped) valve (bicuspid)– 2 flaps

Semilunar Valves

• These valves are near the origin of the pulmonary trunk and the aorta.

• Each has 3 semilunar (half moon-shaped) valves– Attach to artery wall

• Permit blood flow in one direction• Pulmonary valve—pulmonary trunk• Aortic valve– opening by ascending aorta and

ventricle

What is the advantage of a 4-chambered heart?

• Let’s look at some zoology!

• There are several different delivery systems.

Fish—2 Chambered Heart

Amphibians—3 Chambered Heart

Reptiles—3 Chambers

• Reptiles have a partially developed septum between the two ventricles

• Blood still mixes

Mammals—4 Chambered Heart

Differences

• What does endothermic and exothermic mean?

• Where does blood get oxygenated?

• How does blood get deoxygenated?

• Why does the body need oxygen?

• What else is needed?

Vascular System-To the Tissues

• Taking blood to the tissues and back– Arteries– Arterioles– Capillaries– Venules– Veins

Blood Supply of the Heart

• Heart has its own blood vessels

• This is called coronary circulation– Left and Right Coronary Arteries– Originate as branches of the ascending aorta.

• Coronary sinus – Collects the deoxygenated blood– Empties into right atrium

Some Heart Problems

• Many result from faulty coronary circulation• Ischemia

– Local obstruction of vessels (anemia)– Chest pain– Some other factors

• Stress• Strenuous exercise• High blood pressure

Valvular Disease

• Heart murmur– result of turbulent blood flow which is sufficient to

produce audible noise.– This most commonly results from narrowing or leaking

of valves or the presence of abnormal passages through which blood flows in or near the heart

• Mitral stenosis– Narrowing of the mitral (bicupsid) valve by scar

formation or congenital defect.– Mitral valve prolapse

• Portion of mitral valve is pushed too far back• Blood flows back into left atrium

• Myocardial infraction (MI)– Heart attack– Death of tissue because of interrupted blood

supply– Result from a blood clot in coronary artery– Scar tissue forms

• Non-contractile

– CPR

How is heartbeat maintained?

• Conduction system is the route for nerve impulses (action potentials)

• Begins in sinoatrial node (SA)– Inferior to opening of vena cava into the

atrium– Gap junctions in the intercalated discs

conduct– Atria contract– http://www.pennmedicine.org/encyclopedia/e

m_DisplayAnimation.aspx?gcid=000001&ptid=57

• Impulse reaches atrioventricular node (AV)– Action potential slows

• Travels to the atrioventricular (AV) bundle which is also called the Bundle of His– Action potential conducts from atria to

ventricle here

• Nerve impulse reaches left and right bundle branched– Travel toward the apex of the heart

• Conduction myofibers called Purkinje fibers conduct to remainder of ventricular myocardium– Ventricle contract!!!

Rates of Nodes

• SA node– 90-100 times per minute– Called pacemaker of the heart– Hormones and neurotransmitters speed or

slow heartbeat– Typical heartbeat is 75 beats per minute– If SA node is diseased or damaged the AV

node can take over• 40-50 beats per minute

• AV bundle will take over if necessary– Only 40-50 beats per minute– Blood flow to the brain is inadequate– Brain uses 20% of the blood

Blood Pressure

• Regular blood pressure is 120/ 80

• Systole vs Diastole

• Atria contract and then relax

• Ventricles contract then relax

• Systole is contraction

• Diastole is relaxation

Heart Sounds

• Lub—AV valves closing

• Dub—Semilunar valves closing

• Murmurs– Abnormal sounds– Sometimes thinner walls– Sometimes valve doesn’t close tightly

Electrocardiogram

• See handout!

• Depolarization - Thus, changes in membrane voltage in which the membrane potential becomes less positive or less negative are both depolarizations. Due to the sodium or calcium.– Causes contraction

Normal EKG

• Pulse rate lies between 60 and 100 beats/minute • P-R interval is the time required for completion

of atrial depolarization. The normal P-R interval is 0.12 to 0.20 seconds.

• The QRS interval represents the time required for ventricular cells to depolarize. The normal duration is 0.06 to 0.10 seconds.

• The Q-T interval is the time required for depolarization and repolarization of the ventricles.