Outline-2, BIO 2320, Heart

I. CARDIOVASCULAR SYSTEM, HEART

A. Location (mediastinum)

B. Pericardial sac, fluid, cavity (Parietal pericardium)

C. Heart wall

1. Epicardium

2. Myocardium

– Trabeculae carneae – Irregular ridges of myocardium adding strength without weight

3. Endocardium

D. Chambers

1. Atria, Auricles, Interatrial septum

Upper chambers with “ear-like” auricles

2. Ventricles, Interventricular septum

Lower chambers

3. Coronary sulcus

External groove separating atrium from ventricle and contain coronary blood vessels

E. Valves

1. Atrioventricular (tricuspid, bicuspid or mitral)

a. Chordae tendineae

Heart strings anchoring AV valves to papillary muscles

b. Papillary muscles

Muscle columns in ventricles

2. Semilunar valves

a. Pulmonary

b. Aortic

F. Associated vessels

1. Superior vena cava

Drains superior body into RA, deoxygenated blood

2. Inferior vena cava

Drains inferior body into RA, deoxygenated blood

3. Pulmonary trunk and arteries

RV to lungs, deoxygenated blood

4. Pulmonary veins

Lungs to LA, oxygenated blood

5. Aorta

LV to systemic circuit, oxygenated blood

G. Coronary circulation

Provides nutrients to myocardium; aorta; coronary arteries serving the four chambers; deoxygenated blood is collected by cardiac veins which empty into large coronary sinus (vein), which empties into the RA

H. Cardiac muscle

1. Myocardium

2. Differences from skeletal muscle

a. Automated excitement

b. No graded responses

c. No tetany

d. No anaerobic metabolism

3. Striated, involuntary

4. Intercalated discs, Stimulus passed btwn cells

5. Refractory period prevents tetany

6. Energy

a. ATP; Aerobic metabolism

b. Coronary circulation

7. Excitation

a. Depolarization to threshold

Spontaneous, likely due to gradual decrease in membrane permeability to potassium ions causing a decreased outflow of potassium ions

b. Sinoatrial node

Specialized cardiac muscle cells in wall of right atrium

1. At rest, depolarizes every .8 sec; 60-80 x/min

2. Change in permeability [potassium ions]

3. Pacemaker

8. Conduction from SA Node:

a. AV node (.1 sec delay)

b. AV Bundle (Bundle of His)

c. Purkinje = Conduction fibers

d. Myocardial cells of ventricle

9. Cardiac cycle

a. Systole(RV=30mmHg; LV=120mmHg)

Contraction phase of cardiac cycle

b. Diastole

Heart chambers relax and refill with blood

c. Time

1. Entire cycle .8 sec

2. Atrial systole .1 sec; diastole .7 sec

3. Ventricular systole .3 sec; diastole .5

4. Pressure curves(refer to your book)

a. Atrial (Left)

b. Ventricular (Left)

c. Aortic

5. Heart sounds

a. S1= AV valves closures

b. S2= Semilunar valves closures

10. Cardiac Output

a. CO = HR x SV (5-6 liters/min=70 b/min x 80 ml/bt)

Volume of blood pumped by either ventricle per minute

b. Cardiac reserve[Increase CO 600-700%]

Difference between maximum CO and resting CO

c. Heart rate control

1. Sympathetic stimulation

Increases heart rate

2. Parasympathetic stimulation

Decreases heart rate

d. Stroke volume

Volume pumped from ventricle per beat

SV= end diastolic volume – end systolic volume

1. End-diastolic volume

– Length of diastole

– Venous return

2.  End-systolic volume

– Frank- Starling Law

Stretch wall of ventricle leads to increased force of contraction

– Sympathetic N.S.

Decreases end systolic volume

– Parasympathetic N.S.

Increases end systolic volume

11. Factors influencing cardiac function

a. Cardiac center

Brain stem

b. Exercise

Chronic exercises enlarges cardiac muscle and thus increases stroke volume; can have good CO with lower HR due to increased SV

c. Temperature

Heat increases SA node discharge

d. Ions (K, Ca, Na)

e. Sex, age

HR faster in females, youngsters

12. Electrocardiography/Electrocardiogram (ECG,EKG)

a. Leads

Placement of electrodes on body for ECG

b. P wave– atrial depolarization

c. QRS– ventricular depolarization

d. T– Ventricular repolarizationInfo. derived: HR, Blocks, Orientation…

13. Heart disease – If time but not on exam.

Blood Flow Through the Heart

Cardiac Cycle Video

Location and Protective Layers of the Heart Video

Conduction Pathway of the Heart Video