Ch 21 - Cardiovascular System: The Heart

Interstitial Fluid (IF)

Monitored by Autonomic Nervous System

• Adjusts heart rate

Pulmonary Circuit

Carries blood to the LUNGS for OXYGENATION

Systemic Circuit

Carries oxygen rich blood to the BODY

At the Heart

Each circuit BEGIN and ENDS at the

• 2 circuits are completed in sequence

1. OUTER FIBROUS Pericardium

2. INNER SEROUS Pericardium

The Pericardium surrounds the heart and is composed of 2 parts called

OUTER FIBROUS Pericardium

Composed of dense network of COLLAGEN fibers that stabilize the position of the heart

INNER SEROUS Pericardium

Composed of an outer PARIETAL layer & inner VISCERAL layer

• Parietal cavity lies b/w these layers

• Parietal fluid here (cushions heart)

The Visceral Layer OR Epicardium

Covers the outer surface of the heart

Myocardium

Cardiac muscle tissue that forms the atria and ventricles

Endocardium

Covers the inner surface of the heart including the valves

Cardiac Muscle Characteristics

• Smaller & UNInucleate

• Depends on AEROBIC RESPIRATION

• large # of blood vessels

• Contract W/O nervous stimulation

• Interconnected by special cell junctions:

  • Intercalated Discs

Desmosomes

Plasma membrane of 2 adjacent cells are bound together by

GAP Junctions

Allow passage of ions and small molecules

Cardiac Skeleton (elastic sheath of fibers) Functions:

• Stabilize POSITION of heart

• Distribute force of contraction

• Reinforce valves & provide elasticity to heart

• ISOLATES Atrial & Ventricular muscle cells

A shallow INTERATIAL Grove

______ separates the L/R Atria

Deeper CORONARY Sulcus

______ separates the ATRIA from the VENTRICLES

SAME SIDE of the heart

Blood flows from ea. Atria to the Ventricle on the

InterATRIAL Septum

Separates the ATRIA

InterVENTRICULAR Septum

Separates the Ventricles

3x Thicker

The wall of the Lt Ventricle is _______ than that of the right

AORTIC Semilunar Valve

Blood leaving the ventricle passes through the

Systole

Heart muscles are CONTRACTED

Diastole

Heart muscles are RELAXED

NODAL Cells

Establish the rate of contraction

• Plasma mem. can depolarize quickly

• When depolarization occurs an action potential is generated

• The action potential starts the cardiac cycle

Conducting Cells

Distribute the contractile STIMULUS to the myocardium

Which cell reach threshold first

The normal rate of contraction is determined by