Ch 20 The Cardiovascular System

Layers of the heart

Serous pericardium, epicardium, myocardium, endocardium

Epicardium

Protection: visceral pericardium

Pericardial cavity filled with pericardial fluid which reduces friction

Myocardium

Thick cardiac muscle layer

Endocardium

Smooth lining of heart chambers and valve coverings

Atria walls

Deliver blood to the ventricles

Ventricle walls

Thicker, pump blood greater distances

Right ventricle

Thinner than left - pump blood into lungs

Left ventricle walls

Thicker - pump blood through the body

Heart fibrous skeleton

Dense connective tissue laid out in rings

Operation of heart valves

Valves open/close in response to pressure changes as the heart contracts and relaxes

Semilunar valves

Allow ejection of blood from heart into arteries but prevent back flow of blood into the ventricles. Valves open when pressure in contracted ventricles exceeds pressure in the arteries. Ventricles relax, blood flows back into heart

Atrioventricular valves - bicuspia/tricuspid

Prevent flow from ventricles back into atria by papillary muscles tightening the chordae tendineae (prevents valve cusps from everting)

Blood flow in heart

Vena cava → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk. Pulmonary veins → left atrium → bicuspid valve → left ventricle → aortic valve → aorta

1% of cells are _____ and 99% are ____

Autorhythmic, contractile

Diffusion

sodium ions- large quantities on outside of cell

potassium ions- large quantities on inside of cell

calcium ions- large quantities on outside of cell and sarcoplasmic reticulum

*opem channel, they diffuse down concentration gradient

Autorhythmic cells

Unstable resting membrane potential

Pace maker potential steps

K+ channels close and F type Na+ channels open, second T type Ca+ channels open, brings membrane to threshold

Depolarizing phase

Rising action - L type voltage gated calcium channels open

Repolanization

Falling action - L type voltage gated calcium channels close and voltage gated potassium channels open

Depolarization of atrial contractile fibers

P wave

Atrial systole

Contraction

Depolarization of ventricular contractile fibers produces…

QRS complex

Ventricular systole

Contraction

Repolanication of ventricular contraction fibers produces…

T wave

Ventricular diastole

Relaxation

Electrocardiogram

Records signals of the heart, consists of waves, intervals, and segments

P wave

Atrial depolarization followed by atrial contraction

QRS complex

Ventricular depolarization followed by ventricular systole

T wave

repolarization of ventricle followed by ventricular diastole