Animal Anatomy & Physiology

Functions of the Cardiovascular System:  delivers vital nutrients (e.g., oxygen) to all body cells  eliminates waste products and carbon dioxide  transports chemical messengers (e.g., hormones) from one part of the body to another  helps to maintain a constant body temperature

Open Circulatory System – Hemolymph (mix of blood and tissue fluid) is pumped directly into the body cavity. -

Closed Circulatory System – Blood is separate from the rest of the body in a network of tubes.

Single-circuit circulatory system – Only one track the blood can travel Two-circuit circulatory system - Circulation to the lungs is separated from circulation to the rest of the body.

1. The Heart: a muscular organ that continuously pumps blood through the body, generating blood flow. 2. The Blood Vessels: a system of hollow tubes through which the blood moves. 3. The Blood: The fluid that transports nutrients, O 2, CO 2 and many other materials throughout the body.

Circulation to the lungs is separated from circulation to the rest of the body.  pulmonary circuit: the part of the circulatory system that delivers blood to the lungs  systemic circuit: the part of the circulatory system that delivers blood around the body

 Has four chambers  Atria: the two top chambers that fill with blood returning from the body or the lungs (singular atrium).  Ventricles: two bottom chambers that receive blood from the atria and pump it out to the body or the lungs.

 The tricuspid valve separates the right atrium from the right ventricle  The mitral (bicuspid) valve separates the left atrium from the left ventricle  The pulmonary (semi- lunar) valve separates the right ventricle from the pulmonary artery  The aortic (semi-lunar) valve separates the left ventricle from the aorta

 The vena cavae bring oxygen-poor blood from the body to the right atrium.  The oxygen-poor blood flows from the right atrium into the right ventricle.  The right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary arteries.

 The pulmonary veins bring oxygen-rich blood from the lungs back to the heart through the left atrium.  Oxygen-rich blood flows from the left atrium to the left ventricle.  The left ventricle pumps the oxygen-rich blood to the body through the aorta.

 Valves prevent the blood from flowing backwards.  The “LUB” sound is caused by the closing of the atrioventricular (AV) valves (tricuspid & mitral valves) as blood is pumped from the atria to the ventricles.  The “DUB” sound is caused by semilunar valves (pulmonary & aortic), as blood is pumped from the ventricles into the arteries

 A bundle of specialized muscle tissue, called the sinoatrial (SA) node, stimulates the muscle cells to contract and relax rhythmically.  Also referred to as the pacemaker, because it sets the pace for cardiac activity  Located in the wall of the right atrium.

 The SA node generates an electrical signal that spreads over the two atria and makes them contract simultaneously.  As the atria contract, the signal reaches another node, called the atrioventricular (AV) node.

 The AV node transmits the electrical signal through a bundle of specialized fibers, called Purkinje fibres, that run down the septum and up around the ventricles  This initiates the almost simultaneous contraction of all cells of the right and left ventricles.

 Force of the blood on the walls of the arteries.  Normal BP 120/80 mm Hg; decreases as you move away from the heart.  Systole (120 mmHg): Pressure of contraction  Diastole (80 mmHg): Pressure at relaxation (re-filling of heart)  Stroke Volume: volume of blood leaving heart (L)‏  Heart Rate: number of beats (contractions) per minute (bpm)‏

Two factors determine BP: 1. Cardiac Output (CO): amount of blood pumped from the heart each minute = Heart Rate (HR) x Stroke Volume (SV)  ⇡ CO = ⇡ BP  increase CO by ⇡ HR or ⇡ Stroke Volume (stronger heart)‏ 2. Arteriolar resistance: diameter of the arteriole determines the amount of blood flow  ⇡ diameter = ⇣ BP

 Diameter of blood vessels regulated by the medulla oblongata.  Vasoconstriction: nerve impulses cause muscle to contract, reducing diameter of vessel, reduces flow to tissue, increases pressure  Vasodilation: nerve impulses cause muscles to relax, increasing diameter of vessel, increases flow to tissue, decreases pressure