Identify substances found in animalcirculationš Compare and contrast variations of closedcirculatory systemsš Describe the structure of the mammalianheartš Explain how blood flows throughout a fourchambered heartš Describe how electrical impulses result incontraction of the heartš Understand the intrinsic and extrinsicmechanisms that control heart activityš Identify the phases of the cardiac cycleš Differentiate cardiac output with bloodpressure

Substances found in animal circulation: These include nutrients (like glucose, amino acids, and fatty acids), gases (like oxygen and carbon dioxide), hormones, waste products (like urea and lactic acid), and cells (like red and white blood cells).

Variations of closed circulatory systems: In a closed circulatory system, blood is enclosed in blood vessels and is separate from the interstitial fluid. In mammals, this system is highly developed with arteries, veins, and capillaries. In contrast, invertebrates like annelids and cephalopods have a simpler closed system with fewer vessels.

Structure of the mammalian heart: The mammalian heart is a four-chambered organ, consisting of two atria and two ventricles. The right side of the heart pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the rest of the body.

Blood flow in a four-chambered heart: Blood flows from the body into the right atrium, then to the right ventricle, which pumps it to the lungs. From the lungs, blood flows into the left atrium, then to the left ventricle, which pumps it to the rest of the body.

Electrical impulses and heart contraction: The heart's contraction is controlled by electrical impulses generated by the sinoatrial node (or pacemaker). These impulses spread through the heart muscle, causing it to contract and pump blood.

Intrinsic and extrinsic control of heart activity: Intrinsic control refers to the heart's internal pacemaker and conduction system. Extrinsic control refers to the influence of the nervous system and hormones, which can speed up or slow down the heart rate.

Phases of the cardiac cycle: The cardiac cycle consists of the systole (contraction) and diastole (relaxation) of both the atria and ventricles.

Cardiac output and blood pressure: Cardiac output is the amount of blood the heart pumps per minute, while blood pressure is the force that blood exerts on the walls of the blood vessels. They are related in that an increase in cardiac output can lead to an increase in blood pressure.