Bio1331 Animas - Physiology - Cardiovascular Physiology (Lectures Fifteen And Sixteen)

Pacemaker cells are specialized cells that generate electrical impulses to regulate the heart's rhythm. These cells are found within the sinoatrial (SA) node, which is often referred to as the sino-atrial node or simply SA node.

Blood flow velocity is slowest in capillary beds because capillaries have the smallest diameter among all blood vessels. This narrow diameter creates a large total cross-sectional area, which causes a decrease in blood flow velocity. This slow velocity allows for efficient exchange of gases, nutrients, and waste products between the blood and surrounding tissues in the capillary beds. In contrast, veins, arteries, and arterioles have larger diameters, resulting in faster blood flow velocities.

The correct equation for cardiac output is heart rate x stroke volume. Cardiac output is the amount of blood pumped by the heart per minute, and it is determined by the heart rate (the number of times the heart beats per minute) and the stroke volume (the amount of blood pumped by the heart with each beat). Multiplying the heart rate by the stroke volume gives us the total volume of blood pumped by the heart per minute, which is the cardiac output.

The hepatic portal system occurs when blood containing nutrients and toxic substances originating from the digestive system goes through the liver before returning to the heart. The liver plays a crucial role in processing and detoxifying substances absorbed from the digestive tract. It receives blood from the gastrointestinal organs through the hepatic portal vein, allowing it to filter out harmful substances and metabolize nutrients before the blood is returned to the systemic circulation. This ensures that the liver can regulate the levels of nutrients and remove any toxins or waste products before they reach the rest of the body.

Correct spelling is 'haemolymph'.
Variations of spelling accepted here as you'll probably not have to write it.

Haemolymph is characterized by a high volume but low pressure. This means that it has a large amount of fluid circulating throughout the body, but the force exerted by this fluid on the blood vessels is relatively low. This is in contrast to the circulatory system found in vertebrates, where blood has high pressure due to the pumping action of the heart. In insects and other invertebrates, the haemolymph is responsible for transporting nutrients, hormones, and waste products, but it does not play a major role in oxygen transport.

Veins vary from arteries because they have valves, which are responsible for aiding unidirectional blood flow. Valves are one-way flaps that prevent blood from flowing backward and ensure that it moves only towards the heart. This is essential in veins, as they carry deoxygenated blood back to the heart, against the force of gravity. The presence of valves helps maintain the flow of blood in one direction, preventing backflow and ensuring efficient circulation throughout the body.

In an open circulatory system, arteries and veins are not joined. Unlike in a closed circulatory system, where blood is contained within vessels and flows in a closed loop, in an open circulatory system, blood is not enclosed in vessels and instead directly bathes the tissues. This means that there are no distinct arteries and veins in an open circulatory system.

Portal systems have two capillary beds in sequence, before returning to the heart. This means that blood flows from one capillary bed to another before it reaches the heart. This is different from most other systems in the body, where blood flows directly from capillaries to veins and then back to the heart. Portal systems are found in specific areas of the body, such as the hepatic portal system in the liver and the hypophyseal portal system in the brain.

All vertebrates have a closed circulatory system because their blood is contained within a network of blood vessels. This closed system allows for efficient transportation of oxygen, nutrients, and waste products throughout the body. In contrast, in an open circulatory system, such as that found in insects, the blood is not contained within vessels and instead bathes the organs directly. Therefore, the statement that all vertebrates have a closed circulatory system is true.

The smooth muscle fibers wrapped around the arterioles are called sphincters. These sphincters play a crucial role in regulating blood flow into the capillaries. When relaxed, they increase blood flow by dilating the arterioles, allowing more blood to enter the capillaries. Conversely, when contracted, they constrict the arterioles, reducing blood flow. Therefore, the term "sphincters" accurately describes these smooth muscle fibers and their function in controlling blood flow.

The heart is myogenic, meaning that it has the ability to generate its own contractions within the heart muscle itself. This is in contrast to other muscles in the body that require external stimuli, such as nerve signals, to contract. The myogenic nature of the heart allows it to maintain a regular and coordinated rhythm, ensuring proper blood flow throughout the body.

Blood leaving the two-chambered heart of a fish passes through two capillary beds before returning to the heart. In a two-chambered heart, blood is pumped out of the heart into the gills where it undergoes oxygenation. After passing through the first set of capillaries in the gills, the oxygenated blood then returns to the heart. From the heart, the blood is pumped to the rest of the body where it passes through a second set of capillaries for nutrient and gas exchange before returning to the heart again. Therefore, blood in a fish passes through two capillary beds before completing its circulation.

Octopus is the correct answer because it is an invertebrate that has a closed circulatory system. A closed circulatory system is one in which the blood is contained within blood vessels and does not directly come into contact with the body tissues. Octopuses have a highly developed circulatory system with a three-chambered heart and a network of blood vessels that transport oxygen and nutrients throughout their body.

Amphibians and reptiles have two atria and one ventricle. This is because their circulatory system is not fully divided into separate pulmonary and systemic circuits like in mammals and birds. The single ventricle pumps both oxygenated and deoxygenated blood, which limits their ability to efficiently separate oxygenated and deoxygenated blood. However, the presence of two atria allows for some separation of oxygenated and deoxygenated blood, improving the efficiency of their circulatory system compared to having just one atrium and one ventricle.

Diving mammals undergo bradycardia, which is a decrease in heart rate. This physiological adaptation helps to lessen the need for bloodstream oxygen, allowing more oxygen to be available for vital organs.

The correct equation for mean arterial blood pressure is the diastolic blood pressure plus one-third of the pulse pressure. This equation takes into account both the diastolic blood pressure, which represents the pressure in the arteries when the heart is at rest, and the pulse pressure, which represents the difference between the systolic and diastolic blood pressure. By adding one-third of the pulse pressure to the diastolic blood pressure, we get an estimate of the average pressure in the arteries over time, which is the mean arterial blood pressure.

Most invertebrates do not have a closed circulatory system. Instead, they have an open circulatory system where the blood or hemolymph is pumped into a cavity called the hemocoel. From there, it bathes the organs and tissues directly before being collected and pumped back to the heart. This is different from a closed circulatory system found in vertebrates, where blood is contained within vessels and pumped through the body. Therefore, the statement is false.

The equation provided is calculating the rate of O2 consumption. It is given that the equation is equal to "x" multiplied by the difference between arterial and venous O2. To complete the equation, we need a variable that represents the "x" value. The two options that can represent this variable are blood flow rate and cardiac output. Both blood flow rate and cardiac output are measures of the volume of blood pumped by the heart per unit of time. Therefore, either of these variables can be used to complete the equation.