31 Questions
What is the main difference between open and closed circulatory systems?
In open circulatory systems, blood is confined to vessels, while in closed circulatory systems, internal fluid circulates through the body cavity.
Why do open circulatory systems require faster heart rates or accessory hearts?
To maintain pressure gradients for efficient circulation.
Which organisms commonly possess open circulatory systems?
Arthropods, insects, and most molluscs.
Why are closed circulatory systems considered more efficient than open circulatory systems?
Because they maintain pressure gradients by confining blood to vessels.
What is the approximate total length of blood vessels in an adult human body?
~200,000 km
Which statement accurately describes the function of interstitial fluid in closed circulatory systems?
Interstitial fluid is distinct from blood and helps transport substances between blood and cells.
What type of organisms typically rely on diffusion for material exchange with the environment?
Unicellular organisms
Why is diffusion only efficient over small distances?
Diffusion takes time proportional to the square of the distance.
What is a key advantage of specialized circulatory systems in multicellular organisms?
Efficient exchange of materials over large distances
Which of the following animals usually have little or no specialized circulatory systems due to living in fluid environments and having thin body walls?
Jellies
What do larger animals typically possess as part of their circulatory system to facilitate material exchange?
A circulatory fluid, interconnecting vessels, and a muscular pump
Why are gastrovascular cavities important for some simple-bodied animals like flatworms and jellies?
To minimize diffusion distances for digestion and circulation
What is the function of the atria in the human cardiovascular system?
Serve as collection chambers for blood returning to the heart
Which valves in the human heart prevent backflow of blood?
Atrioventricular (AV) valves
What is the function of the semilunar valves in the human heart?
Control blood flow to the aorta and pulmonary artery
During which phase of the cardiac cycle do the ventricles begin to fill with blood?
When the atria fill with blood
What causes a heart murmur in humans?
Backflow of blood through defective valve
Which phase of the cardiac cycle is known as the pumping phase?
Systole
What sets the rate and timing at which cardiac muscle cells contract?
Sinoatrial node
Where do impulses from the SA node travel next?
Atrioventricular node
What part of the nervous system can slow down the pacemaker?
Parasympathetic division
Which node is responsible for delaying impulses before they reach the ventricles?
Atrioventricular node
Which hormone speeds up the pacemaker?
Norepinephrine
What regulates the pacemaker in addition to the nervous system?
Hormones
What is the role of nitric oxide in blood vessels?
Causes smooth muscle relaxation in arterioles
Which type of blood cell lacks nuclei and mitochondria?
Erythrocytes
What is the primary function of platelets in blood clotting?
Forming a solid clot
Which condition is caused by abnormal hemoglobin proteins deforming erythrocytes into a sickle shape?
Sickle-cell disease
What is the primary role of the lymphatic system in the body?
Returning leaked fluid from capillary beds
In which vessels does blood flow mainly due to gravity and muscle action back to the heart?
Veins
Which factor increases the risk of cardiovascular disease?
Low-density lipoprotein (LDL)
Study Notes
Circulatory Systems
- There are two types of circulatory systems: open and closed
- Open circulatory systems are found in insects, arthropods, and most mollusks
- In open systems, internal fluid is circulated through the body cavity
- There is no distinction between blood and interstitial fluid (hemolymph)
- Closed circulatory systems are found in some invertebrates and all vertebrates
- In closed systems, blood is confined to vessels and is distinct from interstitial fluid
- Substances move from blood to interstitial fluid and then to cells
Organization of Vertebrate Circulatory Systems
- By adulthood, humans have approximately 100,000 km of blood vessels
- The circulatory system is responsible for exchanging materials with the environment
- Diffusion is only efficient over small distances and is not sufficient for most cells in multicellular organisms
Heart Structure and Function
- The heart wall consists of muscle (myocardium), inner lining (endocardium), and a fibrous, protective sheath (pericardium)
- The heart has four valves that prevent backflow of blood
- The cardiac cycle consists of systole (contraction) and diastole (relaxation) phases
- The sinoatrial (SA) node is the pacemaker that sets the rate and timing of cardiac muscle contractions
- The atrioventricular (AV) node delays and then transmits impulses to the Purkinje fibers, which make the ventricles contract
Regulation of the Heart's Rhythmic Beat
- The pacemaker is regulated by the sympathetic and parasympathetic divisions of the nervous system
- The sympathetic division speeds up the pacemaker, while the parasympathetic division slows it down
- Hormones, such as thyroid hormone, and temperature also regulate the pacemaker
- Baroreceptors provide blood pressure information to the medulla, which then regulates the SA node
Blood Vessels
- Arteries, capillaries, and veins have distinct structures and functions
- Arteries have thicker walls than veins to accommodate high blood pressure
- Capillaries have thin walls to facilitate the exchange of materials
- Veins have one-way valves to prevent backflow of blood
Blood Pressure and Flow
- Blood pressure is the force exerted by blood on vessel walls
- Blood flow is slowed down in capillaries to facilitate the exchange of materials
- Blood pressure and velocity depend on vessel diameter
- The lymphatic system returns fluid that leaks out of capillaries back to the bloodstream
Blood Composition
- Blood is a connective tissue made up of cells suspended in a liquid matrix called plasma
- Plasma contains inorganic salts, proteins, and specialized proteins that influence blood pH and osmotic balance
- Erythrocytes, leukocytes, and platelets are suspended in plasma
- Erythrocytes contain hemoglobin, an iron-containing protein that transports oxygen
- Leukocytes function in defense against foreign substances
- Platelets are fragments of bone marrow cells that serve a structural and molecular function in blood clotting
Cardiovascular Disease
- Cardiovascular diseases account for more than one-third of deaths in Canada
- Atherosclerosis, heart attacks, and strokes are types of cardiovascular diseases
- Cholesterol plays a central role in cardiovascular disease
- Inflammation is also a factor in cardiovascular disease
- Risk factors for cardiovascular disease include high LDL to HDL ratio, hypertension, and smoking
Test your knowledge on animal circulatory systems, blood components, heart structure and function, regulation, blood vessels, circulation, gas exchange, and more covered in Campbell Biology Chapter 42. Explore topics like maintaining blood flow, controlling heart output, and the lymphatic system.
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