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29 Cards in this Set

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What is a circulatory system or a cardiovascular system is composed of?
1) Pump (heart)
2) Fluid (blood)
3) Conduits (blood vessels)
Some simple aquatic animals do not have circulatory systems. Tell me about them…
In small animals, nutrients, gases, and wastes can diffuse between the cells and the environment and a circulatory system is not needed
What happens in open circulatory systems and what does it consist of?
The blood or circulating fluid is not kept separate from the tissue fluid
> There is usually a pump or heart to help propel the fluid, and vessels direct it, but the fluid leaves the vessels to trickle through tissues
What is the function of a closed circulatory system?
It keeps the blood and tissue fluid separate
What are some advantages that closed systems have over open systems?
1) Blood flow, nutrient delivery and waste removal are more rapid
2) Closed systems can direct the blood to specific tissues
3) Cellular elements and large molecules that aid in transport can be kept within the vessels
4) Closed systems generally support higher levels of metabolic activities (higher pressure)
What types of circulatory systems do vertebrates have?
Closed systems and hearts with two or more chambers
What is the function of the valves?
They prevent blood backflow when the heart contracts
What is a theme in vertebrate evolution?
A progressive separation of the blood that goes to the lungs from blood that goes to the rest of the body
> This culminates in two circuits:
1) A pulmonary (lung) circuit
2) A systematic (body) circuit
What is the function of arteries?
They carry blood away from the heart
What do arteries give rise to and what is their function?
Smaller vessels called arterioles
> They feed blood into the capillaries
What are capillaries?
Thin-walled vessels through which materials are exchanged between the blood and the tissue fluid
What type of hearts do reptiles and crocodiles have?
- Reptiles: their hearts have two atria and a ventricle
- Crocodiles: a true four-chambered heart
What type of hearts do birds and mammals have?
- Four-chambered hearts that completely separate the pulmonary and systemic circuits
- No mixing of blood whatsoever
What are the advantages of separate circuits?
1) Oxygenated and deoxygenated blood cannot mix
2) Gas exchange is maximized because the lungs receive only blood with low O2 and high CO2 content
3) The separate circuits can operate at different pressures
What is the definition of systole and diastole?
- Systole = ventricle contraction
- Diastole = ventricle relaxation
How do cardiac muscle cells interact and what does this permit?
They are in electrical contact with one another through gap junctions
> This permits coordinated contraction for effective blood pumping
What are pacemaker cells and what is their function?
Cardiac muscle cells that initiate action potentials without nervous stimulation
What is the primary pacemaker of the heart?
The sinoatrial node
What is the path blood takes through the heart?
1) The sinoatrial node
2) The atrioventricular node is stimulated by depolarization of the atria
Where do capillary beds lie and what is their function?
Lie between arterioles and venules
- Exchange materials between blood and tissue fluid through their thin walls
- The high pressure in the arteries is dissipated by the vast number of arterioles and still greater number of capillaries
- The total cross-sectional area of the capillary beds is much greater than that of any of the other vessels
Where does blood tend to accumulate and why are they also known as capacitance vessels?
Veins
- Because of their high capacity to store blood
- Contraction of skeletal muscles pushes blood toward the heart because one-way valves in veins prevent backflow
What is tissue fluid that accumulates outside of capillaries is moved by and how does this system work?
The lymphatic system
1) Lymph moves from small to larger vessels and finally empties into the thoracic ducts that empty into large veins at the base of the neck
2) Lymph is moved through vessels by skeletal muscle contractions, and the vessels have one-way valves to prevent backflow.
What is the function of lymph nodes?
1) Major sites of lymphocyte production
2) Filters that have phagocytic cells to remove microbes and foreign matter
What is a heart attack or stroke often the end result of?
Atherosclerosis (hardening of arteries)
What happens when the smooth internal lining of arteries becomes damaged?
Deposits called plaque form at damaged sites
- These make the artery wall less elastic (“hardening”), and the plaque narrows the lumen of the artery
- Blood platelets stick in the plaque and form blood clots (a thrombus), further blocking the artery
If the smooth internal lining of arteries becomes damaged, what happens if the coronary arteries are affected?
Blood supply to the heart decreases
- A thrombus here (coronary thrombosis) can block an artery, causing a heart attack (myocardial infarction, or MI)
- If part of the thrombus breaks away (an embolism), lodges in the brain, and blocks blood flow, stroke may occur
What is blood?
Connective tissue: it consists of living cells within an extracellular matrix
What are the cellular components of blood?
1) Red blood cells (erythrocytes)
2) White blood cells (leukocytes)
3) Platelets (cell fragments)
Tell me about erythrocytes…
1) They are the majority of cells found in blood
2) At maturity they are biconcave, flexible discs packed with hemoglobin
3) The hemoglobin carries O2, and the flexible shape of the cell lets them squeeze through narrow capillaries
- This production is controlled by erythropoietin, a hormone from the kidney