What is the purpose of the circulatory system?
Delivery of O2, energy containing substrates, vitamins, hormones, and other nutrients.
Removal of CO2, cellular wastes, and secretory products.
Besides the heart, what can be considered the additional components of the circulatory system?
The medulla vasomotor center, the SNS, PNS, and the blood.
Describe the different components and % of each in blood.
55% Plasma (water, ions, hormones, proteins...)
45% RBCs, called the hematocrit
< 1% Buffy coat - WBCs, platelets...
What factors make up the blood plasma?
Proteins - albumin, globulin, fibrinogen,
Ions, glucose, amino acids, wastes.
What type of proteins are found in the plasma?
Albumin - smallest plasma protein, contributes to the osmotic pressure, involved in trasnport.
Globulin - Alpha, Beta - involved in transport, Gamma - antibodies produced by the immune systme
Fibrinogen - involved in clotting
Describe the O2 concentration of the blood.
3% dissolved in the plasma, 97% stored in the RBCs bound to hemoglobin
Describe the life span of an RBC.
120 days, due to the fact they do not have mitochondria, ribosomes, or nucleus.
Describe the structure of hemoglobin.
4 heme groups each consisting of 4 pyrole rings and 4 globin molecules (blood proteins).
What molecules bind to the heme groups?
O2 and CO
What molecules bind to the globin chains?
CO2, H+, Nitric oxide, 2,3 bisphosphoglycerate (BPG)
Describe the regulation for an increase of O2 delivery to the cells.
A lack of O2 delivery to the cells could be the result of insufficient number of RBCs. This causes the kidney to detect a change. The kidney then releases the hormone, erythropoietin, stimulating the bone marrow to produce more RBCs. The bone marrow will produce more RBCs which increases the ability to carry more O2.
Describe the regulation for an decrease of O2 delivery to the cells.
A decrease of O2 delivery to the cells would be caused by an increased number of RBCs. The kidney would detect the increased number of RBCs and decrease secretion of the hormone, erythropoietin. The decreased secretion would decrease the stimulation of the bone marrow to produce RBCs, lowering the O2 delivery to the cells.
What is anemia?
Defined as a lack of RBCs. Specifically defined as less than 30% of normal.
Name the 7 pathological variations in RBCs.
1. Iron deficiency
2. Lack of folic acid in the diet
How does iron deficiency cause anemia?
Iron is required to manufacturer hemoglobin. A lack of iron means you cannot make enough hemoglobin. If you can't make enough hemoglobin, then you can't make enough RBCs.
How does lack of folic acid in the diet cause anemia?
Folate is a vitamin that is used in the process of making RBCs. If you can't make RBCs, then as RBCs die, they are not replaced and the body becomes anemic.
How does pernicious anemia cause a decrease in RBC count?
Loss of gastric parietal cells resulting in decreased amounts of intrinsic factor secreted into the stomach. Intrinsic factor binds to vitamin B12 protecting it from the harsh acidic environment of the stomach until it can be absorbed in the sm intestine. V B12 is also a key vitamin in the production of RBCs.
How does hemorragic anemia cause a decrease in RBC count?
Caused by hemorrhage. If someone is constantly bleeding, those RBCs are not being used to carry out their normal duties and the % of RBCs available for normal use decreases.
How does aplastic anemia cause a decrease in RBC count?
A condition where the bone marrow does not produce enough new cells to replenish the RBCs.
How does hemolytic anemia cause a decrease in RBC count?
Body produces enough RBCs, but they are of inferior quality and fall apart prematurely. Ex, sickle cell anemia.
How does renal anemia cause a decrease in RBC count?
Caused by a tumor or growth in the kidneys near the cells responsible for producing erythropoietin. Decreased secretion of erythropoietin causes decreased production of RBCs.
Describe the regulation for an increase of blood pO2.
Inc in blood pO2 is recognized by receptors in the kidney. Kidney responds by secreting more erythropoietin which in turn stimulates bone marrow to produce more RBCs which increases the pO2.
Describe the regulation for a decrease of blood pO2.
Dec in blood pO2 is recognized by the kidney and causes a decrease in the secretion of erythropoietin which in turn decreases the stimulation to the bone marrow, decreasing the number of RBCs.
What is polycythemia?
Genetic disease that causes excess creation of RBCs. Their blood becomes too viscus and they are at greater risk for heart attack/stroke.
What is chronic high altitude mountain sickness?
Occurs in people living at high altitudes for extended periods of time. Their bodies produce an excess amount of RBCs and their blood becomes too viscus.
How many mLs of O2 can 1 gram of hemoglobin carry?
1.33 ml O2/ g Hemoglobin
How much hemoglobin is typically found in 100 ml of blood?
Describe the flow of O2 from the alveolus to the cell.
O2 is inspired and ends up in the Alveolus where it will diffuse across the membrane into the blood plasma. If the pO2 of the RBC is less than the pO2 of the blood plasma, the O2 will diffuse into the RBC and attach to a hemoglobin molecule. The fully saturated RBC will move to an area where cells require O2. The O2 will work its way down the concentration gradient from being attached to the hemoglobin to the cellular matrix of the RBC, across the membrane to the blood plasma across the membrane to the interstitial space and across another membrane into the cells requiring O2.
Describe the solubility of O2 in H2O and blood.
O2 is not very soluble, CO2 is much more soluble.
Does the O2 bound to the hemoglobin contribute to the pO2 in the blood?
List the two key points on the hemoglobin saturation curve.
75-80% at 40 mmHg
97% at 100 mmHg
Steepest part around 20-80 mmHg
What factors can affect the position of the oxygen dissociation curve?
1. [H+], [CO2]
3. 2,3 bisphosphoglycerate
Why/how does a change in the [H+]/[CO2] in the blood change the oxygen saturation curve?
An inc in [H+]/[CO2] means, more oxygen is needed. This results in a rightward shift of the curve, allowing less hemoglobin to be saturated at the same pO2.
A dec in [H+]/[CO2] means less O2 is needed, causing a leftword shift in the curve allowing hemoglobin to be fully saturated at lower pO2.
Why/how does a change in the blood temp change the oxygen saturation curve?
Blood temp is related to the amount of cellular activity being performed by that particular cell. An increase in temp, normally means, more ATP production, which means an increased need for O2. This will shift the curve right
A decrease in temp will shift the curve left, as not as much O2 is needed by the cells for a given pO2.
Why/how does a change in the [2,3 BPG] in the blood change the oxygen saturation curve?
2,3 BPG will bind to hemoglobin and decrease the ability of hemoglobin to bind O2. An increase in 2,3 BPG causes a rightward shift in the curve allowing less hemoglobin to be saturated at the same pO2 and making more O2 available for the cells.
A decrease in 2,3 BPG will cause a leftward shift, causing less more hemoglobin sat at the same pO2.
Compared to the normal hemoglobin saturation curve, an inc in [H+]/[CO2], body temp, or [2,3 BPG] will cause the curve to shift which direction?
To the right.
What factors affect the O2 unloading during exercise?
2. Body Temp
3. pO2 of the tissues
How is CO2 transported in the blood?
10% is dissolved in the plasma or the RBC cytoplasm
30% is bound to the globin chains forming a carbamino complex.
60% as HCO3-
Describe what happens to CO2, H+, O2, and Hb between an RBC and a tissue cell.
1. CO2 from the tissue cell will dissolve into the blood plasma and into the cytoplasm of the red blood cells
2. CO2 will bind to Hb to form the carb-amino complex
3. CO2 and H20 will form H+ and HCO3-
4. H+ will bind to the Hb
5. HCO3- is transported out of the cell into the plasma and exchanged for Cl- ions to balance the charge.
Describe what happens to CO2, H+, O2, and Hb between an RBC and the alveolus.
1. CO2 will dissolve from the RBC into the plasma and into the alveolus to be exhaled.
2. HCO3- is transported into the cell and Cl- is transported out of the cell.
3. H+ and HCO3- will be combined to form H2O and CO2. CO2 will move out of the RBC to replace the decreasing amount in the blood plasma and possible move into the alveolus.
4. The Hb H+ and Hb CO2 complexes will release CO2, H+, make Hb available to bind with O2.
5. O2 will flow from the alveolus to the cell and bind to the free Hb.
What is the main purpose of the heart?
To create a hydrostatic pressure gradient that causes blood to flow.
What is a functional syncytium? What is one example?
When you have many cells, each with it's own nucleus but acting as one cell. The heart is an example.
What structures give rise to the intercalated discs found in cardiac muscle tissue?
The desmosomes and gab junctions.
What is the purpose of a desmosome?
To hold cardiac muscle cells together and prevent the cells from being ripped apart.
What is the purpose of a gap junction?
Allows for a very fast transfer of ions between cells enabeling the cell to operate as functional syncytium.
Describe the role of the sinoatrial node.
Sinoatrial node is responsible for creating a rhythmic pattern of action potentials.
Describe the action potential created by the cells in the sinoatrial node.
The action potential is generated by changing the "leakiness" of the cells ion channels to Ca++ and K+.
Begins with a small increase in the amount of Ca++ ions moving into the cell. Once the threshold is reached, Ca++ gates open and the influx of Ca++ causes depolarization of the cell until the voltage reaches just over 0 V. At that point Ca++ gates close, K+ gates open and K+ is moved out of the cell lowering the voltage back to resting. (~-60 mV)
Describe the path of conduction from the the SA node to the rest of the heart.
SA Node stimulates all the atrial cardiac muscle fibers and then stimulates the AV node which will send the electrical impulse down the Bundle of His to the Purkinje fibers and begin the contraction at the bottom of the heart.
Describe the action potential of the cardiac muscle fibers.
Resting potential is around -90 mV. Na+ gates open, allowing Na+ to rush into the cell triggering the depolarization to +30 mV. Na+ gates close, Ca++ gates open. Na+ is actively transported out of the cell and the decrease of Na+ causes cell potential to drop. Ca++ is used for muscle contraction. After a certain amount of time, K+ gates will open allowing K+ out of the cell bringing the potential back to the resting membrane potential. (-90 mV)
How does the SNS regulate heart rate?
SNS releases norepinephrine onto the pacemaker cells. The norepinephrine will decrease the permeability of the membrane to K+, decreasing the amount of K+ ions that are moved out of the cell after an action potential. Less K+ ions means more positive resting potential and less time to reach the threshold voltage which means an increase in heart rate.
How does the PNS regulate heart rate?
PNS releases acetylcholine onto the pacemaker cells. Acetylcholine will increase the permeability of the membrane to K+, resulting in a greater amount of K+ ions diffusing out of the cell during depolarization. This causes the cell potential to be more negative which will increase the amount of time it takes to generate another action potential, decreasing the heart rate.
What are the main sources of cholesterol?
Produced by the liver and ingested as part of your diet.
List some of the uses of cholesterol.
1. Used in the creation of steroid hormones
2. Used to create bile salts
3. Used to enhance rigidity in cell membranes.
How is cholesterol transported in the blood?
Via high density lipoproteins (HDL - good), and low density lipoproteins (LDL - bad).
What is athlerosclerosis?
Injury to an artery wall by invasion of LDLs, oxidized cholesterol, free radicals, high blood pressure, chemicals from fat cells, and bacteria causing inflammation. Build up of plaque.
Describe the process of athlerosclerosis.
1. Cholesterol carried by LDLs becomes oxidized by free radicals in the blood.
2. Endothelial cells recruit WBCs to the site to attack the LDL forming a "fatty streak"
3. Over time, proliferation of smooth muscle cells and fibrous connective tissue cover the fatty streak.
4. Ca++ deposited in the streak causes the vessel to harden making it difficult to dilate or contract.