E3 complete

The cardiovascular system is composed of?

blood, heart, and blood vessels

TBW and Fluid compartments

Total body water percent varies with age: infants (80%), middle aged (60%), elderly (55%)

In the magical mythical male model the average weight is 70kg, 60% will be water weight (70×0.6), giving us a total of 42L.

42L

• about 2/3, 28L makes up the ICF (fluid inside cells)

• about 1/3, 14L makes up the ECF (water found outside cells)

From the 14L of ECF

• 10-11L makes up interstitial fluid (surrounds and bathes cells)

• 3L makes up plasma (60% of total blood)

• 0-1L is transcellular fluid, fluid that crosses cells, such as CSF, synovial fluid, and aqueous humor.

What is the total blood volume? What is its percentage in TBW?

TBV= plasma (58-60%) + formed elements (40-42%)

When estimating blood volume its about 8% of body weight (in kg)

What are the major functions of blood?

Transport, protection, and temperature regulation

F: Transportation

Takes O2, nutrients, hormones, and water to cells, and removes CO2

• Gases: N2, O2, CO2

  • mainly have N2, but physiologically, it plays no role

• Nutrients: biological molecules (aa, glucose, lipids)

• Signaling molecules: hormones to target cells

• Water: cells are 80-90% water, and water is brought by blood

• Wastes: picks up waste and brings it to the system that eliminates them

F: Protection

Immunity: has nonspecific and specific cells that protect

Clotting: has platelets and proteins that prevent blood loss by forming clots

F: Temperature regulation

Blood carries heat and it maintains core temperature. Subcutaneous blood vessels can vasodilate or vasoconstrict to regulate temperature. When its hot, vessels dilate and more blood circulates the periphery of the skin, allowing more heat to be released from the body. When its cold, vessels constrict so blood is kept at the core of the body to keep vital organs warm.

What are the general characteristics of blood?

Blood is about 50% water with a salt content of 0.9%. Its pH is slightly basic, ranging from 7.35 to 7.45, with venous blood being more acidic because it carries CO2 (weak acid), which is primarily present as carbonic acid. While arterial blood has a lower partial pressure of CO2.

Blood also has a high viscosity (thick and sticky), which is good because it prevents blood loss, but bad when it becomes very viscous, increasing the difficulty of blood to circulate through BV.

What are the % of blood contents?

Plasma (58-60%)

Formed elements (40-42%)

Characteristics of blood: Formed elements, normal range and functions

RBCs / Erythrocytes

• make up 95% of formed elements

• normal: 5 million/microliter (anemic: <4million)

• function: carries the majority of O2 (97%), the 3% dissolved in plasma

WBCs/Leukocytes

• normal is 5000 - 10,000/microliter (leukopenia <5000

• function: immunity

Platelets/ Thrombocytes

• normal: 200,000 - 400,000/microliter (thrombopenia <200,000)

• clotting

Thromb

clot

Composition of blood: Plasma

Plasma makes up 50-60% of whole blood: ~3L

Composition

• Of the 3L, 90% is water

• 8% are proteins: albumins, gamma globulins, and fibrinogen

• 2% everything else

  • charged ions: Na+, K+, Ca2+, Cl-

  • gas: N2, O2, CO2

  • nutrients: glucose, aa, etc.

  • waste: CO2, ammonia, urea

What is serum?

plasma without clotting factors is serum

Plasma proteins: Function of albumins

Of the 8% of plasma proteins, albumins are the most abundant, making up 60%.

1) They increase the viscosity of blood

2) Contributes to colloid osmotic pressure, drawing fluid back into the venous end of the capillary, preventing edema

• Blood that enters the arteriole end of capillary comes under BP because blood is constantly pumping blood into the arteries

• liquid portion begins to leave and cells + proteins stay in the capillary

• As we go through the capillary to the venous end protein concentration gradient increases, building the osmotic pressure. This begins to draw fluid back into the capillary.

Plasma proteins: Function of gamma globulins

Gamma globulins are antibodies produced by B cells that protect against SPECIFIC foreign invaders. They have antigen binding sites and ONE antibody recognizes ONE antigen, as they are very specific. Gamma globulins are the most varied plasma protein because they are very specific to the individual and what antigens they’ve come in contact with.

Plasma proteins: Fibrinogen + blood clotting process

Fibrinogen: inactive and soluble protein precursor in blood.

• becomes activated by sharp edges and chemicals becoming →

Fibrin: active and insoluble protein that begins to form a net around damaged area. The net catches platelets and RBCs, together forming a blood clot.

Plasminogen: inactive protein, when area is healed, the healed cells secrete factors that activate plasminogen into →

Plasmin: active protein that removes the blood clot from healed BV

What are carrier proteins? Which ones are we focusing on?

Carrier proteins transport hydrophobic molecules in aqueous blood

HDL, LDL, and transferrin

Carriers: HDL + LDL

High/low density lipoproteins. They carry cholesterol, steroids, and free fatty acids

HDL

high density lipoprotein.

As they are more dense compared to lipids, the carrier is very soluble and gets to the liver with no issue

LDL: What is it? What problem does it cause? Problem with clots?

Low density lipoprotein

Problem: As there is more lipid than proteins, that carrier is sticky and less soluble. When in transport fats begin to stick to BV, it forms fatty deposits and plaques, aka atherosclerosis. The build up of fatty plaques clogs up BV, narrowing them, and increasing BP (hypertension). If a BV near the heart clogs up the heart may become ischemic, and part of the heart muscle dies due to the lack of O2. causing a myocardial infarction. If its to the brain it can cause a stroke.

Problem: Fatty plaques for sharp edges causing fibrinogen to activate into fibrin, forming a blood clot. This blood clot will never dissolve because the “cells” (no cells involved) will not heal, therefore plasminogen will not be activated into plasmin and the blood clot will not be removed. Which may either clog up an entire vessel or become loose and begin to travel.

Carriers: Transferrin

Transferrin carriers Fe to red bone marrow (RBM)

Where is RBM when you’re young? older?

In a young person, every bone has RBM. As the person gets older RBM is substituted by YBM in long bones. In adults RBM is only in the spine, ribs, pelvis, and the proximal ends of long bones.

Where are RBCs, WBCs, and thrombocytes made?

RBCs: RBM

WBCs: RBM and lymphatic tissue (myeloid + lymphoid origin)

Thrombocytes: RBM

What is hematopoiesis? What are its subtypes?

“Blood production,” is the synthesis of blood cells

erythropoiesis, leukopoiesis, and thrombopoiesis

Where do all blood cells originate from?

pluripotent hematopoietic stem cell: “many capable blood producing stem cell”

All formed elements come from the hematopoietic stem cell located in the RBM.

What is erythropoiesis?

Erythropoietin (EPO) is produced by the kidney.

As blood is filtered in the kidney, it checks the O2 capacity of the blood. EPO production is induced by low levels of O2. EPO is then released and travels through the bloodstream to RBM, stimulating hematopoietic pluripotent stem cells to go through erythropoiesis.

Athletes and high altitude training: What does it do? What are the synthetic methods?

At higher altitudes the partial pressure of O2 is lower, as a result blood carries less O2. The low levels of O2 will be detected by the kidney, inducing the release of EPO which will stimulate erythropoiesis, and increase the number of RBCs so even more O2 can be carried. This is why some athletes train at higher altitudes so they have a greater advantage at sea level.

Some athletes may not train in higher altitudes but blood dope to increase RBC #s. One drug is Recombinant human EOP (rhEPO), which signals to pluripotent hematopoietic stem cells to go through erythropoiesis. Amgen (darbepoetin alfa) is a synthetic agonist of rhEPO that improved stability.

How does an increase in RBC #s affect blood viscosity?

In athletes: Increase in RBC # also increases blood viscosity, but because they are healthy its okay

In smokers: they inhale less O2, inducing the release of EPO from kidneys, stimulating erythropoiesis and increasing RBC #. Because they are a smoker and the inhale less O2, more RBCs are made but the body does not carry any more O2 than it regularly does, making the smokers blood more viscous.

• Increases hypertension

Thrombopoiesis

Thrombopoietin turns pHSC into a megakaryocyte “big nucleus cell”

→ megakaryocyte will begin to break off pieces of cytoplasm with organelles forming thrombocytes.

Leukopoiesis

needs two signals

1) Leukopoietin signals to pHSC to turn into a generic WBC

2) Colony-stimulating factors (CSF) specify what the generic WBC will become

Bone marrow production of RBCs and WBCs. Which makes up the most? Why?

RBCs make up 95% of formed elements. Out of all the cells produced at a moment RBC make up 25% and WBCs make up 75%. Why? Because of the lifespan. RBCs live 3 to 4 months while the lifespan of WBCs span from seconds, minutes, to a life time depending on the type of cell. Since the majority live for a few seconds (neutrophils 60-70%) WBCs are produced at a higher rate.

Note about RBC and thrombocytes

RBCs are also called red blood corpuscles because they have no nucleus or organelles.

Platelets are not cells, they are fragments of a cell that has organelles

RBCs characteristics

RBC are anucleate (no nucleus or organelles), allowing more space for Hb, since they have no organelles (specifically mitochondria) they rely on anaerobic glycolysis for energy. Their biconcave disc shape, as a result of being anucleate allows RBCs to be flexible and squeeze through capillaries. Also their shape is osmosis induced, it changes depending to the concentration of solutes in the solution. If is hypertonic it shrinks, hypotonic it swells. Additionally they biconcave disc increases SA/volume ratio for the greater diffusion of oxygen (cytoskeleton responsible for shape)

What is reticulocyte?

committed but immature RBC with a nucleus

What are RBCs also called? Why?

Red blood corpuscle because they lack a nucleus and organelle

What is hemoglobin?

Hemoglobin is a protein found in RBCs. It is a tetramer composed of 4 subunits (2 alpha and 2 beta), and each subunit contains a heme group where Fe is located. One O2 binds onto one Fe within the heme group. With 4 subunits, each with Fe = 4O2/Hb

What is the function of Hb?

1) oxygen carrier: O2/heme, 4O2/Hb

2) Serves as a buffer: by accepting and donating H+ ions because of the amino groups in the protein.

How many Hb in one RBC? About how much O2 does it carry? What is the normal concentration?

About 280 million Hb in one RBC, carrying over a billion O2 molecules. The normal concentration is 14g/dL.

Hb carries many molecules, what are the names?

Oxyhemoglobin: O2 is bound to the heme group

• When O2 binds to Fe, it oxidizes it (Fe3+) and gives the red color to blood

Deoxyhemoglobin: Hb without O2

• Fe is reduced (Fe2+) without O2, giving blood a blue color (leading to cyanosis)

Carbaminohemoglobin: CO2 bound to protein portion (aa) of Hb

Carboxyhemoglobin: Carbon monoxide (CO) is bound to the heme group

Why is carboxyhemoglobin so dangerous?

CO is a competitive inhibitor of O2 because it can bind to the Fe portion of heme and has a 200x greater affinity to heme than O2. O2 binds and lets go while CO binds and holds on.

CO is very dangerous because it has no smell, taste, or color. It binds to heme and the body cannot tell you are suffocating.

What is the process of breaking down Hb?

RBCs live 3-4 months and are removed by microphages in the spleen. As RBCs are broken down so is Hb into three different parts: protein, Fe, and heme.

Hb: Removal of proteins

Protein → through proteolysis its broken down it amino acids → AA may be reused or be used for energy production if needed.

Hb: Removal of Fe

Fe is extracted from heme and is transported to RBM by transferrin to be reused

Hb: Removal of heme

Heme is extracted from proteins and without Fe it is bilirubin, which is somewhat toxic and hydrophobic.

Bilirubin is taken to the liver to be conjugated with glucuronic acid, increasing its water solubility and forming conjugated bilirubin. → C bilirubin can now be removed by bile or urine which is what gives feces its brown color (otherwise whitish/gray) and urine its yellow color.

If Hb cannot be conjugated by the liver it accumulates and begins to color the skin yellow, causing jaundice

Hb: Baby Jaundice, how does it happen?

`Babies in the womb need more RBC to receive O2 from the mother, but when babies are born they don’t need as many because they can now breathe air. As a result RBCs will begin to be destroyed and because the liver of the newborn babies are not fully developed, it cannot keep up with the destruction of RBCs, developing jaundice.

Hb: Is jaundice harmful to adults? babies? why? Treatment?

Jaundice itself is not harmful; it mainly brings up concerns about the liver. Jaundice in the baby is harmful because the baby's BBB is not fully developed; because of this, jaundice can go into the brain, which may lead to severe developmental effects. Babies are monitored for a few days to ensure Jaundice does not get too high. They may be put in UV light or the sun if jaundice is not severe, which will make bilirubin more water-soluble

What three things is O2 carrying capacity influenced by?

1) RBC count, the normal is 5 million/microliter

2) Concentration of Hb, the normal concentration is 14d/dL

3) Hematocrit, the packed RBC volume obtained by centrifuging.

• Normal is 42. Men it can be 40-50, women 38-46. Anything less than 37 is considered anemia

Hb saturation in blood

The ratio of oxygenated hemoglobin (oxyhemoglobin) to the total amount of hemoglobin in the arterial blood (lungs →tissues). Hb is 99% saturated with O2. In venous blood (tissues → lungs) 70% of Hb is saturated with O2, the rest is deoxyhemoglobin.

A person can tolerate down to 30% saturation, but for long periods, they need 50%

What is anemia? How can it be diagnosed?

Anemia is the compromised ability to carry O2, it is diagnosed using indicators like low RBC count (less than 4 million/microliter), low hemoglobin concentration (less than 12g/dL) or inadequate hemoglobin (quality problem)

What are the potential causes of anemia?

Low RBC count

• Decrease in production

  • Dietary deficiencies

    • Fe: Not eating enough Fe or absorbing enough due to increase of Hepcidin production.

    • B12: Not enough enough V B12 or cannot produce intrinsic factor to absorb, leading to a decrease in RBC production

    • Folic acid: an important vitamin essential for RBC production

  • Bone marrow disease

  • Inadequate EPO, potential damage to kidney

• Increase in destruction

  • Weakened RBC: hereditary spherocytosis, a genetic disorder where RBCs break easily

  • Increase of blood loss: menstruation, bleeding ulcer, or acute blood loss

Insufficient Hb

• Generally a Fe deficiency and not producing enough Hb

Inadequate Hb

• ex) sickle cell anemia where there is a mutation in Hb gene and it does not fold correctly. The misshapen Hb results is misshapen RBC that cannot efficiently carry O2

How are anemias classified?

Anemias are classified by size and color

Cell size: usually caused by defects in DNA synthesis

• Microcytic: below 82

• Normocytic: 82-92

• Macrocytic: above 92

Hb concentration: usually caused by defects in RNA synthesis

• Hypochromic: below 32

• Normochromic: 32-36

• Hyperchromic: above 36

Microcytic, hypochromic anemia. What is it? What causes it? What is its prevalence in the US?

Iron deficiency anemia, the most prevalent. The main cause is Fe deficiency but it can also be due to chronic infections because the liver sequesters Fe to hide from pathogens, as most require Fe for survival.

Women: 20%

Children: 20% because kids grow fast and many times they do not consume enough Fe as they increase their production of RBC

Men: 3%

Pregnancies: 50% mother is sharing Fe with baby and its easy to not eat enough

Macrocytic, normochromic anemia. What is it? What causes it?

Pernicious anemia, characterized by defective DNA synthesis that results in ineffective erythropoiesis, causing an unusually large number or enlarged stem cells which mature into large erythrocytes. The defects in DNA synthesis are caused by vitamin B12 deficiency, whether the person is not eating enough or has no intrinsic factor to absorb (also folate deficiency). Since RNA synthesis is unaffected Hb concentration remains normal

What blood loss can cause anemia?

Blood loss of 2-4 ml/day is sufficient to cause anemia. (hemorrhoids, etc.)

Myeloproliferative disorders: To many

RBCs

Polycythemia Vera (PV) “Many cells in the blood.”

Causes erythopoiesis, an excessively large number of RBC. Considered a neoplastic disorder characterized by an abnormal proliferation of stem cells.

• Ok, in athletes who train in high altitudes, because they are healthy

• Abnormal: In smokers, they inhale less O2. Their kidneys detect this, secrete EPO, stimulating erythropoiesis. So more RBC are made, but they do NOT carry more O2, but have more RBC, increasing blood viscosity and probability of thrombi.

Myeloproliferative disorders: To little

RBCs

Anemia is the compromised ability to carry O2, it is diagnosed using indicators like low RBC count (less than 4 million/microliter), low hemoglobin concentration (less than 12g/dL) or inadequate hemoglobin (quality problem)

What is the normal WBC count? What is it called if its under? over?

Normal WBC count is 5000 to 10000 WBC/μl. If its under 5000μl its called leukopenia, if its over 10000μl it is called leukocytosis.

Which WBCs are granulocytes? agranulocytes?

G: Neutrophils, Eosinophils, and Basophils

A: Lymphocytes and Monocytes

What is diapedesis?

WBCs that can squeeze through BV into the tissue to fight infection or injury

Neutrophils: percentage, appearance, and functions

60-70%

multilobed nucleus and neutral stained granules

First responders phagocytes capable of diapedesis. The numbers of neutrophils increases during bacterial/acute infections. They have a very short lifespan, lasting from seconds to minutes, reason why 75% of production is WBC as they make 60-70% of them.

Lymphocytes: percentage, appearance, and functions

20-25%

smallest in size with a large nucleus with a thin rim of cytoplasm

Myeloid and lymphoid origin, lymphocytes are capable of diapedesis and have three different subtypes: natural killer cells (nonspecific), B cells, and T cells (specific). The main functions of lymphocytes is immunomemory, organ rejection, and allergic reactions.

Lymphocytes: NK cells, T cells, and B cells

NK cells: rapid-response lymphocytes of the innate immune system that detect and destroy virus-infected cells and early-stage cancer cells

T cells: myeloid origin, mature in thymus, and migrate out to lymph tissue.

• Helper T cells: activate cytotoxic T cells and B cells

• Cytotoxic T cells: fight virus infected or cancer cells, binding and secreting chemicals to kill them

B cells: myeloid origin, mature in RBM, migrate out to lymph nodes

• produce antibodies, fighting specific infections by binding onto antigen

Lymphocyte Functions: immunomemory, organ rejection, and allergic reactions.

immunomemory: when antigen is met B and T cells produce memory B and T cells that remained stored in your body, so when the antigen is met again a quick response is amounted and possibly may not even get sick

organ rejection: a downside of immunomemory in which it amounts an immune response against an organ transplant (why immunosuppressants are taken)

Causes allergies: stimulates inflammation response against an antigen that normally should not cause a response

Monocytes: percentage, appearance, and functions

3-8%

largest in size with a u or bean shaped nucleus

Myeloid and lymphoid origin, monocytes are the strongest and longest lasting WBC. They are stronger, more effective, but slower phagocytes than neutrophils that fight infections. When a person is fighting a chronic infection numbers increase.

When monocytes migrate out from blood to tissues (diapedesis) they become macrophages.

Eosinophils: percentage, appearance, and functions

2-4%

bilobed nucleus with reddish- pinkish (eosin) granules

Capable of diapedesis and fighting parasitic worm infections by binding onto them and secreting chemicals. They also protect against hypersensitivity by making an antihistamine (fighting allergies). Numbers increase when fighting a parasitic worm infection

Eosinophils, what has been noted between parasitic infections and allergies?

Found that areas where there are a lot of parasitic worm infections there is rarely any allergies, but places where parasitic worms have been eliminated there is a spike of allergies

Basophils: percentage, appearance, and functions

0-1%

s shaped nucleus typically hidden by dark purple stained granules

Only WBC not capable of diapedesis because mast cells in the tissue do the same thing. Basophils function to enhance allergic (inflammatory) response by releasing histamine to dilate blood vessels, serotonin to increase capillary permeability, and heparin as an anticoagulant, preventing the clotting of blood.

What is leukopenia?

When the Total WBC count is lesser than 5000μl, it is leukopenia, a pathological condition that is NEVER normal because it means the person is immunocompromised. As the individual does not have enough WBCs to fight an infections we begin to see some not normally seen in people that are not immunocompromised.

What may be some causes for leukopenia?

It could be hormones: the body is not producing enough leukopoietin to stimulate pluripotent hematopoietic stem cell or colony stimulating factors to specify generic WBC

Bone marrow disease

HIV: virus that infects lymphocytes and destroys them

Chemotherapy: because it destroys any cells that divides rapidly, therefore affecting WBCs that produce at a greater rate (75%)

What is leukocytosis? Is it good or bad?

When the total WBC count is greater than 10000μl. Leukocytosis can be both good and bad. It’s good when a person is fighting an infection. It is bad when it’s leukemia (bone cancer), where there is uncontrolled proliferation of WBCs, but they are not effective. Leukemia has two origins: myeloid (problems with RBCs, WBCs, and platelets) and lymphoid (problems with WBCs)

What are thrombocytes? Normal amount? Lifespan? Function

Thrombocytes are small fragments of megakaryocytes produced in RBM. Their normal value is 200,000 - 400,000 / microliter and have a 5 - 9 day lifespan. They are an active tissue that is anucleate but contains ER, giving platelets the ability to produce clotting chemicals. Its function is clotting, activated by chemical signals

What is thrombocytosis? Good or bad?

Increased blood clotting.

Okay when the person is injured, as it prevents blood loss

Bad when its thrombosis because clots begin to form that can either be stationary or travel and and block BV

What is thrombopenia?

Decreased clotting, the individual loses a lot of blood easily

The cause is hemophilia, a genetic disorder in which the person is missing of CSF

How is the human system “closed” compared to an “open” system?

The circulatory system is a closed system where blood is pumped through vessels to tissues and returns to the heart without necessarily leaving the system.

Arthropods in comparison have an open system where the heart pumps hemolymph (interstitial fluid) and the BV are open.

What is the function of the heart? These states are determined by? What does it consist of?

The heart functions as a pump, it goes through a series of contractions (systole) and relaxations (diastole) in order to function. These states are governed by Boyle’s Law, where pressure is inversely proportional to volume.

The heart consists of four chambers: Two atria, the thin walled receiving chambers. Two ventricles the thick walled pumping chambers. The LV has the thickest wall as it pumps blood to the rest of the body.

What is systole? diastole?

Systole is contraction, it pumps blood out as the volume decrease the pressure increases

Diastole is relaxation, in this state chambers are filling up with blood by increasing the volume and decreasing the pressure

What are the two circuits?

Pulmonary circuit: from the right side of the heart to the lungs

Systemic circuit: from the left side of the heart to the rest of the body

What is the pathway of blood?

Superior (head and arms) and inferior vena cava (lower portions) deliver deoxygenated blood (70%) to the → RA → Tricuspid/Right AV valve → RV → Pulmonary SL valve → Pulmonary artery → in the pulmonary capillaries blood is oxygenated (99%) → pulmonary veins → LA → Bicuspid/Mitral/Left AV valve → LV → aortic SL valve → aorta → arteries → arterioles → capillaries → venules → veins → cycle repeats

What determines blood flow?

Pressure differences dictate the flow of blood which ALWAYS flows from HIGH to LOW pressure

How is one way flow of blood ensured?

Valves ensure one way blood flow and prevent backflow.

Atrioventricular (AV) valves: Located between the atria and the ventricles they are cusps that are attached to the papillary muscles via chordae tendineae. So when ventricles contract chordae tendineae pull on the cusps preventing the backflow of blood. On the right side is the tricuspid or right AV valve with three “flimsy” cusps. On the left side is the mitral/bicuspid/left AV valve made of two sturdy cusps that withstand the high pressure of the LV.

Semilunar (SL) valves: Between the ventricles and the arteries.

How are the four chambers separated?

Each chamber is separated by septa.

Interatrial septum: Made of cardiac muscle, electrical signals can still pass, it separates the atria to prevent the mixture of blood

Interventricular septum: Made of cardiac muscle, electrical signals can still pass, it separates the ventricles to prevent the mixture of blood

Atrial ventricular septum: Made of connective tissue, it separates the atria from the ventricles and prevents the direct passage of AP between them.

Due to contraction and relaxation of the atria/ventricles what type of pressure do we have?

We have systolic and diastolic pressure

Atria SP and DP

5/0 mmHg

The systolic pressure (SP) of the atria when the contract is 5mmHg. During atrial systole or “atrial kick” the last 1/3 of blood is pushed into the ventricles that are is diastole

The diastolic pressure (DP) of the atria when they relax is 0mmHg.

Ventricles SP and DP

RV: 15/0mmHg LV: 120/0mmHg

The SP of the ventricles has to be greater than the arteries so blood flows

The DP has to be 0mmHg so they can receive blood from the atria

Venous Pressure: Why is it so low? What does this ensure?

Much of the initial pressure generated by the heart decreases as blood travels through the systemic circuit and lost once it enters the veins. The normal range is 4-8 mmHg and it has to be above zero to ensure flow back into the heart, specifically the RA.

Where is oxygen exchanged? Whats the % saturation?

Oxygenated blood from the lungs to tissues is 99% saturated with O2 (pulmonary system). Deoxygenated blood from the tissues to the lungs is 70% saturated with O2 (systemic system).

To survive a person requires 30% saturation of O2. For a prolonged period of time the person requires 50%. W

What is a portal system? What three do we have?

A portal system is when there is two capillary beds in succession: artery → capillary → portal vessel → capillary → vein

Digestive system: hepatic portal vein

Urinary system: efferent arteriole

Hypothalamus and pituitary:

What is the heart mostly composed of?

The heart is 99% cardiac muscle and 1% epithelial and connective tissue

How are cardiomyocytes connected? How can the heart contract?

Cardiomyocytes are electrically coupled via gap junctions, as the connexon proteins connect adjacent cells, allowing the passage of ions. As ions pass from one cell to the other it depolarizes the next.

As connexons are channels, ions can flow in either direction, determined by the chemical gradient. Meaning that the heart can contract in either direction as it depends on which cardiomyocyte initiates contraction and spreads it.

What type of network are cardiomyoctes?

A syncytium, a network of interconnected cells that work together as a synchronized unit as cardiomyocytes are electrically joined via intercalated discs they directly pass electrical signals. Allows for coordinated systole and diastole

All cardiomyocytes are?

All cardiomyocytes are autorhythmic. They can all generate AP but some generate them faster than others and inhibit the AP through overdrive suppression

What is the conductive system?

The conductive system is made up of cardiac nodes, special clusters of cells that make up a small portion of heart tissue (~1%). They can spontaneously generate AP at a higher and faster pace than other cardiomyocytes

What is the pathway through the conduction system?

The fastest pacemaker, which sets the sinus rhythm, is the sinoatrial (SA) node, located in the walls of the RA. Once the SA node generates AP, it causes a wave of depolarization in the atria. → The wave of depolarization reaches the AV node, which pauses conduction to allow the atria to contract the final 1/3 of blood into the ventricles → Depolarization continues to the Bundle of His → Splits into the Left and Right bundle branches, traveling down the interventricular septum towards the apex of the heart → From the apex, depolarization spreads upwards through the Purkinje fibers into the ventricles causing them to contract from the tip to an upward direction, ejecting blood into the arteries.

Nodal Tissue Inherit rates

SA node: 70-100 BPM, is the pacemaker, sets the sinus rhythm

• The SA node suppresses all other nodes through overdrive suppression. As the fastest node it inhibits slower nodes because it hyperpolarizes them before they can generate their own AP. (syncytium)

AV node: 40-50 BPM

Ventricular nodes: 20-30BPM

If the SA node is the pacemaker, why do we need other nodes? How can it fail?

We have multiple nodes as a backup system if the SA node fails. What can cause it is a myocardial ischemia, a lack of O2 can lead to the death of cells causing a myocardial infarction.

What would be the most important node? Why?

The AV node would be the most important as it passes electrical signals from the atria to the ventricles. If the SA node fails, AV node takes over. The HR will decrease but the time for the ventricles be filled extends.

SA node does not pass the signal to the ventricle

V node would cause the heart to contract in all sorts of ways

What is a premature ventricular contraction? What do people feel? Causes? Concerning?

PVC occurs when the SA node fails to suppress other nodes (AV or V node) through overdrive suppression. As a result, one of the slower nodes fires its own AP before the signal of the SA node can reach it, causing a long pause while waiting for the next wave. Because the ventricle beats early, the filling time is shortened, and the volume of blood is lowered.

People do not feel the early contraction but the long pause that follows as the heart waits for the next regular wave of depolarization

Causes

• Low HR, like in athletes or a normal person, where reduced SA node firing leads to a lack of overdrive suppression

• Stimulants: Coffee, cocaine, or other drugs

• Ventricular irritability or disease

Generally not concerning, it’s normal for a PVC to occur every once in a while, but it gets concerning when it’s frequent.

Heart Rates: Normal, elevated, and lowered

Heart rate is measured using the R to R interval

• Normal resting HR: 60-100BPM

• Bradycardia: HR<60BPM

  • Can be genetic: an inherently slow SA node, or an active PSNS

  • Exercise: the heart becomes stronger and more efficient, increasing the stroke volume and decreasing the HR to maintain the CO

  • Disease: heart attack, fatigue

• Tachycardia: HR>100BPM

  • Normal when genetic, due to gender (females have a greater HR), size (smaller the faster the HR), and exercise

What is an ECG? What does it measure? What activity is it reading out on? What principle does it rely on?

The ECG relies on the principle of volume conductance. When the heart depolarizes it forms a dipole moment as ions go into cells and change the polarity. The change of polarity can be conducted through the body fluids because of the ions within them. So the flow of ions in the heart pulses onto the fluids of the body, as a result the electrical activity of the heart can be measured by electrodes. W

Why should a person sit still when getting an EKG?

We have more skeletal muscles than cardiac muscle, and when they contract, they generate action potentials that overcome the signal of the heart.