Bio Chapter 32- Circulation

Two examples of typical circulatory layouts- see slide 9

*Note the complete separation of pulmonary and systemic circuits in mammals and birds

Simplified diagram of circulatory system

*See notes

At the arteriole end of the capillary bed, there is typically a net ___ of fluid; at the venule end, there is a net ___ of fluid

*See slide 32 -Loss, gain -If the force pulling liquid in is the same as the force pushing liquid out, there is no net change -Since osmotic pressure is constant, the change in blood pressure determines whether fluid is lost or gained -Blood pressure higher at arteriole end- net secretion of fluid -When osmotic pressure is greater than blood pressure, there is a net uptake of fluid -Overall, some fluid is lost- it can enter the blood at a later point

Oxygen dissociation curve

*See slide 39 -O2 is released from hemoglobin readily when O2 concentration is low, but not when it is high -PO2 is highest in the lungs, so "loading" of hemoglobin occurs there -"Unloading" is a consequence of decreases in PO2 by tissues that use O2 -Not linear- sigmoidal in nature. The slope is low at the bottom, highest above that, and levels off at the top -X axis- partial pressure of O2 in the blood -This increases the amount of oxygen that binds to hemoglobin -Limited based on the amount of hemoglobin present and how many of the sites on the hemoglobins are already bound -Exercise, start losing oxygen. When all of the hemoglobin has 4 oxygens bound, it can give up oxygen easily. When partial pressure of O2 in the blood drops, cells are using oxygen. You need more oxygen to come off of hemoglobin. When you get to low partial pressures of oxygen, the rate at which it comes off of hemoglobin increases *Slope shows that when you need oxygen, it will come off of hemoglobin really fast

General strategy

*See slide 6 -In closed systems, a heart pumps oxygenated blood into the arteries, which branch extensively to carry the blood away from the heart into the peripheral tissues -Heart pumps oxygenated blood into the arteries -Arteries will branch -The branching causes the vessels to become smaller and smaller -Veins go from more branched to less branched -Veins take deoxygenated blood back to the heart

What propels the blood?

-A beating heart propels the blood

Steps of the cardiac cycle

-A cardiac cycle is a complete heartbeat. It consists of two main phases: systole and diastole, which are defined by whether the ventricles are contracted or relaxed. -Diastole- ventricles relax -Systole- ventricles contract -During the cycle, valves open and close, producing the heart's lub dub sound -During diastole, the ventricles relax. As they relax, they expand and fill with blood that flows in from the atria -The atria contract and top off the ventricles with blood -During systole, the ventricles contract. The increasing pressure in the ventricles closes the atrioventricular valves, causing the "lub" sounds -Pressure builds up in the ventricles until the pulmonary and aortic valves open and blood is pumped out through aorta and pulmonary artery -As the ventricles relax again, the pressure in the ventricles falls -Since the pressure is now greater in the aorta and pulmonary arteries, the aortic and pulmonary valves slam shut, creating the "dub" sound -As the ventricular pressure continues to drop, the AV valves open again, and the cardiac cycle continues -Heart acts as a pump, providing the force to circulate blood throughout the body -As the ventricles contract, pressure goes up *Pressure of the ventricles opens the valves and pushes blood into aorta/pulmonary artery *The decrease in ventricular pressure slams the valves shut during diastole -Valves opening and closing are a consequence of the pressure changes that happen in the heart

Heat conservation

-Arrangement of blood vessels can help animals conserve heat -Animals use a countercurrent exchange mechanism to exchange heat -Heat and blood flow in opposite directions -The heat is coming from the artery (carries blood away from the heart to the rest of the body) -Muscles contracting uses ATP, and that generates heat -The heat enters the foot. When the blood carrying heat gets to the base of the foot of an animal walking on ice, some of the heat is lost and radiates out. There's not a lot of distance between the foot and the ground -Distance between vessels can vary -Rather than lose all heat, exchange heat with the capillary next to it and prevent it from getting lost -Gradient of heat- net flow of heat from the artery into the vein *Bringing vessels close together allows heat to move from the warmer blood to the colder blood- this relies on gradients.

Arteriole and venule ends

-Arteriole end- loss of fluid (due to blood pressure at the arteriole end) -Venule end- reuptake of fluid -Two ways to take fluid back into the circulatory system: 1. Reuptake at the venule end 2. Reuptake by lymphatic circulation *Most of the liquid that is lost will be taken back up by the same capillary bed. Otherwise, it is taken up by the lymphatic system -If the amount of fluid that is reabsorbed is the same as the amount of fluid that is secreted, there is a net balance of zero

Valves

-Besides the two atrioventricular valves, two additional valves include: -The pulmonary valve -The aortic valve *The pressure of the the fluid allows valves to open and close

Cooperative binding

-Binding of oxygen to hemoglobin makes it easier for another to bind- called cooperative binding

Bird and mammalian circulatory systems

-Birds and mammals have four-chambered hearts: two atria and two ventricles

Blood pressure

-Blood pressure forces water and small solutes out -Blood pressure is stronger at the arteriole end

Catheter

-Can put a catheter through the aorta and inject dye into the chamber of the heart -Dye goes through all of the arteries -Can view where the dye has gone -If there is a blockade, the dye will not go all the way down the vessels

A closer look at solute and gas exchange

-Capillaries are highly permeable to many blood solutes, such as glucose, O2, and CO2 -This is where materials are exchanged with the surrounding tissues -Capillaries are NOT very permeable to large proteins, which stay in the blood and contribute to its osmotic pressure -Capillaries are so permeable that fluid can exit or enter -The relative balance of blood pressure (outward) and osmotic pressure (inward) determines whether there is a net loss or net gain of fluid from the capillary bed -If one is greater than the other, you get a net flow in one direction -More fluid is lost at the arteriole end, net uptake at venule end

Kwashiorkor

-Coincides with very low protein in blood -Fluid accumulating in the abdomen. -Fluid has been pushed out of the capillary beds because of starvation -The body tries to get every source of energy it can (protein in the blood) -Protein concentration goes down -Water is not able to go back into the circulatory system

Basic mammalian heart anatomy- see slide 15

-Deoxygenated blood enters the right side of the heart and into the atrium first -It goes from the right atrium to the right ventricle -Next, because the blood is deoxygenated, it will go to the lung -The artery that takes the blood away from the heart and to the lungs is the pulmonary artery -Lung will cause gas exchange- add oxygen, remove CO2 -Return the oxygenated blood back to the heart before it gets pumped to the rest of the systemic circuit -It enters the left side of the heart through pulmonary veins (bring blood to the heart) -Blood goes to the left atrium and then to the left ventricle -Oxygenated blood gets pumped to the rest of the systemic circuit -It will go through an artery (carries blood away from the heart) called the aorta -AV valves (atrioventricular valves) separate the atria from the ventricles -Blood goes through systemic circuit. Has to go through veins (bring blood to the heart). Enters through the vena cavae *Right side of the heart receives deoxygenated blood - goes to pulmonary circuit *Left side of the heart receives oxygenated blood - goes to systemic circuit

Diastole

-Diastole is when the ventricles relax -Atria contract for most, but not all, of diastole -Blood goes from the atria to the ventricles -The valves have to be open. We need an increase in pressure in the atria. If the pressure in the atria exceeds the pressure in the ventricles, there is an opening of the valves between the two chambers -The pressure in the atria increases until it is large enough for the valves to open

O2 transfer by hemoglobin

-Equilibrium between gaseous and dissolved form of oxygen -Oxygen is not very soluble in liquid -Add another equilibrium- aqueous water associates with a protein called hemoglobin -Hemoglobin is bound to dissolved oxygen -O2(g) --> O2 (aq) --> Hb-O2(aq) -A central function of blood is transporting O2 and CO2 -Hemoglobin (Hb) is the most common O2-carrier -It can also bind some of the CO2. In what form is most of the CO2 transported in the blood? -One hemoglobin protein can bind up to four oxygen molecules -When O2 concentration (partial pressure) is plentiful, hemoglobin holds onto O2 molecules tightly -When it is sparse, binding is much weaker

Exercise

-Exercise increases contractile force and beats per minute (BPM) -As you exercise, you need more blood circulating faster through your body because the cells need more oxygen -The ventricles can adjust the force of their contractions to meet the demands of exercise -When cardiac muscles are stretched more due to increases in returning volume, they contract more forcefully -If more blood is returning to the atria, the atria and the ventricles will contract faster and stronger -The heart's beats per minute (BPM) will also increase

Fish circulatory systems

-Fish hearts are two-chambered: they have an atrium and a ventricle *Blood always flows from the atria to the ventricle

Solute and gas exchange graph

-Graph with blood pressure, velocity, and total area -Velocity goes down as you go from the large arteries to the capillary bed. There is more branching, the diameters are smaller. The smaller the capillaries become, and the more branching you have, the less velocity the blood has as it goes through the capillaries -Blood pressure also goes down as you go from the large arteries to the capillary bed. It stays low in the veins -Total area goes up because of the branching

Mammal and bird circulatory layouts

-High metabolic demand- flow in fish is too slow to get oxygen to the systemic tissues fast enough -Systemic tissues return O2 poor blood to the heart -The heart pumps the blood first to the lungs and then back to the heart -When it comes out of the heart, it can go to the systemic tissues without having to go through the pulmonary circuit -Speed going to the lungs and systemic circuit are both faster

How would a decrease is blood plasma protein concentrations affect fluid secretion and/or reuptake from capillary beds?

-If you decrease blood plasma protein concentration, there is a decreased force of fluid going in. The osmotic pressure goes down -Less water moving from outside to inside because there is lower force pushing water in if the protein concentration goes down -More fluid is outside, so there is a net loss of fluid from the capillary bed -Increase osmotic pressure- more protein inside- more fluid comes in -Decrease proteins- less fluid comes in

Closed systems

-In closed systems, circulatory fluid (blood) is always enclosed within vessels and its not continuous with the tissue fluid -Humans have closed circulatory systems

Open systems

-In open systems, blood vessels are open at one end -The circulatory fluid leaves the vessels and moves between cells and tissues before returning to the heart -An open system is open at one end -In an open system, the circulatory fluid leaves the blood vessels and becomes part of the fluid in the organism (tissue fluid) -The blood in the capillaries/vessels and the tissue fluid mix -Heart distributes fluid -Small crevices where blood finds its way back to the capillaries and gets pumped again -Open circulatory systems are found in arthropods and mollusks

One-way valves assist in return of blood of the heart

-In veins, blood pressure is nearly zero -Contraction of skeletal muscles squeezes veins and helps propel the blood back to the heart -Veins have one-way valves to prevent backflow -Muscles contracting and valves allowing one-way flow back to heart help blood move from leg back to heart fast enough that you don't run out of oxygen -Prolonged standing without muscle contractions can become problematic -When you are standing, blood goes down to your foot. The velocity of the blood going through the capillaries in the foot is really low. It has to come back up to be pumped in the right side of the heart. It has to be propelled up. You need help from your muscles -Muscles constrict around some of the major vessels and force the blood in the veins to move

Atrioventricular (AV) node

-Once the atria contract, the ventricles have to contract -Electrical signals in the atria then stimulate the atrioventricular (AV) node, which initiates contraction of the ventricles -Atria have already contracted -Electrical signal flows through the conducting system -The coordinated electrical signal allows the ventricles to contract in unison. This happens for every single heartbeat/cardiac cycle

Osmotic pressure

-Osmotic pressure is caused by large proteins remaining in the blood, which pulls water back into the capillaries -Osmotic pressure is CONSTANT along the capillary

Advantages of having separate circuits

-Oxygenated blood can be distributed at a higher pressure and flow than is possible in fishes -Blood in each system cannot mix. The systemic circuit always receives blood with higher O2 content -Pulmonary and systemic circuits can operate at different pressures

Pacemaker cells

-Pacemaker cells are located in the sinoatrial node (SA) node of the right atrium -Electrical signals initiated here spread to the left atrium, stimulating its contraction -This causes both atria to contract simultaneously *Simultaneous contraction of atria occurs first -If the electrical signal doesn't work, one atrium will contract without the other. This can cause atrial fibrillations

Sound of a heartbeat

-Physicians can use the sound of someone's heartbeat to gauge whether there is a problem with the valves -Blood can pool or not go through the valves correctly

Changes in pressure- get notes from Megan?

-Pressure is caused by the blood in the ventricles -Pressure increases as ventricles contract -The beginning of systole is when the pressure is going to be low because all the blood has just been pumped out at the end of systole -Will go up, but not instantaneously. It takes time for the chamber to contract -Stay for a short period of time near a maximum pressure. That is the time at which the ventricle is maximally contracted and the blood is being pumped into the aorta or pulmonary artery -Valves open, ventricle starts to relax, and pressure starts to go back down -As the volume increases, relative to the pressure in the aorta or pulmonary artery, the pressure is now lower -When the pressure increases, this will open the valve. When the pressure decreases, the valve closes because the pressure in the artery (into which the blood is going) is greater

Ventricle in fish

-Receives blood from the atrium and sends it to the gills to become oxygenated -From the gills, it goes to the rest of the body

Atrium in fish

-Receives oxygen-depleted blood from the body that is returning from the systemic tissues

Smooth muscles

-Smooth muscles allow regulation of vessel diameter -Arteries and veins (but not capillaries) are surrounded by connective tissue and smooth muscle -The smooth muscle can contract or relax in order to expand (dilate) or constrict the diameter of the vessels as needed -Blood goes back the brain, and consciousness is restored -Layer of smooth muscle around your vessels -Sometimes, you have to change the diameter of the blood vessels -Constrict blood vessels in the peripheral body- blood pressure increases. More resistance for the heart to pump against -Dilation- decreased blood pressure -Blood vessels dilate to cool down- complexion of skin becomes pink- radiating heat

Solute and gas exchange - see slide 27

-Solute and gases are exchanged between blood and tissues in the capillaries -Each artery splits into many capillaries, which together have a large surface area -Blood pressure and blood flow is lower through the capillaries *Know how blood pressure and velocity are related to surface area -Large artery - small artery - arterioles - capillaries (smallest type of vessel) - venules - veins -The capillary has an anteriole end and a venule end

Do all animals need circulatory systems?

-Some organisms don't need circulatory systems, if they are simple enough -For example, single-celled organisms exchange nutrients, wastes, etc. directly with the external environment

Starling's forces

-Starling's forces are two opposing forces that affect water balance in the capillaries -Blood pressure -Osmotic pressure

Systemic tissues

-Systemic tissues are all tissues and organs other than the breathing organs

Systole

-Systole is when the ventricles contract -As the valves open, the pressure in the ventricles increases during systole

"Lub dub" sound of the heartbeat

-The "lub dub" sound of the heartbeat heard with a stethoscope is caused by the repetitive closing of the valves

Arteries

-The arteries are vessels that always carry blood away from the heart (A = away) -The arteries carry oxygenated blood to the tissues -Tissues use the oxygen during aerobic respiration. This deoxygenates the blood -Blood is returned to the heart to be reoxygenated, either in the gill of a fish or the lung of a human

Standing for a prolonged period of time without muscle contraction

-The blood is not getting to the upper parts of your body, including the brain -Body lays you flat (you faint) and causes blood to move up to where it needs to go

Breathing organs and systemic tissues

-The breathing organs and systemic tissues are usually, but not always, in series

Breathing-organ circuit (pulmonary circuit)-

-The breathing-organ circuit is the circuit that includes arteries and veins carrying blood between the heart and breathing organs -Take blood to and from the lungs

Coronary circulation

-The coronary circulation comprises the arteries, veins, and capillaries that supply blood to the heart muscle cells (since heart cells also need oxygen!) -Coronary circulation refers to the blood vessels that supply blood to the heart muscle itself -Coronary arteries branch off of the aorta -Blockage of the coronary arteries by plaques can cause death of heart muscle cells. The heart will not beat correctly and causes an atrial fibrillation. If it is severe enough, it can cause heart attacks -Coronary disease is the number 1 killer in this country

Cardiac cycle

-The cycle of cardiac contraction and relaxation during one heartbeat is called the cardiac cycle -Cardiac cycle- contraction and relaxation of the atria and the ventricles -The cardiac cycle has two phases: diastole and systole *Diastole and systole are from the perspective of the ventricle ONLY -The atria contract just before the ventricles in order to add blood volume to the ventricles -The two atria and the two ventricles contract at the same time, synchronously

Blood flow through the human heart

-The human heart has four chambers -O2-depleted blood enters the right atrium, then proceeds to the right ventricle -Oxygenated blood returns via pulmonary veins to the left atrium -Oxygenated blood proceeds from the left atrium to the left ventricle -From there, it enters the systemic circulation

In some types of heart disease, the left AV valve constricts and impedes blood flow. 1. How might you expect this to affect the pressure in the left atrium?

-The left AV valve separates the left atrium from the left ventricle -If you constrict the AV valve over time, the pressure in the left atrium will go up -What impedes the flow of blood into the ventricle is the smaller opening between the atrium and the ventricle. -Unless the pressure/force of contraction of the ventricle increases, it will back up into the atrium. Every time the atrium contracts, it has more blood to pump through it and the pressure increases.

Left atrium and left ventricle

-The left atrium receives O2-rich blood from the lungs -The left ventricle pumps O2-rich blood into systemic tissues

Right atrium and right ventricle

-The right atrium receives O2-depleted blood from the body -The right ventricle pumps O2-depleted blood through the lungs

In some types of heart disease, the left AV valve constricts and impedes blood flow. 2. Sometimes, a consequence of this valve constriction is that fluid builds up around the capillaries in the lungs. What is the likely cause of this fluid buildup?

-The source of blood entering the left atrium is coming from the pulmonary veins (they come from the right and left lungs) -Fluid trying to enter the left atrium is facing higher pressure in the atrium and starts to back up -Pressure in the pulmonary veins increases -Fluid is present in the lungs because the blood pressure exceeds the osmotic pressure. Net influx of fluid from the capillary bed into the surrounding tissue -Capillaries are very close to the alveoli in the lung. Membranes are very thin. If fluid is leaking out, fluid will go between the alveoli and the capillaries. This slows the rate of diffusion from the gaseous environment in the alveoli into the blood -Changed the medium of diffuse- has to diffuse through a layer of liquid and make it hard to breathe *Diffusion coefficient changes- hard for oxygen to come into the lungs

Systemic circuit

-The systemic circuit includes arteries and veins carrying blood between the heart and the systemic tissues

Fish circulatory layout

-The systemic circuits take the oxygenated blood and use the oxygen (because the muscles of the fish need oxygen) -They return the O2 poor blood to the heart -That blood goes through the gills, where it is reoxygenated (often occurs through countercurrent exchange mechanisms between the water and the blood- oxygen comes from water) -The heart pumps the blood through the gills, and since there is a lot of branching as the blood enters the gills, the speed of the blood coming out of the gills is slower than the blood going into the gills. Putting blood into smaller capillaries (want distance between blood and water to be as small as possible)

Pulmonary valve

-The valve that allows blood to enter the pulmonary arteries

Aortic valve

-The valve that represents the aorta

Fluid lost from the capillaries

-There is a slight excess of fluid that is lost from the capillaries compared to what is returned -However, this fluid is eventually returned to the blood by the lymphatic system -It is a separate fluid transport system, but eventually mixes with blood -There is more fluid that leaves at the arteriole end vs. the venule end. There is an overall loss of fluid in the capillary. -Loss of blood in the capillary bed- blood volume decreases. BUT you reabsorb the net fluid that is lost by allowing that fluid to join another circulatory system called the lymphatic system. The fluid inside the lymphatic system is called lymph fluid

Atrioventricular (AV) valves

-Two atrioventricular (AV) valves prevent backflow of blood from ventricles to atria

Vericose and spider veins

-Valves in veins allow blood to flow both ways- blood pools and veins get larger -Blood is not going back to the heart as normal

Veins

-Veins return blood to the heart

Can the heart beat continuously on its own?

-Yes! -A subset of modified muscle cells called pacemaker cells can initiate heart muscle contractions on their own. -Pacemaker cells can send an electrical system to neighboring cells and cause them to beat -No nervous system input is required for the heart to beat! Nervous system input can modify the heart beat -BUT the heart is still under the control of the nervous system. If you get scared, the heart will beat faster- caused by nervous system input

The blood transports...

...O2 and CO2

Valves prevent...

...backflow -Two atrioventricular (AV) valves prevent backflow

Circulatory systems can be...

...open or closed

One-way valves assist in...

...return of blood to the heart

Many key processes occur in the...

...vascular system

Why do animals need a circulatory system?

1. The circulatory system delivers oxygen and nutrients to cells 2. The circulatory system distributes heat and hormones -Heat is distributed by warm blood to tissues 3. The circulatory system removes waste products of metabolism

Transposition of the great arteries- drawing exercise

1. Which structure or region contains blood with the relatively highest partial pressure of oxygen? 2. Which sequence best represents the flow of blood in a baby with TGA? -Result: Deoxygenated blood circulates through the right side of the heart and systemic circuit -Oxygenated blood circulates through the left side of the heart and pulmonary circuit 3. Babies born with his disorder can live for a short period of time- some of the blood from the aorta mixes with the blood from the pulmonary artery because they are fused at the beginning of life

A red blood cell has just arrived in the right ventricle of a mammal. Where will it go next?

Pulmonary artery

Great arteries

There are two great arteries leaving the heart: -Pulmonary artery -Aorta