Ch. 7: The Cardiovascular System Flashcards
what are the three components of the cardiovascular system?
- heart
- blood vessels
- blood
what does the heart act as?
a pump: distributing blood throughout the vasculature
what are the 3 components of the vasculature?
- arteries
- capillaries
- veins
what is the basic two step summary of how blood flows in the heart and vasculature?
- after blood travels through veins, it is returned to the right side of the hart where it is pumped to the lungs to be reoxygenated
- then, the oxygenated blood returns to the left side of the heart where it is once again pumped to the rest of the body
defn: heart
defn = a four-chambered structure composed predominantly of cardiac muscle
is the heart actually a pump?
no it is actually composed of two pumps supporting two different circulations in series
defn: pulmonary circulation
the right side of the heart accepts deoxygenated blood returning from the body and moves it to the lungs by way of the pulmonary arteries
this is the first pump of the heart
defn: systemic circulation
the left side of the heart receives oxygenated blood from the lungs by way of the pulmonary veins and forces it out of the body through the aorta
this is the second pump of the heart
defn + func: atria
thin-walled structures where blood is received from either the venae cavae or the pulmonary veins
push blood into the ventricles
what kind of blood is received to atria from the venae cavae?
deoxygenated blood entering the right side of the heart
what kind of blood is received to atria from the pulmonary veins?
oxygenated blood entering the left side of the heart
what happens after the ventricles fill with blood?
they contract to send blood to the lungs (right ventricle) and the systemic circulation (left ventrile)
why are ventricles more muscular than the atria?
to allow for more powerful contractions that are necessary to push blood through the rest of the body
defn: atrioventricular valves (what are the 2?) + mnemonic
separate the atria from the ventricles
tricuspid valve, bicuspid valve
LAB RAT
Left atrium = bicuspid
Right atrium = tricuspid
defn: semilunar valves (what are the 2?)
separate the ventricles from the vasculature
pulmonary valve, aortic valve
func: atrioventricular + semilunar valves
allow the heart muscle to create the pressure within the ventricles necessary to propel the blood forward within the circulation, while also preventing backflow of blood
defn + char: tricuspid valve
the valve between the right atrium and the right ventricle
three leaflets
defn + char + aka: bicuspid valve
aka: mitral valve
the valve between the left atrium and the left ventricle
two leaflets
defn: pulmonary valve
the valve separating the right ventricle from the pulmonary circulation
defn: aortic valve
the valve separating the left ventricle from the aorta
how many leaflets do the semilunar valves have?
3
why is the left side of the heart more muscular than the right side of the heart?
what would happen if the right side of the heart were that muscular?
blood leaving the left side of the heart must travel a far distance, so blood pressure must be maintained as far away as the feet
if the right side of the heart were that muscular, this would damage the lungs
where does the coordinated, rhythmic coordination of cardiac muscle originate from?
in an electrical impulse generated by and traveling through a pathway formed by four electrically excitable structures
what is the pathway of electrical conduction of the heart? what is the order based on?
the order is based on order of excitation
- sinoatrial (SA) node
- atrioventricular (AV) node
- bundle of His (AV bundle)
- Purkinje fibers (branches of the bundle of His)
func (3) + loc: SA node
- where impulse initiation occurs
- generates 60-100 signals per minute without requiring any neurological input
- as the depolarization wave spreads from the SA node, it causes the two atria to contract simultaneously
located: in the wall of the right atrium
is most ventricular filling passive or active? what does that mean?
passive
blood moves from the atria to the ventricles based solely on ventricular relaxation
defn: systole
atrial contraction
results in an increase in atrial pressure that forces a little more blood into the ventricles
defn: atrial kick
the additional volume of blood
accounts for ~5-30% of cardiac output
func (1) + loc: AV node
sits at the junction of the atria and ventricles
- the electrical signal is delayed here to allow the ventricles to fill completely before they contract
func + loc: bundle of His + Purkinje fibers
embedded in the interventricular septum
distribute the electrical signal through the ventricular muscle
func + loc: intercalated discs
connected to the ventricular muscle cells
contain many gap junctions directly connecting the cytoplasm of adjacent cells
what is allowed for by the connection between ventricular muscle cells and intercalated discs?
allows for coordinated ventricular contraction
why is the normal human heart rate 60 - 100 bpm?
because the SA node has an intrinsic rhythm of 60 - 100 signals per minute
what is the reaction of the heart to sympathetic (2) and parasympathetic (1) signals?
SYMP
1. speed up the heart rate
2. increase the contractility of cardiac muscle
PARA
1. slow down the heart rate
func: vagus erve
provides parasympathetic signals to the heart
what are the two phases of each heartbeat?
- systole
- diastole
process: systole
ventricular contraction and closure of the AV valves occurs and blood is pumped out of the ventricles
process: diastole
the ventricles are relaxed, the semilunar valves are closed, and blood from the atria fills the ventricles
how does pressure vary throughout systole and diastole?
SYSTOLE: contraction of the ventricles generates a higher pressure
DIASTOLE: relaxation causes the pressure to decrease
what does the elasticity of the walls of the large arteries allow for?
what would happen if this elasticity didn’t exist?
the large arteries stretch to receive the volume of blood from the heart, allowing the vessels to maintain sufficient pressure while the ventricular muscles are relaxed
if no elasticity: diastolic blood pressure drops to 0
defn + eqn: cardiac output
the total blood volume pumped by a ventricle in a minute
CO = HR x SV
cardiac output = heart rate (beats per minute) x stroke volume (volume of blood pumped per beat)
what does the fact the the two pumps are connected in series imply about the volume of blood?
the volume of blood passing through each side must be the same
what is the value of cardiac output in humans?
5 liters per minute
how is cardiac output affected by periods of exercise or rest?
exercise: sympathetic increases cardiac output
rest: parasympathetic decreases cardiac output
func + loc of major arteries: arteries
blood travels away from the heart in arteries
major arteries branch of the aorta to distrbute the blood flow toward different peripheral tissues
what is the largest artery?
the aorta
how does vasculature branching work after arteries?
aorta –> arteries –> arterioles –> capillaries
arteries divide as they divert blood to specific tissues and organs until they reach their target and branch into arterioles, which ultimately lead to capillaries that perfuse the tissues
func + loc: coronary arteries
at the base of the aorta
sends blood to perfuse the heart musculature
organization: venous side of a capillary network
capillaries join together into venules which join together to form veins
where does venous blood empty into?
the superior and inferior venae cavae for entry into the right side of the heart
what are all blood vessels lined with?
endothelial cells
func (3): endothelial cells of the heart
- helps to maintain the vessel by releasing chemicals that aid in vasodilation and vasoconstriction
- can allow white blood cells to pass through the vessel wall and into the tissues during an inflammatory response
- release certain chemicals when damaged that are involved in the formation of blood clots to repair the vessel and stop bleeding
what causes a heart attack/myocardial infarction? (2)
- a lack of bloodflow through the coronary arteries, which results in decreased oxygen delivery to the cardiac muscle itself
- anaerobic respiration cannot produce enough ATP to keep up with demand, so the muscle tissue begins to die
what is treatment for a heart attack and how does it work? (2)
a beta-blocker
- blocks the sympathetic stimulation of the heart, resulting in lower heart rate and lower contractility
- the heart doesn’t work as hard with a beta-blocker, so its oxygen demand is diminished, which helps to prevent further damage to cardiac tissue
main diff vs. similarity: veins vs. arteries
the same types of cells comprise the different vessels
arteries have much more smooth muscle than veins
func + char (2): arteries
move blood away from the heart to the lungs and other body parts
char: 1. contain oxygenated blood
2. highly muscular and elastic (creates tremendous resistance to the blood flow)
what are the only 2 arteries that carry deoxygenated blood?
- pulmonary arteries
- umbilical arteries
defn: arterioles
smaller, muscular arteries
why must the left side of the heart generate much higher pressures?
to overcome the resistance caused by systemic arteries
what happens to arteries after they are filled with blood?
the elastic recoil from their walls maintains a high pressure and forces blood forward
char (3): capillaries
char: 1. single endothelial cell layer
2. so small that red blood cells must pass through in a single-file line
3. delicate
why are capillaries the interface for communication of the circulatory system with the tissues?
the thin wall of the capillary allows easy diffusion of gases (O2 and CO2), nutrients (most notably, glucose) and wastes (ammonia and urea)
blood also carries hormones, so capillaries allow endocrine signals to arrive at their target tissues
what happens when capillaries are damaged?
blood can leave the capillaries and enter the interstitial space
if this occurs in a closed space, it results in a bruise
defn + char: veins
thin-walled, inelastic vessels that transport blood to the heart
char: carry deoxygenated blood
defn: venules
smaller venous structures that connect capillaries to the larger veins of the body
why do veins have less recoil than arteries?
the smaller amount of smooth muscle in the walls of veins
are veins or arteries able to stretch to accommodate larger quantities of blood?
veins (in fact, 3/4 of total blood volume may be in venous circulation at any one time)
what is true about the volume of blood passing through either side of the heart despite the fact that the volume of arterial blood is normally much less than the volume of venous blood?
the total volume passing through either side of the heart per unit time (cardiac output) is the same
what is the impact in the inferior vena cava of the fact that bloodflow in most veins is upward against gravity? (2)
- there is a large amount of blood in a vertical column
- the pressure at the bottom of this venous column in the large veins of the leg can be quite high
why must veins have structures to push the blood forward and prevent backflow?
the heart is located in the chest, so bloodflow in most veins is upward from the lower body back to the heart, against gravity
how do valves in larger veins work? (2)
- as blood flows forward in the veins, the valves open
- when blood tries to move backward, the valves will slam shut
what can failure of the venous valves result in?
the formation of varicose veins, which are distended where blood has pooled
why are pregnant people especially susceptible to varicose vein formation?
due to an increase in the total blood volume during pregnancy and compression of the inferior vena cava by the fetus
what are the 3 reasons that blood clots may form in the deep veins of the legs?
- as a result of injury
- inactivity (blood stasis)
- a hypercoagulable state (a tendency for the blood to clot excessively)
defn + effect + aka: pulmonary emboli
defn: blood clots may dislodge and travel through the right atrium and right ventricle, through the pulmonary artery, and into the lungs
effect: block segments of the pulmonary arteries and produce rapid, labored breathing and chest pain, death may occur if they are large
aka: thromboemboli
defn: heparin and warfarin
mediations used to prevent the formation of clots
why must veins rely on an external force to generate the pressure to push blood toward the heart? how is this accomplished?
why: the small amount of smooth muscle creates a challenge for propelling blood forward
how: most veins are surrounded by skeletal muscles, which squeeze the veins as the muscles contract, forcing the blood up against gravity (like squeezing toothpaste)
defn: DVT
deep vein thrombosis
a clot in the deep veins of the legs
cause: pulmonary embolus
a DVT may become dislodged and travel through the right side of the heart to the lungs, causing this life-threatening condition
what is circulation by definition?
circular!
shorthand diagram of the pathway of bloodflow through the heart
diagram: bloodflow through the heart
describe the pathway of blood through the body beginning with the return of blood to the right atrium
- blood returns to the heart from the body via the venae cavae, which are divided into the superior vena cava (SVC) and the inferior vena cava (IVC)
- deoxy blood enters the right atrium
- travels through the tricuspid valve
- and enters the right ventricle
- on contraction, the blood from the right ventricle passes through the pulmonary valve
- and enters the pulmonary arteries, where it travels to the lungs and breaks up into continuously smaller vessels
- once the blood reaches the capillaries that line the alveoli, it participates in gas exchange, with carbon dioxide leaving the blood and oxygen entering the blood
- the blood then travels into pulmonary venules and into the pulmonary veins, which carry the blood to the left side of the heart
- oxygenated blood enters the left atrium
- travels through the mitral valve
- and enters the left ventricle
- on contraction, the blood from the left ventricle passes through the aortic valve and enters the aorta
- from the aorta, blood enters arteries
- then arterioles
- then capillaries
- after gas and nutrient exchange occurs at the capillaries, the blood enters the venules
- which lead to the larger veins
- the veins then empty into either the SVC or IVC for return to the right side of the heart
func: superior vena cava vs. inferior vena cava
SUPERIOR = returns blood from the portions of the body above the heart
INFERIOR = returns blood from portions of the body below the heart
how many capillary beds does blood pass through before returning to the heart?
only one, in most cases
defn: portal systems
blood will pass through 2 capillary beds in series before returning to the heart
what are the 3 portal systems of the body?
- hepatic portal system
- hypophyseal portal system
- renal system
setup: hepatic portal system
blood leaving capillary beds in the walls of the gut passes through the hepatic portal vein before reaching the capillary beds in the liver
setup: hypophyseal portal system
blood leaving capillary beds in the hypothalamus travels to a capillary bed in the anterior pituitary to allow for paracrine secretion of releasing hormones
setup: renal portal system
blood leaving the glomerulus travels through an efferent arteriole before surrounding the nephron in a capillary network called the vasa recta
what does a centrifuge do to blood?
it separates the complex fluid into its components based on density by spinning it at a rapid rate
what % liquid is blood? what % cells?
55% liquid
45% cells
defn: plasma
the liquid portion of blood
an aqueous mixture of nutrients, salts, respiratory gases, hormones, and blood proteins
how can plasma be further refined?
via removal of clotting factors into serum
what are the 3 categories of the cellular portion of blood?
- erythrocytes
- leukocytes
- platelets
what are all blood cells formed from?
hematopoietic stem cells, which originate in the bone marrow
why is serum considered preferable to plasma for many applications (such as antibody testing and blood typing)?
due to the lack of clotting factors and fibrinogens
where are oxygen, nutrients, carbon dioxide, and other wastes delivered to and from in the body?
OXYGEN and NUTRIENTS: delivered to the peripheral tissues
CARBON DIOXIDE and OTHER WASTES: picked up from the peripheral tissues and delivered to the organs that process them (lungs, liver, and kidneys)
defn + aka: erythrocyte
aka: red blood cell
a specialized cell designed for oxygen transport
why doesn’t oxygen simply dissolve in the cytoplasm of the red blood cell? how is this issue dealt with?
molecular oxygen is nonpolar and thus has low solubility in aqueous environments
dealt with: each erythrocyte contains about 250 million molecules of hemoglobin, each of which can bind 4 molecules of oxygen (so each red blood cell can carry ~ 1 billion molecules of oxygen)
char: red blood cells
- biconcave (indented on both sides)
- when they mature, the nuclei, mitochondria, and other membrane-bound organelles are lost
what are the 2 purposes of the red blood cells biconcavity?
- the shape assists them in traveling through tiny capillaries
- it increases the cell’s surface area, which increases gas exchange
what 2 impacts does the loss of organelles or mitochondria in red blood cells at maturation have?
- loss of organelles makes space for the molecules of hemoglobin
- the loss of mitochondria means that the red blood cell does not consume the oxygen it is carrying before it is delivered to peripheral tissues
what do red blood cells do and do not do to generate ATP?
do NOT: carry out oxidative phosphorylation
DO: rely entirely on glycolysis for ATP, with lactic acid (arising from fermentation) as the main byproduct
why are red blood cells unable to divide?
they lack nuclei
how long can erythrocytes live in the bloodstream? what happens after this?
120 days
after this, cells in the liver and spleen phagocytize senescent (old) red blood ells to recycle them for their parts
what does a CBC measure?
the quantity of each cell type in the blood
what are 2 common measures for red blood cells?
- hemoglobin
- hematocrit
what does hemoglobin measure? + unit
the quantity of hemoglobin in the blood in g/dL
what does hematocrit measure? + unit
how much of the blood sample consists of red blood cells, given as a %
value: normal hemoglobin
males: 13.5 - 17.5 g/dL
females: 12.0 - 16.0 g/dL
value: normal hematocrit
males: 41-53%
females: 36-46%
defn: leukocytes
white blood cells
what % of total blood volume do leukocytes comprise?
< 1% of total blood volume
when does the number of white blood cells increase?
most notably, during infection
white blood cells are a crucial part of WHAT system, how?
IMMUNE
they act as our defenders against pathogens, foreign cells, cancer, and other materials not recognized as self
what are the 2 groups of leukocytes and the 5 types across those groups?
GROUP: granulocytes
1. neutrophils
2. eosinophils
3. basophils
GROUP: agranulocytes
4. lymphocytes
5. monocytes
defn: granulocytes
contain cytoplasmic granules that are visible by microscopy and contain a variety of compounds that are toxic to invading microbes
these compounds can be released through exocytosis
what 4 immune responses are granular leukocytes involved in?
- inflammatory reactions
- allergies
- pus formation
- destruction of bacteria and parasites
char: agranulocytes
do not contain granules that are released by exocytosis
func (sum + 2 spec): lymphocytes
important in the specific immune response (help our body learn from experience and are prepared to mount a fast response upon repeated exposure to familiar pathogens)
- some are primary responders against infection
- others maintain a long-term memory bank of pathogen recognition
defn: specific immune response
the body’s targeted fight against particular pathogens, such as viruses and bacteria
how do many vaccines work (4)?
by training lymphocytes
- through exposure to a weakened pathogen, or an antigenic protein of the pathogen, memory cells can be created
- when the vaccine is administered, the virus is recognized as foreign and an immune response is activated
- during this, certain immune cells form a memory of the virus
defn: antigenic protein
a protein that can be recognized by the immune system
defn: T-cells vs. B-cells
T-CELLS: lymphocytes that mature in the thymus and kill virally infected cells and activate other immune cells
B-CELLS: lymphocytes that mature in the bone marrow and are responsible for antibody generation
func: monocytes
phagocytize foreign matter such as bacteria
defn: macrophages
monocytes renamed once they leave the bloodstream and enter an organ
each organ’s macrophage population may have a specific name, what are 3 examples in CNS, skin, and bone
CNS = microglia
Skin = Langerhans cells
bone = osteoclasts
defn + aka: thrombocytes
aka: platelets
cell fragments or shards released from cells in bone marrow called megakaryocytes
func + char: thrombocytes
to assist in blood clotting
char: present in high concentrations
defn: hematopoiesis
the production of blood cells and platelets
what triggers hematopoiesis?
a number of hormones, growth factors, and cytokines
what secretes erythropoietin and thrombopoietin? what func do these have?
ERYTHROPOIETIN
- secreted by the kidney
- stimulates red blood cell development part of hematopoiesis
THROMBOPOIETIN
- secreted by the liver and kidney
- stimulates platelet development part of hematopoeisis
defn: antigen
any specific target (usually a protein) to which the immune system can react
surface proteins expressed by red blood cells
what are the 2 major antigen families?
- ABO antigens
- Rh factor
basics (2): ABO system
- comprised of 3 alleles for blood type
- A and B alleles are codominant, so a person may express one, both, or none of the ABO antigens
- the O allele is recessive to both A and B alleles
alleles: AB blood type
the A allele is present on one chromosome
the B allele is present on the other chromosome
both are expressed
alleles: type O blood
do not express A or B antigen of this protein
have a homozygous recessive genotype
what are the four blood types and what are they named based on?
- A
- B
- AB
- O
named based on the presence or absence of the protein variants (A or B antigen)
what impact does A B codominance have on the genotypes for type A and type B blood?
what is the equivalent way of writing the O blood type?
i
what happens if a person with type A blood receives type AB blood?
the body will recognize the type A protein as self but the type B protein as foreign and will make antibodies to types B and AB
what type of blood are universal donors? why?
O
their blood will not cause ABO-related hemolysis in any recipient
O blood cells express neither antigen variant, and so will not initiate any immune response
what type of blood can type O people receive?
only type O
they will produce both anti-A and anti-B antibodies
what type of donors are universal recipients? why?
AB
they can receive all blood types; no antigen is foreign to their bodies, so no adverse reactions will occur
what form of blood is given in a transfusion? what type is not?
NOT: whole blood
YES: packed red blood cells with no plasma
what part of a donor’s blood do we care about when determining if hemolysis will occur?
the donor’s red blood cell antigens (and not the plasma antibodies)
table: ABO blood types
why are antibodies created and what is their function
they are created in response to an antigen and they specifically target that antigen
what are antigens in relationship to B-cells?
antigens are the stimuli for B-cells to make antibodies
after exposure of a B-cell to its specific antigen, the cell becomes an antibody-producing factor
what is Rh factor?
it is a surface protein expressed on red blood cells
when left unmodified what do Rh-positive (Rh+) and Rh-negative (Rh-) refer to? how else can this be indicated?
the presence or absence of a specific allele called D
this can be indicated with a plus or minus superscript on the ABO blood type (such as O+ or AB-)
what type of inheritance does Rh-positivity follow?
autosomal dominant
one positive allele is sufficient for the protein to be expressed
in what way is Rh factor status particularly important in obstetrics?
Pregnant person is Rh-, fetus is Rh+ = the pregnant will become sensitized to the Rh factor and the person’s immune system will begin making anitbodies against it
- this is NOT a problem for the first child; by the time the person starts producing antibodies, the child has already been born
- any subsequent pregnancy in which the fetus is Rh+ will present a problem because maternal anti-Rh antibodies can cross the placenta and attack the fetal blood cells, resulting in hemolysis of the fetal cells
- this is known as erythroblastosis fetalis and can be fatal to the fetus
how can erythroblastosis fetalis be avoided?
by giving the Rh- parent Rh-immunoglobulin (RhoGAM) during pregnancy and immediately after delivery
administration of immunoglobulin will absorb the fetus’s Rh+ cells, preventing the production of anti-Rh antibodies by the parent
what are the 4 main functions of the cardiovascular system?
- maintenance of blood pressure
- gas and solute exchange
- coagulation
- thermoregulation
what must be true about blood pressure for the circulatory system to function properly?
blood pressure must be sufficiently high to propel blood forward
aka + effect: high blood pressure
aka: hypertension
may result in damage to the blood vessels and organs
defn: blood pressure
a measure of the force per unit area exerted on the wall of the blood vessels
what is blood pressure measured with? + how do these work
a sphygmomanometer
measure the gauge pressure in the systemic circulation (the pressure above and beyond atmospheric pressure)
how is blood pressure expressed?
as a ratio of the systolic (ventricular contraction) to diastolic (ventricular relaxation) pressures
does pressure increase or drop from arterial to venous circulation? where is the largest change/why? + graph
pressure gradually drops from the arterial to venous circulation
the largest drop is across the arterioles (capillaries are thin-walled and unable to withstand the pressure of the arterial side of the vasculature)
what is normal blood pressure considered?
between 90/60 and 120/80
draw an analogy between circulation and an electric circuit
electromotive force (voltage) drives a current through a given electrical resistance, just as the pressure gradient across the circulatory system drives cardiac output through a given vascular resistance
how can we translate Ohm’s law (V = IR) to circulation?
how can we equate arterioles and capillaries to resistors in a circuit?
the longer a blood vessel, the more resistance it offers
the larger the cross-sectional area of a blood vessel, the less resistance it offers
how can we equate opening capillary beds to an electrical circuit?
opening capillary beds will decrease vascular resistance (like adding another resistance in parallel) and increase cardiac output
how is blood pressure regulated?
using baroreceptors in the walls of the vasculature
defn: baroreceptors
specialized neurons that detect changes in the mechanical forces on the walls of the vessel
what do baroreceptors do when blood pressure is too low?
they stimulate the sympathetic nervous system, causing vasoconstriction, and increasing blood pressure
what do chemoreceptors do when the osmolarity of the blood is too high?
this could indicate dehydration
promotes the released of ADH, which increases the reabsorption of water, thus increasing blood volume and pressure, while diluting the blood
what happens if blood pressure is too high? (2)
- sympathetic impulses could decrease, permitting relaxation of the vasculature with a concurrent drop in blood pressure
- in the heart, specialized atrial cells are able to secrete the hormone ANP (atrial natriuretic peptide) which aids in the loss of salt within the nephron, acting as a natural diuretic with loss of fluid
what is impacted by the fact that ANP is a weak diuretic?
some fluid is lost, but not enough to counter the effects of a high-salt diet on blood pressure
what happens when blood reaches the capillareis?
- oxygen and nutrients diffuse out of the blood into tissues
- waste products diffuse into the blood
- hormones are secreted into the capillaries, travel with the circulation, and diffuse into their target tissue
what allows for the movement of gases and solutes by diffusion in capillaries?
in each case, one side of the capillary wall has a higher concentration of a given substance than the other
what is oxygen carried by in blood?
hemoglobin
defn: hemoglobin
a protein composed of 4 cooperative subunits, each of which has a prosthetic heme group that binds to an oxygen molecule
where does the binding of oxygen occur on hemoglobin?
at the heme group’s central iron atom, which can undergo changes in its oxidation state (the binding or releasing of oxygen to or from the iron atom in the heme group is a redox reaction)
does any oxygen diffuse into blood and dissolve in plasma?
yes, but it is negligible compared to the amount of oxygen bound to hemoglobin
how is the level of oxygen in the blood measured?
what is a normal measure?
as the partial pressure of O2 within the blood
a normal PaO2 is ~ 70-100 mmHg
but this is inconvenient to do, so oxygen saturation is usually taken (easily measured with a finger probe) –> normal is >97%
defn: oxygen saturation
the percentage of hemoglobin molecules carrying oxygen
where does oxygen diffuse into in the lungs?
the alveolar capillaries
explain the cooperative binding of oxygen and hemoglobin (5)
- when the first oxygen binds to a heme group, it induces a conformational shift in the shape of hemoglobin from taut to relaxed
- this shift increases hemoglobin’s affinity for oxygen, making it easier for further molecules of oxygen to bind to the remaining 3 unoccupied heme groups
- as other heme groups acquire an oxygen molecule, the affinity continues to increase, creating a positive feedback-like (spiraling forward) mechanism
- once all of the hemoglobin subunits are bound to oxygen, the removal of one molecule of oxygen will induce a conformational shift, decreasing the overall affinity for oxygen, making it easier for the other oxygen molecules to leave the heme group
- this is also a positive feedback process; as oxygen molecules leave hemoglobin, it becomes progressively easier for more oxygen to be removed
what type of regulation is cooperative binding? what shape of oxyhemoglobin dissociation curve does this produce? + diagram
a form of allosteric regulation
a sigmoidal dissociation curve
where does oxygen go when it is released from hemoglobin?
the tissues!
delivering oxygen to tissues is part of the job of transporting respiratory gases, what is the other important role?
removing CO2, the primary waste product of cellular respiration
char (2): CO2 gas
- nonpolar
- has low solubility in the aqueous plasma (only a small % of the total CO2 being transported in the blood to the lungs will be dissolved in the plasma)
how is CO2 transported? (3)
- small % is dissolved in plasma
- can be carried by hemoglobin (but hemoglobin has a much lower affinity for CO2 than oxygen)
- vast majority of CO2 exists in the blood as bicarbonate ion (HCO3-)
what happens when CO2 enters a red blood cell? (3)
- in encounters the enzyme carbonic anhydrase, which catalyzes the combination reaction between carbon dioxide and water to form carbonic acid (H2CO3)
- carbonic acid, a weak acid, will dissociate into a proton and the bicarbonate anion
- the hydrogen ion (proton) and bicarbonate ion both have high solubilities in water, making them a more effective method of transporting metabolic waste products to the lungs for excretion
what happens when the metabolic waste products reach the alveolar capillaries in the lungs?
the same reactions that led to the formation of the proton and bicarbonate anion can be reversed, allowing us to breathe out CO2
why is the following chemical reaction important?
- it provides an effective means of ridding the body’s tissues of CO2 gas
- the concentration of free protons in the blood affects pH (the pH in turn can have allosteric effects on the oxyhemoglobin dissociation curve)
what impact does increase CO2 production have on the bicarbonate buffer equation and what are the subsequent effects? (3)
- cause a right shift in the bicarbonate buffer equation
- this results in increased [H+] (decreased pH)
- these protons can bind to hemoglobin, reducing hemoglobin’s affinity for oxygen
- this decreased affinity allows more oxygen to be unloaded at the tissues
defn: Bohr effect
a shift to the right in the oxyhemoglobin curve that represents the decreased affinity of hemoglobin for oxygen
what are the 3 triggers for the right shift in the oxyhemoglobin curve?
- increase PaCO2
- increased [H+]
- decreased pH
what do higher rates of cellular metabolism result in?
increased carbon dioxide production and accumulation of lactic acid, both of which decrease pH
diagram: shifts in the oxyhemoglobin dissociation curve
mnemonic: causes of a right shift of the oxyhemoglobin curve
Exercise is the RIGHT thing to do
The following occur during exercise:
Increased PaCO2
Increased [H+] (decreased pH)
Increased temperature
why does fetal hemoglobin have a left-shifted curve compared to adult hemoglobin?
because fetal hemoglobin (HbF) has a higher affinity for oxygen than adult hemoglobin (HbA)
why does fetal hemoglobin (HbF) have a higher affinity for oxygen than adult hemoglobin (HbA)?
fetal red blood cells must literally pull oxygen off of maternal hemoglobin and onto fetal hemoglobin
what are 2 other causes of a right shift in the oxyhemoglobin curve?
- increased temperature
- increased 2,3-BPG (a side product of glycolysis in red blood cells)
5 causes of a left shift in the oxyhemoglobin curve?
- decreased PaCO2
- decreased [H+]
- increased pH
- decreased temperature
- decreased 2,3-BPG
how are the respiratory and renal systems connected by the bicarbonate buffer system? + 3 examples
disturbances in either system can lead to blood pH changes
EX 1: 1. person hyperventilates
2. excess CO2 is blown off, shifting the bicarb buffer system to the left and decreasing proton concentration
3. this leads to a pH increase (respiratory alkalosis)
4. kidney compensates for this change by increasing excretion of bicarbonate, bringing pH back to normal
EX 2: 1. renal tubular acidosis type I –> kidney is unable to excrete acid effectively
2. this leads to a buildup of protons in the blood (metabolic acidosis), causing the buffer system to shift left
3. excess CO2 formed in the process can be exhaled, and the person may increase respiratory rate to compensate, bringing pH back to normal
what are 3 wastes that are carried by blood? how are they transported by blood (2)?
- carbon dioxide
- ammonia
- urea
- enter the bloodstream by traveling down their respective concentration gradients from the tissues to the capillaries
- the blood eventually travels to the kidneys, where the waste products are filtered or secreted for elimination from the body
how are hormones transported in blood? (4)
- they enter the circulation in or near the organ where the hormone is produced
- this usually occurs by exocytosis, allowing for secretion of hormones into the bloodstream
- certain hormones are carried by proteins in the blood and are released under specific conditions
- once hormones reach their target tissues, they can activate cell-surface receptors (peptide hormones) or diffuse into the cell to activate intracellular or intranuclear receptors (steroid hormones)
what are hydrostatic and osmotic pressures and what is their function (as a group)?
they are two pressure gradients in the bloodstream
they are essential for maintaining a proper balance of fluid volume and solute concentrations between the blood and the interstitium (the cells surrounding the blood vessesls)
they are opposing but related
defn: hydrostatic pressure
the force per unit area that the blood exerts against the vessel walls
what generates hydrostatic pressure? how can it be measured? what impact does hydrostatic pressure have?
GENERATED by: the contraction of the heart and the elasticity of the arteries
MEASURED: upstream in the large arteries as blood pressure
IMPACT: pushes fluid out of the bloodstream and into the interstitium through the capillary walls
defn: osmotic pressure
the “sucking” pressure generated by solutes as they attempt to draw water into the bloodstream
aka: osmotic pressure (+ why)
aka: oncotic pressure
called this because it is attributable to plasma protein
what is true of hydrostatic and oncotic pressure at the arteriole end of the capillary bed?
hydrostatic pressure (pushing fluid out) is much larger than oncotic pressure (drawing fluid in) and there is a net efflux of water from the circulation
what is true of hydrostatic and oncotic pressure as fluid moves out of the vessels?
the hydrostatic pressure drops significantly, but the osmotic pressure stays about the same
what is true of hydrostatic and oncotic pressure at the venule end of the capillary bed?
hydrostatic pressure (pushing fluid out) has dropped below oncotic pressure (drawing fluid in), and there is a net influx of water back into the circulation
defn: Starling forces
the opposing pressures of hydrostatic and oncotic pressure
what is the balance of Starling forces essential for? what happens if they are imbalanced
maintaining the proper fluid volumes and solute concentrations inside and outside the vasculature
if imbalanced: these pressures can result in too much or too little fluid in the tissues
defn: edema
a condition consisting of accumulation of excess fluid in the interstitium
func: thoracic duct
most lymphatic fluid (lymph) is returned to the central circulatory system by way of this channel
func + overall statement: Starling equation
quantifies the net filtration rate between two fluid compartments
overall: the movement of solutes and fluid at the capillary level is governed by pressure differentials
diagram: starling forces at a capillary bed
comparison (func + what is it dependent on): hydrostatic vs. oncotic pressure
HYDROSTATIC
- pushes fluid out of vessels
- is dependent on blood pressure generated by the heart and the elastic arteries
OSMOTIC
- pulls fluid back into the vessels
- is dependent on the number of particles dissolved in plasma
func: platelets
protect the vascular system in the event of damage by forming a clot
func + components: clots
composed of coagulation factors (proteins) and platelets
prevent (or minimize) blood loss
explain the 7 steps of how a clot forms
- when the endothelium of a blood vessel is damaged, it exposes the underlying connective tissue, which contains collagen and tissue factor (a protein)
- when platelets come into contact with exposed collagen, hey attach to the matrix, and they sense this as evidence of injury
- in response, they release their contents and begin to aggregate, or clump together (the attachment of platelets to the matrix activates quiescent aIIbB3 integrin molecules, causing them to adhere to circulating proteins (including fibrinogen, which forms bridges to additional platelts)
- at the same time, coagulation factors sense tissue factor and initiate a complex activation cascade
- the endpoint of this cascade is the activation of prothrombin to form thrombin by thromboplastin
- thrombin can then convert fibrinogen to fibrin
- fibrin ultimately forms small fibers that aggregate and cross-link into a woven structure, like a net, that captures red blood cells and other platelets, forming a stable clot over the area of damage (together the cells and proteins form a network of cells and fibers dense enough to plug the injury and prevent blood loss until the wound can be repaired)
what organ secretes most coagulation factors?
the liver
defn: scab
a clot that forms on a surface vessel that has been cut
aka: blood clotting
thrombus formation
when does blood clotting occur?
when blood vessels are injured
func + what generates it: plasmin
generated from plasminogen
breaks down the clot
