If a person has a stroke volume of 55 ml and a heart rate of 80 beats per minute, what is his or her cardiac output? Is this a normal value? If not, how is it abnormal?
The person would have a cardiac output of 4400 ml/min (4.4 liters/min). Although this is a little
lower than the 5+ liters/min often considered average, there are numerous normal factors that
affect cardiac output (e.g. body temperature, gender, size), as well as abnormal factors (e.g. high
blood pressure, reduced stroke volume) which could account for this value.
Does a high ESV signify a high stroke volume or a low stroke volume? What could cause a high ESV, and what would this do to cardiac output?
A high ESV signifies a low stroke volume, as less blood was ejected, and more remains in the
ventricles at the end of systole. High blood pressure is one factor that could causes this, and it
would reduce cardiac output.
Why does left ventricular failure cause pulmonary congestion and edema? Why do both right and left ventricular failure cause peripheral edema?
In left ventricular failure, pulmonary edema may follow as blood backs up in the pulmonary
circuit, increasing pulmonary vessel pressure, and driving fluid out of the pulmonary capillaries
and into the lungs. Similarly right and left ventricular failure may cause peripheral edema, in
which blood backs up in the systemic capillaries, forcing fluid out of the capillaries and into the
tissues.
What are the main functions of blood?
functions to exchange gases, distribute solutes, immune functions, clotting, acidbase homeostasis, maintains body temperature and blood pressure
What are the four types of plasma proteins, and what are their functions?
The four types of plasma proteins are albumin (responsible for blood's colloid osmotic pressure),
antibodies (defend against pathogens), transport proteins (carry molecules that would otherwise
be difficult to dissolve and transport in blood), and clotting proteins (stop blood loss from
damaged blood vessels).
How does the structure of an erythrocyte allow it to carry out its functions?
The erythrocyte's biconcave disc structure increases surface area for gas exchange. It also has no nucleus or organelles, which suggests how specialized it is for its function of carrying
hemoglobin and respiratory gasses.
Why is blood red? What makes venous blood darker than arterial blood?
Like rusted iron, oxidized hemoglobin (oxyhemoglobin) turns red. Venous blood has less
oxyhemoglobin and more deoxyhemoglobin, making it darker and less red in color.
What is the stimulus for erythropoietin production and release? What action does erythropoietin trigger, and how does this return the variable to the homeostatic range?
Low blood oxygen levels as detected by kidney chemoreceptor cells trigger erythropoietin
production and release. Erythropoietin speeds up the rate of erythropoiesis and reduces the
amount of time needed for new erythrocytes to mature. Additional erythrocytes entering the
blood increase hematocrit and oxygen-carrying capacity of the blood.
What are the three causes of anemia? How does each cause decrease the oxygencarrying capacity of the blood?
The three causes of anemia are: decreased levels of functional hemoglobin, in which
erythroblasts cannot make hemoglobin without functional iron-containing heme groups;
decreased hematocrit or reduced numbers of erythrocytes in the blood; and abnormal hemoglobin (e.g. sickle cell) which may result in the blood carrying less oxygen (e.g. sickle cells are
destroyed or clog up capillary beds
What are the key differences between erythrocytes and leukocytes?
Leukocytes are larger than erythrocytes and have prominent, sometimes unusually shaped,
nuclei. Leukocytes also often do their protective work when they leave the blood, unlike
erythrocytes that remain within blood vessels to function in gas transport/exchange.
How do lymphocytes differ from all other cells in terms of their development in the bone marrow?
Unlike the other leukocytes which develop from the myeloid cell line, lymphocytes are formed
from the lymphoid cell line. They also produce two distinct types, the B and T lymphocytes,
which are immature when first produced, and mature later (in bone marrow for B-lymphocytes
and in the thymus gland for T-lymphocytes).
Are platelets cells? Explain your answer
Platelets are not truly cells, but instead are small fragments of cells surrounded by a plasma
membrane. They lack nuclei and most other organelles, and do not perform most functions
typically associated with living cells.
What is hemostasis? What are the five steps of hemostasis?
Hemostasis is a series of mechanisms that minimize the amount of blood lost from an injured
blood vessel. The five steps are: vascular spasm, platelet plug, coagulation, clot retraction, and
thrombolysis.
How and why does vascular spasm occur?
vasoconstriction and increased tissue pressure, both cause a decrease in the blood vessel diameter.
What are the fundamental differences between the intrinsic and extrinsic pathways?
In the intrinsic pathway, all of the factors required for it to proceed are located within the blood.
The extrinsic pathway is initiated by a factor outside the blood - a "tissue factor" released from
subendothelial cells in damaged areas.
What is the overall purpose of coagulation?
Is to produce fibrin threads that form a mesh which glues together the platelet plug (and other materials) to seal the damaged blood vessel.
It is obviously important to clot a broken blood vessel. Why is it equally important to eventually break down that clot?
In addition to being an unnecessary partial blockage in the vessel once the vessel is healed, there is the danger that a portion of it could break off (a thromboembolus) and produce a blockage in smaller vessels.
What is an anticoagulant? Why is it important to regulate positive feedback loops like coagulation?
Anticoagulants are drugs that prevent one step in the blood clotting process. Positive feedback
loops like coagulation can easily produce "too much of a good thing" and cause (specific to this
case) thromboemboli such as pulmonary emboli which lodge in the vessels of the lungs.
What are antigens? What are the key antigens on erythrocytes?
Antigens are surface marker molecules. The key antigens on human erythrocytes are the A, B,
and Rh antigens.
What is the difference between a neurotransmitter and a hormone?
Neurotransmitters are released by neurons at a synapse that come into close contact with their
target cells, thus are fast acting, while hormones travel in the bloodstream to reach the receptors on their target cells which act much slower.
Why does a hydrophilic hormone generally have difficulty crossing the plasma
membrane? Why does a hydrophobic hormone generally cross the plasma membrane easily?
Hydrophilic hormones cannot
enter target cells because they are repelled by the fatty acid tails of the phospholipid bilayer.
Hydrophobic hormones are able to cross membranes for the opposite reason.
Why is the anterior pituitary also called the adenohypophysis? Why is the
posterior pituitary also called the neurohypophysis?
The prefix "adeno" means gland, and the anterior pituitary is composed of hormone-secreting
glandular epithelium. The prefix "neuro" refers to the fact that the posterior pituitary is made up of
nervous tissue.
What are the advantages of multiple tiers of control in hormone secretion?
Multiple levels or multiple tiers of control allow the endocrine system to tightly regulate
conditions within the body, which is critical to the maintenance of homeostasis.
How are the effects of growth hormones different from the other anterior pituitary
hormones? What is the difference between growth hormone's short-term and long-term effects?
Most hormones of the anterior pituitary gland are limited to controlling the secretion of
hormones by other endocrine glands or tissues, whereas growth hormone affects a large variety
of different body tissues. Short-term effects of GH are mainly metabolic (e.g. stimulation of fat
breakdown, gluconeogenesis). GH's long-term effects (often mediated by insulin-like growth
factor) include increasing protein synthesis and cell division, leading to increased bone growth
and muscle development.
What would you expect to happen to the metabolic rate if thyroid hormone synthesis decreased? Why? Be specific.
In general, metabolic rate would decrease. This is because thyroid hormone increases basal
metabolic rate, stimulates liver to promote production of glucose from amino acids and fats
(gluconeogenesis), and stimulates the breakdown of proteins in skeletal muscle and fats in
adipose tissue in order to provide molecules for gluconeogenesis. All of these anabolic and
catabolic reactions decrease with less TH.
What is the importance of iodine to thyroid hormone synthesis? What do you
think would happen if insufficient iodine were available?
Iodine atoms are required for thyroid hormone synthesis, as TH is a core of two amino acids
surrounded by iodine. Without iodine, levels of active thyroid hormones would decrease.
Why does the level of TSH increase in hypothyroidism? What happens to the level of TSH in hyperthyroidism? Explain.
TSH increases when levels of T3 and T4 fall, so it follows that the low T3 and T4 levels found in
hypothyroidism would trigger an increase in TSH release. Conversely, the high levels of T3 and
T4 found in hyperthyroidism would decrease TSH release.
How are parathyroid hormone and calcitonin antagonists?
PTH increases blood calcium levels by stimulating osteoclasts to break down the extracellular
matrix of bone, and by increasing absorption of dietary calcium ions by the small intestine.
Calcitonin inhibits osteoclast activity, thereby allowing osteoblasts to deposit extra calcium in
bone tissue.
Are aldosterone and cortisol hydrophobic or hydrophilic hormones? What does this mean about how they likely interact with their target cells?
Aldosterone and cortisol are hydrophobic hormones (steroids). As such they would be able to
directly enter target cells without the aid of plasma membrane-bound receptors and would
directly exert their influence inside the cell.
How are the cells of the adrenal cortex and medulla different, structurally and functionally?
The adrenal cortex is composed of true glandular cells that produce steroid-based hormones. The
adrenal medulla consists of neuroendocrine cells which are derived from nervous tissue and produce the catecholamines which are amino acid based hormones.
What role does the adrenal medulla play in the sympathetic nervous system response? What hormones does it release, and what are their effects on target organs?
The adrenal medulla enhances the sympathetic response. It releases the catecholamines,
(epinephrine and norepinephrine) which have the same effects on target cells as when released as
neurotransmitters. These effects include increasing heart rate and force of contraction, dilating
bronchioles, constricting blood vessels supplying the skin, dilating the blood vessels supplying
skeletal muscles, and increasing blood pressure.
How are glucagon and insulin antagonists?
Glucagon stimulates glycogen breakdown and thereby increases the levels of glucose in the
blood. Insulin promotes glucose uptake and storage which lowers the level of glucose in the blood.
Mr. Sorgi is a type I diabetic patient who forgot to take his insulin and is now feeling faint. Will his blood glucose be high or low? Why? Will giving him glucose help his
condition?
His blood glucose would be high, since without insulin, cells such as liver cells would not be
able to absorb glucose. Since his weakness or faintness is likely due to other metabolic issues,
and his cells cannot absorb the additional glucose, giving him glucose would not help (giving
insulin would).
The pineal gland is located in the
epithalamus
The thymus gland is located in the
mediastinum
What are the key differences between the right side and left side of the heart?
Functionally, the right side of the heart pumps blood to the lungs (the pulmonary pump), whereas
the left side of the heart pumps blood to the rest of the body (the systemic pump). The pressure
generated is also higher on the left side due to the need to pump blood to the entire body.
How does the serous pericardium envelop the heart? What is its function?
The serous pericardium has two continuous layers: the parietal pericardium that is fused to the
inner surface of the fibrous pericardium, and the visceral pericardium (aka epicardium) which
lies directly on the heart as the most superficial layer of the heart wall.
What happens when blood flow through one or more of the coronary arteries is blocked? What can cause blockage of coronary arteries?
Because of anastomoses and collateral circulation, blockage of only one coronary artery may
allow alternate routes of blood flow. However blockage of more and/or larger coronary arteries
may cause myocardial infarction (MI), or heart attack. This often follows when plaques in the
coronary arteries rupture and a clot forms that obstructs blood flow to the myocardium.
How is the right side of the heart different structurally from the left side? Why?
The right ventricle is wider and has thinner walls than the left ventricle. This is because of the
pressure differences in the pulmonary and systemic circuits; the right ventricle has less resistance to overcome, and the left ventricle pumps against much greater resistance. Also, the right ventricle is shorter and crescent-shaped in cross-section.
Why is it important to prevent backflow of blood in the heart? Which structures prevent back flow, and how do they function?
Blood flow through the heart must occur in only one direction so that deoxygenated blood goes
to the pulmonary circuit and oxygenated blood goes to the systemic circuit. Valves with
overlapping flaps close when pressure increases on one side such that blood cannot flow back
where it came from.
Why can the heart continue beating even when the brain has ceased most of its functions?
Cardiac muscle has the property of autorhythmicity and it sets its own rhythm without a need for input from the nervous system. Specialized pacemaker cells generate action potentials that trigger the other cardiac muscle cells to contract
What is the importance of the intercalated discs to heart function? Why do
skeletal muscle fibers lack intercalated discs?
Intercalated discs join pacemaker cells to contractile cells, and join contractile cells to one
another. They contain gap junctions which provide for electrical synapses between cells for easy
spread of action potentials.
Why is there a delay at the AV node? What would happen if the delay were too short? What would happen if it were too long?
The AV node delay allows extra time for the action potential to spread from the SA node to the
AV bundle, which allows the atria to depolarize (and contract) before the ventricles. This gives
the ventricles time to fill with blood before they contract. Too long a delay might allow time for
the atria to start to relax and pull blood back in their direction before the ventricles could contract
and force closure of the AV valves.
What causes the plateau phase of the contractile cardiac cell action potential? Why is the plateau phase so important to the electrophysiology of the heart?
Calcium ion channels open and Ca++ enters as K+ exits, prolonging the depolarization. These
calcium ion channels are also slow to close, which allows the plateau phase to last much longer
than the initial depolarization phase. The plateau phase lengthens the cardiac action potential to
about 200-300 msec, which slows the heart rate, providing the time required for the heart to fill
with blood.
What part of the heart has an anomaly if the P wave is abnormal on an ECG? Explain.
The P wave represents the depolarization of the cells within the atria (except the SA node). So, P
wave anomalies would point to atrial abnormalities such as atrial fibrillation.
How do pressure gradients drive blood flow through the heart? How do pressure gradients influence the functioning of the heart valves?
Contraction of the heart muscle increases pressure in the chambers. Blood fills the heart when
pressure is low during relaxation (diastole), and blood moves from ventricles to the great arteries
during contraction (systole). High pressure in the ventricles during systole causes blood flow
that pushes the semilunar valves open (and causes the AV valves to close). Higher pressure from
the blood in the ventricles closes the semilunar valves during diastole.
You notice that a patient has QRS waveforms on his ECG, indicating that his ventricles are undergoing electrical activity. Does this finding always mean that a heart is
actually pumping blood? Explain
In the normal functioning of the heart, electrical activity in the ventricles should lead to a
physical contraction. However, pumping blood is most directly related to pressure-volume
changes, so there can be electrical activity with no heartbeat.
What happens when antibodies bind their specific antigens?
When antibodies bind their specific antigens a clumping process called agglutination occurs.
Agglutination promotes hemolysis and destruction of the erythrocytes.
When considering blood donation, do we consider the antigens on the donor's erythrocytes, the antibodies in the donor's blood, or both? Explain.
The main concern is the donor's antigens. A patient cannot receive blood containing antigens
that the immune system would recognize as foreign, or a transfusion reaction will occur. It is true that the small amount of antibodies present in the donor's blood in a compatible but not exact
match would react with a small number of the recipient's erythrocytes. However, this is almost
insignificant compared to the value of the blood transfusion.