Chapter 42: Circulatory System Flashcards
In hydras, jellies, and other cnidarians, a central ____ functions in the distribution of substances
throughout the body, as well as in digestion
gastrovas-
cular cavity
Compare and open circulatory system to a closed system
open: fluid, called hemolymph, is also the interstitial fluid. Contraction of heart pumps hemolymph through the circulatory vessels into interconnected sinuses, where gas is exchanged. Relaxation of the heart draws hemolymph back in through its pores
closed: blood is confined to vessels and distinct from interstitial fluid
The lower hydrostatic pressures in ____ circulatory systems allow them to use less energy
open
The benefits of c losed circulatory systems include
blood pressure high enough to enable effective delivery of O2 and nutrients
capillary beds are
networks of capillaries that infiltrate tissues
Portal veins are responsible for
carrying blood between pairs of capillary beds
How is the flow of hemolymph through an open circulatory
system similar to the flow of water through an outdoor
fountain?
In both an open circulatory system and a fountain, fluid is pumped through
a tube and then returns to the pump after collecting in a pool.
The heart of a normally developing human fetus
has a hole between the left and right atria. In some cases,
this hole does not close completely before birth. If the hole
weren’t surgically corrected, how would it affect the O2 con-
tent of the blood entering the systemic circuit?
The
O2 content would be abnormally low because some oxygen-depleted blood
returned to the right atrium from the systemic circuit would mix with the
oxygen-rich blood in the left atrium.
Compared with atria, ventricles have ___ walls and contract ___ forcefully, particularly the __ ventricle
thicker walls more forceful
left ventricle, pumps throughout systemic circuit
Although the left ventricle
contracts with greater force than the right ventricle, it pumps
____ volume of blood as the right ventricle during each
contraction.
the same
When the heart contracts, it ___ blood. When it relaxes, it ____ blood.
pumps blood when it contracts
fills with blood when it relaxes
Cardiac output is calculated by
the heart rate multiplied by the stroke volume
The AV valve lies between
each atrium and ventricle
Semilunar valves are located at
the exits: pulmonary artery and aorta
The SA node acts as a
pacemaker, sets the rate and timing at which all cardiac muscle cells contract via electrical impulses
Describe the path of electrical signals through the heart to establish a rhythm
- signals from SA node spread through atria
- Signals delayed at AV node
- bundle branches/purkinje fibers pass signals to heart apex
- signals spread throughout ventricles
The delay of electrical impulses at the AV node are important because
they allow the atria to empty completely before the ventricles contract
Explain why blood has a higher O2 concentration in the pul-
monary veins than in the venae cavae, which are also veins
The pulmonary veins carry blood that has just passed through capillary beds
in the lungs, where it accumulated O2 . The venae cavae carry blood that has
just passed through capillary beds in the rest of the body, where it lost O2 to the
tissues.
Suppose that after you exercise regularly for
several months, your resting heart rate decreases, but your
cardiac output at rest is unchanged. Based on these observa-
tions, what other change in the function of your heart at rest
likely occurred?
The heart, like any other muscle, becomes stron-
ger through regular exercise. You would expect a stronger heart to have a greater
stroke volume, which would allow for the decrease in heart rate.
Why is it advantageous for the endothelial layer of blood vessels to be smooth?
minimizes resistance to fluid flow
Why do arteries have thicker walls than veins?
They need thicker walls to accommodate blood pumped at high pressure by the blood
Compare capillary cell walls to arteries and veins
capillaries have one thin walls of endothelium surrounded by a basal lamina
Arteries and veins have two layers of tissue: connective and smooth muscle
Why does blood slow as it moves from arteries to arterioles to capillaries?
because each artery conveys blood to so many capillaries that the total cross sectional area is greater than any other part of the system
NO, a gas, is a major inducer in vaso____ and endothelin, a peptide, is a major inducer in vaso___
No vasodilation
endothelin vasoconstriction
Given that capillaries lack smooth muscle, how is blood
flow in capillary beds altered?
constric-
tion or dilation of the arterioles that supply capillary beds
precapillary sphincters, rings
of smooth muscle located at the entrance to capillary beds
What short-term changes in an animal’s cardiovascular
function might facilitate using skeletal muscles to escape
from a dangerous situation?
An increase in blood
pressure and cardiac output combined with the diversion of more blood to the
skeletal muscles would increase the capacity for action by increasing the rate of
blood circulation and delivering more O2 and nutrients to the skeletal muscles.
Plasma consists of __, ___, and ___
ions, proteins, nutrients, waste products, respiratory gases, hormones
Albumins are responsible for
pH changes and osmotoic balance
Immunoglobulins, or antibodies, are responsible for
combating viruses and other foreign agents
Apolioproteins are responsible for
escorting lipids
Fibrinogens are responsible for
clotting factors
The biconcave shape of erythrocytes is important because
it increases surface area and enhances rate of diffusion of O2
Erythrocytes, leukocytes, and platelets all develop from ___ cells located…
stem cells located in red marrow
Lymphoid progenitor cells created from stem cells make
lymphocytes or B and T cells
Myeloid progenitor cells made from stem cells make
erythrocytes, neutrophils, basophils, monocytes, platelets, eosinophils
If the O2 level falls, kidneys synthesize the erythropoietin (EPO) hormone, which
stimulates generation of more RBCs
Describe the steps of blood clotting
- begins when endothelium of a vessel is damaged, exposing connective tissue in vessel wall to blood. Platelets adhere to collagen fibers and release a substance that makes nearby platelets sticky
2.platelets form a plug that provides protection against blood loss - plug is reinforced by a fibrin clot
LDL is responsible for
delivering cholesterol to cells for membrane protection
HDL is responsible for
scavenging excess cholesterol to return to the liver
If an individual has a high ratio of ___ to ___, they are at increased risk of atherosclerosis
LDL to HDL
Explain why a physician might order a white cell count for
a patient with symptoms of an infection.
. An increase in the number of white blood cells (leukocytes) may indicate that
the person is combating an infection
Clots in arteries can cause heart attacks and strokes. Why,
then, does it make sense to treat people with hemophilia by
introducing clotting factors into their blood?
Clotting factors do not initiate clot-
ting but are essential steps in the clotting process.
Partial pressure is defined as
the pressure exerted by a particular gas in a mixture of gases
A gas always undergoes net dif-
fusion from a region of ___ partial pressure to a region of
___ partial pressure.
Higher to lower
air is much ___dense and ___ viscous than water,
so it is easier to move and to force through small passageways
less
Why is an internal location for gas exchange tissues advan-
tageous for terrestrial animals?
Their interior position helps gas exchange tissues stay moist. If the respiratory sur-
faces of lungs extended into the terrestrial environment, they would quickly dry out,
and diffusion of O2 and CO2 across these surfaces would stop
mammals employ
negative pressure breathing…
—pulling, rather than push-
ing, air into their lungs
Tidal volume is
The volume of air inhaled and exhaled with each breath,
called tidal volume, averages about 500 mL in resting
humans.
Vital capacity is
The tidal volume during maximal inhalation and
exhalation is the vital capacity
Residual volume is
The air that remains
after a forced exhalation is called the residual volume
How does an increase in the CO2 concentration in the blood
affect the pH of cerebrospinal fluid?
An increase in blood CO2 concentration causes an increase in the rate of
CO2 diffusion into the cerebrospinal fluid, where the CO2 combines with
water to form carbonic acid. Dissociation of carbonic acid releases hydrogen
ions, decreasing the pH of the cerebrospinal fluid.
A drop in blood pH causes an increase in heart rate. What is
the function of this control mechanism?
Increased heart rate
increases the rate at which CO2 -rich blood is delivered to the lungs, where CO2
is removed.
What is the Bohr shift
Low pH decreases the affinity of hemoglobin for O2, an
effect called the Bohr shif
What determines whether O2 and CO2 undergo net
diffusion into or out of capillaries? Explain.
. Differences in partial pressure between the capillaries and the surround-
ing tissues or medium; the net diffusion of a gas occurs from a region
of higher partial pressure to a region of lower partial pressure
How does the Bohr shift help deliver O2 to very active
tissues?
The
Bohr shift causes hemoglobin to release more O2 at a lower pH, such as
is found in the vicinity of tissues with high rates of cellular respiration
and CO2 release.
A doctor might give bicarbonate (HCO3-) to a
patient who is breathing very rapidly. What is the doctor
assuming about the patient’s blood chemistry?
The doctor is assuming that the rapid breathing is the
body’s response to low blood pH. Metabolic acidosis, the lowering of blood
pH as a result of metabolism, can have many causes, including complica-
tions of certain types of diabetes, shock (extremely low blood pressure),
and poisoning
Which of the following respiratory systems is independent
from a fluid-based circulatory system?
(A) the lungs of a vertebrate
(B) the gills of a fish
(C) the tracheal system of an insect
(D) the skin of an earthworm
the tracheal system of an insect
Blood returning to the mammalian heart in a pulmonary vein
drains first into the
(A) left atrium.
(B) right atrium.
(C) left ventricle.
(D) right ventricle
left atrium.
Pulse is a direct measure of
(A) blood pressure.
(B) stroke volume.
(C) cardiac output.
(D) heart rate.
heart rate
When you hold your breath, which of the following blood gas
changes first leads to the urge to breathe?
(A) rising O2
(B) falling O2
(C) rising CO2
(D) falling CO2
rising CO2
One feature that amphibians and humans have in common is
(A) the number of heart chambers.
(B) a complete separation of circuits for circulation.
(C) the number of circuits for circulation.
(D) a low blood pressure in the systemic circuit.
the number of circuits for circulation.
A molecule of CO2 released into the blood in your left toe can
be exhaled from your nose without passing through which of
the following structures?
(A) the pulmonary vein.
(B) the trachea.
(C) the right atrium.
(D) the right ventricle.
the pulmonary vein
Compared with the interstitial fluid that bathes active muscle
cells, blood reaching these cells in arterioles has a
(A) higher PO2
(B) higher PCO2
(C) greater bicarbonate concentration.
(D) lower pH
lower pH
