Chapter 42: Circulatory System

Question 1

In hydras, jellies, and other cnidarians, a central ____ functions in the distribution of substances
throughout the body, as well as in digestion

Answer 1

gastrovas-
cular cavity

Question 2

Compare and open circulatory system to a closed system

Answer 2

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

Question 3

The lower hydrostatic pressures in ____ circulatory systems allow them to use less energy

Answer 3

open

Question 4

The benefits of c losed circulatory systems include

Answer 4

blood pressure high enough to enable effective delivery of O2 and nutrients

Question 5

capillary beds are

Answer 5

networks of capillaries that infiltrate tissues

Question 6

Portal veins are responsible for

Answer 6

carrying blood between pairs of capillary beds

Question 7

How is the flow of hemolymph through an open circulatory
system similar to the flow of water through an outdoor
fountain?

Answer 7

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.

Question 8

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?

Answer 8

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.

Question 9

Compared with atria, ventricles have ___ walls and contract ___ forcefully, particularly the __ ventricle

Answer 9

thicker walls more forceful
left ventricle, pumps throughout systemic circuit

Question 10

Although the left ventricle
contracts with greater force than the right ventricle, it pumps
____ volume of blood as the right ventricle during each
contraction.

Answer 10

the same

Question 11

When the heart contracts, it ___ blood. When it relaxes, it ____ blood.

Answer 11

pumps blood when it contracts
fills with blood when it relaxes

Question 12

Cardiac output is calculated by

Answer 12

the heart rate multiplied by the stroke volume

Question 13

The AV valve lies between

Answer 13

each atrium and ventricle

Question 14

Semilunar valves are located at

Answer 14

the exits: pulmonary artery and aorta

Question 15

The SA node acts as a

Answer 15

pacemaker, sets the rate and timing at which all cardiac muscle cells contract via electrical impulses

Question 16

Describe the path of electrical signals through the heart to establish a rhythm

Answer 16

1. signals from SA node spread through atria
2. Signals delayed at AV node
3. bundle branches/purkinje fibers pass signals to heart apex
4. signals spread throughout ventricles

Question 17

The delay of electrical impulses at the AV node are important because

Answer 17

they allow the atria to empty completely before the ventricles contract

Question 18

Explain why blood has a higher O2 concentration in the pul-
monary veins than in the venae cavae, which are also veins

Answer 18

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.

Question 19

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?

Answer 19

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.

Question 20

Why is it advantageous for the endothelial layer of blood vessels to be smooth?

Answer 20

minimizes resistance to fluid flow

Question 21

Why do arteries have thicker walls than veins?

Answer 21

They need thicker walls to accommodate blood pumped at high pressure by the blood

Question 22

Compare capillary cell walls to arteries and veins

Answer 22

capillaries have one thin walls of endothelium surrounded by a basal lamina

Arteries and veins have two layers of tissue: connective and smooth muscle

Question 23

Why does blood slow as it moves from arteries to arterioles to capillaries?

Answer 23

because each artery conveys blood to so many capillaries that the total cross sectional area is greater than any other part of the system

Question 24

NO, a gas, is a major inducer in vaso____ and endothelin, a peptide, is a major inducer in vaso___

Answer 24

No vasodilation
endothelin vasoconstriction

Question 25

Given that capillaries lack smooth muscle, how is blood flow in capillary beds altered?

Answer 25

constric- tion or dilation of the arterioles that supply capillary beds precapillary sphincters, rings of smooth muscle located at the entrance to capillary beds

Question 26

What short-term changes in an animal’s cardiovascular function might facilitate using skeletal muscles to escape from a dangerous situation?

Answer 26

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.

Question 27

Plasma consists of __, ___, and ___

Answer 27

ions, proteins, nutrients, waste products, respiratory gases, hormones

Question 28

Albumins are responsible for

Answer 28

pH changes and osmotoic balance

Question 29

Immunoglobulins, or antibodies, are responsible for

Answer 29

combating viruses and other foreign agents

Question 30

Apolioproteins are responsible for

Answer 30

escorting lipids

Question 31

Fibrinogens are responsible for

Answer 31

clotting factors

Question 32

The biconcave shape of erythrocytes is important because

Answer 32

it increases surface area and enhances rate of diffusion of O2

Question 33

Erythrocytes, leukocytes, and platelets all develop from ___ cells located...

Answer 33

stem cells located in red marrow

Question 34

Lymphoid progenitor cells created from stem cells make

Answer 34

lymphocytes or B and T cells

Question 35

Myeloid progenitor cells made from stem cells make

Answer 35

erythrocytes, neutrophils, basophils, monocytes, platelets, eosinophils

Question 36

If the O2 level falls, kidneys synthesize the erythropoietin (EPO) hormone, which

Answer 36

stimulates generation of more RBCs

Question 37

Describe the steps of blood clotting

Answer 37

1. 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 3. plug is reinforced by a fibrin clot

Question 38

LDL is responsible for

Answer 38

delivering cholesterol to cells for membrane protection

Question 39

HDL is responsible for

Answer 39

scavenging excess cholesterol to return to the liver

Question 40

If an individual has a high ratio of ___ to ___, they are at increased risk of atherosclerosis

Answer 40

LDL to HDL

Question 41

Explain why a physician might order a white cell count for a patient with symptoms of an infection.

Answer 41

. An increase in the number of white blood cells (leukocytes) may indicate that the person is combating an infection

Question 42

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?

Answer 42

Clotting factors do not initiate clot- ting but are essential steps in the clotting process.

Question 43

Partial pressure is defined as

Answer 43

the pressure exerted by a particular gas in a mixture of gases

Question 44

A gas always undergoes net dif- fusion from a region of ___ partial pressure to a region of ___ partial pressure.

Answer 44

Higher to lower

Question 45

air is much ___dense and ___ viscous than water, so it is easier to move and to force through small passageways

Answer 45

less

Question 46

Why is an internal location for gas exchange tissues advan- tageous for terrestrial animals?

Answer 46

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

Question 47

mammals employ negative pressure breathing...

Answer 47

—pulling, rather than push- ing, air into their lungs

Question 48

Tidal volume is

Answer 48

The volume of air inhaled and exhaled with each breath, called tidal volume, averages about 500 mL in resting humans.

Question 49

Vital capacity is

Answer 49

The tidal volume during maximal inhalation and exhalation is the vital capacity

Question 50

Residual volume is

Answer 50

The air that remains after a forced exhalation is called the residual volume

Question 51

How does an increase in the CO2 concentration in the blood affect the pH of cerebrospinal fluid?

Answer 51

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.

Question 52

A drop in blood pH causes an increase in heart rate. What is the function of this control mechanism?

Answer 52

Increased heart rate increases the rate at which CO2 -rich blood is delivered to the lungs, where CO2 is removed.

Question 53

What is the Bohr shift

Answer 53

Low pH decreases the affinity of hemoglobin for O2, an effect called the Bohr shif

Question 54

What determines whether O2 and CO2 undergo net diffusion into or out of capillaries? Explain.

Answer 54

. 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

Question 55

How does the Bohr shift help deliver O2 to very active tissues?

Answer 55

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.

Question 56

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?

Answer 56

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

Question 57

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

Answer 57

the tracheal system of an insect

Question 58

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

Answer 58

left atrium.

Question 59

Pulse is a direct measure of (A) blood pressure. (B) stroke volume. (C) cardiac output. (D) heart rate.

Answer 59

heart rate

Question 60

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

Answer 60

rising CO2

Question 61

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.

Answer 61

the number of circuits for circulation.

Question 62

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.

Answer 62

the pulmonary vein

Question 63

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

Answer 63

lower pH