The Cardiovascular System; The Respiratory System

Question 1

Systemic circulation

Answer 1

Circulatory path of the blood (heart to body).

Beginning with the left atrium,
to the left ventricle,
blood is pumped through the aorta.
Then branch into smaller arteries,
which branch into still-smaller arterioles,
which branch into still-smaller capillaries.
Blood from the capillaries is collected into venules,
which collect into larger veins,
which collect into the superior and inferior vena cava.
The vena cava empty into the right atrium of the heart.

Question 2

Pulmonary circulation

Answer 2

Pulmonary path of the blood (heart to lungs).

Blood is delivered from the superior and inferior vena cava into the right atrium,
then is squeezed into the right ventricle, which pumps blood through the pulmonary arteries,
to arterioles,
to the capillaries of the lungs.
Blood then collects in venules,
then in veins,
and finally in the pulmonary veins leading to the heart.

The pulmonary veins empty into the left atrium, which fills the left ventricle.

Note that the left ventricle contracts with the most force to propel the blood through the systemic circulation.

Question 3

Closed circulatory system

Answer 3

Since there are no openings for the blood to leave the vessels, the entire systemic and pulmonary circulatory systems are said to be closed.

Question 4

Heart

Answer 4

A large muscle. Its fibers form a net, and the net contracts upon itself, squeezing blood into the arteries.

Question 5

Sinoatrial node

Answer 5

AKA SA node. Located in the right atrium. The heart contracts automatically, paced by a group of specialized cardiac muscle cells called the sinoatrial node.

The SA node contracts by itself at regular intervals, spreading its contractions to the surrounding cardiac muscles via electrical synapses made from gap junctions.

Question 6

Electrical synapses/gap junctions

Answer 6

The SA node contracts by itself at regular intervals, spreading its contractions to the surrounding cardiac muscles via electrical synapses made from gap junctions.

Question 7

Vagus nerve

Answer 7

The pace of the SA node is faster than normal heartbeats but the parasympathetic vagus nerve innervates the SA node, slowing the contractions.

Question 8

Atrioventricular node

Answer 8

AKA AV node. Located in the interatrial septa, the wall of cardiac muscle between the atria. The AV node is slower to contract, creating a delay which allows the atria to finish their contraction and to squeeze their contents into the ventricles before the ventricles begin to contract.

Question 9

Bundle of His

Answer 9

From the AV node, the action potential moves down conductive fibers called the bundle of His, which is located in the wall separating the ventricles.

Question 10

Purkinje fibers

Answer 10

From the bundle of His, the action potential branches out through the ventricular walls via conductive fibers called Purkinje fibers. From there, the action potential is spread through gap junctions from one cardiac muscle to the next.

The Purkinje fibers in the ventricles allow for a more unified and stronger contraction.

Question 11

Arteries

Answer 11

Elastic, and stretch as they fill with blood. When the ventricles finish their contraction, the stretched arteries recoil, keeping the blood moving more smoothly.

Wrapped in smooth muscle typically innervated by the sympathetic nervous system.

Larger arteries have less smooth muscle per volume than medium sized arteries, and are less affected by sympathetic innervation. Medium sized arteries, on the other hand, construct enough under sympathetic stimulation to reroute blood.

Question 12

Epinephrine

Answer 12

A powerful vasoconstrictor which causes arteries to narrow.

Question 13

Arterioles

Answer 13

Very small. Wrapped by smooth muscle. Construction and dilation of arterioles can be used to regulate blood pressure as well as to reroute blood.

Question 14

Capillaries

Answer 14

Microscopic blood vessels. Nutrient and gas exchange with all tissues (other than vascular) takes place ONLY across capillary walls– not arterioles or venules.

Capillaries are found close to all cells of the body. The total cross sectional area of all the capillaries together is much creater than the cross sectional area of a single aorta or a few arteries.

4 methods for materials to cross capillary walls:

1. Pinocytosis,
2. Diffusion or transport through capillary cell membranes,
3. Movement through pores in the cells called fenestrations,
4. Movement through the space between cells

Question 15

Venules and veins

Answer 15

Comparable in structure to arterioles and arteries. The lumen is larger than the lumen of comparable arteries, and veins contain a far greater volume of blood.

Veins, venules and venus sinuses in the systemic circulation hold about 64% of the blood in a body at rest, and act as a reservoir for blood.

(Arteries, arterioles and capillaries in the systemic circulation contain about 20% of the blood.)

Question 16

Pulmonary arteries

Answer 16

Contain the most deoxygenated blood in the body.

Question 17

Continuity equation

Answer 17

Blood flow follows this equation, Q = Av. Velocity is greatest in the arteries where cross sectional area is smallest, and velocity is lowest where cross sectional area is greatest.

Question 18

Blood velocity

Answer 18

Inversely proportional to cross sectional area

Question 19

Blood pressure

Answer 19

Does not follow Bernoulli’s because blood is NOT an ideal fluid! Memorize figure 7.6 on page 167.

Blood flows more rapidly where pressure is higher, for instance, in arteries (vs. veins).

Question 20

Diaphragm

Answer 20

Dome shaped muscle. Made of skeletal muscle fibers, separates the thoracic and abdominal cavities. Innervated by the phrennic nerve.

Question 21

Inspiration

Answer 21

Inspiration (breathing in) occurs when the medulla oblongata of the midbrain signals for the diaphragm to contract. Flattens upon contraction, expanding the chest cavity and creating negative gauge pressure.

Atmospheric pressure forces air into the lungs.

Upon relaxation of the diaphragm, the chest cavity shrinks and the elasticity of the lungs- along with the increased pressure in the chest cavity- forces air out of the body.

Question 22

Respiratory system

Answer 22

Know anatomy. Basic job is to deliver oxygen to the blood and expel carbon dioxide. Part of the respiratory tract functions to warm, moisten, and clean air.

Question 23

Microtubules

Answer 23

Microtubules are found in cilia, and ciliated cells are found:

1. In the respiratory tract
2. In the Fallopian tubes
3. In the ependymal cells of the spine

A problem in microtubule production might result in a problem in breathing, fertility, or circulation in cerebrospinal fluid.

Question 24

Nasal cavity

Answer 24

Space inside the nose. Filters, moistens, and warms incoming hair.

Coarse hair at the front of the cavity traps large dust particles.

Question 25

Mucus

Answer 25

Secreted by goblet cells traps smaller dust particles and moistens the air

Question 26

Capillaries within the nasal cavity

Answer 26

Warm the air

Question 27

Cilia

Answer 27

Move mucus and dust back toward the pharynx, so it may be removed by spitting or swallowing.

Question 28

Pharynx

Answer 28

Throat. Functions as a passageway for food and air.

Question 29

Larynx

Answer 29

Voice box. Contains the vocal cords.

Sits behind the epiglottis.

When nongaseous material enters the larynx, a coughing reflex is triggered, forcing the material back out.

Question 30

Epiglottis

Answer 30

Cartilaginous member that prevents food from entering the trachea during swallowing.

Question 31

Trachea

Answer 31

Windpipe. Lies in front of the esophagus. Composed of ringed hyaline cartilage covered by ciliated mucous cells.

Like the nasal cavity, the mucus and cilia in the trachea collect dust and usher it toward the pharynx.

Question 32

Respiratory path

Answer 32

Nasal cavity, pharynx, larynx, trachea.
Before entering the lungs, the trachea splits into the right and left bronchi. Each bronchus branches many more times to become tiny bronchioles. Bronchioles terminate in grape-like clusters called alveolar sacs composed of tiny alveoli. From each alveolus, oxygen diffuses into a capillary where it is picked up by red blood cells. The red blood cells release carbon dioxide, which diffuses into the alveolus, and is expelled upon exhalation.

Question 33

Composition of air

Answer 33

Inspired air: 79% nitrogen, 21% oxygen, other trace gases

Exhaled air: 79% nitrogen, 16% oxygen, 5% carbon dioxide, other trace gases

Question 34

Partial pressure of oxygen and CO2

Answer 34

Inside the lungs:

Oxygen ~110 mmHg
Carbon dioxide ~40 mmHg

Question 35

Hemoglobin

Answer 35

98% of the oxygen in the blood binds rapidly and reversibly with the protein hemoglobin inside the erythrocytes forming oxyhemoglobin.

Hemoglobin is composed of 4 polypeptide subunits, each with a single heme cofactor. The heme cofactor is an organic molecule with an atom of iron at its center.

Each of the four iron atoms in hemoglobin can bind with one oxygen molecule.

When one oxygen molecule binds with an iron atom in hemoglobin, oxygenation of the other heme groups is accelerated. Similarly, release of an oxygen molecule by any of the heme groups accelerates release by the others.

This phenomenon is called cooperativity.

Question 36

Hemoglobin dissociation curve

Answer 36

As oxygen pressure increases, the oxygen saturation of hemoglobin increases sigmoidally. Shows the percent of hemoglobin bound with oxygen at various partial pressures. IN the arteries of a normal person breathing room air, the oxygen saturation of 97%. The flat portion of the curve shows that small fluctuations of oxygen pressure have little effect.

Question 37

Oxygen dissociation curve

Answer 37

Oxygen saturation of hemoglobin depends on carbon dioxide pressure, pH, and temperature of the blood.

The O2 dissociation curve is shifted to the right (indicating a decrease in hemoglobin’s binding affinity to oxygen) by:

• an increase in carbon dioxide pressure,
• hydrogen ion concentration,
• temperature,
• 2, 3 BPG, a chemical found in red blood cells.

(Note that carbon monoxide has more than 200x greater affinity for hemoglobin than does oxygen, but shifts the curve to the left.)

Question 38

3 ways carbon dioxide is carried to the blood

Answer 38

1. In physical solution,
2. As bicarbonate ions (10x as much),
3. In carbamino compounds

(As the blood moves through the systemic capillaries, oxygen diffuses to the tissues, and carbon dioxide diffuses to the blood)

Question 39

Carbonic anhydrase

Answer 39

Bicarbonate ion formation is governed by the enzyme carbonic anhydrase, which is found in red blood cells, in the reversible reaction:

CO2 + H20 –> HCO3- + H+

Question 40

Carbon dioxide

Answer 40

CO2 has its own dissociation curve, which relates blood content of carbon dioxide with carbon dioxide pressure. The greater the pressure of carbon dioxide, the greater the blood content of carbon dioxide. However, when hemoglobin is saturated with oxygen, its capacity to hold carbon dioxide is reduced. This facilitates the transfer of carbon dioxide from the blood to the lungs, and from the tissues to the blood.

Question 41

Rate of breathing

Answer 41

There is a connection between rate of breathing and carbon dioxide, pH, and oxygen levels in the blood.

In the case of acidosis– too much acid in the blood– the body compensates by increasing the breathing rate, thereby expelling carbon dioxide and raising the pH of the blood.

Question 42

Blood pressure and heart rate

Answer 42

Systole occurs when the ventricles contract (blood pressure max), diastole occurs during relaxation of the entire heart and then contraction of the atria (blood pressure min).

The blood is propelled by the hydrostatic pressure created by the contraction of the heart. The RATE of these contractions is controlled by the autonomic nervous system, but the heart contracts automatically.

Question 43

Which is faster: the SA node? Or normal heartbeats?

Answer 43

The pace of the SA node is faster than normal heartbeats but the parasympathetic vagus nerve innervates the SA node, slowing the contractions. The action potential generated by the SA node spreads around both atria causing them to contract, and at the same time, spreads to the AV node.

(Note that “to innervate” means to supply with nerves.)