The Cardiovascular System; The Respiratory System Flashcards
Systemic circulation
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.
Pulmonary circulation
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.
Closed circulatory system
Since there are no openings for the blood to leave the vessels, the entire systemic and pulmonary circulatory systems are said to be closed.
Heart
A large muscle. Its fibers form a net, and the net contracts upon itself, squeezing blood into the arteries.
Sinoatrial node
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.
Electrical synapses/gap junctions
The SA node contracts by itself at regular intervals, spreading its contractions to the surrounding cardiac muscles via electrical synapses made from gap junctions.
Vagus nerve
The pace of the SA node is faster than normal heartbeats but the parasympathetic vagus nerve innervates the SA node, slowing the contractions.
Atrioventricular node
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.
Bundle of His
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.
Purkinje fibers
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.
Arteries
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.
Epinephrine
A powerful vasoconstrictor which causes arteries to narrow.
Arterioles
Very small. Wrapped by smooth muscle. Construction and dilation of arterioles can be used to regulate blood pressure as well as to reroute blood.
Capillaries
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:
- Pinocytosis,
- Diffusion or transport through capillary cell membranes,
- Movement through pores in the cells called fenestrations,
- Movement through the space between cells
Venules and veins
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.)
Pulmonary arteries
Contain the most deoxygenated blood in the body.
Continuity equation
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.
Blood velocity
Inversely proportional to cross sectional area
Blood pressure
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).
Diaphragm
Dome shaped muscle. Made of skeletal muscle fibers, separates the thoracic and abdominal cavities. Innervated by the phrennic nerve.
Inspiration
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.
Respiratory system
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.
Microtubules
Microtubules are found in cilia, and ciliated cells are found:
- In the respiratory tract
- In the Fallopian tubes
- 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.
Nasal cavity
Space inside the nose. Filters, moistens, and warms incoming hair.
Coarse hair at the front of the cavity traps large dust particles.
Mucus
Secreted by goblet cells traps smaller dust particles and moistens the air
Capillaries within the nasal cavity
Warm the air
Cilia
Move mucus and dust back toward the pharynx, so it may be removed by spitting or swallowing.
Pharynx
Throat. Functions as a passageway for food and air.
Larynx
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.
Epiglottis
Cartilaginous member that prevents food from entering the trachea during swallowing.
Trachea
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.
Respiratory path
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.
Composition of air
Inspired air: 79% nitrogen, 21% oxygen, other trace gases
Exhaled air: 79% nitrogen, 16% oxygen, 5% carbon dioxide, other trace gases
Partial pressure of oxygen and CO2
Inside the lungs:
Oxygen ~110 mmHg
Carbon dioxide ~40 mmHg
Hemoglobin
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.
Hemoglobin dissociation curve
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.
Oxygen dissociation curve
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.)
3 ways carbon dioxide is carried to the blood
- In physical solution,
- As bicarbonate ions (10x as much),
- In carbamino compounds
(As the blood moves through the systemic capillaries, oxygen diffuses to the tissues, and carbon dioxide diffuses to the blood)
Carbonic anhydrase
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+
Carbon dioxide
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.
Rate of breathing
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.
Blood pressure and heart rate
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.
Which is faster: the SA node? Or normal heartbeats?
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.)
