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MCAT Biology > Respiratory System > Flashcards

Respiratory System Flashcards

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1
Q

How are the circulatory and the respiratory system related?

A

They all concern the transport and delivery of important substances throughout the body
Deliver oxygen to tissues, allowing cells to perform metabolism, generating energy (ATP)
Make the use of branching structures to generate high surface area for exchange of materials

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2
Q

How is the blood the link between the respiratory and cardiovascular systems?

A

Blood carries oxygen throughout the body for delivery, after oxygen diffuses into blood
Oxygen binds to a carrier molecule and is carried throughout the body for delivery to the tissues
Cardiovascular system deposits excess fluid into tissues which is carried away by the lymphatic system

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3
Q

What is the overall function of the respiratory system?

A

Used by body to ensure that the cells have a constant supply of oxygen and can prevent buildup of carbon dioxide in tissues
Oxygen used in last step of chemiosmotic synthesis of ATP
Carbon dioxide is produced by Krebs cycle, need to prevent buildup along with other waste products

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4
Q

What are additional functions of the respiratory system?

A

Traps potentially harmful incoming particulate matter and ushers out of body (protects against disease)
Involved in thermoregulation or regulation of body temperature. Panting increases respiration rate, bringing more water into upper part of respiratory tree that can evaporate and cool the body
Nasal and tracheal capillary beds participate in a method of thermoregulation
Prepares air by moistening, warming, and cleaning it

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5
Q

How might a defect in microtubule production affect breathing?

A

Ciliated cells in the respiratory tract play a role in filtering the air by trapping foreign particles
Microtubules are found in cilia (also Fallopian tubes and ependymal cells of spinal cord)
therefore, defect in microtubules leads to defected cilia and improper filtering of air

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6
Q

What is the movement of oxygen and carbon dioxide in the respiratory system governed by?

A

Changes in pressure differential between the chest cavity and external environment

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7
Q

What is the path of air through the respiratory system?

A

Air enters and moves through the pharynx, larynx, trachea, bronchi, bronchioles, and into the alveoli where oxygen is exchanged for carbon dioxide from the blood

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8
Q

Nasal Cavity

A

Space inside the nose
Structures and substances in nasal cavity act to filter, moisten, and warm incoming air
Nasal hairs at front of cavity trap large dust particles
Mucus secreted by goblet cells trap smaller dust particles that bypass course nasal hair, and moistens air
Capillaries in nasal cavity warm the air

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9
Q

How does nasal cavity participate in immune function?

A

Cilia move mucus and dust back toward the pharynx to be removed by spitting or swallowing
Prevents potentially harmful substances from entering the body

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10
Q

Pharynx

A

Passageway for food and air

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11
Q

Larynx

A

Contains the vocal chords and sits behind the epiglottis, which blocks opening of trachea during swallowing

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12
Q

Epiglottis

A

Cartilaginous structure that rises to block the opening of the trachea during swallowing, preventing entry of food into airway
Nongaseous material that enters the larynx triggers a coughing reflex (forced back out)

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13
Q

Trachea

A

AKA windpipe
Lies in front of esophagus
Composed of ringed cartilage covered by ciliated mucous cells
Mucus and cilia in trachea collect particulate matter and usher back out towards pharynx
Trachea splits into right and left bronchi

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14
Q

Bronchi

A

Splits of the trachea before entering the lungs into right and left branches

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15
Q

Bronchioles

A

Smaller branches off of the bronchi

Terminate in grape-like clusters called alveolar sacs

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16
Q

Alveoli

A

Alveolar sacs are clusters which terminate the bronchioles and contain the alveoli
Location where diffusion of oxygen occurs into adjacent capillaries, where oxygen is picked up by red blood cells
Carbon dioxide diffuses from red blood cells to the alveolus and expelled upon exhalation

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17
Q

How does the branching of the airways allow for better gas exchange?

A

Large surface area allows for increased surface area of gas exchange, thus allowing for very efficient process

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18
Q

When does air flow into the lungs? When does it flow out of the lungs?

A

When airway and alveoli are at a negative gauge pressure, air flows inwards
When airways and alveoli pressure becomes greater than atmospheric air pressure, air flows out towards environment

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19
Q

What is the pressure of the chest cavity at rest

A

Pressure of chest cavity at rest is negative compared to atmospheric pressure
Lungs have natural tendency to collapse inward due to their elasticity, while rib cage expands outwards in opposite direction

Alveolar pressure is equal to atmospheric pressure, so air does not flow inwards

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20
Q

When does inspiration begin?

A

Medulla oblongata of midbrain signals the diaphragm to contract via the phrenic nerve
Diaphragm is a thin sheet of skeletal muscle that is dome-shaped when relaxed, and flattens more upon contraction, expanding chest cavity
Intercostal muscles in ribs help expand chest cavity also
Pressures in airway and alveoli also become negative at this point

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21
Q

When does chest cavity shrink?

A

Medulla oblongata stops stimulating the phrenic nerve, causing the chest cavity to shrink
Elasticity and resiliency of lungs, and increased pressure in chest cavity forces air out
Known as expiration, usually passive unless exercising

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22
Q

How can expiration become an active process?

A

Forced expiration is needed during exercise to increase the amount of oxygen delivered to tissues
Shrinking of chest cavity aided by abdominal muscles and set of intercostal muscles distinct from those involved in inspiration

23
Q

Surface tension

A

Force present in alveoli due to high ratio of surface area to volume, and thin layer of water which has high intermolecular forces that cover the inner surface of the alveolus
Generates pressure that tends to collapse alveolus and oppose lung expansion
Counteracts ability of lungs to expand in response to changing pressure

24
Q

Surfactant

A

Material composed of amphipathic phospholipids
Coats the alveolar surface and breaks up the intermolecular forces between water molecules, reducing surface tension
Surfactant decreases surface tension and assists the expansion of the lungs

25
Q

When other factors are held constant, how does an increase in volume affect pressure?

A

As with PV=nRT, we can see that an increase in V with all other variables constant leads to a decrease in pressure
Therefore, when the lungs and chest cavity expands, the pressure will decrease

26
Q

What process does alveolar gas exchange use?

A

Diffusion, tendency of gas to travel towards an area of lower concentration or pressure
Differing partial pressures of oxygen and carbon dioxide ensure movement in correct direction

27
Q

What is the composition of the air we breathe and exhale?

A

Breathe in: 79% N, 21% O, negligible trace gases
Breathe out: 79% N, 16% O, 5% CO2, trace gases
Lungs: pO2 110mm Hg, pCO2 40 mm Hg
Deoxygenated blood in pulmonary capillaries: pO2 40 mm Hg, pCO2 46 mm Hg

28
Q

Differential partial pressure

A

Causes oxygen to diffuse from 110 mm Hg in lungs to capillaries with 40 mm Hg
Causes CO2 to diffuse from 46 mm Hg in capillaries to 40 mm Hg in lungs
Blood transported CO2 away from cells as waste, so has high pCO2 compared to alveoli
High pO2 in alveoli compared to low pO2 in deoxygenated blood in adjacent capillaries promote diffusion

29
Q

How does O2 and CO2 diffuse

A

Small nonpolar molecules like CO2 and O2 can diffuse passively through cell membrane

30
Q

Fick’s Law

A

Rate of diffusion across a membrane is directly proportional to the surface area and differential partial pressure across the membrane
Inversely proportional to thickness of membrane

31
Q

What law describes the amount of gas that can be dissolved into the blood?

A

Henry’s Law
Amount of gas that can be dissolved in solution is directly proportional to partial pressure of gas in equilibrium with liquid
C = P x solubility (C is conc. Of dissolved gas, P is partial pressure)
As partial pressure of gas increases, conc. Of gas dissolved in solution increases

32
Q

Explain how the dissolution of Oxygen in blood occurs

A

As inhalation occurs, pO2 of O2 rises in alveoli, and therefore O2 diffuses into the capillaries from the alveoli down the concentration gradient. As pO2 of the blood rises, the amount of O2 dissolved in the blood rises until it reaches the high pO2 found in the alveoli
Facilitates dissolution of O2 in blood

33
Q

Is the solubility of O2 in blood high enough for sufficient O2 to be dissolved for transport to the body’s cells?

A

No, the solubility is not high enough
Therefore, the body requires hemoglobin to transport O2
98% of O2 in the blood binds rapidly and reversibly with the protein hemoglobin in erythrocytes, forming oxyhemoglobin

34
Q

Hemoglobin

A

Composed of four polypeptide subunits, each with a single heme cofactor
Heme cofactor is organic molecule with an atom of iron at its center
Each Four iron atoms can bind with one O2 molecule

35
Q

Cooperativity of Hemoglobin

A

When one iron atom binds O2 molecule, oxygenation of other heme groups is accelerated
When one O2 molecule is released by any heme groups, accelerates release of other O2 molecules

36
Q

What is an oxygen dissociation curve of hemoglobin?

A

A figure that shows percent of hemoglobin that has bound oxygen at various partial pressures of O2, shows oxygen affinity
Similar to modified Michaelis-Menten enzyme curve (although hemoglobin not an enzyme), although increases sigmoidally (S-shaped) instead of linearly
% saturation of hemoglobin increases as pO2 increases and then levels off when all subunits have bound O2

37
Q

What environmental factors can affect the oxygen saturation of hemoglobin?

A

Carbon dioxide pressure, pH, temperature of blood
Increase in pCO2, H+ ion conc., or temperature -> rightward shift of curve
Reflect’s hemoglobin’s lower affinity for O2 under these conditions

38
Q

Bohr shift

A

A rightward shift in hemoglobin’s oxygen dissociation curve due to increasing hydrogen ion concentration (decreased pH)
Also when CO2 increases, because increased CO2 causes lowered pH in blood
CO2 and H+ ions affect O2 dissociation curve through allosteric effects, binding to deoxygenated hemoglobin and discouraging binding of O2

39
Q

2,3- DPG

A

AKA 2,3-BPG
Chemical found in red blood cells that shifts hemoglobin’s O2 dissociation curve to right by binding deoxygenated hemoglobin and decreasing affinity for O2
Increases in response to low O2 environments, such as high altitudes
Ensures all tissues still receive sufficient O2, by releasing O2 at low pO2s

40
Q

What does a rightward shift in the oxygen dissociation curve of hemoglobin indicate?

A

At the same pO2, percent saturation of hemoglobin with O2 will be lower.
Means that more O2 will be left at the tissues at lower pO2s

41
Q

Haldane Effect

A

Oxygenation of hemoglobin means it has a lower affinity to bind CO2
Facilitates transfer of CO2 from blood to lungs, because where there are high pO2s at the interface between blood and lungs, CO2 will be released and then diffuse into alveoli
In tissues, where pO2s are lower, CO2 binds to hemoglobin and is carried to lungs

42
Q

Reduced hemoglobin

A

Hemoglobin without Oxygen

Can act as a blood buffer by accepting excess protons produced by conversion of CO2 to bicarbonate ion

43
Q

What type of inhibitor is Carbon monoxide to Oxygen binding to hemoglobin?

A

Competitive inhibitor
binds to same location
Affinity of hemoglobin for CO is 200x greater than affinity for O2
CO shifts O2 dissociation curve to the left, reflecting heightened affinity in remaining sites for O2
Max saturation is lowered as well, related to amount of CO present
O2 does not unload in tissues as it should, so O2 delivery severely limited

44
Q

Where is CO2 at high partial pressures in body?

A

High in tissues, because produced as a waste product from aerobic respiration and builds up
CO2 diffuses back into blood

45
Q

What three forms is CO2 carried in the blood?

A
  1. Dissolved in solution (10x as much as other types)
  2. Bicarbonate ion
  3. Carbamino compounds (combined with hemoglobin and other proteins)
46
Q

Formation of Bicarbonate

A

Catalyzed by carbonic anhydrase in reversible reaction
CO2 + H2O HCO3- + H+
Predominant direction predicted according to Le Chatelier’s Principle
Forward reaction dominates in tissues, forming bicarbonate ion
Backward reaction dominates in lungs, forming CO2 for expiration
When blood is too basic, forward reaction dominates

47
Q

Chloride Shift

A

When CO2 absorbed from tissue by RBCs, bicarbonate builds up and is exchanged for chloride into plasma so that blood remains neutral and RBCs release bicarbonate into plasma
Chloride shift occurs in opposite direction in the lungs- chloride ions flow into plasma in exchange for bicarbonate ions
RBCs then convert bicarbonate back to CO2 to expire

48
Q

Respiratory Centers of Nervous System

A

Medulla oblongata
Regulates breathing rate and can respond to changes in chemical composition of blood
Monitor pCO2 with central and peripheral chemoreceptors (located in medulla and carotid arteries/aorta, respectively)
High CO2 sensitivity, quickly triggers increased respiration, bc can lead to acidosis, dangerous decreases in pH in blood

49
Q

Is pO2 or pCO2 monitored more closely in nervous system respiratory centers?

A

In medulla, pCO2 is monitored more closely, because can lead to dangerous acidosis
- monitored by central and peripheral chemoreceptors
Partial pressure of O2 must drop significantly in order to change respiratory rate
- mainly monitored by peripheral chemoreceptors

50
Q

Inspiratory Center

A

Area in medulla which stimulates inspiration by signaling the diaphragm to contract

51
Q

Expiratory center

A

Signals muscles that assist in forced exhalation (intercostal) when necessary

52
Q

PH Control

A

Nervous system controls levels of pH in blood by adjusting breathing rate
Increases breathing rate when pH decreases to remove more CO2, thus removing H+ ions in blood

53
Q

What effect does Nitrogen in air have on body?

A

Nitrogen is extremely stable due to strong triple bond
Diffuses into blood, but doesn’t react with chemicals in blood
When diving in deep areas, more N diffuses into blood and as divers emerge from water the pressure decreases and gas volume increases
This can form dangerous bubbles in the blood if not enough time is allowed to emerge, leading to decompression sickness, can occlude vessels and cause death

54
Q

Hydration of CO2

A

Conversion of CO2 to bicarbonate

Produces H+, requires H2O

MCAT Biology (14 decks)

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