Respiratory physiology

what are carotid bodies?

small and chemosensitive

\-highly vascularized

\-high metabolic rate

\-contains type 1 glomus cells (chemosensitive) and type 2 sustentactular cells (support carotid bodies)

what are some features of glomus cells?

neuron-like characteristics

\-lots of voltage gated ion channels

\-depolarization triggers action potentials

\-numerous vesicles with neurotransmitters

what are 4 examples of changes that may require changes in rhythm of breathing?

1\.) pulmonary and non-pulmonary diseases

2\.) metabolic demands (reflected by changes in blood P02, PCO2, ph)

3\.) varying mechanical conditions (ex. posture change)

4\.) non-ventilatory behaviours (ex. speaking, sniffing, eating)

tidal volume and respiratory frequency change depending on need

what is the parafacial respiratory group?

neuron group in the ventral respiratory group

\-generates rhythmic excitatory active expiratory rhythmic activity that excites expiratory muscles via polysynaptic pathway

\-expiratory muscles are only active during activity, not at rest

what is the prebotzinger complex?

neuron group in the ventral respiratory group

\-generates excitatory inspiratory rhythmic activity that excites inspiratory muscles via polysynaptic pathway

how is neutral breathing modified?

higher structures of the CNS

\-inputs from central and peripheral chemo/mechanoreceptors in lung and chest wall

where is breathing rhythm indicated?

medulla of the CNS

\-pontine, dorsal and ventral respiratory groups

how do H+ ions transport between tissues and lungs?

H+ made during HCO3- formation

\-deoxyhemoglobin has higher affinity for H+ than oxyhemoglobin

\-large amount of H+ is bound to hemoglobin and not dissolved in RBC or plasma

\-hemoglobin has a role in buffering production of H+ in peripheral tissues and capillaries

\-in lungs, equilibrium is reversed and H+ interacts with HCO3- and hemoglobin is available for binding oxygen

how does CO2 move at the level of the respiratory membrane?

before diffusion: PCO2alv<< PCO2 blood

\-dissolved CO2 in blood diffuses into alv

\-lower PCO2 in plasma cells recalls CO2 from RBC and change equilibrium from CO2/H2O reactions and CO2/hemoglobin reactions

how does CO2 move in the peripheral tissues?

CO2 exits cells, is dissolved in interstitial fluid and diffuses to blood

\-can remain in plasma as dissolved CO2

\-can enter RBCs and remain dissolved as CO2, bound to deoxyhemoglobin or react with water to make HCO3- and H+

what are carbamino compounds?

combine CO2 with an amino group in blood proteins (globins in hemoglobin)

\-produced carbaminohemoglobin

\-requires no enzyme

what is respiration?

exchange of gas molecules through a membrane or liquid

what is pulmonary vs cellular respiration?

pulmonary: exchange CO2 and O2 in lungs

cellular: exchange O2 and CO2 in individual cells

what is ventilation?

mechanical movement of gas through openings

what are peripheral chemoreceptors?

carotid bodies

\-decrease in arterial PO2 is primary stimulation

\-glomus cells increase firing rate

\-also sensitive to PO2 and PH

\-ventilation is stable over 60-120 mmHg PO2, stimulation occurs below 60

\-ventilation is stable over 40-48mmHg PCO2

what conditions relating to PH, PO2, PCO2 cause an increase in ventilation?

PH: acidosis (low PH)

PO2: hypoxia (low PO2)

PCO2: hypercapnia (high PCO2)

what is the structure of the trachea and primary bronchi?

C shaped cartilage (anteriorly) and smooth muscle posteriorly

what is the structure of bronchi vs bronchioles?

bronchi: plates of cartilage (spotty) and smooth muscle

bronchioles: just smooth muscle

what is the conducting zone?

leads to the gas exchanging region of the lungs

\-anatomical dead space (150mL air)

\-no alveoli, no gas exchange

\-composed of trachea, bronchi, bronchioles and terminal bronchioles

what is the respiratory zone?

where gas exchange occurs- alveoli

\-respiratory bronchioles have occasional alveoli

\-composed of respiratory bronchioles, alveolar ducts, and alveolar sacs

what are the parasternal intercostal muscles?

inspiratory pump muscles

\-contract and pull sternum forward, increasing anterior posterior dimension of rib cage

\-pump handle motion

what is diffusion?

random movement of molecules from high to low concentration

what are 6 functions of the respiratory system?

1\.) provides O2 and eliminates CO2

2\.) filtering action

3\.) regulates blood PH

4\.) contributes to phonation

5\.) contributes to olfaction

6\.) is a reservoir for blood

what are the 6 structures that compose the respiratory system?

1\.) upper airways: nasal/oral cavities, pharynx, larynx

2\.) trachea

3\.) lungs

4\.) muscles of respiration

5\.) rib cage and pleura

6\.) parts of the CNS

what 4 structures make up the nasal cavity?

1\.) superior nasal concha

2\.) middle nasal concha

3\.) inferior nasal concha

4\.) vestibule

what 3 structures make up the pharynx?

1\.) nasopharynx

2\.) oropharynx

3\.) laryngopharynx

what 3 structures make up the larynx?

1\.) epiglottis

2\.) thyroid cartilage

3\.) cricoid cartilage

what are the 2 types of tonsils?

1\.) palatine

2\.) lingual

what are the 2 inspiratory accessory muscles?

1\.) sternocleidomastoid (attached to sternum)

2\.) scalene

what is the diaphragm?

inspiratory pump muscle

\-dome shaped, flattens during contraction

\-abdominal contents forced down and forward, rib cage widens

\-increase in volume of thorax

what are the external intercostal muscles?

inspiratory pump muscles

\-contract and pull ribs upward, increasing thorax lateral volume

\-bucket handle motion

what are the determinants of alveolar PO2 vs PCO2?

PO2: PO2 in atmosphere, alveolar ventilation, metabolic rate, perfusion

PCO2: PCO2 in atmosphere is negligible, alveolar ventilation, metabolic rate, perfusion

increasing metabolic rate decreases alveolar PO2, increasing alveolar ventilation increases alveolar PO2

what are the 3 main reasons that PO2 in the air is greater than PO2 in alveoli?

1\.) warming and humidification of air in tract decreases pressure

2\.) loss of O2 to blood diffusion

3\.) mixing inspired air with FRV

what is Henry’s law?

amount of gas dissolved in a liquid is proportional to the partial pressure of gas in which the liquid is in equilibrium

\-only gas dissolved in solution contributes to partial pressure

how does gas get across the blood-gas barrier?

fick’s law

\-rate of transfer of a gas through a sheet of tissue per unit time is proportional to the tissue area and the difference in gas partial pressure between the 2 sides, a diffusion constant and inversely proportional to thickness

\-CO2 solubility is higher than O2

what is Dalton’s law?

in a mixture of gases, each gas operates independently

\-total pressure is the sum of individual pressures

what are the regional differences in PIP?

top:0

middle: -7

bottom: -4

very bottom: -2

weight of lungs increases in regions near bottom

alveoli at the bottom of the lungs start more deflated, so they get more inspired air

what are the regional differences in ventilation? what causes them?

upper zone has the lowest ventilation

\-lowest zone has the greatest ventilation

\-caused by gravity and posture

what are the 5 steps of respiration?

1\.) ventilation: exchange of air between atmosphere and alveoli by bulk flow

2\.) exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion

3\.) transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow

4\.) exchange of O2 and CO2 between blood in tissue capillaries and cells in tissue by diffusion

5\.) cellular utilization of O2 and production of CO2

what are the 4 steps to producing respiratory airflow?

1\.) CNS sends rhythmic excitatory drive to respiratory muscles

2\.) respiratory muscles contract rhythmically and in an organized pattern

3\.) changes in volume and pressures at the level of chest and lung occur

4\.) air flows in and out

what are the 3 inspiratory and 2 expiratory pump muscles?

inspiratory

1\.) diaphragm

2\.) external intercostals

3\.) parasternal intercostals

expiratory

1\.) internal intercostals

2\.) abdominals

what are the 3 inspiratory and 1 expiratory airway muscles?

inspiratory

1\.) tongue protruders

2\.) alae nosi

3\.) muscles around airway (larynx and pharynx)

expiratory

1\.) muscles around airway (larynx and pharynx)

what is carbonic anhydrase?

forms carbonic acid from carbon dioxide and water

\-carbonic acid is further broken down into bicarbonate which goes into and out of an RBC by exchanging positions with a chloride ion

what 3 forms is carbon dioxide carried as in the blood?

1\.) dissolved (5%)

2\.) bicarbonate (60-65%)

3\.) carbamino compounds (25-30%)

on an oxygen hemoglobin binding curve, what does a shift right vs a shift left correlate to? what shift occurs when increasing temp, PCO2, PH, and DPG?

shift right: oxygen affinity for hemoglobin is reduced, more unloading

shift left: oxygen affinity for hemoglobin is increased, less unloading

increase temp: shift right

increase PCO2: shift right

increase ph: shift left

increase DPG: shift right

how does oxygen diffusion occur in the peripheral tissue?

before diffusion: PO2 blood>PO2 of interstitial fluid>PO2 cell> PO2 mit.

\-causes net diffusion from blood to cell and into mitochondria

how does oxygen diffusion occur at the level of the respiratory membrane?

before diffusion: PO2 alv>> PO2 blood

at equilibrium, they are equal

\-most oxygen is bound to hemoglobin, and PO2 values only count dissolved O2

How does anemia and polycythemia change the amount of hemoglobin to be bound by oxygen?

normal: 15g/ 100mL blood

anemia: 10g due to RBC destruction; decrease hemoglobin

polycythemia: 20 g due to increase in red blood cells; increase hemoglobin

what 3 pressures are involved in movement of air in and out of lungs?

1\.) intrapleural pressure (PIP)

2\.) alveolar pressure (Palv)

3\.) transpulmonary pressure (PTP)

what is intrapleural pressure?

pressure in the pleural cavity

\-acts as a vacuum

\-fluctuates with breathing but is always subatmospheric due to opposing directions of recoil of lungs and thoracic cage

what is alveolar pressure?

pressure of the air inside the alveoli

\-when glottis is open and no air flows, the pressure in all parts of the respiratory tree and equal to Patm

\-Palv-Patm governs gas exchange

what is transpulmonary pressure?

a transmural pressure

PTM= Palv-PIP

Palv is always greater than PIP

keeps alveoli open

determines lung volume

what are the values of Palv, Patm, and PIP at rest?

Palv: 0mmHg

Patm: 0 mmHg

PIP: -4mmHg

what are the values of Palv, Patm, and PIP during forced inspiration?

Palv: -2mmHg

Patm: 0mmHg

PIP: -7mmHg

what are the values of Palv, Patm, and PIP during quiet inspiration?

Palv: -1mmHg

Patm: 0mmHg

PIP: -6mmHg

what are the values of Palv, Patm, and PIP during quiet expiration?

Palv: 1 mmHg

Patm: 0mmHg

PIP: -4mmHg

what is functional residual capacity?

the volume of air remaining in lungs at the end of a normal expiration?

FRC= RV+ ERV

What is total lung capacity?

volume of air in lungs at the end of a max inspiration

TLC= FRC + TV+ IRV

TLC= VC+ RV

What is the common tidal volume? What is total/minute ventilation? What is alveolar ventilation?

TV= 0.5L

total/minute ventilation: total amount of air moved into respiratory system per minute

TV X respiratory frequency (\~7.5L/min)

alveolar ventilation: amount of air moved into alveoli per minute, depends on anatomical dead space (\~5.25L/min)

for the 3 breathing patterns, how is alveolar ventilation impacted if minute ventilation is kept constant?

1\.) shallow and fast: no alveolar ventilation

2\.) normal and quiet: medium alveolar ventilation

3\.) deep and slow: large alveolar ventilation

what is the plateau in the sigmoidal dissociation curve? what is the steep portion?

plateau: saturation stays high over a wide range of alveolar PO2

steep portion: PO2 40-60mmHg; unload large 02 amounts with only small decrease in PO2, increase in metabolic rate causes further decrease in tissue PO2 (10-40mmHg)

what are some features of oxygen transport in the blood?

O2 is carried in 2 forms: dissolved (2%) and hemoglobin (98%)

\-very low solubility, higher when bound to hemoglobin

\-O2 content is proportional to PO2 and solubility

\-CO= 5L/min, so O2 content in blood that’s carried to peripheral tissues is 1000mL O2/min

\-hemoglobin saturation of arterial blood with 1000mmHg PO2 is 97.5%, 75% for venous blood and 40mmHg PO2

\-hemoglobin saturation is sensitive to PH, PCO2 and temperature

how is ventilation and perfusion in alveoli matched?

\- decrease in airflow to region of lung causes a decrease in PO2 in pulmonary blood, causing vasoconstriction of pulmonary vesicles and a decrease in blood flow

\-a decrease in blood flow to regions of the lung causes a decrease in alveolar PCO2, resulting in broncho constriction and a decrease in airflow

\-decreases in ventilation match decreases in perfusion and vice versa

what is pulmonary hypoxic vasoconstriction?

unique response of pulmonary capillaries to low O2

\-send blood to other regions where there are better ventilated alveoli

how does the ventilation perfusion relationship change throughout a healthy lung?

top of lung: ventilation greater than perfusion

bottom of lung: ventilation less than perfusion

homeostatic mechanisms exist to limit mismatch

what is a shunt?

lowV/Q ratio, airway obstruction

\-portion of venous blood doesn’t get oxygenated and goes back to arterial blood

\-decrease in O2 and increase in CO2

\-value will continue to drop until values between alveoli and blood are the same

what is anatomical dead volume?

volume of conducting airways that don’t participate in gas exchange

what is alveolar dead volume?

regions of the lungs with high V/Q ratios

\-areas that are overventilated and underperfused

\-portion of fresh air reaching alveoli cannot be taken up by blood

in alveoli: increase in PO2 and a decrease in PCO2

what is the ventilation perfusion ratio?

balance between ventilation and perfusion

\-effects alveolar levels of O2 and CO2

\-increase in ventilation= closer alveolar PO2 and PCO2 approach their respective values in inspired air

\-increase in perfusion= closer composition of local alveolar air approaches mixed venous blood

in alveoli: O2= 100mmHg, CO2= 40mmHG

in blood: O2= 40mmHg, CO2= 45mmHg

what are some features of pulmonary capillaries?

blood passes at 0.75 seconds at rest, but 0.3 seconds when CO increases

\-collapsible, if pressure falls below alveolar pressure, capillaries close off and divert blood to other capillary beds with higher pressure

what are 3 characteristics of the pulmonary circulatory system?

1\.) low pressure: need to pump blood only to top of lungs, important for avoiding rupture of respiratory membrane and edema formation

2\.) low resistance: resistance is less than 1/10 that of systemic circulation because vessels are shorter and wider

3\.) high compliance vessels: increase number of arterioles with a low resting tone due to little smooth muscle, thin walls and less smooth muscle means they can accept large amounts of blood, dilate in response to modest increases in arterial pressure

what is perfusion of the lung? what is it determined by?

blood flow

\-determined by cardiac output (volume of blood pumped by the heart in 1 minute)

\-flow systemic circulation= flow pulmonary circulation

what is alveolar surfactant?

produced by type 2 alveolar cells

\-lowers surface tension of lining fluid to breathe with less effort and makes alveoli stable against collapse

\-contains phospholipids, calcium ions, surfactant apoproteins and phosphatidyl-choline

\-is amphphipathic so it can get in air-water interface and decrease density of water molecules

\-easier to expand lungs

\-increasing surface area decreases surfactant thickness

\-premature infants lack surfactant which can cause infant respiratory distress

what is alveolar surface tension?

air entering the lungs is humidified and saturated with water vapour at body temperature

\-water molecules cover alveolar surface which creates surface tension

\-an inward recoil leads to alveolar collapse (decrease V and increase P)

\-alveolar collapse is prevented by surfactant

what is Laplace’s equation?

P= 2T/r

\-T is surface tension and remains constant over different r values

\-this leads to greater pressure in smaller sacs

what is surface tension?

measure of the attracting forces acting to pull a liquid’s surface molecules together at an air-liquid interface

\-arises from H-bonding of water molecules

\-is eliminated in a saline filled lung

what two factors are lung compliance determined by?

1\.) elastic components of the lungs and airway tissue (elastin, collagen)

2\.) surface tension at the air-water interface within alveoli; accounts for 2/3 of elastic recoil of the lungs

\-surface tension decreases lung compliance

what is pulmonary fibrosis?

collagen deposition in alveolar walls

\-due to lung injury, silica dust or asbestos

\-reduces lung compliance (stiff lungs)

\-higher PTP changes are necessary to change lung volume

what is emphysema?

floppy lungs as a result of elastin destruction and alveolar wall destruction

\-increases compliance with less elastic recoil

\-small changes in PTP result in large changes in lung volume

what are the values of Palv, Patm, and PIP during forced expirtion?

Palv: 2mmHg

Patm: 0mmHg

PIP: -3mmHg

what are the 7 steps of quiet inspiration?

1\.) diaphragm and inspiratory intercostals contract

2\.) thorax expands

3\.) PIP becomes more subatmospheric

4\.) increase in transpulmonary pressure

5\.) lungs expand

6\.) Palv becomes subatmospheric

7\.) air flows into alveoli

what are the 8 steps of quiet expiration?

1\.) diaphragm and inspiratory intercostals stop contracting

2\.) chest wall recoils inward

3\.) PIP moves back toward pre-inspiration value

4\.) transpulmonary pressure moves back toward pre-inspiration value

5\.) lungs recoil toward pre-inspiration size

6\.) air in alveoli becomes compressed

7\.) Palv becomes greater than Patm

8\.) air flows out of lungs

what are the 3 sources of friction that cause airway resistance?

1\.) lung tissue past itself during expansion

2\.) lung and chest wall tissue surfaces gliding past eachother- reduced by intrapleural fluid

3\.) frictional resistance to flow of air through airways (80% of total airway resistance)

what is laminar airflow?

subject invests little energy in airflow resistance

\-characteristic to small airways that are distal to terminal bronchioles

what is Poiseville’s law?

airway resistance is proportional to gas viscosity and tube length, and inversely proportional to airway radius

where in the respiratory tract is resistance highest vs lowest? what values does R vary between?

highest: medium sized bronchi

lowest: respiratory zone (due to low aggregated resistance because of lots of alveoli/ terminal bronchi)

R ranges between 0.6-2.3

how does airway resistance change for people with disease?

small airways are greater impacted

\-smooth muscle contraction in walls

\-edema in walls of alveoli and bronchioles

\-mucus collecting in lumen of bronchioles

what is lung compliance?

measure of lung elastic properties and how easily the lungs can expand

\-magnitude of change in lung volume produced by a given change in transpulmonary pressure

\-slope measured in a pressure volume curve

C= change in lung volume/ change in PTP

\-can measure static and dynamic compliance

what is static compliance?

lung compliance during periods of no gas flow

\-P/V slope when measured at FRC

\-abnormally high due to emphysema

\-abnormally low due to pulmonary fibrosis

what is dynamic compliance?

compliance during periods of gas flow

\-when transpulmonary pressure is continuously changing

\-reflects lung stiffness and airway resistance

\-less than or equal to static lung compliance

\-falls when lung stiffness or airway resistance increases

what is hysteresis?

difference between inflation and deflation compliance paths

\-a greater pressure difference is required to open a previously closed/narrowed airway than to keep an open airway from closing

what are the elastic components of airways?

localized in alveolar walls, around blood vessels and bronchi

\-has to do with geometrical arrangements

\-elastin: weak spring, low tensile strength, extensible

\-collagen: strong twine, high tensile strength, inextensible

\-decreases with age

what is the restrictive pattern shown on a spirometry test?

can’t fully fill the lungs

\-restricted from fully expanding

\-condition of lung stiffness, chest wall stiffness, weak muscles, or damaged nerves

\-could be caused by lung fibrosis, neuromuscular disease, or lung tissue scarring

\-reduces FEV and FVC

\-FEV/FVC is almost normal

what is the helium dilution method?

gas dilution technique

\-functional residual capacity

\-helium is insoluble in blood and equilibrates after several breaths

\-concentration C2 is measured at the end of an expiratory effort

V2=FRC

\-measures only communicating gas or ventilated lung volume

\-can measure residual volume

what are the static properties of the lung?

mechanical properties when no air is flowing

\-necessary to maintain lung and chest wall at certain volumes

\-interpleural pressure (PIP), transpulmonary pressure (PTP)

\-static compliance of lung

\-surface tension of lung

what are dynamic properties of the lung?

mechanical properties when lungs are changing volume and air is flowing

\-alveolar pressure

\-dynamic lung compliance

\-airway and tissue resistance

what is Boyle’s law?

for a foxed amount of an ideal gas at a fixed temperature, pressure and volume are inversely proportionals

\-expiration: decrease in volume=increase in pressure; compression

\-inhalation: increase in volume=decrease in pressure; decompression

what pressures are of interest for ventilation?

alveolar and atmospheric

\-inspiration: Palv

what are the 2 types of pleurae and the pleural cavity?

1\.) visceral: covers external lung surface

2\.) parietal: covers thoracic wall and superior face of diaphragm

pleural cavity: has interpleural fluid (10mL) which reduces friction between lung and thoracic wall

what is the elastic recoil of the lungs and chest wall?

lungs: collapse inward

chest wall: pull thoracic cage outward

at equilibrium, lung and chest wall recoils balance eachother out, but there is no direct interaction- occurs through interpleural space between visceral and parietal pleurae