respiratory Flashcards
1
Q
respiratory physiology
A
the study of how oxygen is brought into the lungs and then delivered to the tissue and how carbon dioxide is eliminated from the tissue and from the system
2
Q
functions of the respiratory system
A
- provides oxygen and eliminates carbon dioxide
- protects against microbial infection
- regulates blood ph (kidneys)
- contributes to phonation (the passage through the vocal cords of air allowing speech formation)
- contributes to olfaction (smell)
- a reservoir for blood
3
Q
alveoli
A
fundamental unit of the respiratory system
- embedded in a dense network and tissue characterized by the presence of smooth muscle tissue, cells and connective tissue
4
Q
pharynx
A
composed of the nasopharynx and laryngopharynx
5
Q
larynx
A
contains the vocal cords
6
Q
air passage
A
larynx -> trachea -> two primary bronchi -> lungs
7
Q
trachea and bronchi
A
characterized by a structure that is semi-cartilaginous
- c-shaped rings (made of cartilage) in front and smooth muscle in the back
- provides protection for the airway and gives elasticity
8
Q
bronchi
A
still have some cartilaginous structures but the air pathways are no longer c-shaped, replaced by plates of cartilage and smooth muscle
9
Q
broncioles
A
structure is provided by smooth muscle
10
Q
two classifications of tracheobronchials
A
conducting zone
repiratory zone
11
Q
conducting zone
A
contains the trachea, primary bronchi, bronchioles, and terminal bronchioles
- NO ALVEOLI therefore no gas exchange
- called anatomical dead space
12
Q
respiratory zone
A
further down in the branching of the airways and CONTAINS ALVEOLI
contains the respiratory bronchioles, alveolar ducts and alveolar sacs
where gas is exchanged
13
Q
terminal bronchioles
A
smallest airway without alveoli
14
Q
respiratory bronchioles
A
have occasional alveoli
15
Q
alveoli sacs
A
contains a large number of alveoli
16
Q
tracheobronchial tree
A
each branching is called a generation
- gen 0 (trachea) to gen 23 (alveolar sacs)
both diameter and length of airway decrease at each gen
17
Q
alveoli
A
tiny sacs with a very thin wall
highly vascularized (many capillaries that contact the alveolar surface)
amount of blood in capillaries is variable and changes with metabolic demand
18
Q
type 1 alveolar cells
A
flat epithelial cells
the internal surface of the alveoli is lined with liquid that contains a surfactant (stabilization)
do not divide, susceptible to inhaled or aspirated toxins
19
Q
type 2 alveolar cells
A
not frequently found in the alveoli
- produce surfactant
can act as a progenitor cell (ability to replicated and differentiate into type 1 alveolar cells, which are produced in the late stage of development and stop replication)
can not be replaced when damaged by inhaled toxic agents
20
Q
respiratory membrane
A
respiratory surface made of the alveolar epithelial cell (type 1) and the pulmonary capillary endothelial cell
- very thin, easily damaged
- contain alveolar fluid (with surfactant), alveolar epithelium, basement membrane of alveolar epithelium, interstitial space, basement membrane of capillary endothelium, capillary endothelium
21
Q
pneumocyte
A
one of the cells lining the alveoli of lung (type 1 and 2 alveolar cells)
22
Q
steps of respiration
A
- ventilation
- exchange of oxygen and carbon dioxide btw alveoli and the blood system by diffusion - transport of oxygen and co2 through pulmonary and systemic circulation by bulk flow
- exchange of oxygen and co2 btw blood in tissue capillaries and cells in tissues by diffusion
- cellular utilization of oxygen and production of co2
23
Q
how is respiratory airflow (ventilation) produced?
A
- CNS sends an excitatory drive to respiratory motor neurons that innervate the respiratory muscles
- respiratory muscles contract
- changes the thoracic volume, thoracic pressure, and intrapulmonary pressures
- air flows in and out with different muscle contractions and relaxations
24
Q
3 categories of muscles involved
A
pump muscles
airway muscles
accessory muscles
25
pump muscles
make changes in pressure and volume at the level of the lungs
inspiratory - diaphragm
expiratory
26
airway muscles
muscles located at the level of the airways and have an important role in keeping the upper airways open
- mostly inspiratory but some active in expiration
27
accessory muscle
facilitate respiration when there is an increased metabolic drive (exercising)
28
diaphragm
most important muscle for respiration
- separates the lungs from the abdominal content
29
what happens when the diaphragm contracts
it moves down, allowing the abdominal content to be pushed down, and the rib cage to be pushed outward or widened; overall effect is an increase in the thoracic volume when it contracts
30
external intercostals
inspiratory pump muscles
- contract and lift the rib cage, and promotes a lateral increase in the thoracic volume
- contribute to the expansion of the thorax
- bucket handle motion
31
parasternal intercostals
inspiratory pump muscles
contract and pull sternum forward, increasing anterior posterior dimension of the rib cage
- pump handle motion
32
abdominals
expiratory pump muscles
33
when are expiratory pump muscles active
when you are making an effort to breathe in and out (stress, exercising, coughing)
do not contract during expiration at rest
34
what does deeper, faster breathing require
active contraction of abdominal and internal intercostal muscles to return the lungs to its resting position
35
inernal intercostals
expiratory pump muscles
relaxed at rest and recruited during forced expiration
push the rib cage down to reduce the amount of air or reduce the volume of the thoracic cage
36
accessory inspiratory muscles
not commonly active during resting breathing; active during exercise and forced respiration
37
what happens during quiet inspiration (rest)
diaphragm contracts, pushing abdominal content down and expanding the thorax as air comes in, and the external intercostals and parasternal intercostals
38
obstructive sleep apnea
tone of the upper respiratory muscles is depressed and they become a floppy muscle
- reduction in upper airway patency during sleep
- air cannot go in and out, resulting in snoring and large drops in oxygen saturation in the blood
- due to lack of excitatory drive
39
regions involved in the filtering action
conducting zone and at the level of the alveoli
40
muco-ciliary escalator
filtering action in the conductin zone
41
two types of cells that line the surface of the trachea
goblet cells - sparse, produce mucus, no cilia
ciliated cells - layer of cells with cilia on the apical surface
-- both cell types function in a coordinated manner to entrap inhaled biological and inert particles and remove them from the airways
42
ciliary activity in the removal of deposited particles in the tracheobronchial tree
require ciliary activity and respiratory tract fluids
- ciliated cells produce periciliary fluid that has a very low density; allows cilia to move freely
- fluid sits on top of the ciliated cells) called the SOL layer)
43
goblet cells in the removal of deposited particles in the tracheobronchial tree
produce a very dense, thick mucus called the gel layer
- trap particles that enter the respiratory system during inhalation
- mucus eliminated through cilia movements
44
role of macrophages in alveoli
last defense for eliminating particulates
- silica dust or asbestos - macrophages identify, but cannot digest therefore killing the macrophages resulting in increase of collage, stiffening the lungs
45
spirometry
a pulmonary function test that determines the amount and the rate of inspired and expired air
46
tidal volume
the volume of air moved in or out of the respiratory tract (breathed) during each ventilatory cycle
- 500mL
47
expiratory reserve volume
the additional volume of air that can be forcibly exhaled following a normal expiration, it can be accessed simply by expiring maximally to the max voluntary expiration
48
inspiratory reserve volume
the additional volume of air that can by forcibly inhaled following a normal inspiration, it can be accessed simply by inspiring maximally, to the max possible inspiration
49
residual volume
the volume of air remaining in the lungs after a maximal expiration, it cannot by expired no matter how vigorous or long the effort
-- cannot be measured with a spirometry test
RV = FRC -ERV
50
capacities
measurements of lung volume
- correspond to the sum of 2 or more lung volumes
51
vital capacity (VC)
the max volume of air that can be forcible exhaled after a max inspiration
VC = TV + IRV + ERV
52
inspiratory capacity (IC)
the max volume of air that can be forcible inhaled
IC = TV + IRV
53
functional residual capacity (FRC)
the volume of air remaining in the lungs at the end of a normal expiration
FRC = RV + ERV
54
total lung capacity (TLC)
the volume of air in the lungs at the end of a max inspiration TLC = FRC + TV + IRV = VC + RV
55
total/minute ventilation
the amount of air that is exchanged within a rate time, or within a minute
total/minute ventilation = tidal volume x respiratory frequency 0.5L x 15/min = 7.5L/min -- not all is available for gas exchange
56
alveolar ventilation
(TV - anatomical dead space) x respiratory frequency
(0.5 - 0.15)L x 15/min = 5.25L/min
the amount of air moved into the alveoli per min
57
how do we improve alveoli ventilation
inhale slowly and deeply; improves ventilation of the lung
58
two volumes that can be determined from a spirometry test
forced expiratory volume in 1 second (FEV-1) - how much of the vital capacity volume that can be expelled in 1 sec
forced vital capacity (FVC) - the max volume of air that can be forcible exhaled after a max inspiration
~ 5L in a healthy person
59
obstructive lung disease
- have shortness of breath due to difficulty in exhaling all the air from their lungs
- bronchial asthma, chronic obstructive pulmonary disease, cystic fibrosis
60
restrictive lung disease
- cannot fully fill their lungs with air; lungs are restricted from expanding
- caused from stiffness in lungs themselves, stiffness of chest wall, weak muscles, or damaged nerves
- ratio of FEV-1/FVC similar to healthy person but volumes will be reduced
- lung fibrosis, neuromuscular disease, scarring of lung tissue
61
helium dilution method
measure the functional residual capacity or the amount of air that remains in the lungs at then end of a normal expiration
V2=V1(C1-C2)/C2
62
static properties of lungs
mechanical properties that are present in the lungs when no air is flowing
- necessary to maintain lung and chest wall at a certain volume
- intrapleural pressure (Pip), transpulmonary pressure (Ppt), static compliance of the lung and surface tension of the lung
63
dynamic properties of the lung
mechanical properties when the lungs are changing volume and air is flowing
- alveolar pressure, dynamic lung compliance, airway and tissue resistance
64
ventilation occurs due to
change in pressure, or the generation of a pressure difference, between the atmosphere and the alveoli that will move air into and out of the lungs
65
Boyle's law
for a fixed amount of an ideal gas that is kept at constant temp, the pressure and volume are inversely proportional
P1V1=P2V2
66
flow equation
flow = delta P/R
67
relationship of lungs and chest wall
closely connected to a double layer of pleural tissue
- lungs are embedded inside pleural tissue called visceral pleura
- inside of chest wall is lined by another pleural tissue called parietal pleura
these two pleura are separated by intrapleural fluid - allows the 2 pleural tissues to slide around at each inspiratory effort
68
relationship of lungs and chest wall
closely connected to a double layer of pleural tissue
- lungs are embedded inside pleural tissue called visceral pleura
- inside of chest wall is lined by another pleural tissue called parietal pleura
these two pleura are separated by intrapleural fluid - allows the 2 pleural tissues to slide around at each inspiratory effort
69
during inspiration and expiration air moves in and out of the lungs due to variations of the
intrapleural pressure
alveolar pressure
transpulmonary pressure
70
intrapleural pressure (Pip)
pressure in the pleural cavity
acts as a relative vacuum
always negative
always subatmospheric
71
alveolar pressure (Palv)
pressure of the air inside the alveoli
when no air flow in lungs, equal to atmospheric pressure
Palv-Patm governs the gas exchange btw the lungs and the atmosphere, gives flow
72
transpulmonary pressure (Ptp)
the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall
Ptp = Palv - Pip
always positive
73
forces that can affect resistance to air flow
inertia of the respiratory system
friction
74
friction forces
1 between the different alveolar sacs
2 between the lung and the chest wall (intrapleural fluid significantly decreases this friction)
3 majority of the resistance that is generated is caused by the resistance that the airflow incurs when it enters the airway (80%)
75
laminar airflow
linear fashion
in small airways like the terminal bronchioles
76
transitional airflow
it takes extra energy to produce vortices -> the resistance increases; airflow is transitional throughout most of the bronchial tree, at the ramifications or branches of the bronchial tree
77
turbulent flow
found in larger airways, trachea, larynx, pharynx
the airways are larger and the velocity of the gas molecules is higher resulting in turbulent flow
78
poiseuille's law
r = 8nl/pir^4
for laminar flow
is radius is reduced, resistance will increase
79
for airways arranged in series
the resistance is simply the sum of the individual resistances
80
for airways arranged in parallel
the resistance at each specific gen, when there is respiratory airflow, will be given by the inverse of each specific resistance; as a consequence, the respiratory resistance, at the level of the small airways at the level of the respiratory zone, is minimal
81
small airways are surrounded by
smooth muscle, contraction of the smooth muscle will increase resistance
82
edema
may alter resistance as the presence of fluid in the small airways can reduce the space available for airflow to move in or for the air to flow into the alveolar sacs
83
mucus accumulation
can reduce the alveolar space at the level of the bronchioles
84
lung compliance
a measure of the elastic properties of the lungs and a measure of how easily the lungs can expand
- determined from a plot of transpulmonary pressure (x) and lung volume (y) -- compliance is the slope of the curve
85
static compliance
represents the lung compliance when no air is flowing through
86
pulmonary fibrosis
lung compliance is low
overproduction of collagen
slope is reduced
87
emphysema
lung compliance is high
gradual reduction in lung elastic components
slope is increased
floppy lungs have lost alveolar tissue resulting in less surface respiratory membranes available for gas exchange
88
dynamic compliance of the lung
measured during periods of gas flow
takes into consideration elastic properties and airway resistance
usually less or equal to static compliance
89
hysteresis
defines the difference between the inflation and deflation compliance path
- has to do with elastic properties
90
lung compliance is determined by
elastic components of lungs that are part of the anatomic structures of the lungs and the airway tissue (elastin and collagen)
surface tension at the water-air interface within the alveoli
91
elastin and collagen localized in
alveolar walls, around blood vessels and bronchi
92
surface tension
property or phenomenon that occurs at the level of the interface between the surface and the air
- makes the lungs collapse of gives the lungs elastic recoil
surface tension decreases lung compliance
93
laplace's equation
P = 2T/r
94
what is the result of this pressure difference
as a result of surface tension, the gas that is present in the smaller alveoli will move to the large alveoli, moving from a region of higher pressure to a region of lower pressure
the smaller alveoli will collapse and we will no longer have a multi-faceted, multi-alveolar lung
- this does not occur physiologically due to the presence of surfactant
95
alveolar surfactant
produced by type 2 alveolar cells
functions to reduce the surface tension at the level of the alveoli
improves lung compliance allowing a reduction in the work of breathing
makes the alveoli stable against collapse
allows alveolar communication btw alveoli of different sizes without collapsing
96
regional ventilation changes have to do with
gravity and posture
97
how do we explain the difference in ventilation between different regions of the lungs
there is a negative pressure in the intrapleural space described as subatmospheric which changes between the top of the lung and the bottom of the lung
98
gas exchange
involves the diffusion of gas molecules from the alveoli to the capillary system and the diffusion of gas molecules from the capillary system to the alveoli
99
Dalton's law
states that in a mixture of gas each gas has its specific pressure and the total pressure of this mixture of gas is given by the sum of the individual pressures
100
respiratory membrane
a very thin layer of tissue that contains the fluid, epithelial cells in the alveoli, interstitial space, basement membrane of the capillary epithelium and the epithelium
101
fick's law
the rate of transfer of a gas through a sheet of tissue per unit of time is proportional to the surface area of the membrane and depends on the difference in partial pressures between the two environments, and inversely proportional to the thickness of the membrane
102
diffusion constant (D)
the amount of gas transferred between the alveoli and the blood per unit time is also proportional to the gas solubility in fluids or in tissue
103
henry's law
the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in which the liquid is in equilibrium
104
at the level of the alveoli partial pressure of oxygen is
reduced
105
at the level of the alveoli partial pressure of carbon dioxide is
increased
106
determinants of alveolar PO2
- PO2 in the atmosphere
- alveolar ventilation (more ventilation = more air in system)
- metabolic rate (exercising lowers)
- lung perfusion (change in CO will alter amount of blood that passes through)
107
determinants of alveolar PCO2
- PCO2 in the atmosphere (essentially 0)
- alveolar ventilation (decrease in ventilation will lead to less exhalation of CO2, therefore PCO2 will be increased)
- metabolic rate (inc in rate will inc CO2 production, higher level of PCO2 that diffuses)
- lung perfusion
108
effect of alveolar ventilation
inc Va will inc alveolar PO2 and dec alveolar PCO2
109
inc of PO2 occurs within the first
third of the capillary length; advantageous in a disease condition as the diffusion process can contribute for an extra length of time of length of the capillary compared to a healthy person
110
ventilation/perfusion ratio
the balance between the ventilation (bringing O2 into/removing CO2 from the alveoli) and the perfusion (removing O2 from the alveoli and adding CO2)
normal ratios: PO2 ~ 100-105 mmHg, PCO2 ~ 40 mmHg
111
a high ventialtion/perfusion ratio
- seen when there is a collapsing of the lung capillaries, pleurisy or other diseases that affect the vasculatory system
- blood flow is obstructed or occluded
- alveoli are normally ventilated but there is very little gas exchange that occurs across the respiratory membrane because there is no blood available for gas exchange
- PO2 levels of the alveoli will be inc bc there in no oxygen that passes through the lungs to the vasculature
- PCO2 levels of the alveoli will be dec bc there is no CO2 that is delivered and diffuses from the capillary system to the alveoli
112
low V/Q ratio
- airway obstruction (collapsed bronchi or bronchioles)
- no gas exchange btw alveolar air or alveolar space and the atmosphere
- in alveolar space there will be a decrease in PO2 and inc in PCO2
shunt - portion of the venous blood that does not get oxygenated, that is not available for gas exchange bc of alveolar occlusion
113
changes in lung perfusion can be measured by
injecting a patient with radioactive xenon
- patient holds breath as soon as the radioactive material is injected to measure radioactivity in the different regions of the lung
114
at the base of the lungs
we have 0.6ntimes of the ideal V/Q ratio
- there will be a slightly reduced PO2 level and slightly inc PCO2 level at the bottom of the lung compared to ideal values
115
at the top of the lung
there is 3 times the ideal V/Q ratio
- alveolar PO2 will be inc and PCO2 will be dec compared to ideal values
116
bronchoconstriction in an alveoli
makes diameter of the airway smaller leading to a reduction in local ventilation of that area
- will inc PCO2 and dec PO2
- this reduction in PO2 will have a local effect to cause vasoconstriction of the arterioles; physiological response of reduced ventilation is a reduced perfusion locally; blood will be diverted to the regions where ventilation is still effective
117
oxygen is carried in two forms
dissolved in plasma (2%)
combined with hemoglobin (98%)
118
hemoglobin molecule
protein composed of 4 amino acid subunits called globins (2 alpha and 2 beta) and 4 heme groups
119
heme group
porphyrin ring structure in which an iron atom binds to oxygen
120
PO2 = 100 mmHg
value of PO2 in the blood when it exits the lung capillaries soon after gas exchange occurs at the level of the alveoli
when blood exits the pulmonary capillaries, the percentage of hemoglobin saturation is ~100%
121
PO2 = 40mmHg
PO2 level in the peripheral tissue where the percentage of hemoglobin saturation is ~75%
122
oxygen caoacity
the max amount of oxygen that can be combined with hemoglobin
- depends on how much hemoglobin is present in the blood; a change in the amount of hemoglobin will change the oxygen capacity
123
hemoglobin satursation
the percentage of the available hemoglobin binding sites that have the oxygen attached
124
factors that influence the interaction between hemoglobin and oxygen
- arterial PO2 - most important, as PO2 changes, the percentage of hemoglobin saturatio changes
- ph in the blood
- PCO2
- temp
125
interaction between hemoglobin and oxygen curve
curve is not a linear relationship
as PO2 inc, there will not be a linear inc in the percentage of hemoglobin saturation
- S-shaped due to cooperative binding
126
cooperative binding
occurs due to the fact that we have deoxyhemoglobin
- first molecule of oxygen interacts with the heme group and changes the conformation of the heme group and the globin chains
- the next ones will bind much easier
127
regions of the sigmodial dissociation curve
flat portion: btw 60-100mmHg
steep portion: btw 10-60mmHg
128
plateau
saturations remain high over a wide range of alveolar PO2
many conditions result in reduced alveolar PO2 and therefore arterial PO2
- provides safety factor so that even a significant limitation of lung finction still allows almost normal O2 saturation of Hb
129
steep portion
region btw 10-40mmHg - during high metabolic rate; inc in metabolic rate cause further dec is tissue PO2, which facilitates diffusion from plasma which leads to drop in plasma PO2, diffusion of O2 from RBC, drop in PO2 in RBC, additional dissociation of O2 from Hb
region btw 40-60mmHg - unload large amounts of O2 with small decrease in PO2
- it is important that PO2 remains relatively high in the capillary of peripheral tissue since this pressure is necessary to drive diffusion of O2 from RBC to blood to cells and mitochondria
130
3 conditions shown by sigmoidial curve with different amounts of Hb in the blood
Hb at 10gm/100mL of blood - low Hb as seen in anemia
Hb at 15gm/100mL of blood
Hb at 20gm/100mL of blood - high Hb as in polycythemia
131
what is the difference btw these curves
if the hemoglobin is fully functional, it will still be able to bind to oxygen and therefore the sigmoidal curve will not be affected
132
movement of oxygen
oxygen moves from RBC -> plasma -> interstitial fluid -> space btw cells -> internal space in cell -> MIT; oxygen use by MIT creates pressure gradients
133
factors affecting binding btw Hb and O2
arterial PO2
134
changes to right
O2 affinity of Hb is reduced = more unloading
135
factors which cause a shift to the right of the oxygen dissociation curve
factors which inc metabolism will cause more oxygen unloading
- inc body temp
- inc in PCO2
- inc in hydrogen ion production
136
2,3 diphosphoglycertae (DPG)
present in RBC and is an end product of RBC metabolism
shifts oxygen dissociation curve to the right
137
changes to the left
O2 affinity of Hb is increase = less unloading
138
CO2 is carried in the blood in 3 forms
dissolved (5%)
bicarbonate (60-65%)
carbamino compounds (25-30%)
139
carbonic acid
CO2 reacts with H2O - extremely fast due to presence of carbonic anhydrase
dissociates into hydrogen ions and bicarbonate
140
chloride shift
a rise in intracellular bicarbonate leads to bicarbonate export and chloride intake
- bicarbonate exits the RBC into the plasma; the movement of chloride anions into the RBC maintains electrical neutrality in the RBC
to maintain electrical neutrality, H will inc in venous blood (dec ph)
141
CO2 transport
CO2 interacts with the globin chain of hemoglobin to form a carbamino compound called carbaminohemoglobin
CO2 has a higher affinity for deoxyhemoglobin and will shift equilibrium towards a more dissociated hemoglobin-oxygen molecule
- if PCO2 inc, the oxygen-dissociation curve shift to the right and there is a lower percentage of hemoglobin that is bound to oxygen
in the presence of high CO2 levels, there is inc oxygen unloading from hemoglobin bc CO2 will bind preferentially to deoxyhemoglobin
142
when RBCs and plasma arrive at the level of the alveoli
- a pressure gradient will drive CO2 from the plasma to the alveoli
- cause more CO2 to move from inside RBC to plasma
- bicarbonate will diffuse back into RBC -> react with hydrogen ions to produce carbonic acid and more CO2
143
importance of interaction btw hemoglobin and hydrogen ions
- unloading of oxygen - lower ph reduced hemoglobin saturation of oxygen
- hemoglobin buffers the change in ph at the level of the venous blood
144
respiratory acidosis
hypoventilation (CO2 production > CO@ elimination) not only PCO2 inc but also H conc inc
145
respiratory alkalosis
hyperventilation (CO2 production < CO2 elimination) not only PCO2 dec but also H conc dec
146
metabolic acidosis
inc in blood H conc independent from changes in PCO2
147
metabolic alkalosis
dec in blood H conc independent from changes in PCO2
148
3 regions in the brainstem that control breathing
pontine respiratory group, dorsal respiratory group, ventral respiratory group
149
breathing is
initiated in the medulla by specialized neurons
modified by higher structures of the CNS and inputs from central and peripheral chemoreceptors and mechanoreceptors in the lung and chest wall
150
pre-botzinger complex
inspiratory rhythm generator
group of neurons in the ventral respiratory group
generate excitatory inspiratory rhythmic activity that excites inspiratory muscles
151
parafacial respiratory group
group of neurons within the ventral respiratory group
important for generation of active contraction of abdominal muscles
152
why must the rhythm of breathing change
accommodate changes in:
metabolic demands
varying mechanical conditions
non-ventilatory behaviors
pulmonary and non-pulmonary diseases
153
rhythm of breathing
- generated in the ventral respiratory group in medulla
- prebotc and pfrg neurons drive activity in premotor neurons, which excite motorneurons that activate rhythmically respiratory muscles
- rhythmic activity is influenced by sensory and neuromodulatory inputs origniating from different regions within and outside the cns
154
pre-botzinger and parafacial respiratory groups
fundamental for generating rhythm which is influenced by several factors
- neuromodulatory factors (neurotransmitters)
- suprapontine influences that are volitional or emotional
- sensory inputs can also influence the rhythm of breathing
155
chemical control of ventilation
peripheral and central chemoreceptors sense changes in levels of PCO2 PO2 and pH
- provide an excitatory drive to the centres in the brainstem that control respiratory activity (dorsal respiratory group and the ventral respiratory group)
156
peripheral chemoreceptors
carotid and aortic bodies
- mostly sense changes in arterial PO2 and will also be activated by changes in pH
157
carotid bodies
extremely small
chemosensitive
highly vascularized
high metabolic rate
2 cell populations
- type 1 glomus cell
- type 2 sustentacular cells
158
glomus cell
characteristics that are similar to neurons
- have voltage-gated ion channels
- can generate action potential following depolarization
- inc respiratory drive to the muscles and therefore inc ventilation
159
peripheral chemoreceptors
respond to changes in arterial PO2; at physiological conditions, little changes in PO2 will not affect minute ventilation very much; it is not until arterial PO2 levels are below 60mmHg, as occurs in certain lung diseases or high altitude, that there is a very strong inc in minute ventilation
160
central chemoreceptors
specialized neurons located close to the ventral surface of the medulla
sense changes in PCO2
stimulated by inc in production of hydrogen ions
161
hypercapnia
a condition where there is too much carbon dioxide in the blood; arterial PCO2 levels are high
162
metabolic acidosis
occurs with the production of acids which are carried in the blood and are not associated with changes in PCO2 (lactic acid)
