Respiration Flashcards
1
Q
What are the 6 functions of the respiratory system?
A
- Provide oxygen, eliminate carbon dioxide.
- Protect against infection.
- Regulate blood pH.
- Phonation (speaking)
- Olfaction.
- Reservoir for blood.
2
Q
What structures comprise the respiratory system?
A
- Upper airways.
- Trachea.
- Lungs.
- Muscles of respiration.
- Rib cage, pleura.
- CNS (brainstem).
3
Q
What structures are in the upper airways?
A
Nasal and oral cavities.
Pharynx.
Larynx.
4
Q
Morphology of trachea and primary bronchi
A
C-shape cartilage (semi-cartilaginous)
Posterior smooth muscle for elasticity.
5
Q
Morphology of bronchi
A
Plates of cartilage and smooth muscle (not c-shaped)
6
Q
Morphology of bronchioles
A
Smooth muscle only
7
Q
What are the two zones of the airways beyond the larynx?
A
- Conducting zone.
2. Respiratory zone.
8
Q
The function of conducting zone?
A
Leads gas to the gas exchanging ‘respiratory zone’.
9
Q
Anatomical dead space
A
Conducting zone: no gas exchange.
10
Q
The function of the respiratory zone
A
Gas exchange happens (contains alveoli)
11
Q
Structures in conducting zone
A
trachea, bronchi, bronchioles, terminal bronchioles.
12
Q
Structures in the respiratory zone
A
Respiratory bronchioles, alveolar ducts, alveolar sacs,
13
Q
Which zone has the greatest total cross-sectional area? (C or R)
A
Respiratory zone
14
Q
Morphology of alveoli
A
Tiny, thin-walled.
Capillary rich.
15
Q
Function of alveoli
A
Exchange of oxygen and carbon dioxide.
16
Q
The function of type 1 alveolar cells
A
Most of the surface of alveolar walls.
Do not divide.
Susceptible to toxins.
Respiration.
17
Q
The function of type 2 alveolar cells
A
Rare alveolar cell.
Product surfactant to reduce surface tension.
Progenitor cells (differentiation)
18
Q
What are the 5 steps of respiration?
A
- Ventilation
- Exchange in lungs.
- Transport.
- Exchange through circulation.
- Cellular metabolism.
19
Q
Bulk flow
A
Movement of a body of molecules due to a pressure gradient.
20
Q
Diffusion
A
The gradual movement of molecules/dispersion of gradient (no net movement).
21
Q
How is ventilation produced?
A
- CNS sends rhythmic excitatory drive to muscles.
- Muscles contract.
- Changes in volume and pressure in chest/lungs.
- Air flows in/out.
22
Q
What are the three subtypes of respiratory muscles?
A
Pump muscles, airway muscles, accessory muscles.
23
Q
What muscles are pump type?
A
Diaphragm, external intercostals, parasternal intercostals.
Internal intercostals, abdominals.
24
Q
What muscles are airway type?
A
Tongue protruders, alae nasi, muscles around airways.
Pharynx/larynx.
25
What muscles are accessory?
Sternocleidomastoid, scalene.
26
What muscles are involved in inspiration?
Sternocleidomastoids, scalenes.
External intercostals, parasternal intercostals.
Diaphragm.
27
What muscles are involved in expiration?
Internal intercostals.
External abdominal oblique.
Transversus abdominis.
Rectus abdominis.
28
Morphology and function of the diaphragm
A dome-shaped muscle that flattens during contraction (inspiration)
Forces abdominal contents down and forward; pushes rib cage wide to increase volume in the thorax.
29
Function of external intercostal muscles
Bucket-handle motion: contract and pull ribs upwards to increase lateral volume.
30
Function of parasternal intercostal muscles
Pump handle motion: contract and pull sternum forward, increasing anterior/posterior dimension of rib cage.
31
Function of abdominals
Relaxed at rest, involved in deep/fast breathing (contracts). Involved in other physiological functions.
32
Function of internal intercostals
Relaxed at rest; pulls ribcage down during exercise to decrease thoracic volume.
33
Function of scalenes
Elevates upper ribs (exercise)
34
Function of sternocleidomastoids
raises sternum (exercise)
35
Muscles involved in forced inspiration
Sternocleidomastoids move the sternum up and down.
Pectoralis minor elevates ribs.
The diaphragm contracts more.
36
Muscles involved in forced expiration
Posterior internal intercostals pull ribs down and inward.
| Abdominal organs compressed by the abdominal wall, forces the diaphragm higher.
37
Obstructive sleep apnea
Reduction in upper airway patency during sleep caused by reduction in muscle tone or anatomical defects.
38
What is the mucosa?
A superficial layer of epithelial cells: contains Goblet cells and ciliated cells.
39
What is the function of the mucosa?
To entrap inhaled biological and inert particulates and remove them from the airway.
40
Function of ciliated cells
To produce periciliary fluid that comprises the sol layer.
41
Function of goblet cells
Produce mucus that comprises the gel layer of the mucus blanket.
42
How does the mucus blanket get rid of entrapped particulates?
Cilia move upward and downward based on relative proximity to stomach, sweep particulates to high acidity environment.
43
Function of macrophages in alveoli
Last defence to inhaled particulate.
44
What is a spirometer?
Pulmonary function test used to determine the amount and the rate of inspired and expired air.
45
Atelectasis
Complete or partial collapse of a lung or lobe of a lung; develops when alveoli become deflated/collapse.
46
FRC
Functional residual capacity: volume remaining in lungs after normal, passive exhalation
47
TLC
Total lung capacity: volume of air in the lungs after maximum effort inspiration.
48
TV
Tidal volume: volume of air moved in or out of the respiratory tract during each ventilatory cycle.
49
IRV
Inspiratory reserve volume: additional volume that can be forcibly inhaled to the maximum possible inspiration.
50
ERV
Expiratory reserve volume: additional volume that can be forcibly exhaled to the maximum voluntary expiration. ONLY AFTER NORMAL INSPIRATION.
51
RV
Residual volume: volume of air remaining in lungs after a maximal expiration.
52
VC
Vital capacity: maximal volume of air that can be exhaled after maximal inspiration.
53
Inspiratory capacity
Maximal volume of air that can be forcibly inhaled. TV + IRV
54
How to calculate total/minute ventilation
TV x respiratory frequency
55
Total/minute ventilation
Total amount of air moved into the respiratory system per minute.
56
Alveolar ventilation
Amount of air moved into the alveoli per minute, less than total/minute ventilation.
57
Why is alveolar ventilation smaller than total/minute ventilation?
Anatomical dead space.
58
How do you increase alveolar ventilation?
Slow deep breaths.
59
FEV1
Forced expiratory volume in 1 second
60
FVC
Forced vital capacity: total amount of air that is blown out in one breath after max inspiration as fast as possible.
61
FEV1/FVC
Proportion of the amount of air that is blown out in 1 second.
62
What are the three FEV1/FVC patterns in spirometry?
1. Normal
2. Obstructive
3. Restrictive
63
What causes the obstructive pattern? What are underlying conditions?
Difficulty in exhaling all of the air from their lungs, low FEV1/FVC.
Possibly asthma, COPD, cystic fibrosis.
64
What causes the restrictive pattern? What are underlying conditions?
Lungs are restricted from fully expanding (stiff lungs).
Reduced VC.
Almost normal FEV1/FVC, slightly shallow FEV1/FVC.
Possibly lung fibrosis, neuromuscular diseases, or scar tissue build up.
65
Helium Dilution Method
Measures communicating gas or ventilated lung volume. Helium is insoluble in blood so FRC can be measured.
66
Static properties of the lung (no air flow)
Intrapleural pressure, transpulmonary pressure.
Static compliance of the lung.
Surface tension of the lung.
67
Dynamic properties of the lung (air flow)
Alveolar pressure
Dynamic lung compliance
Airway and tissue resistance
68
Ventilation
Exchange of air between the atmosphere and the alveoli
69
Boyle's Law:
P1V1=P2V2
70
Plurae morphology
Thin double-layered envelope consisting of visceral and parietal pleura.
Visceral: covers external surface of lung.
Parietal: covers thoracic wall and superior face of diaphragm.
71
Intrapleural fluid function
Reduces friction of lung against the thoracic wall during breathing.
72
What causes the lung's tendency to collapse?
Elastic recoil.
73
What occurs at equilibrium (recoil)
Inward elastic recoil exactly balances outward elastic recoil.
74
Air moves in and out of the lungs due to (3)
1. Intrapleural pressure.
2. Alveolar pressure.
3. Transpulmonary pressure.
75
Intrapleural pressure
Acts as a vacuum.
Pressure in pleural cavity.
Fluctuates with breathing, but is always subatmospheric.
76
Alveolar pressure
Pressure of air inside the alveoli.
| Fluctuates depending on inspiration/expiration.
77
Transpulmonary pressure
Force responsible for keeping the alveoli open.
The static parameter does not cause airflow but controls lung volume.
PTP= PALV-PIP
78
8 Steps of inspiration (pressure)
1. CNS stimulatory signal
2. Diaphragm and inspiratory intercostals contract
3. Thorax expands.
4. Intrapleural pressure decreases.
5. Transpulmonary pressure increases.
6. Lungs expand.
7. Alveolar pressure becomes subastmospheric
8. Air flows into alveoli.
79
8 steps of expiration (pressure)
1. Diaphragm and inspiratory muscles stop contracting.
2. Chest wall recoils inward.
3. Interpleural pressure increases.
4. Transpulmonary pressure decreases.
5. Lungs decrease in size.
6. Alveolar air becomes compressed (smaller volume)
7. Alveolar pressure increases.
8. Air flows out of lungs.
80
What are the two resistive forces in the airway?
1. Inertia of the respiratory system.
| 2. Friction.
81
What three forms of friction contribute to resistive force?
1. Lung tissue moves past itself during expansion.
2. Lung and chest wall tissue surfaces glide past each other (slightly reduced by intrapleural fluid)
3. Frictional resistance to flow of air.
82
What is Laminar Flow?
gas particles move in a linear fashion and invest little energy in airflow resistance.
83
What is Transitional airflow?
Vortices produced that require extra energy and produce resistance.
84
Where is airflow transitional?
Bronchial tree
85
What is turbulent flow?
Irregular fluctuations and mixing that results in highest effective resistance. Occurs in large airways where velocity is the highest.
86
Where does turbulent airflow occur?
Trachea, larynx, pharynx.
87
Where is effective resistance the lowest?
Respiratory zone.
88
In disease conditions, small airways play a greater role in determining airflow. Why is this?
1. Smooth muscle contractions.
2. Edema (swelling) of alveolar and bronchiolar walls.
3. Mucus collection in the lumens of bronchioles.
89
What is lung compliance?
A measure of the elastic properties of the lungs.
90
How is lung compliance measured?
The magnitude of lung volume change produced by a given change in transpulmonary pressure.
91
Static compliance
Lung compliance measured during periods of no gas flow.
92
Dynamic Compliance
Pulmonary compliance during periods of gas flow.
93
What does dynamic compliance reflect?
Lung stiffness and airway resistance.
94
At low lung volume, does transpulmonary pressure have an effect on volume and opening airways?
No. It is difficult to immedietaly open a collapsed airway at low volume, so increasing pressure has no effect.
95
What happens to lung compliance at high lung volume?
It decreases.
96
Hysteresis
Defines the difference between inflation and deflation compliance paths.
97
Why does the hysteresis exist?
Because it takes a greater pressure to open closed airways than to maintain an open airway.
98
What is lung compliance determined by? (2)
1. Elastic components of lungs and airway tissue.
| 2. Surface tension at the air-water interface within the alveoli.
99
Where are elastic components of the airways localized?
Alveolar walls around blood vessels and bronchi.
100
Elastin
Weak spring, low tensile strength, extensible
101
Collagen
Strong twine, high tensile strength, inextensible.
102
Emphysema
Elastin deconstruction resulting in increased lung compliance with much less elastic recoil.
103
Pulmonary Fibrosis
Collagen deposition in alveolar walls in response to lesions. Reduces lung compliance to stiffen lungs. Therefore a higher transpulmonary pressure is required to increase lung volume.
104
What effect does surface tension have on lung compliance?
Decreases lung compliance.
105
What accounts for 2/3 of the elastic recoil of the lungs?
Surface tension at the air-water interface.
106
Surface tension
Measure of the attracting forces acting to pull a liquid's surface molecules together at an air-liquid interface.
107
What happens to air as it enters the lungs?
It is humidified and saturated with water vapour at body temperature.
108
What is the mechanism of surface tension in the alveoli?
Surface water molecules covering the alveolar surface create surface tension that causes an inward recoil. This recoil leads to alveolar collapse, decreasing the volume of compressible gas inside the alveoli and therefore increasing its pressure.
109
What is Laplace's equation? What does it represent?
At equilibrium, the tendency of increased pressure to expand the alveolus balances the surface tension induced recoil.
P=2T/r; therefore as the radius of the alveoli increases, so too does the pressure required to maintain its opening.
110
Why do small alveoli collapse into larger alveoli?
Less pressure is required to hold large alveoli open, as surface tension is equal in all alveoli.
111
What is alveolar surfactant produced by?
Type II alveolar cells
112
What is the function of surfactant?
Lowers the surface tension of the lining fluid so we can breathe without too much effort. Makes the alveoli stable against collapse (decreases T)
113
What are the four most important components of surfactant?
1. DPPC
2. Phosphatidyl-choline
3. Surfactant apoproteins
4. Calcium ions
114
How does surfactant equalize pressures between different sized alveoli?
Causes surface tension to increase with increasing alveolar diameter because thickness of surfactant decreases in larger alveoli (greater surface area).
115
Why do premature infants have decreased compliance?
No surfactant produced yet.
116
Infant respiratory distress
Caused by increased effort required to breathe in infants as a result of decreased surfactant production.
117
What are the regional differences in interpulmonary pressure across the lungs? What region has the greatest ventilation and why?
The weight of the lungs causes increased pressure in the lower airways (lower alveoli), therefore less pressure is required to open the airway than upper airways.
Since the alveoli at the lower airways are more deflated, they are able to expand more (increased ventilation)
118
What is Dalton's Law?
In a mixture of gases each gas acts independently. Therefore, the total pressure is the sum of individual pressures of separate gases.
119
What is Fick's Law?
The rate of transfer of a gas through a sheet of tissue per unit of time is proportional to the tissue area abd the difference in gas partial pressure between the two sides, a diffusion constant, and inversely proportional to the tissue thickness.
Therefore as tissue thickness increases, rate of transfer decreases. However, as tissue area increases, pressure difference increases, and diffusion constant increases, so too does the rate of transfer.
120
Diffusion constant
The amount of gas transferred between the alveoli and the blood per unit time. Also proportional to the gas solubility in fluids/tissue.
121
Which has a higher solubility, CO2 or O2?
CO2.
122
What is 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.
123
How do you determine the concentration of a gas in a liquid?
Take the product of the partial pressure of the gas and its solubility.
124
What are the 4 components of alveolar air?
Water, carbon dioxide, oxygen, nitrogen.
125
Why is the partial pressure of oxygen greater in air than in alveoli?
1. Warming and humidification of air in respiratory tract decreases pressure of oxygen.
2. Oxygen is diffused into blood.
3. Inspired air mixes with functional residual volume.
126
What determines alveolar oxygen pressure? (4)
Oxygen in the atmosphere
Alveolar ventilation
Metabolic rate
Perfusion
127
What determines alveolar carbon dioxide pressure? (4)
Pressure of CO2 in the atmosphere
Alveolar ventilation
Metabolic rate
Perfusion
128
By increasing alveolar ventilation, what is the responding partial pressure of O2 and CO2 in the alveoli?
P O2: Increased
| P CO2: Decreased
129
By Increasing the metabolic rate, whatis the responding partial pressures of O2 and CO2 in the alveoli?
P O2: decreased
| P CO2: increased
130
Partial pressure of gas in alveoli determines _______.
Pressure of gas in arteries.
131
Cardiac Output
The volume of blood pumped by the heart per minute
132
Systemic Circulation (pressure)
High-pressure system necessary to deliver blood in peripheral tissue and overcome high resistance system.
133
Pulmonary circulation (pressure)
Low pressure system , needs to deliver blood only to the lungs and high pressures are risky.
134
Edema
Swelling caused by fluid trapped in tissue.
135
Resistance in the pulmonary circulatory system
Low resistance due to short and wide vessels.
136
Compliance in the pulmonary circulation system. How ? (3)
High compliance due to:
- High number of arterioles with low resting tone.
- Thin walls, low smooth muscles,
- Dilation due to modest pressure changes.
137
Why are alveolar capillaries collapsible?
If capillary pressure falls below alveolar pressure, the capillaries need to be able to close off and divert blood to other pulmonary capillary beds with higher pressure.
138
Ventilation/Perfusion ratio
Balance between ventilation and perfusion. Major factor affecting alveolar levels of O2 and CO2.
139
Describe the partial pressure gas exchange of oxygen and carbon dioxide in the pulmonary circulation.
Atmospheric oxygen and carbon dioxide enter the alveolar space and increase oxygen pressure. Venous oxygen pressure is very low after metabolic transaction and carbon dioxide pressure is high. Therefore as oxygen diffuses into circulation, carbon dioxide diffuses into alveolar space and into the atmosphere upon exhalation.
140
Ventilation
Bring O2 into alveoli, removing CO2 from alveoli.
141
Perfusion
Bring CO2 into alveoli, removing O2 from alveoli.
142
What does a low ventilation/perfusion ratio entail?
No ventilation is present due to "shunt" or airway obstruction that prevents oxygen from entering alveoli and carbon dioxide from leaving.
143
What does a high V/Q ratio entail?
Obstruction of the pulmonary artery or capillary that lowers the rate of perfusion of carbon dioxide into the alveolar space. Because there is no pressure difference due to the obstruction, alveolar pressures are equivalent to atmospheric pressure and alveoli becomes physiological dead space that does not participate in gas exchange.
144
Where in the lungs is V/Q ratio the highest?
Top of lungs (alveoli arent as squished)
145
Where in the lungs is the V/Q ratio the lowest?
Bottom of lungs.
146
How is the differences in local V/Q ratio managed?
Homeostatic mechanisms that control vasoconstriction and bronchoconstriction alter flow of gas and blood to certain regions.
147
How does the body respond to low O2?
If low levels of oxygen are flowing into a region of the lungs, the vessels leading to that alveoli will constrict in order to divert blood to a more oxygenated and open alveoli. This is known as pulmonary hypoxic vasoconstriction.
148
What two forms is oxygen carried in?
Bound to hemoglobin.
| Dissolved.
149
What primary form is oxygen in inside circulation?
Bound to hemoglobin in red blood cells.
150
What is hemoglobin?
Molecule composed of 4 amino acid chains called Globins (2 alpha, 2 beta chains). Each chain is bound to ferrous iron atom (Heme).
151
What two forms does hemoglobin exist as?
Deoxyhemoglobin, oxyhemoglobin.
152
Describe the relationship between hemoglobin saturation and oxygen pressure.
Sigmoidal; initially a steep and rapid increase in saturation as pressure increases. However, this saturation increase flattens as the pressure reaches 100 due to cooperative binding.
153
When is hemoglobin saturation the lowest?
In systemic venous oxygen pressure sites (after offloading oxygen to peripheral tissue)
154
What is cooperative binding?
When a heme group binds to an oxygen it changes to a relaxed state to expose the ferrous ion. This change in conformation also spreads to surrounding heme groups to create an exponential saturation increase.
155
What other physiological changes can influence hemoglobin saturation?
Blood pH and temperature.
156
What is the steepest portion of the sigmoidal hemoglobin curve caused by?
Increased metabolic rate increases diffusion and dissociation of blood from hemoglobin and into peripheral tissue.
157
Anemia
Reduction in hemoglobin concentrations.
158
Polycythemia
Increase in hemoglobin concentration.
159
What is the effect of carbon monoxide in the blood?
Carbon monoxide has a high affinity for hemoglobin and will kick oxygen out of binding as a result. This will reduce oxygen-hemoglobin binding as well as oxygen concentration in the blood. The hemoglobin will switch conformations which make it difficult to release oxygen (physiological survival response) and decrease oxygen offloading.
160
What does reduction in blood oxygen pressure cause?
Reduction in the affinity of hemoglobin for oxygen; more oxygen is offloaded into peripheral cells.
161
What does a right shift generally entail?
Increase in oxygen off-loading.
162
Increasing temperature effect on oxygen dissociation
Increased temperature increases offloading
163
Increasing pH effect on oxygen dissociation
Decreases offloading
164
What effect does DPG have on oxygen dissociation?
Increases offloading
165
What three forms is carbon dioxide carried in?
Dissolved, bicarbonate, carbamino compounds.
166
How is carbon dioxide transformed into bicarbonate?
Carbon dioxide produced in periphery cells diffuse into plasma and dissolve into RBC. Dissolved CO2 joins water to synthesize carbonic acid (promoted by enzyme carbonic anhydrase). Carbonic acid dissociates by exchanging an ion (hydrogen) and is transported out of the cell in exchange for chlorine. Results in higher RBC acidity.
167
How are carbamino compounds formed?
CO2 in the blood combines with globins in Hb. No enzyme is required as CO2 has a high affinity for deoxyhemoglobin. This exchange will help unload oxygen (pushes).
168
How is carbon dioxide moved during lung exchange?
Carbamino compounds dissociate into dissolved CO2 and hemoglobin. Pressure gradients pull CO2 from the RBC into the plasma and then into the alveoli. Bicarbonate may also enter the RBC and dissociate.
169
How is hydrogen transported in the RBC? What is its purpose?
Hydrogen is produced when carbonic acid decomposes into bicarbonate. Its presence increases cellular acid content. Hydrogen has a strong affinity for deoxyhemoglobin and will also push oxygen out of conformation to encourage offloading in peripheral cells. Therefore a decrease in pH will increase oxygen dissociation. The equilibrium is reversed in the lungs and hydrogen interacts with bicarbonate to allow oxygen binding.
170
Respiratory acidosis
Caused by hypoventilation; PCO2 increases alongside hydrogen conecntration. CO2 production is greater than elimination.
171
Respiratory alkalosis
Caused by hyperventilation; CO2 production is lower than elimination causing a decrease in hydrogen and PCO2 levels.
172
Metabolic acidosis
Increase in hydrogen concentration without an increase in carbon monoxide.
173
Metabolic Alkalosis
Decrease in hydrogen concentrations without a decrease in PCO2.
174
Where is breathing initiated?
In the medulla by specialized neurons (dorsal and ventral neuron groups)
175
How is breathing modified?
Higher structures in the CNS and inputs from central and peripheral chemoreceptors and mechanoreceptors in the lungs and chest walls.
176
What are the three respiratory groups? (cns)
Pontine, dorsal, and ventral.
177
PreBotzinger Complex
Group of neurons in the ventral r.group, generates excitatory inspiratory rhythmic activity via the polysynaptic pathway.
178
Parafacial respiratory group
Group of neurons in the ventral respiratory group. Generates rhythmic excitatory active expiratory rhythmic activity that excites expiratory muscles via the polysynaptic pathway.
179
Where is the rhythm of breathing generated?
Ventral respiratory group in the medulla. PreBotC and pFRG drive activity in premotor neurons which excite motorneurons that activate respiratory muscles.
180
How is rhythmic activity modified?
Sensory and neuromodulatory inputs originating from different regions within and outside the CNS.
181
Neuromodulatory inputs
Seratonin in Raphe.
Norepinephrine in the locus coerulus
Glutamate in the dorsolateral pons.
Orexin in hypothalamus.
182
Neuro-respiratory pathway for inspiration
1. PreBotC to inspiratory premotor neuron via the rostral ventral respiratory group.
2. Phrenic and thoracic motor neurons exciteed.
3. Diaphragm and external intercostal muscles contract.
Or
1. PreBotC instigates excitation in inspiratory premotor neuron in the rostral ventral respiratory group.
3. Parahypoglossal regioin also activated.
4. Cranial motor neuron in medulla activated, tongue and airway muscles contract.
183
Neuro-respiratory pathways in active expiration
1. Activation of pFRG, activation of expiratory muscles via the caudal ventral respiratory group.
2. Thoracic and lubar motor neurons stimulated.
3. Internal intercostal and abdominal muscles activated.
184
Hypoxia
Low oxygen pressure in blood
185
Hypercapnia
High carbon dioxide pressure in blood
186
Acidosis
Low pH in blood.
187
What are the peripheral chemoreceptors? What do they sense?
Carotid and Aortic Bodies. They sense oxygen pressure levels and pH.
188
What two types of cells are present in the carotid bodies? Functions?
```
Glomus (chemosensitive) TYPE 1.
Sustentacular cells (supportive) TYPE 2.
```
189
What are the features of the carotid bodies?
Highly vascularized, high metabolism rate.
190
What cell are glomus cells similar to? Why?
Neurons.
| They have voltage-gated ion channels, contain vesicles containing NTS, and can trigger an action potential.
191
What is the primary stimulus for peripheral chemoreceptors?
Decrease in arterial PO2.
192
At what PO2 value does hyperventilation initiate?
60
193
Describe the peripheral response to hypoxia
1. Inspired air contains low oxygen pressure.
2. Alveolar PO2 drops as a result.
3. Arterial PO2 drops (60)
4. Peripheral chemoreceptors are activated (Glomus cells in carotid body)
4. Reflex via the medullary respiratory neurons trigger an increase in ventilation.
5. Restoration of equilibrium.
194
How do changes in PCO2 affect ventilation?
Small changes greatly decrease/increase ventilation rate.
195
What are the central chemoreceptors?
Neurons in the rostral, intermediate, and caudal medullary region.
196
Which set of chemoreceptors are more sensitive to blood pH? Why?
Periphery; hydrogen cannot easily cross the BBB.
197
What are the central chemoreceptors sensitive to?
PCO2
