Respiration Physiology Flashcards
At rest; what is the arterial partial pressure of oxygen?
100mmHg.
At rest; what us the arterial partial pressure of carbon dioxide?
40mmHg
What is present in the trachea that traps inhaled particles?
Goblet cells secrete mucus which traps particles. Mucus removed out of the system by rhythmic beating of the cilia.
What volume is ventilated at rest?
6L/min
What is the maximum ventilation volume?
160L/min
How far does the diaphragm contract in quiet breathing?
1cm
Describe inspiration of quiet breathing.
Active.
External intercostals pull ribs outwards and upwards.
Describe expiration of quiet breathing.
Passive
Elastic recoil
How far does the diaphragm contract in strenuous breathing?
10cm
Describe inspiration of strenuous breathing.
Active
Accessory muscles activated e.g. sternocleidomastoid and alae nasi
Describe expiration of strenuous breathing.
Active
Describe the relationship between volume and pressure.
Inversely related.
What pleural and alveolar pressure do the lungs need to be before air can move in?
Negative
What is function residual capacity
Volume of air in the lung after quiet breathing.
What is the resting tidal volume of the lungs?
500ml
How is vital capacity measured?
Breathe in to the max, breathe out to the max. As quick as possible.
How are lung volumes measured?
Vitalograph or spirogram.
In a healthy individual what is the FEV1/FVC ratio?
70-80% in the first second.
In an individual with COPD; what is the FEV1/FVC ratio?
<70%
What is atmospheric pressure?
760mmHg
What are conducting airways?
Anatomical dead space, non-respiratory bronchioles don’t participate in gas exchange.
What are respiratory airways?
Alveoli present on the bronchioles, therefore gas exchange occurs.
Name some characteristics of the alveoli. (3)
Elastic recoil.
Thin walled.
Large surface area.
What are alveolar cells composed of?
Type 1 and type 2 cells.
What are type 1 alveolar cells?
Primary site of gas exchange.
What are type 2 alveolar cells?
Produce pulmonary surfactant which reduces surface tension.
What does bronchial circulation supply blood to?
Lung parenchyma. (functional lung tissue in gas transfer)
What gas is easier to diffuse/more soluble?
CO2 diffuses easily.
In pulmonary blood circulation, what gas enters and what gas leaves?
Oxygen enters and C02 leaves.
In systemic blood circulation, what gas enters and what gas leaves?
C02 enters and Oxygen leaves.
What must the sum of partial pressure equal?
Total pressure.
What are the 2 ways oxygen can be transported around the body?
Dissolved.
Bound to haemoglobin.
What method is the primary mode of oxygen transport?
Bound to haemoglobin.
How many haem groups are in haemoglobin?
4
What compromises the protein globin?
2 Alpha and 2 beta chains.
What does the oxygen bind to in haemoglobin?
Iron molecule.
The process of oxygen binding to haemoglobin is…?
Reversible.
Initially haemoglobin affinity for oxygen is low, how does this change as it progresses?
When binding occurs, conformation changes happen to increase the affinity for oxygen.
Define oxygen saturation
The amount of oxygen bound to the haem group relative to the maximum amount that can bind.
how many molecules of oxygen can bind to haemoglobin?
4
How many mls of oxygen does 1g of haem combine with?
1.39mls
How many grams of haem is in normal blood circulation?
15g
What is the respiratory exchange rate?
Expired carbon dioxide: Inhaled oxygen.
80: 100
0. 8
In a healthy individual, how much CO2 is produced?
200ml/min
What are the 3 ways C02 is transported?
Dissolved
Bound to haemoglobin
Bound to bicarbonate.
What is formed when carbon dioxide binds to bicarbonate?
Carbonic acid.
What enzyme catalyses the binding of carbon dioxide to bicarbonate?
Carbonic anhydrase.
In systemic capillaries what direction is the bicarbonate equation pushed? Why?
Bicarbonate equation pushed to he right as there is lots of CO2/bicarbonate in systemic capillaries.
What regulates bicarbonate concentration? How does this happen?
The kidneys via chemoreceptors.
With regards to oxygen binding; what occurs in more acidic pH conditions?
Oxygen released from haemoglobin
With regards to oxygen binding; what occurs in more alkaline pH conditions?
Tighter binding of oxygen to haemoglobin.
With regards to oxygen binding; what occurs in higher temperatures?
Less oxygen bound to haemoglobin
With regards to oxygen binding; what occurs in lower temperatures?
More oxygen bound to haemoglobin
What structure is breathing controlled by?
Brainstem/medulla oblongata
What factors modulate breathing? (3)
Voluntary control
Vocalisation (singing)
Emotional events (crying)
List the neuronal controls of breathing.
Establishes a rhythm, no conscious action.
Responds to episodic non ventilatory behaviour, like speaking, eating etc.
What is eupnea?
Normal rhythmic breathing.
What is dyspnea?
Shortness of breath, conscious awareness of difficulty.
What input does the brain receive in order to control breathing?
Mechanoreceptor input
Chemoreceptor input
What is normal rhythmic breathing controlled by?
Respiratory related neurons
Central pattern generator
Frequency of CPG changes.
Respiratory motor neurons.
What is the function of the CPG (central pattern generator)?
In brainstem: Independently generates respiratory rhythm.
Respiratory motor neurons innervate respiratory muscles; how does this occur?
Axons in the phrenic nerve innervate contractions of the diaphragm.
Where is the signal from chemoreceptors replayed back to in the brain?
The nucleus tractus solitarius.
brainstem
Where are peripheral chemoreceptors found?
In the carotid sinus
(signal sent via CN9)
Aortic arch
(Signal sent via CN10)
What do the peripheral chemorecetos respond to?
Hypoxia: Decrease in oxygen levels.
Response causes increased ventilation.
What is hypercapnia?
Increased CO2
Hyperventilation occurs If the concentration of oxygen in the blood falls beneath what value?
60mmHg.
Where are central chemoreceptors found?
The brainstem
When are the central chemoreceptors activated?
Hypercapnia: When Co2 increases.
or
when pH decreases.
What gas (O2 or CO2) are individuals most sensitive to?
C02 increase.
How do mechanoreceptors detect movement of the lung/chest wall?
Via pulmonary stretch receptors.
Mechanoreceptor signals travel the nucleus tracts solitarus via what nerve?
Vagus (CN:10)
Where are the receptors located that terminate inspiration (end of a single breath)?
Airway smooth muscle.
Where are the receptors located that trigger a sigh?
Airway epithelium
Describe how respiratory rhythm neurons are arranged in the brainstem.
Bilateral arrangement.
Respiratory rhythm neutrons require…?
No stimuli
What kind of neurons are contained within the dorsal aspect of the brain?
Inspiratory
What kind of neurons are contained within the ventral aspect of the brain?
Inspiratory and expiratory neurons.
What is the function of the pontine?
Modulates respiratory output.
Voluntary control, e.g. breath holding, can be overridden by what?
Chemoreceptors.
What is ventilation?
Process of air moving in and out of the lung.
What is perfusion?
Process of deoxygenated blood passing through the lung and becoming oxygenated.
Where in the lung are the alveoli most expanded (upright position)?
Apex
Where in the lung is pleural pressure most negative?
Apex
Where in the lung is the transpulmonary pressure greatest?
Apex
What does compliance mean?
Ability to stretch
In terms of compliance; describe the alveoli at the apex.
Alveoli at the apex are less compliant as they are already expanded.
List reasons for reduced compliance.
Scaring of the lung tissue.
Reduced surfactant production.
Fluid in the lung
Emphysema: reduced elasticity of the lung.
What conditions increase resistance within the lungs?
COPD:
Chronic bronchitis
Asthma
Name the two types of dead space?
Anatomical
Physiological
Define anatomical dead space.
Fills conducting airways.
Define physiological dead space.
Reaches the alveoli yet no gas exchange occurs.
Alveoli perfused but not ventilated.
What is the V/Q ratio?
Rate of ventilation to blood flow.
In a healthy adult, what should the V/Q ratio be?
0.8
What is an anatomical shunt?
Where arterial blood is shunted directly into venous blood, bypassing gas exchange by the alveoli.
Where do most anatomical shunts occur?
In the heart via septal defects.
What is a physiological shunt?
When air no longer reaches some alveoli.
What is atelectasis?
Obstruction of alveoli as a result of; tumours, mucus build up, foreign bodies.
Give 2 exams of a COPD?
Emphysema and chronic bronchitis.
What are the symptoms/Signs of COPD?
Chronic cough
Shortness of breath
Tight chest
Increased mucous
What is emphysema?
Lungs lose elasticity due to overinflation of the alveoli.
What becomes an issue for those with emphysema?
Exhaling
What is chronic bronchitis?
Inflamed and swollen bronchi. Mucus narrows the airways.
What is pulmonary fibrosis?
Scarring and thickening of lung tissue = decreased elasticity and gas exchange.
