Physiology Flashcards
(106 cards)
1
Q
Internal respiration refers to the intracellular organisms which
A
consume O2 and produce CO2
2
Q
External respiration refers to the sequence of events that leads to
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the exchange of O2 and CO2 between external environment and the cells of the body
3
Q
4 steps of external respiration
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- Ventilation
- Gas exchange between alveoli and blood
- Gas transport in blood
- Gas exchange at tissue level
4
Q
Ventilation
A
Process of moving gas in and out of lungs
5
Q
Boyle’s Law
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At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas
6
Q
Linkage of Lungs to Thorax
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- Intrapleural fluid cohesiveness
2. Negative intrapleural pressure
7
Q
Intrapleural fluid cohesiveness
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Water molecules in intrapleural fluid are attracted to each other and resist being pulled apart
Pleural membranes stick together
8
Q
Negative intrapleural pressure
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Below atmospheric pressure in intrapleural space creates a transmural pressure gradient across lung wall and chest wall
Lungs expand and chest tightens
9
Q
Inspiration
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Active Volume of thorax increases External intercostal muscles contract Ribs move up and out Diaphragm contracts (phrenic nerve from C3,C4,C5) Intra-alveolar pressure falls Air enters lungs down pressure gradient
10
Q
Expiration
A
Passive
Lungs recoil to normal size
Alveolar pressure rises
Air leaves down pressure gradient
11
Q
Pneumothorax
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Air in pleural space
12
Q
Complications of pneumothorax
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Can cause lung to collapse
13
Q
Treatment of tension pneumothorax
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Decompression by insertion of IV cannula in 2nd intercostal space, midclavicular line, on affected site
14
Q
Causes of tension pneumothorax
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Asthma Injury penetrating chest Rupture of sub-pleural pleb TB Infection Growth (Carcinoma) Hereditary Tissue (connective)
15
Q
Presentation of tension pneumothorax
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Pleuritic chest pain Tracheal deviation Hyper-resonance Onset sudden Reduced breath sounds Asymptomatic sometimes Xray shows collapse
16
Q
What causes recoil during expiration?
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Alveolar surface tension
Elastic connective tissue in lungs
17
Q
Alveolar surface tension
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Attraction between water molecules at liquid air interface
Produces a force in alveoli that resists stretching of lungs
18
Q
Law of LaPlace
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Smaller alveoli are more likely to collapse
19
Q
Pulmonary surfactant
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Complex mixture of lipids and proteins secreted by type II alveoli
Lowers alveolar surface tension
Lowers that of smaller alveoli more, preventing them from collapsing
20
Q
Respiratory Distress Syndrome in New Born
A
Foetal lungs unable to produce surfactant
Causes RDS
Baby makes strenuous respiratory efforts to overcome high surface tension
21
Q
Alveolar interdependance
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If an alveolus starts to collapse, the surrounding alveoli are stretched and then recoil, bringing collapsing alveoli with them to reopen it
22
Q
Major inspiratory muscles of respiration
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Diaphragm and external intercostal muscles
23
Q
Accessory muscles of inspiration
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Sternocleidmastoid, scalenus, pectoral
24
Q
Muscles of active expiration
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Abdominal muscles and internal intercostal muscles
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tidal volume
Volume of air entering or leaving lungs in a single breath
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Residual volume
minimum volume of air remaining in lungs after maximal expiration
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Inspiratory capacity
maximum volume of air that can be inspired at the end of a normal expiration
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Total lung capacity
Vital capacity + residual volume
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FVC
Forced vital capacity
| Maximum volume that can be forcibly expelled from lungs following maximum inspiration
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FEV/FEC
should be >70%
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parasympathetic stimulation causes
bronchoconstriction
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sympathetic stimulation causes
bronchodilatation
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Pulmonary compliance
Measure of effort that has to go into stretching of distending the lungs
Less compliant = more work required
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Increased pulmonary compliance
Emphysema
| Patients have to work harder to inflate lungs
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Decreased pulmonary compliance
Pulmonary fibrosis, pulmonary oedema, pneumonia
| Shortness of breath
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Pulmonary ventilation
Volume of air breathed in and out per minute
| Tidal volume x resp rate
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Alveolar ventilation
Volume of air exchanged between atmosphere and alveoli per minute
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Ventilation
Rate at which gas passes through lungs
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Perfusion
Rate at which blood passes through lungs
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Alveolar Dead Space
Ventilated alveoli that aren't adequately perfused with blood
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Perfusion > ventilation
Increased Co2
Dilatation of airways
Decreased O2
Constriction of blood vessels
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Ventilation > perfusion
Decreased Co2
Constriction of airways
Increased O2
Dilatation of blood vessels
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4 factors affecting Rate of Gas Exchange Across Alveolar Membrane
1. Partial pressure gradient of O2 and Co2
2. Diffusion coefficient for Co2 and O2
3. Surface area of alveolar membrane
4. Thickness of alveolar membrane
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Daltons Law
Total pressure exerted by a gaseous mixture = sum of all partial pressures of each individual gas
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Alveolar Gas Equation
PAO2 =
| PiO2 - (PaCO2/0.8)
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Diffusion coefficient for Co2
Solubility of Co2 in membranes
| 20 X that of O2
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Large gradient between PAO2 and PaO2
Problems with gas exchange in lungs or a right to left shunt in heart
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Henry's Law
Amount of gas dissolved in a given type and volume of liquid at a constant temp is proportional to the partial pressure of the gas in equilibrium with the liquid
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2 forms O2 present in blood
Bound to haemoglobin
| Physically dissolved
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Oxygen binding to haemoglobin
Binds reversibly
| Each Hb has 4 haem groups
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Oxygen delivery index
DO2I = CaO2 X CI
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Oxygen delivery to tissues can be impaired by
Respiratory disease
Heart Failure
Anaemia
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Sigmoid curve of haemoglobin
Binding of one O2 to haemoglobin increases affinity of Hb for O2
Flattens when all sites occupied
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Bohr Effect
Shift of haemoglobin curve to right
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Foetal haemoglobin
Higher affinity for O2, curve shifted to left
| Allows mother to transfer O2 at low partial pressures
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Myoglobin
```
Present in skeletal and cardiac muscles
One haem group per myoglobin molecules
Dissociation curve hyperbolic
Releases O2 at VERY LOW pO2
Provides short term storage of O2 for anaerobic conditions
```
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Presence of myoglobin in blood indicates
Muscle damage
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Ways Co2 is transported around blood
Solution (10%)
As bicarbonate (60%)
As carbamino compounds (30%)
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Co2 as bicarbonate
Co2 + H20 -> H2Co3
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Catalyst for Co2 forming a bicarbonate
Carbonic Anhydrase
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Where does Co2 become H2Co3
Red blood cells
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How are carbanimo compounds formed
Combination of Co2 with terminal amine groups in blood proteins
Especially globin from haemoglobin
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Haldane Effect
Removing O2 from Hb increases ability of Hb to pick up Co2 and Co2 generated H+
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The Bohr Effect and Haldane Effect work in synchrony to facilitate
O2 liberation and uptake of Co2
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How does the Bohr Effect facilitate the removal of O2
Shifts curve to right meaning Hb has a lower affinity to O2
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Neural control of rhythm of heart
Medulla
| Pre-Botzinger complex
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How is rhythm generated by Pre-Botzinger Complex
1. Excites dorsal respiratory group neurones
2. Fire in bursts
3. Firing leads to contraction of inspiratory muscles
4. When firing stops = passive expiration
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Pneumotaxic centre
Stimualtion terminates inspiration
Occurs when dorsal neurones fire
Prevents inspiration being too long - deep breaths (apneusis)
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Examples of involuntary modifications of breathing
1. Pulmonary stretch receptors
2. Joint receptors reflex in exercise
3. Cough reflex
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Pulmonary Stretch Receptors
Activated during inspiration
Afferent discharge inhibits inspiration
Hering Breur Reflex
DOESN'T HAPPEN NORMALLY, BABIES
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Joint receptors
Impulses from moving limbs increase breathing
| Increased ventilation during exercise
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Increased ventilation during exercise
Adrenaline released
Impulses from cerebral cortex
Increase body temp
Accumulation of Co2 and H+ created by active muscles, that must be removed
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Cough reflex
Afferent discharge stimulates:
1. Short intake of breath
2. Closure of larynx
3. Contraction of abdominal muscles
4. Increases alveolar pressure
5. Opening of larynx and expulsion of air at high speed
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Peripheral Chemoreceptors
Sense tension of oxygen, Co2 and H+ in blood
| Found in carotid bodies and aortic bodies
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Central Chemoreceptors
Respond to H+ in cerebrospinal fluid
| Found near surface of medulla
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Cerebospinal fluid
Separated by blood brain barrier
Co2 diffuses readily
Responsive to PCo2
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Rise in arterial PCo2 results in
increased ventilation
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Fall in arterial PO2 results =
Hypoxia
| Stimulates peripheral chemoreceptors
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When are peripheral chemoreceptors stimulated
<0.8 Kpa
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Hypoxic Drive
Important in high altitudes
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Rise in H+ only
Stimulates peripheral receptors
Causes hyperventilation
Increase elimination of Co2 from body
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Chronic adaptations of hypoxia
Increased RBC production
Increased number of capillaries
Increased number of mitochondria
Kidneys converse acid (Arterial pH drops)
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Type 1 Respiratory Failure
Short of oxygen
| Hypoxia
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Type 2 Respiratory Failure
Short of Oxygen
Too much Co2
Hypoxia + Hypercapnia
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Hypercapnia
Too much Co2
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V/Q mismatch
ventilation and perfusion not matched
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Restrictive thoracic disease causes outwith the lungs
Skeletal
Muscle Weakness
Obesity
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DPLD
Diffuse Parenchymal Lung Disease
or
Interstitial Lung Disease
Group of disease that effect the interstitum (tissue space around alveoli)
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Effort Dependant Pulmonary Function Tests
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FEV
Flow rates (spirometry)
```
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Effort Independant Tests
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Relaxed vital capacity (spirometry)
Helium/N2 washout static lung volumes
Whole body plethysmography
Impulse oscillometry
Exhaled nitric oxide
Gas diffusion tests
```
91
Spirometry Graph for Asthma and COPD
Asthma depressed but ends same volume
| COPD ends lower volume
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Obstructive Disease Lung Function Patterns
PEFR decreased
FEV decreased
FVC normal in asthma, decreased in COPD
FEV/FVC = <75%
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Restrictive Disease Lung Function Patterns
PEFR normal
FEV decreased
FVC decreased
FEV/FVC = >74%
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Forceful expiration
Active process controlled by firing ventral neurons in the medulla
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Results in increased pulmonary compliance, produces overinflated lungs and will show an obstructive defect on spirometry
Emphysema
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Causes shortness of breath on exertion, a restrictive defect on spirometry and reduced pulmonary compliance but no sign of infection
pulmonary fibrosis
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Will show low FVC, low FEV and low FEV/FVC%
Combined restrictive lung disease
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Chronic adaptation by hypoxia
Increased mitochondria, 2,3-BGP capillaries and polycythaemia with a metabolic acidosis
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Acute mountain sickness
Fatigue, headache, tachycardia, dizziness and shortness of breath, slipping into unconciousness
100
Diabetic Ketosis
Hyperventilation with severe metabolic acidosis
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Chemoreceptors that detect arterial oxygen partial pressure and cause hyperventilation and increased cardiac output
Peripheral Chemoreceptors
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Chemoreceptors found in brainstem. Respond to CSF
Central chemoreceptors in medulla
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Chemoreceptors that when stimulated can compensate for metabolic acidosis by increasing elimination of Co2
Peripheral Chemoreceptors
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Volume of air left in lungs after maximal expiration
Residual volume
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Sum of inspiratory reserve volume, tidal volume and expiratory reserve volume
Vital capacity
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Volume of air left in lungs after normal expiration
Functional residual capacity
