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Respiratory Systems Flashcards

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1
Q

What are the 3 key features of any respiratory system?

A
  • specialised body surfaces for gas exchange
  • Mechanisms to ventilate the environmental face of this surface
  • Mechanisms to perfuse the internal face of this surface
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2
Q

How do some organisms have no specialised respiratory systems?

A
  • O2 obtained by simple diffusion across body surfaces
  • Requires thin, moist integument
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3
Q

What is ficks law and the 3 key relationships we can gather from it?

A

Ficks law - Q = D A (PE - PI) / L
Q = rate of diffusion
D A = surface area
PE - PI =partial pressure difference
L = thickness of interface
* Q directly proportional to partial pressure difference
* Q directly proportional to surface area
* Q inversely proportional to thickness of interface

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4
Q

What respiratory organs help provide a large surface area?

A
  • external gills, internal gills, lungs, trachea
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5
Q

What is the respiratory system like for animals in liquid environments?

A
  • gills are highly branched and folded extensions of the body surfaces - invaginations
  • Maximises surface area
  • Thin tissue, which minimises diffusion path length
  • New medium flows continuously over surfaces
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6
Q

What are the respiratory systems like for animals in gaseous environments?

A
  • invaginations - protects respiratory surface
  • Increases internal surface area
  • Thin tissue, which minimises diffusion path length New
  • Lungs are elastic - increased capacity
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7
Q

In descending order, name the key components of the respiratory system in humans.

A
  • nasal cavity
  • mouth
  • pharynx
  • larynx
  • trachea
  • primary bronchi
  • lungs
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8
Q

What are the consequences of tidal ventilation? What are the benefits of dead space?

A
  • incoming air mixes with used gas
  • Alveoli provide reservoir of O2
  • ‘Dead space’ does not participate in gas exchange
  • Befits of dead space:
    - warming/humidifying, protection (mucus/ cilia)
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9
Q

What is alveolar ventilation rate and what is it made up of?

A

Air entering lungs ventilates both the dead space and the alveoli
VE = VD + VA
VE = minute ventilation of the entire lung
VA = amount of fresh air available for gas exchange

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10
Q

What makes up VA? How can it be increased?

A

VA = (tidal volume - dead space) x breathing rate
= (500ml - 150ml) x 12 breaths / minute
= 4200ml/min

VA can be increased by increased tidal volume or increased respiratory frequency

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11
Q

How is ventilation in mammalian lungs tidal?

A

Ventilation in the mammalian lung is tidal
* incoming mixes with ‘stale air’ in the alveoli

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12
Q

What term is used to describe avian ventilation?

A

Avian ventilation is unidirectional across the lung
* birds use unidirectional airflow to maximise gas exchange
* incoming air does not mix with ‘stale air’

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13
Q

What is the primary role of respiration?

A

*Primary role of a respiratory system is to meet the metabolic demands of the organism

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14
Q

What are the key principles of ventilation?

A
  • convection of respiratory medium over the gas exchange surfaces (Active or passive)
  • This movement maintains partial pressure gradient at the respiratory interface
  • Fresh O2 is delivered and CO2 is removed
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15
Q

What is happening when the respiratory system is at rest?

A
  • at rest, lungs are expanded to fill thoracic cavity because intrapleural pressure is negative (w.r.t atmospheric pressure)
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16
Q

What is intrapleural space?

A

Intrapleural space - fluid filled space between the parietal and visceral pleura, the membranes lining the chest wall and lungs, containing a small amount of lubricating serous fluid

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17
Q

When does ventilation occur?

A
  • ventilation occurs when active muscle force is applied to the replaced respiratory system
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18
Q

What are the mechanisms behind inspiration?

A

Inspiration is an active process -
Volume of thorax increased as:
* diaphragm contracts
* External intercostal muscles contact
*external intercostals on outside of ribcage
* diaphragm lines underneath the ribcage

AS the volume of the thorax increases
* intrapleural pressure falls (same amount of gas, increased space)

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19
Q

What is Boyles law, what does it state?

A

Boyles law = P1V1 = P2V2
* a gas law stating that pressure and volume of gas have an inverse relationship
* If volume increases then pressure decreases, when temperature is held constant
* Therefore when volume is halved, the pressure is doubled, and if the volume is doubled, the pressure is halved

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20
Q

What happens as the volume of the thorax increases?

A
  • intrapleural pressure falls
  • Alveoli expand
  • Alveolar pressure < atmospheric pressure
  • Air flows into lungs until alveolar pressure = atmospheric pressure
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21
Q

What are the mechanisms behind expiration?

A

expiration is largely a passive process
Elastic recoil of lungs and chest wall reduced volume of thorax (passive mechanism)
* intrapleural pressure rises
* Alveoli recoil
* P alv > P atmos
* Air is expelled from lungs

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22
Q

How does air move passively?

A

Air moves passively from a region of high pressure to low pressure.

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23
Q

Describe inspiration and expiration in terms of pressure.

A

During inspiration:
Alveolar pressure < atmospheric pressure
Therefore air moves into the lungs

During expiration:
Alveolar pressure > atmospheric pressure
Therefore air is expelled from lungs

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24
Q

What is the equation for lung volume change?

A

C = change in V / change in P
C = compliance

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25
What is meant by FRC and peak of inhalation?
*FRC - functional residue capacity (the volume of air remaining in the lungs after a normal, passive exhalation) *peak of inhalation - lungs expand to maximum capacity
26
Why does the pressure curve deviate to the right during inspiration?
During inspiration, curve deviates to right because of resistive forces which oppose airflow: * airway resistance - resistance to movement of air * Pulmonary tissue resistance - friction between lungs and chest wall * Inertia of the air and tissues
27
During expiration, why does the pressure curve deviate to the left?
During expiration, curve deviates to left because resistive forces assist airflow: * elastic recoil of lungs and chest wall * Surface tension in alveoli * Expiration can be active during forced exhalation (internal intercostals and abdominal muscles contract)
28
Describe ventilation in birds.
In a seagull - trachea, anterior air sacs, bronchus, lungs, posterior air sacs * bird volume changes less than in mammals * Air moves through lungs from interconnected air sacs * Sacs do not participate in gas exchange
29
Describe ventilation in frogs.
* air forced into lungs * Lungs emptied from abdominal contraction
30
Describe air movement in insects?
* airways penetrate each body segment, allowing diffusion * Abdominal muscles ‘pump’ air through trachae * Thoracic spiracles, abdominal spiracles, air sacs, tracheae
31
How is water moved across gills? What is required?
* energy is required to pump water across gills * Water ‘pulled’ across gills when opercular cavity expands and opercular flaps open * Water ‘pushed’ over gills when fish closes mouth *mouth opened, jaw lowered *mouth closed, operculum opened
32
What is poiseuilles law?
- describes the flow of a fluid through a cylindrical pipe or tube. It gives a relationship between the volume flow rate (the amount of fluid flowing through the pipe per unit time) and the various factors that affect the flow, such as the pressure difference, the radius of the pipe, the length of the pipe and the viscosity of the fluid
33
What are the key relationships gathered from Poiseuilles law? What does it assume?
the flow rate Q is directly proportional to the fourth power of the radius of the pipe, meaning that even small changes in the radius can lead to large changes in flow rate * the flow rate is inversely proportional to the viscosity of the fluid and the length of the pipe * It assumes laminar (non-turbulent) flow, meaning the fluid moves smoothly in parallel layers.
34
What are the 3 types of flow?
Laminar flow Turbulent flow Transitional flow
35
What is laminar flow?
* slow flow rate * Parallel stream lines
36
What is turbulent flow?
* high flow rate * Disorganised stream lines
37
What is transitional flow?
* intermediate flow rate * Eddy currents
38
What is airway resistance? (RAW)
Majority of resistance to inhaled air is resistance to air movement through conducting airways * 30% in upper airways (nose, pharynx, larynx) * 70% in trachea and bronchial tree
39
What are the factors affecting airway resistance?
RAW decreases with increasing lung volume - radial traction - dynamic compression
40
What is radial traction?
* as lung expands, connective tissue pulls on brochioles, so their diameter expands and RAW falls * As lung volume is reduced, RAW rises rapidly because radial traction is relieved
41
What is dynamic compression?
* occurs at low lung volume or when intrathoracic pressure > alveolar pressure (forced expiration) * Airways are compressed and may close
42
What is bronchial smooth muscle tone affected by?
Affected by nervous activity, hormones or external factors
43
What is bronchioconstriction and what does it cause?
Bronchioconstriction - increased RAW * irritants cause reflex constriction (trachea, large bronchi) * Parasympathetic (vagal) stimulation * Fall in PCO2 * Asthma
44
What is bronchiodilation and what does it cause?
Bronchiodilation - lowered RAW * autonomic stimulation (circulating catecholamines) * Sympathomimetic agents (beta2 agonists)
45
How can infection significantly increase RAW?
* inflammation of the tissues lining the upper airways * overproduction / accumulation of mucus *inflammation - airways narrowed *mucus - airways occluded *inflammation and mucus accumulation
46
What is the link between airway resistance and flow? What is PEFR?
Most of the work of inspiration is in overcoming airway resistance Greater airway resistance means slower PEFR (peak expiratory flow rate)
47
What are the elastic properties of the lung? What is it determined by?
When inflated, lungs show tendency to recoil or collapse back to resting volume Elastic recoil is determined by: * elastic properties of lung tissue * Surface tension in the alveoli
48
Describe the elastic tissue in the lung.
* elastin and collagen fibres in alveolar wall and around vessels and bronchi * Network of fibres allows distension bur recovers geometry when pressure is released
49
What causes surface tension in alveoli? What can this be minimised by?
Alveoli are lined with fluid, presence of air-fluid interface creates potential problems: * attractive forces in liquid (surface tension) oppose expansion by inspired air * Promotes collapse of smaller alveoli * Causes transduction of fluid from capillaries *transudation - process by which a liquid (usually protein poor fluid) passes through a membrane or tissue often due to altered pressure * these problems are minimised by a surfactant
50
What is a pulmonary surfactant? What does it do?
* phospholipoprotein secreted from Type II alveolar cells * Lowers the surface tension in the liquid layer * Prevents alveolar collapse at low pressures * present in air-breathing animals (and some fish)
51
When is compliance reduced?
* surface tension is increased (decreased production of surfactant) * Elasticity is impaired (fibrous tissue in the lung)
52
How is pulmonary circulation specialised?
* gas composition of blood in pulmonary arteries and veins opposite to those in systemic circulation * Pressures in the pulmonary circulation are very low * Pulmonary arterial walls are thin and contain little smooth muscle * Pulmonary vascular resistance is low
53
What is the equation for vascular resistance?
Vascular resistance = (input pressure - output pressure) / blood flow
54
What affects ventilation and perfusion in humans?
Gravity influences ventilation and perfusion in humans
55
Describe ventilation and perfusion in an upright individual.
Ventilation - * intrapleural pressure greater (more -ve) at the apex * Atmospheric pressure (Palv) constant Perfusion - Palv > Pv > Palv * distribution is affected by posture, exercise, disease etc
56
What are the regional variations in VA:Q?
Local blood flow falls - 3 times faster than ventilation, so regional VA: Q changes across the lung Regional VA : Q can vary from 0 to infinity 0/Q = 0 - blood passing though the lung without coming into contact with alveolar air (right to left shunt) V/0 = infinity - anatomical dead space, or ventilated alveoli that are not perfused Local matching of ventilation and perfusion is important to optimise gas exchange in lungs
57
What are the mechanisms to defend VA:Q matching?
Principally achieved by modulation of blood flow, rather than ventilation Vasoconstriction by low PO2 (hypoxia) * blood is directed away from poorly-ventilated areas * Response is very non linear
58
What are the differences in air flow between bird lungs and fish gills?
* Bird lungs have continuous air flow over respiratory interface * Fish gills use countercurrent flow to maximise gas exchange
59
Compare efficiency of gas exchange between mammals, birds and fish?
Mammals - tidal bulk flow - 35% O2 extraction Birds - unidirectional flow - 40% O2 extraction Fish - counter current flow - 90% O2 extraction
60
What can transfer of O2 be influenced by?
* diffusion across red blood cell membrane * Combination with haemoglobin
61
What is the key feature of a haemoglobin-O2 dissociation curve?
The bohr shift - increased PCO2 - increased temperature
62
What 4 pigments increase O2 carrying capacity?
* haemoglobin: 4 Fe-containing heme groups * myoglobin: similar to single Hb subunit * Foetal haemoglobin * Haemocyanin: cu-containing molecule packaged in cells
63
How is carbon dioxide carried in the blood?
Carriage of carbon dioxide in blood * CO2 is carried in chemical combination in plasma CO2 + H20 = H2CO3 = H+ + HCO3 -= H+ + CO3- *co2 levels alter pH * can also form carb amino compounds on
64
What controls air and water movement in plants? What do they open in response to?
* guard cells control air and water movement * Open in direct response to K+ influx and increased turgor pressure
65
What 3 neural networks control breathing in mammals?
* brainstem = central controller * Effectors = respiratory muscles * Sensors = receptors
66
How does breathing pattern arise in the medulla?
Pons = medulla - spinal cord - respiratory muscles
67
What are lung receptors?
Lung receptors: * stretch receptors * Juxta-pulmonary ‘j’ receptors * Irritant receptors * Proprioceptors (position/length sensors *other receptors can influence breathing
68
What 3 stimulus are picked up on to match ventilation to metabolism?
Ventilation must be matched to metabolism * CO2 production - estimated from PCO2 * O2 consumption - estimated from PO2 * H+ production - estimated from
69
What changes in blood chemistry are detected by chemoreceptors?
* CO2 production - estimated from PCO2 * O2 consumption - estimated from PO2 * H+ production - estimated from pH
70
Where are central chemoreceptors located?
Located in the brain stem
71
What are central chemoreceptors?
* located near ventolateral surface of the medulla * Sensitive to pH of CSF (index of PCO2) * Relatively slow response time * Relatively insensitive to change in PO2
72
What are peripheral chemoreceptors?
Peripheral chemoreceptors * located in carotid and aortic arteries (high blood flow) * Decreased PO2 - increased firing * increased (H+) or increased PCo2 - increased firing * Respond rapidly (detects…?)
73
What are the 3 key factors that affect ventilation?
* changes in PCO2, pH and PO2 affect ventilation * Increased PCO2 and decreased PO2 act synergistically * A rise in PCO2 is the main drive to breathe
74
How long can humans hold their breath? How long can a weddel seal dive for? Why is this?
Breath-holding in mammals: * humans can dive (breath-hold) for -2 min (world record 11 min) * Weddel seal can dive for 75 min - high myoglobin content in muscle - high RBC count/Hb concentration
75
What is the diving reflex in mammals? What is it triggered by? What does it do?
Diving reflex in mammals: * triggered by cold water * Reduced heart rate * Increased peripheral vasoconstriction * Lactate accumulation in muscle * Energy conserved (delayed increased PCO2)

Structure And Function (8 decks)

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