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1st yr-Med 2022-2023 > CFB Lungs 2 > Flashcards

CFB Lungs 2 Flashcards

1
Q

Describe the basic mechanism of ventilation

A
  1. O2 inhaled, passes into alveoli, diffuses through capillaries into arterial blood
  2. During exhalation, CO2 released into alveoli from venous blood
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2
Q

What components are involved in ventilaion?

A

Upper respiratory tract
Lower respitatory tract
Muscles
Skeletal elements

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3
Q

State the functions of the respirtatory sysem

A
  1. Ventilation of lungs
  2. Extract O2 from air, transfer to blood
  3. Remove CO2 from blood
  4. Maintain Acid base of blood
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4
Q

What is absolute pressure?

A

Atmospheric pressure

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5
Q

If alveolar pressure = 0, what does this tell us?

A

Alveolar pressure = atmospheric pressure

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6
Q

Describe Boyle’s law

A

Gas law

As vol of gas increases, pressure of gas decreases, in closed system

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7
Q

Describe the process of inspiration

A

Active process
Activated by respiratory centre, medulla
Causes diaphragm + external intercostal muscles contract
Diaphragm contracts + moves downwards
External intercostal muscles contract + cause adjascet ribs to move upwards + forwards
These 2 processes increase vol in thoracic cavity
Lower pressure in thoracic cavity
Air flows down pressure gradient into lungs
AIR FLOW CONTINUES UNTIL ALVEOLAR PRESSURE = PRESSURE ATAIRWAY OPENING

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8
Q

Describe the process of expiration

A

Passive
Diapghragm + intercostal muscles relax
Diaphragm = curved / “dome”
Ribs = inwards + downwards
Reduce vol of thoracic cavity
Increase pressure
Atm pressure lower than pressure in lungs
Air moves out

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9
Q

Describe how expiration can become a passive process

A

If airways narrow too much (asthma)
Or if it is needed to get rid of a vas quantity of air quickly, during exercise

INTERNAL INTERCOSTAL MUSCLES CONTRACT
ANTERIOR ABDOMINAL MUSCLES CONTRACT
ACCELERATE EXPIRATION, RAISE AIR PRESSURE IN LUNGS FASTER

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10
Q

Control of breathing

A

Involunary process controlled by respiratory centre in medulla oblongata in brainstem

Controls depth + rate
Important for NORMAL LEVELS of PCO2 and PO2

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11
Q

What are the 3 regions involved in control of respiration?

A
  1. Central controller
  2. Respiratory muscels
  3. Strategically placed sensors
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12
Q

What is the central controller?

A

Respiratory centre:

  1. Medullary respiratory centre (dorsal + ventral respiratory neurones)
  2. Pons respiratory centre (pneumotaxic + apneustic centres)
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13
Q

Describe the role of dorsal neurones in the medullary respiratory centre

A

Dorsal medullary respiratory neurones - INSPIRATION

when activated, send electrical impulses to RETICULO-SPINAL TRACT in spinal cord + intercostal nerves to stimulate respiratory mucles
(maintain basic rythm of breathing)

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14
Q

Describe the role of ventral neurones in the medullary respiratory centre

A

Expiration
But only forced expiration
To increase depth + rate of expiration

How are these neurones activated?

Deep breathing, increases activity of dorsal neurones, which activates ventral neurones

When ventral neurones are stimulated, this inhibits dorsal neurones, so inhibiting inspiratory centre

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15
Q

Describe why respiratory movements are symmetric

A

Dorsal + ventral neurones are bilaterally paired, this allows cross communication, which means they are synchronous

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16
Q

Describe the role of the apneustic centre

A

LOWER PONS
Exact function unknown
Stimulates insipratory centre
Without, breathing becomes shallow, IRREGULAR
Pathological lesions= increased freq of apnoea

17
Q

Describe the role of the of the pneumotaxtic centre

A

Found in pons respiratory centre

Its neurones inhibit the dorsal neurones in the respiratory medullary centre and also inhibit apneustic centre

Therefore, inhibit inspiration

Lesions lead to PROLONGUED DEEP INSPIRATION + shorter expiration due to continuous activation of inspiratory centres

INVOLVED IN REGULATING
-VOL
-RATE

of respiration

18
Q

Describe volunary control of ventilation

A

This is known as cortical influence
Cerebral cortex overrides autonomic meduallary respiratory centre (e.g. when you want to hold breath)

However, if you hold breath for too long, autonomic medullary respiratory centre overrides cerebral cortex.
Too high blood pH
Chemoreceptors override cortical influence, you gasp take a deep breath (inspiration)

19
Q

State the strategically placed sensors

A
  • Mechanoreceptors
  • Chemoreceptors
20
Q

State the role of mechanoreceptors in regulation of breathing

A

Stretch receptor, sensory receptor, activated in response to distortion + pressure

Located in walls of bronchi + bronchioles

Prevent over-inflation of lungs

Activated in response to inflation of lungs

When activated, send APs via VAGAL NERVE FIBRES which inhibit inspiratory centres + activate pneumotaxic centre

21
Q

Describe the Hering-Breuer Reflex

A

Happens more commonly in infants
In adults, when tidal vol is larger than normal e.g. when exercising

When lungs inflated, mechanoreceptors activated, send APs via vagal nerve fibres to inhibit insipratory centre + stimulate pneumotaxic centre

When expiration starts, activation of mechanoreceptor decreases…

22
Q

State the role of chemoreceptors in the control of breathing

A

Sensory receptors, detect changes in blood pH
Detect O2 levels in body, CO2 levels in brain
2 types:
- Peripheral
-Central

23
Q

Describe the role of peripheral chemoreceptors

A
  1. Found at birufication of carotid artery + aortic arcfh
  2. Repond to changes in O2 levels mainly, but sometimes CO2 levels
  3. Connected to respiratory centre via cranial nerves IX and X

-chemoreceptors in carotid artery detect levels of O2 in arterial veseels
-chemoreceptors in aortic arch detect levels of O2 close to heart
-composed of two types of cells: Type I: glomus cells Type II: Glia-like cells
-activated during hypoxia (low O2 levels)
-electrical impulses sent from chemoreceptors to brainstem
-hypoxic drive
-ventilation

24
Q

Describe the role of central chemoreceptors

A

Found at medulla in brainstem
Exposed to local blood flow, metabolsim, CSF
Activated when pCO2 = low
When pCO2 low, high conc of H+ in CSF
Detected by receptors, send APs, to inspiratory centre, stimulate alveolar hyperventlation, therefore, low pCO2 in CSF + blood

As pCO2 decrerases, reduces AP sent, less stimulation of inspiratory centre, hypoventilatiojn

Central chemoreceptors directly respond to H+ conc CSF
Indirectly to blood CO2
These values are linked because arterial CO2 crosses BBB + enters CSF

25
Q

Explain why central chemoreceptors play a more prominent role in cemical regulation of ventilation compared to peripheral chemoreceptors

A

PCO2 = major regulator of respiration, more than PO2

26
Q

State the Respiratory muscles involved in regulation of breathing

A
  1. Diaphagm
  2. Intercostal muscles
  3. Accessory muscles
  4. Abdominal muscles
27
Q

Describe the role of the diaphragm in the control of breathing

A

MOST IMPORTANT COMPONENT

When contract, increases intra-thoracic vol significantly
This decreases pressure
Atmospheric pressure higher than intra-thoracic pressure
Air moves in down pressure gradient

When relaxes, reduces intra-thoracic vol significantly
Increases pressure
Atmospheric pressure lower than intrathoracic pressure
Air moves out, down pressure gradient

28
Q

What method is used by the lungs to expel air?

A

Elastic recoil

29
Q

Describe the role of the intercostal muscles in the control of breathing

A

External intercostal muscles
Have antero-inferior fibres
When they contract, the fibres pull ribcage upwards + outwards + forwards
Increases the intra-thoracic vol, allowing inspiration

Internal intercostal muscels
Have postero-superior fibres
When contract, fibres pull ribcage down
Forced expiratin / active expiration

30
Q

Describe the role of accessory muscles in the control of breathing

A

Two main accessory muscles:
Sternocleidomastoid + scalene

INSPIRATION

Scalane: first 2 ribs upwards (quiet breathing)
Sternocleidomastoid: sternum upwards (heavy breathing)

31
Q

Describe the role of the abdominal muscles during breathing

A

Muscles in abdominal wall:
-Rectus abdominus
-Transversus abdominus
-Internal + external obliques

1st yr-Med 2022-2023 (57 decks)

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