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function of the cardio and resp systems - year 1 > mechanisms of breathing > Flashcards

mechanisms of breathing Flashcards

1
Q

what regulates breathing

A

the diaphragm and intercostal muscles

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2
Q

where are lungs sealed

A

in the pleural membranes

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3
Q

what are pleural membranes joined to

A

the thorax wall

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4
Q

what does change in thorax volume change

A

lung volume

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5
Q

how does air flow in and out of the lungs

A

due to alternately reversing pressure gradients

because air tends to move from area of high pressure to low

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6
Q

what is Boyles law

A

at any constant temp, the pressure exerted by a gas varies inversely with the volume of gas

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7
Q

Boyles law formula

A

P1V1=P2V2

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8
Q

does increase in volume decrease pressure

A

yes and vice versa

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9
Q

what happens when intra-alveolar pressure is low

A

atmospheric pressure is high and air flows into the lungs

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10
Q

what happens when air flows into the lungs

A

the intra-alveolar pressure increases and the atmospheric pressure decreases

air flows out of the lungs

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11
Q

what is the first stage of inspiration

A
  1. the diaphragm contracts and flattens and the external intercostal muscles contract
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12
Q

what is the second stage of inspiration

A

the volume of the thorax and lungs increase

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13
Q

what is the third stage of inspiration

A

the pressure inside the lungs decreases to below atmospheric pressure (-3mmHg) and air flows into the lungs

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14
Q

why do the lungs expand more as air comes in

A

because there is a negative pressure between the lungs and the thorax
(achieved by the pleural membranes)

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15
Q

what does contraction of external intercostal muscles cause

A

elevation of ribs

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16
Q

what does lowering of diaphragm on contraction do

A

increases vertical dimension of thoracic cavity

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17
Q

what happens during passive expiration

A
  • diaphragm relaxes
  • lungs recoil
  • volume of thorax decreases
  • lung volume decreases
  • inside the lung the pressure rises to +3mmHg
  • air moves out along pressure gradient
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18
Q

how do pleural membranes stop the lung collapsing

A

because they join the lungs to the outer wall

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19
Q

what happens with forced inspiration and expiration

A

external intercostal muscles and diaphragm contract

principle stays the same but much larger changes in pressure

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20
Q

what do pleural membranes do

A
  • surround the lung tissue as a double membrane fluid filled bag
  • creates a vacuum round the lungs
  • when the thorax expands the intrapleural pressure decreases
21
Q

what do pleural membranes do in inspiration

A
  • diaphragm contracts
  • thorax expands
  • intrapleural pressure becomes more sub-atmospheric
  • transpulmonary pressure increases
  • lungs expand
  • alveolar pressure sub atmospheric
  • air flows in
22
Q

is normal breathing voluntary or involuntary

A

involuntary - doesnt rely on conscious input

23
Q

what regulates normal breathing

A

neurones in the medulla oblongata and pons

24
Q

what neurons in the medulla oblongata controls inspiration and expiration

A

I neurons = inspiration
E neurons = expiration

25
Q

what do I and E neurons from the medulla oblongata do

A

fire rhythmically and send impulses down the nerve to the diaphragm

26
Q

what happens when one set of I neurons fire

A

it inhibits the second neurons and vice versa

called RECIPROCAL INHIBITION

27
Q

what does the medulla oblongata contain

A
  • the dorsal respiratory group (inspiratory centre)
  • the ventral respiratory group (inspiratory and expiratory centre)
28
Q

where are signals from the medulla oblongata sent to

A

the intercostal muscles and the diaphragm

29
Q

what does centres in the PONS of the brain control

A

further rate of breathing

30
Q

what des the apneustic centre do

A

sends impulses to I neurons to keep inspiration going

31
Q

what does the pneumotaxic centre do

A

sends impulses to the dorsal respiratory group that switches off I neurons limiting the time of inspiration

32
Q

what are mechanoreceptors sensitive to

A

changes in mechanics/movement

33
Q

what are proprioceptors

A

stretch receptors in the smooth muscle of the bronchioles

34
Q

what does stretch in the lung tissues activate

A

mechanoreceptors and proprioceptors to send a nerve impulse to the medulla oblongata to inhibit I neurones

called the Hering Breurer Reflex

35
Q

where are peripheral chemoceptors found

A

outwith brain
in aortic and carotid bodies

36
Q

where are central chemoceptors found

A

within brain
near respiratory centres of medulla oblongata and on the surface of the brain ventricle

37
Q

what does peripheral chemoceptors consist of

A

specialised cells called glomus cells

38
Q

what are peripheral chemoceptors sensitive to

A

changes in arterial blood gas

have high metabolic rate and good blood perfusion which makes them sensitive

39
Q

what do peripheral chemoceptors respond to

A

oxygen - when there is less oxygen there is more firing

can also respond to changes in CO2

40
Q

what happens when decreased O2 is detected by sensor proteins in glomus

A

it leads to increase in calcium which mediates release of neurotransmitters

eg. dopamine, ACh

41
Q

what do central chemoreceptors do

A

respond direct to the H+ ion concentration of the cerebrospinal fluid (CSF)

42
Q

do central chemoceptors respond to changes in plasma pH

A

no as H+ cannot diffuse into the CSF

43
Q

what happens when CO2 diffuses into CSF

A

it forms H+ and decreases pH

44
Q

step 1 of activation of central chemoreceptors

A

blood PCO2 rises

45
Q

step 2 of activation of central chemoreceptors

A

CO2 diffuses into the CSF

46
Q

step 3 of activation of central chemoreceptors

A

CO2 is converted into carbonic acid by the enzyme carbonic anhydrase

47
Q

step 4 of activation of central chemoreceptor

A

carbonic acid dissociates to give bicarbonate ions

48
Q

what does an increase in H+ ions do (activation of central chemoceptors)

A

send impulses to the respiratory centres

function of the cardio and resp systems - year 1 (20 decks)

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