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respiratory lectures > lung physiology 4 > Flashcards

lung physiology 4 Flashcards

1
Q

what are the primary respiratory muscles (2)

A

diaphragm
intercostal muscles

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2
Q

describe involuntary control of breathing

A

1.diaphragm and intercostal muscles are stimulated

  1. by groups of neurones in the pons and medulla
  2. these neurons form the respiratory control centre
  3. they send impulses to the primary respiratory muscles via the phrenic and intercostal nerves
  4. stimulates contraction of respiratory muscles
  5. once the neurons stop firing, the inspiratory muscles relax and expiration occurs.
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3
Q

what are the three main groups of neurons involved in medullar respiration

A
  1. ventral respiratory group
  2. dorsal respiratory group
  3. pontine respiratory group
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4
Q

what does the ventral respiratory group control

A

expiration

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5
Q

what does the dorsal respiratory group control

A

inspiration

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6
Q

what does the pontine respiratory group control

A

the rate and pattern of breathing

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7
Q

how is voluntary respiration controlled

A

via the motor cortex in the cerebrum, which receives inputs from the limbic system and hypothalamus.

signals are thought to be sent to the spinal cord from the motor cortex, which are then passed onto the respiratory muscles

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8
Q

what is phrenic nerve paralysis

A

where damage to the phrenic nerve results in its dysfunction.

can cause paralysis of the diaphragm, therefore causing breathing problems.

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9
Q

what are the 2 types of chemoreceptors

A

peripheral

central

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10
Q

where are peripheral chemoreceptors

A

located in both the carotid body and the aortic body

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11
Q

what do peripheral chemoreceptors detect

A

large changes in the partial pressure of oxygen (pO2) as the arterial blood supply leaves the heart

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12
Q

innervation of peripheral chemoreceptors

A

glossopharyngeal and vagus nerves

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13
Q

what happens when peripheral chemoreceptors detect low oxygen

A

afferent impulses travel via the glossopharyngeal and vagus nerves to the medulla oblongata and the pons in the brainstem.

a number of responses are then coordinated which aim to restore pO2.

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14
Q

responses to restore partial pressue of oxygen (3)

A
  1. respiratory rate and tidal volume are increased - to allow more oxygen to enter the lungs and subsequently diffuse into the blood
  2. blood flow is directed towards the kidneys and the brain - as these organs are the most sensitive to hypoxia
  3. cardiac output is increased to maintain blood flow - and therefore oxygen supply to the body’s tissues
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15
Q

where are central chemoreceptors located

A

in the medulla oblongata of the brainstem

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16
Q

what do central chemoreceptors detect changes in

A

the arterial partial pressure of carbon dioxide (pCO2).

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17
Q

what do central chemoreceptors do when they detect changes

A

they send impulses to the respiratory centres in the brainstem that initiate changes in ventilation to restore normal pCO

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18
Q

what happens when central chemoreceptors detect an increase in pCO2

A
  • leads to an increase in ventilation
  • more CO2 is exhaled
  • the pCO2 decreases and returns to normal.
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19
Q

what happens when central chemoreceptors detect a decrease in pCO2

A
  • leads to a decrease in ventilation
  • less CO2 is retained in the lungs
  • the pCO2 increases and returns to normal.
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20
Q

how much of respiratory control is controlled by central chemoreceptors

A

60%

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21
Q

how do central chemoreceptors detect changes in arterial pCO2

A

by changes in the pH of the Cerebral Spinal Fluid (CSF)

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22
Q

what are baroreceptors

A

sense arterial pressure

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23
Q

where are the most important baroreceptors found

A

carotid sinus

the aortic arch

24
Q

what happens when baroreceptors detect an increase in arterial pressure

A

the walls of these vessels (carotid sinus & aortic arch) passively expand, which increases the firing frequency of action potentials generated by the receptors

25
Q

what are the carotid sinus baroreceptors innervated by

A

he sinus nerve of Hering, which is a branch of the glossopharyngeal nerve (IX cranial nerve)

26
Q

what are the aortic arch baroreceptors innervated by

A

by the aortic nerve, which then combines with the vagus nerve (cranial nerve X) traveling to the NTS.

27
Q

what is the cough reflex

A

an important defence mechanism which clears the airways of irritants by forcefully expelling air from the respiratory tract

28
Q

which 3 main pathways is the cough reflex arc made up of

A
  1. Sensory Afferent Pathway
  2. Central Pathway
  3. Motor Efferent Pathway
29
Q

how is the cough reflex arc initiated

A

by irritation of cough receptors

eg mechanoreceptors or chemoreceptors

irritants are detected by these receptors and they send sensory information to afferent nerves

30
Q

what are the three main types of sensory nerve fibres involved in the afferent pathway

A
  1. Rapidly Adapting Stretch Receptors (RARs)
  2. Slowly Adapting Stretch Receptors (SARs)
  3. C-fibres
31
Q

what are Rapidly Adapting Stretch Receptors (RARs)

A

myelinated fibres found mostly in the pharynx and trachea which rapidly respond to mechanical stimuli, e.g. changes in lung volumes

32
Q

what are Slowly Adapting Stretch Receptors (SARs)

A

myelinated fibres which respond more slowly to mechanical stimuli and are involved in the Hering-Breuer reflex

33
Q

what are C - fibres

A

non-myelinated nerve fibres which respond to mechanical and chemical stimuli

34
Q

how does sensory information travel from the sensory nerve fibres in the afferent pathway

A

through the afferent pathway via the vagus nerve to the medulla oblongata.

35
Q

what happens in the central pathway

A

sensory information travels to the nucleus tractus solitarius (NTS) of the medulla.

the vagus nerve then synapses with motor neurones

delivering information to effector muscles which triggers the cough reflex to occur.

36
Q

in the motor efferent pathway which respiratory muscles contract to allow initiation of the cough reflex

A
  1. diaphragm
  2. laryngeal muscles
  3. external intercostal muscles
  4. rectus abdominis
37
Q

how does the diaphragm contract in the motor efferent pathway

A

contracts to become flattened which increases the thoracic cavity space

38
Q

how do the laryngeal muscles contract in the motor efferent pathway

A

contract to close the vocal cords

39
Q

how do the external intercostal contract in the motor efferent pathway

A

contract to change the space available in the thoracic cavity

40
Q

how does the rectus abdominis contract in the motor efferent pathway

A

contracts to depress the rib cage and decrease space in the thoracic cavity

41
Q

what are the 3 main phases of the cough reflex

A
  1. inspiratory phase
  2. compression phase
  3. expiratory phase
42
Q

what is the inspiratory phase of the cough reflex

A
  1. irritation of cough receptors causes the vocal cords to open more widely- allowing more air to enter the lungs.
  2. the external intercostal muscles and diaphragm then contract - causing expansion of the chest cavity, facilitating movement of air into the lungs, and increasing intra-thoracic pressure
43
Q

what is the compression phase of the cough reflex

A
  1. he epiglottis and vocal cords close - trapping the air within the lungs.
  2. There is expiration against the closed epiglottis, causing a further increase in intra-thoracic pressure.
44
Q

what is the expiratory phase of the cough reflex

A
  1. the internal intercostal muscles and abdominal muscles contract to depress the thoracic cavity.
  2. the vocal cords relax, and the epiglottis opens.
  3. this releases the pressure from the lungs and causes air and the irritant to be rapidly expelled.
45
Q

what are the 3 types of pulmonary stretch receptors in the lungs

A
  1. slow adapting
  2. rapidly adapting
  3. Juxtapulmonary / J-receptors / C-fiber receptors
46
Q

what do slow adapting stretch receptors detect

A

respond to changes in lung volume

47
Q

what do rapidly adapting stretch receptors detect

A

detect pathophysiological processes in the airway, such as chemical irritation, congestion, and inflammation.

48
Q

what do Juxtapulmonary / J-receptors / C-fiber receptors detect

A

respond to events such as pulmonary edema , pulmonary emboli pneumonia, and barotrauma, which cause a decrease in oxygenation and thus lead to an increase in ventilation/respiration.

The stimulation of the J-receptors causes a reflex increase in breathing rate

49
Q

what are the 2 pontine respiratory centres (groups of neurones)

A
  1. Apneustic center
  2. Pneumotaxic center
50
Q

what does the apneustic centre do

A

stimulation of the apneustic center leads to a gradual increase in the firing rate of the inspiratory muscles

acts on DRG (dorsal respiratory group )

51
Q

what does the pneumotaxic centre do

A

sends inhibitory impulses to the inspiratory center

stops inspiration

regulating inspiratory volume and respiratory rate.

52
Q

define respiratory drive

A

the intensity of the output by the respiratory centers and determines the effort of the respiratory muscles

53
Q

which factors contribute to respiratory drive

A

a combination of chemical, mechanical, behavioural, and emotional

54
Q

define alveolar recruitment

A

the re-expansion of previously collapsed lung areas by means of a brief and controlled increase in transpulmonary pressure

55
Q

which receptors are present in the nose, nasopharynx and larynx

A

chemo and mechano receptors

some appear to sense and monitor flow

stimulation of these receptors inhibits the central controller

56
Q

which receptors are in the pharynx

A

receptors that appear to be activated by swallowing

respiratory activity stops during swallowing protecting against the risk of aspiration of food or liquid

respiratory lectures (15 decks)

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