control of breathing (neural reflex control)

Question 1

how does the cortical areas exhibit control over breathing?

Answer 1

• bypassing of the brainstem (medulla/PONs)

Question 2

why is the vagus important?

Answer 2

• it carries both sensory and motor circuits

- major influence on breathing from vagal sensory afferents

Question 3

how are pulmonary stretch receptors stimulated?

Answer 3

• located within the smooth muscle of the trachea and lower airways
• stimulated by lung inflation during inspiration
• greater the inspiration–> more tension in the airways-> stretch is used as an indicator of inflation
• are slowly adapting receptors

Question 4

list the 2 types of activity the PSRs exhibit

Answer 4

• continually active during expiration
• a receptor with phasic activity with a high threshold
• both stimulated by different volumes and different periods of breathing

Question 5

why are these receptors important?

Answer 5

• when a signal from PSRs reaches a certain threshold inspiration ends and expiration begins
• important in timing, and the switching between phases of inspiration and phases of expiration

Question 6

what is the aim of the hering-breuer reflex?

Answer 6

• the promotion of expiration and cessation of Inspiration
• prevents overinflation of lungs in babies (more active)
• important in mammals with lungs that have a low compliance –> shallow and rapid breathing

Question 7

explain the neuronal systems at play with PSRs

Answer 7

• vagal afferents from PSRs excite the NTS (DRG)
• NTS excites the PRG (PONS)
• neurones from the PRG and the NTS both inhibit the neural (I) group at the DRG
• inhibition of I
• PRG influences balance between I and E

Question 8

where are irritant receptors found? and what are they stimulated by?

Answer 8

• vagal nerve endings present between epithelial cells of the trachea and lower airways
• stimulated by noxious gases such as smoke, dust, cold air
• rapidly adapting receptors
• efferents promote increased bronchoconstriction

Question 9

what does activation of irritant receptors promote?

Answer 9

• augmented breaths (sighs)
• occur naturally
• aids in reversing the collapsing of lung during quiet breathing
• release of surfactant (prevents atelectasis)

Question 10

where are the C/J receptors found?

Answer 10

• bronchial walls (unmyelinated C-fibres)

- alveolar walls (juxtacap receptors )- close to capillaries

Question 11

what are C/J receptors stimulated by?

Answer 11

• usually silent
• by mechanical distortion and oedema
• evokes a shallow breathing or apnoea
• responsible for rapid shallow breathing and dyspnoea

Question 12

name receptors of the nose and upper airways

Answer 12

• nasal mucosa contain trigeminal nerve endings

- the larynx and trachea contain vagal afferents

Question 13

what do receptors In the nasal airways promote when activated?

Answer 13

• laryngeal spasm
• evokes sneezing, coughing, bronchoC, E apnoea and bradycardia
• dry drowning

Question 14

what are the receptors of joints and muscles?

Answer 14

• propioceptors
• sense joint position in space and length
• involved in the sensation of dyspnoea if large effort is required (during an obstruction to airways)
• allow for increased force of I and E if movement is impeded
• responsible for increased VE during exercise

Question 15

what are the arterial baroreceptors ?

Answer 15

• aortic arch
• carotid sinus
• increased BP leads to reflex hypoV
• decreased BP leads to reflex hyperV
• involved in complex stimuli such as haemorrhages