Control Of Respiration Flashcards
Briefly describe the neural control of respiration
- central controller = brainstem
Impulses sent from control centre to effectors - effectors = respiratory muscles
Effectors and sensors are linked - sensors = lung receptors, peripheral receptors and chemoreceptors
Impulses sent from sensors to control centre
Where do breathing patterns arise ?
- breathing patterns arise in the medulla
- it modifies the rhythm and pattern of breathing
- there is communication between the pons and medulla to control this
- if something happens to the pons or medulla then the breathing pattern is disrupted
Describe the generation of the respiratory rhythm in the medullary respiratory centre
- the firing of one set of action potentials lead to inspiration
- when these action potentials do not fire then this leads to relaxation
- another set of action potentials also occur but these do not fire at the same time as the other set
How does voluntary control of breathing arise ?
- impulses are sent from the cortex to the spinal cord
- voluntary control of breathing can only happen to a certain extent because eventually chemoreceptors will cause it to return back to normal and an involuntary activity
How do the limbic system and hypothalamus play a role in controlling breathing ?
- limbic system is in involved when emotions affect the rhythm of breathing
- hypothalamus is involved when temperature affects the rhythm of breathing
What are the 2 other names for the pons ?
• pneumotaxic centre - drives rhythm or rate of breathing
• apneustic centre - involved in the duration of the breath
What are the different types of lung receptors ?
- stretch receptors
- juxta-pulmonary “J” receptors
- irritant receptors
- proprioceptors
Summarise the function of stretch receptors
- mechanoreceptors
- respond to stretch (increased firing of action potentials when the lungs are stretched)
- extremely important in the first few breaths of a newborn baby
Summarise the function of juxta-pulmonary receptors
- sensitive to changes in pulmonary circulation
- located in or next to the walls of pulmonary vessels
- when stimulated, they work to reduce or terminate inspiration
Summarise the function of irritant receptors
- located throughout the airways
- detect and respond to irritants e.g. smoke and pollution
- important in protecting the lungs as they generate a large expulsion of air (cough/sneeze)
Summarise the function of proprioceptors
- found in the intercostal muscles
- important role in switching between inspiration and expiration
- respond to change in position and length of these muscles
Give some examples of peripheral receptors that influence breathing
- nociceptors (pain)
- mechanoreceptors (exercise/movement)
- arterial baroreceptors (blood pressure)
- thermoreceptors (heat/core temperature)
Which receptors are the most important in terms of controlling and regulating breathing ?
Chemoreceptors
Describe ventilation-metabolism matching
- if metabolism increases, ventilation should also increase
- important in maintaining blood gas composition
How are changes in blood chemistry detected ?
Detected by -
• central chemoreceptors
• peripheral chemoreceptors
Describe the location of central chemoreceptors
- located in the brainstem near the ventrolateral surface of the medulla
- located close to but anatomically distinct from neurones that cause spontaneous firing of action potentials which are involved in the regulation of breathing
What are central chemoreceptors sensitive to ?
- sensitive to pH of the cerebrospinal fluid
- they are bathed in CSF not blood
Describe the response to changes in pH of the CSF
- if metabolism increases, carbon dioxide produced in the capillary blood increases
- this increases the amount of bicarbonate and hydrogen ions present in the blood
- charged ions can’t move freely across the blood brain barrier but carbon dioxide can
- amount of carbon dioxide in the CSF increases
- causes increases of hydrogen ions in CSF
- detected by central chemoreceptors and so there is an increase in the firing of action potentials and increase in ventilation
- capillary blood contains plasma proteins so this acts as a buffer for the blood but the CSF does not contain plasma proteins so there is no buffering taking place
Where are peripheral chemoreceptors found ?
- found directly in the blood
- located near the carotid and aortic arteries
Describe the function of peripheral chemoreceptors
- sensitive to hypoxia (low oxygen environments) and this causes increased firing of action potentials therefore increasing the rate and depth of breathing
- also detect changes in pH - a decrease in pH causes increased firing
What is the ventilatory response to increased partial pressure of carbon dioxide in the arteries ?
- increased partial pressure of carbon dioxide
- increased minute ventilation rate
What is hypercapnia ?
High levels of carbon dioxide in the blood
What is the ventilatory response to an increase in carbon dioxide partial pressure and decrease in oxygen partial pressure ?
increased minute ventilation very quickly (same response as hypercapnia but over a shorter timeframe)
