Control Of Respiration

Question 1

Briefly describe the neural control of respiration

Answer 1

• 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

Question 2

Where do breathing patterns arise ?

Answer 2

• 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

Question 3

Describe the generation of the respiratory rhythm in the medullary respiratory centre

Answer 3

• 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

Question 4

How does voluntary control of breathing arise ?

Answer 4

• 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

Question 5

How do the limbic system and hypothalamus play a role in controlling breathing ?

Answer 5

• limbic system is in involved when emotions affect the rhythm of breathing
• hypothalamus is involved when temperature affects the rhythm of breathing

Question 6

What are the 2 other names for the pons ?

Answer 6

• pneumotaxic centre - drives rhythm or rate of breathing
• apneustic centre - involved in the duration of the breath

Question 7

What are the different types of lung receptors ?

Answer 7

• stretch receptors
• juxta-pulmonary “J” receptors
• irritant receptors
• proprioceptors

Question 8

Summarise the function of stretch receptors

Answer 8

• 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

Question 9

Summarise the function of juxta-pulmonary receptors

Answer 9

• 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

Question 10

Summarise the function of irritant receptors

Answer 10

• 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)

Question 11

Summarise the function of proprioceptors

Answer 11

• found in the intercostal muscles
• important role in switching between inspiration and expiration
• respond to change in position and length of these muscles

Question 12

Give some examples of peripheral receptors that influence breathing

Answer 12

• nociceptors (pain)
• mechanoreceptors (exercise/movement)
• arterial baroreceptors (blood pressure)
• thermoreceptors (heat/core temperature)

Question 13

Which receptors are the most important in terms of controlling and regulating breathing ?

Answer 13

Chemoreceptors

Question 14

Describe ventilation-metabolism matching

Answer 14

• if metabolism increases, ventilation should also increase
• important in maintaining blood gas composition

Question 15

How are changes in blood chemistry detected ?

Answer 15

Detected by -
• central chemoreceptors
• peripheral chemoreceptors

Question 16

Describe the location of central chemoreceptors

Answer 16

• 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

Question 17

What are central chemoreceptors sensitive to ?

Answer 17

• sensitive to pH of the cerebrospinal fluid
• they are bathed in CSF not blood

Question 18

Describe the response to changes in pH of the CSF

Answer 18

• 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

Question 19

Where are peripheral chemoreceptors found ?

Answer 19

• found directly in the blood
• located near the carotid and aortic arteries

Question 20

Describe the function of peripheral chemoreceptors

Answer 20

• 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

Question 21

What is the ventilatory response to increased partial pressure of carbon dioxide in the arteries ?

Answer 21

• increased partial pressure of carbon dioxide
• increased minute ventilation rate

Question 22

What is hypercapnia ?

Answer 22

High levels of carbon dioxide in the blood

Question 23

What is the ventilatory response to an increase in carbon dioxide partial pressure and decrease in oxygen partial pressure ?

Answer 23

increased minute ventilation very quickly (same response as hypercapnia but over a shorter timeframe)