Control of ventilation

Question 1

what does ventilatory control require the stimulation of?

Answer 1

skeletal muscle of inspiration ie diaphragm, external intercostals (contract to elevate ribs)

Question 2

what does ventilatory control physically occur by

Answer 2

phrenic nerve (to diaphragm) think DIAPHR-ENIC
intercostal nerves (to external intercostal muscles)

Question 3

what are the respiratory centres in the brain and what do they govern

Answer 3

pons and medulla

the rate and depth of respiration

Question 4

is ventilatory control subconscious?

Answer 4

yes but it can be subject to voluntary modulation

Question 5

what is breathing entirely dependent on

Answer 5

signalling from the brain

Question 6

what crosses the blood brain barrier when PCO2 increases

Answer 6

CO2

Question 7

what do central chemoreceptors monitor indirectly in the CSF

Answer 7

PCO2

Question 8

common drugs that depress the respiratory centre

Answer 8

Barbiturates and opioids

Question 9

examples of sitmuli that influence activity of respiratory centres

Answer 9

emotion

Voluntary over-ride (conscious decisions)

Mechano-sensory input from the thorax

chemoreceptor input

Question 10

what is the most important stimuli

Answer 10

chemoreceptor input

Question 11

what 2 types of chemoreceptors are there?

Answer 11

central and peripheral chemoreceptors

Question 12

where are central chemoreceptors found and what do they respond to

Answer 12

in the medulla

respond directly to H+ (derived from CO2)

Question 13

which are the primary ventilatory drive?

Answer 13

central chemoreceptors

Question 14

where are peripheral chemoreceptors found and what do they respond to

Answer 14

carotid and aortic bodies

clusters of cells located on the common carotid artery and the aortic arch

respond primarily to plasma [H+] and PO2 (less so to PCO2)

Question 15

which are the secondary ventilatory drive?

Answer 15

peripheral chemoreceptors

Question 16

what parts of the body do the ventral respiratory group of neurons (VRG) supply?

Answer 16

Tongue, pharnyx, larynx, expiratory muscles

Question 17

what parts of the body do the dorsal respiratory group of neurons (DRG) supply?

Answer 17

inspiratory muscles via the phrenic and intercostal nerves

Question 18

what do central chemoreceptors detect around the brain

Answer 18

changes in H+ concentration in CSF

Question 19

why do H+ levels rise in CSF

Answer 19

due to raised CO2 levels, so raised PCO2 when these rise H+ conc also rises

Question 20

what is a raised PCO2 called

Answer 20

hypercapnea

Question 21

how does hyperventilation occur? mention PCO2, H+ and chemoreceptors

Answer 21

ventilation is reflexly inhibited by a decrease in arterial PCO2
this reduces CSF H+ conc and as a result, switches off central chemoreceptors

Question 22

True or false: central chemoreceptors don’t respond to direct changes in plasma [H+] because of the blood brain barrier

Answer 22

true

Question 23

what happens when arterial PCO2 increases

Answer 23

CO2 moves across the blood brain barrier (gases can, not H+ as it is an ion)

Question 24

what does PCO2 form in the CSF after passing through blood brain barrier

Answer 24

produces bicarbonate and H+

the receptors then respond to this increase in H+

Question 25

what happens at the respiratory centres when PCO2 increases?

Answer 25

the respiratory centres increase ventilation rate

Question 26

what change do peripheral chemoreceptors detect?

Answer 26

changes in arterial PO2 and H+ concentration

Question 27

what happens when there is a significant fall in arterial PO2 or a rise in H+ conc?

Answer 27

Reflex stimularterialation of ventilation

Question 28

if you have chronic lung disease how does your body detect changes in PO2

Answer 28

In people with chronic lung disease their PCO2 is chronically elevated so they become desensitised to PCO2 and instead rely on changes in PO2

Question 29

where are peripheral chemoreceptors found

Answer 29

carotid and aortic bodies

Question 30

if plasma pH falls ([H+] increases) what happens?

Answer 30

ventilation will be stimulated (acidosis)

Question 31

if plasma pH rises ([H+] decreases) what happens?

Answer 31

e.g.vomiting (alkalosis), ventilation will be inhibited

Question 32

CO2 to carbonate equation

Answer 32

CO2 + H20 --> H2CO3 --> HCO3- + H+

Question 33

why can a person have a huge amount of voluntary control over breathing?

Answer 33

Descending neural pathways from cerebral cortex to respiratory motor neurons

Question 34

True or false: Respiration is inhibited during swallowing to avoid aspiration of food or fluids into the airways.

Answer 34

True

Question 35

what is the vagus nerve

Answer 35

the 10th cranial nerve and interfaces with parasympathetic control of the lungs

Question 36

what follows swallowing?

Answer 36

Swallowing is followed by an expiration in order that any particles are dislodged outwards from the region of the glottis.

Question 37

what will happen to resp rate in an anaemic patient with a blood oxygen content half the normal value

Answer 37

stay the same

Question 38

What is anaemia

Answer 38

number of red blood cells or the amount of haemoglobin in red blood cells is less than normal- means less binding sites as less haemoglobin.

Question 39

examples of other aspects of control of breathing

Answer 39

breath holding hyperventilation you cannot override involuntary stimuli such as PCO2 or H+ conc decending neural pathways from cerebral cortex to respiratory motor neurons

Question 40

What are accessory muscles of inspiration and when are they used?

Answer 40

sternocleidomastoid (contracts to elevate sternum) pectoralis major and minor (push/pull ribs inwards/outwards) serratus anterior (on side of rib cage) latissimus dorsi (large muscle on the back) serratus posterior superior. typically only used under conditions of high metabolic demand (e.g. exercise) or respiratory dysfunction (e.g. an asthma attack).