L3-central control of respiration

Question 1

what is respiration controlled by?

Answer 1

mostly controlled by nerve cells or neurones in the medulla oblongata of the brain

Question 2

what influences the rhythm of respiration

Answer 2

the medullary neurones set the basic rhythm but the rhythm can be influenced by inputs from other part of brain and peripheral sensory receptors

Question 3

where is the respiratory centre (RC) located

Answer 3

medulla oblongata

Question 4

2 regions of the RC

Answer 4

inspiratory centre

expiratory centre

Question 5

what does the inspiratory centre consist of?

Answer 5

2 dorsally situated regions of medulla oblongata

Question 6

how does the inspiratory centre function

Answer 6

the neutrons show spontaneous rhythmicity
cyclic form of activity rises every few seconds
the activity sets basic rhythm of respiration
action potential derived from these cells pass along the intercostal nerves and phrenic nerve to muscle of inspiration

Question 7

what does the expiratory centre consist of

Answer 7

consists of 2 groups of neurones

situated more ventrally either side of the medulla oblongata

Question 8

function of the expiratory centre

Answer 8

mostly inactive
during heavy breathing
send action potentials to the muscles associated with expiration

Question 9

what is hering breuer reflex

Answer 9

control mechanism associated with stretch receptors in the walls of the bronchi

Question 10

when is hering breur reflex activated

Answer 10

activated during inspiration and send action potentials via the vagus nerve to the medulla oblongata

Question 11

what does action potential inhibit in HB reflex

Answer 11

action potentials inhibit the inspiratory centres and allow expiration

Question 12

how are the HB reflex inactivated

Answer 12

during expiration the stretch receptors are inactivated which in turn allow activation of the inspiratory centres

Question 13

how is the chemical control of respiration achieved

Answer 13

central and peripheral chemoreceptors

Question 14

where are central chemoreceptors located

Answer 14

located in the medulla oblongata in the chemosensitive area where they influence the respiratory centres

Question 15

where are the peripheral chemoreceptors located

Answer 15

located in the carotid bodies and these connect to the respiratory centres by glossopharyngeal nerve and the vagus nerve respectively

Question 16

chemoreceptor respond to change in what

Answer 16

respond to changes in the concentration of hydrogen ions (pH) and oxygen

Question 17

what is hypercapnia

Answer 17

an excessive PCO2 in the blood

Question 18

what is hypocapnia

Answer 18

lower than average PCO2

Question 19

is carbon dioxide concentration of blood directly detected

Answer 19

no it is not directly detected by the chemoreceptors instead the chemoreceptors detect changes in the bloods pH

Question 20

how is the pH detected by the chemoreceptors

Answer 20

pH is detected by the chemorecptive area in the medulla oblongata and by the peripheral chemorecptors

Question 21

what detects changes in blood pH directly

Answer 21

the chemoreceptive area in the medulla

Question 22

what detects blood pH directly

Answer 22

chemoreceptors in the carotid and aortic bodies

Question 23

effect of pH on respiratory rate

Answer 23

decreases in pH result in an increase in the respiratory rate
increase in pH results in a decrease in the respiratory rate

Question 24

what is the chemosensitive area of the medulla responsible for

Answer 24

80% of total response to pH change

Question 25

what are the peripheral receptors responsible for

Answer 25

20% of the total response to variations in pH

Question 26

what detects the oxygen concentration in the blood

Answer 26

chemoreceptors in the carotid and aortic bodies

Question 27

what happens if PCO2 remains constant

Answer 27

the PO2 has to drop to about 50% of its normal value before blood O2 concentrations have a large stimulatory affect on respiration

Question 28

what is haemoglobin saturated with

Answer 28

virtually saturated with O2 at PO2 of 80mm

Question 29

what needs to happen in order for increase in respiratory rate to be triggered

Answer 29

PO2 levels have to drop significantly in the aorta and the carotid arteries before the low O2 concentration triggers an increase in the respiratory rate