Physiology 6 - Control of Respiration

Question 1

how is ventilation controlled?

Answer 1

by respiratory centres in the brain stem

Question 2

where is the major rhythm generator?

Answer 2

the MEDULLA

Question 3

what section of the medulla allows normal ventilation to be retained?

Answer 3

section ABOVE the medulla

Question 4

what section of the medulla ceases ventilation?

Answer 4

section BELOW the medulla

Question 5

What name is given to the network of neurones that generate the breathing rhythm?

Answer 5

Pre-Botzinge complex

Question 6

where is the pre-botzinge complex located?

Answer 6

located near the upper end fo the medullary respiratory centre

Question 7

what does the pre-botzinge complex excite?

Answer 7

they excite dorsal respiratory group neurones

Question 8

what does the excitement of dorsal respiratory group neurones result in?

Answer 8

fire in bursts

Question 9

what does firing lead to?

Answer 9

contraction of inspiratory muscles which leads to inspiration.
when firing stops - passive expiration

Question 10

what second group is excited when there is increased firing dorsal neutrons?

Answer 10

ventral respiratory group neurones

Question 11

what do ventral respiratory group neurones excite?

Answer 11

excites internal intercostal abdominals

Question 12

what does excitement of internal intercostal muscles lead to?

Answer 12

leads to forceful expiration

Question 13

the rhythm generated in the medulla can be modified by neurones in the pons called?

Answer 13

the PNEUMOTAXIC CENTRE (PC)

Question 14

what does stimulation of pneumotaxic centre terminate?

Answer 14

terminates inspiration

Question 15

what happens to breathing WITHOUT PC?

Answer 15

breathing is prolonged, inspiratory gasps with brief expiration
= APNEUSIS

Question 16

what does the apneustic centre do?

Answer 16

• impulses from these neurones excite inspiratory area of the medulla, prolonging inspiration

Question 17

give 5 examples of how the respiratory centre is influenced by stimuli?

Answer 17

1) higher brain centres
2) stretch receptors in walls of bronchi & bronchioles
3) juxapulmonary receptors
4) joint receptors
5) barareceptors

Question 18

what are the 3 main factors that control respiration?

Answer 18

1) pH
2) PaCO2
3) PaO2

Question 19

how are these 3 chemical factors monitored?

Answer 19

they are monitored by chemo-receptors that prove input to respiratory centres

Question 20

what do the respiratory centres do?

Answer 20

they send nerve impulse to effectors in respiratory muscles that control their frequency & force of contraction, thus change the rate & depth of breathing

Question 21

what are the 2 different types of chemoreceptors?

Answer 21

1) central chemoreceptors

2) peripheral chemoreceptors

Question 22

5 factors that may increase ventilation during exercise?

Answer 22

1) adrenaline release
2) impulses from cerebral cortex
3) increase in body temperature
4) accumulation of CO2 + H+ generated by active muscles
5) reflexes originating from body movement

Question 23

why is the cough reflex present?

Answer 23

vital part of body defence mechanisms

Question 24

what does the cough reflex do?

Answer 24

helps clear airways of dust, dirt or excessive secretions

Question 25

when is the cough reflex activated?

Answer 25

by irritation of airways or high airways (e.g. asthma)

Question 26

where is the activation centre for the cough reflex?

Answer 26

the medulla

Question 27

when do central and peripheral chemoreceptors modify breathing rhythm?

Answer 27

when theres changes in;

1) PaO2
2) PaCO2
3) pH

Question 28

what do peripheral chemoreceptors sense?

Answer 28

they sense TENSIONS OF O2 & CO2 & [H+] in the blood

Question 29

how do the peripheral chemoreceptors respond?

Answer 29

they response by sending more impulses to respiratory centres to increase the rate & depth of breathing & improve excretion of CO2

Question 30

where are central chemoreceptors situated?

Answer 30

they are situated near the surface of the medulla of the brainstem

Question 31

what do central chemoreceptors respond to?

Answer 31

they respond to [H+] of the cerebrospinal fluid (CSF)

Question 32

how is the CSF separated from the blood brain barrier?

Answer 32

it is separated from the bbb by blood.

Question 33

what is hypercapnia?

Answer 33

elevated levels of CO2 in blood.

Question 34

what is hypoxia?

Answer 34

deficiency of amount of O2 reaching the tissues

Question 35

is the hypoxic drive effect done via peripheral of central chemoreceptors?

Answer 35

all done via the peripheral chemoreceptors

Question 36

when is the hypoxic drive stimulated?

Answer 36

when PO2 levels fall below 8.0kPa

Question 37

how is hypoxia at high altitudes caused?

Answer 37

caused by a decreased partial pressure of inspired oxygen (PiO2)

Question 38

what is the acute response to hypoxia at high altitudes?

Answer 38

hyperventilation & increased cardiac output

Question 39

what are some symptoms of acute mountain sickness

Answer 39

• headache
• fatigue
• nausea
• dizziness
• sleep disturbances
• exhaustion
• shortness of breath
• unconsciousness
• tachycardia

Question 40

what re 5 chronic adaptations to high altitude hypoxia

Answer 40

1) increased RBC production (polycythaemia)
- O2 carrying capacity of blood increases

2) increased 2,3-biphosphoglycerate with RBC
- O2 offloaded to tissues more easily

3) increased number of capillaries
- blood diffuses more easily

4) increased number of mitochondria
- O2 can be used more efficiently

5) kidneys conserve acid
- arterial pH decreases