56: Control of Respiration

Question 1

Central Controller

Answer 1

Pons, medulla, other parts of brain

Question 2

Effectors

Answer 2

Respiratory muscles, diaphragm, intercoastals

Question 3

Sensors

Answer 3

Chemo and mechanoreceptors, muscle proprioceptors

Question 4

What are the three respiratory centers in the Medulla Oblongata?

Answer 4

DRG – dorsal resp. group

VRG – ventral resp. group

PRG - Pontine resp. group

Question 5

Dorsal Resp. Group

Answer 5

control muscles during inspiration

Output via the
phrenic nerves and intercostal nerves

Receives sensory info from
peripheral chemo and mechanoreceptors
through cranial nerves IX and X

Question 6

Ventral Resp. Group

Answer 6

active expiration or for greater than normal
inspiration

pre-Botzinger complex

spontaneously firing
neurons, may act as the pacemaker

Question 7

Pontine Resp. Group

Answer 7

tonic input to medulla to control smooth resp. rhythm

Question 8

Latent period

Answer 8

after expiration – then a ramp pattern develops

increase action potentials, increase in diaphragm muscle tone, action potential reach max diaphragm muscle tone, action potential cease and diaphragm relaxes

Question 9

Sensors 1: central

chemoreceptors

Answer 9

ventral surface of the medulla

Responds to a change in PCO2 and pH of (CSF)

Question 10

CSF

Answer 10

separated from the blood by the BBB – which is largely impermeable to
H+ and HCO3-

Question 11

Does metabolic acidosis or alkalosis affect CSF pH?

Answer 11

little effect of CSF pH

Question 12

What is the BBB very permeable to?

Answer 12

O2 and CO2

PCO2 has a strong
effect on CSF pH

raising PCO2, large decrease in CSF pH

Question 13

Sensors 2: peripheral

chemoreceptors

Answer 13

located in carotid and aortic bodies

Detect changes in PCO2, PO2 and pH

Question 14

Carotid body

Answer 14

small sensory organ at carotid artery, signals to CNS via the glossopharyngeal
nerves

detect ↓PO2 (below 100 mmHg) and pH
changes

Question 15

Aortic bodies

Answer 15

multiple bodies along aorta

afferents feed CNS via vagus nerve

Question 16

Glomus cells

Answer 16

site of chemoreception

↓PO2 – depolarizes glomus cell and
stimulates afferents to the CNS

↑PCO2 in the cells causes acidification – also causes depolarization

H+- causes acid loading into cell - depolarization

Question 17

Integrated response

Answer 17

Central chemoreceptors primarily involved

but peripheral chemoreceptors also help and respond faster

Question 18

What is the most important stimulus to ventilatory drive?

Answer 18

PCO2 of arterial blood

Question 19

When PO2 low

Answer 19

PCO2 is high

Question 20

Cerebrum

Answer 20

voluntary control

Question 21

Medulla oblongata

Answer 21

site of dorsal respiratory
center and ventral respiratory center

generate
the basic rhythmic pattern of breathing

Question 22

Pons

Answer 22

apneustic and pneumotaxic centers can
modulate the basic pattern of the medulla but
are not essential

Question 23

limbic system and

hypothalamus

Answer 23

Emotional responses

anxiety, rage, fear

Question 24

Pulmonary Stretch Receptors

Answer 24

in smooth muscle layer of airways

fire in response to transmural pressure

Cause excitation of inspiratory offswitch
& prolongs expiration

Question 25

Irritant Receptors

Answer 25

in airway epithelium

Respond to touch, noxious substances (smoke or particles) or lung edema

stimulated by histamines, serotonins
and prostaglandins (inflammation)

results in coughing/gasping

Question 26

Juxtapulmonary capillary Receptors

Answer 26

AKA C-fiber endings

Alveolar and bronchial groups

Question 27

Alveolar C-fibers

Answer 27

fire in response to lung injury,
overinflation, pulmonary edema, pulmonary embolism

not sensitive to inflammatory mediators

Question 28

Bronchial C-fibers

Answer 28

are sensitive to inflammatory

mediators

Question 29

Stimulation bronchial C fibers

Answer 29

rapid shallow breathing,
bronchoconstriction, airway secretion and cardiovascular
depression (i.e. hypotension and bradycardia)

Question 30

Proprioceptors

Answer 30

Present in joints, tendons and muscle

inform brain of position of body through reception of tension

Question 31

Patient without proprioception…

Answer 31

brain has no

information on the location of your extremities must watch their limbs

Question 32

What is sobriety test testing?

Answer 32

proprioception

Question 33

What happens during repeat inflammation in the lungs?

Answer 33

destruction of alveolar septa and lungs with large air sacs rather than small alveoli

leads to hypoxemia and dyspnea

Question 34

Davenport Diagram

Answer 34

When respiratory acidosis occurs:

Renal Compensation through ‘Metabolic alkalosis’

Secrete H+into urine
blood pH↑
HCO3- ↑

Question 35

CSF pH with chronic hypercapnia

Answer 35

Choroid plexus will restore CSF pH by secreting HCO3 into the CSF to compensate for chronic acidosis

Question 36

Minute ventilation during oxygen

induced hypercapnia

Answer 36

high O2 administered, initial decrease in minute ventilation but then increases

hypercapnia continues to increase

Question 37

Carbon dioxide retention

Answer 37

consequence of
ventilation-perfusion mismatching rather than respiratory
center depression

Question 38

How can you reduce risk of oxygen-induced

hypercapnia in COPD patients?

Answer 38

titrate oxygen delivery to maintain the PaO2 at 60-65 mm Hg

achieve
saturations of 88% to 92%

Question 39

Consequences of Hypoxaemia

Answer 39

Regional pulmonary vasoconstriction

Peripherally vasodilation increase Cardiac output

Erythropoietin secretion increases

Loss of cognitive and motor functions

Impaired judgement

headache,
breathlessness, palpitations, tremor ,
restlessness

loss of consciousness

Detrimental long term effects: pulmonary
HT, Right Ventricular failure, polycythaemia

Question 40

Why treat Hyoxaemia?

Answer 40

Immediate benefits – Alleviate of hypoxaemia,
reduce dyspnea, sleep consolidation

Long term benefits – improves survival
-slight reduction in
pulmonary artery pressure