chapter 18b
DESCRIPTION
Chapter 18b. Gas Exchange and Transport. Reflex Control of Ventilation. KEY. Emotions and voluntary control. 16. CO 2. O 2 and pH. Stimuli. Sensory receptors . 15. 1. Afferent neurons . 2. Higher brain centers. 14. Medullary chemoreceptors. Carotid and aortic chemoreceptors. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 18b
Gas Exchange and Transport
15
16
ExpirationInspiration
Sensoryreceptors
IntegratingcentersEfferentneurons Effectors
Afferentneurons
Stimuli
KEY
Afferent sensoryneurons
Carotid and aorticchemoreceptors
Externalintercostals
Internalintercostals
AbdominalmusclesDiaphragm
Somaticmotor neurons
(inspiration)
Somaticmotor neurons
(expiration)
Medullarychemoreceptors
Emotionsand voluntary
control
Medulla oblongataand pons
Scalene andsternocleidomastoid
muscles
CO2 O2 and pH
Limbicsystem
Higherbrain
centers1314
12
34
5
6
12
11
10
78
9
Reflex Control of Ventilation
Figure 18-16
PRG
PRG = Pontine respiratory group
DRG
VRGOutput to expiratory,
some inspiratory,pharynx, larynx, and
tongue muscles
Outputprimarily toinspiratory
muscles
Sensory inputfrom CN IX, X
(mechanical andchemosensory)
Medullarychemo-
receptors
Higherbrain
centers
NTS
pre-Bötzingercomplex
Pons
Medulla
KEY
DRG = Dorsal respiratory groupVRG = Ventral respiratory groupNTS = Nucleus tractus solitarius
Regulation of Ventilation
Figure 18-17
Regulation of Ventilation• Respiratory neurons in the medulla
control inspiration and expiration• Rhythmicity center Inspiration and Expiration• VRG and DRG of medulla
• Rhythmic pattern of breathing arises from a network of spontaneously discharging neurons
Neurons in the pons modulate ventilation• Ventilation is subject to modulation by
chemoreceptor-linked reflexes and by higher brain centers
• Apneustic and Pneumotaxic• Apenustic – inspiration• Pneumotaxic – anatagonistic – inhibit
inspiration
Rhythmicity of breathing
Regulation of Ventilation
• Neural activity cycles during quiet breathing
Figure 18-18
Regulation of Ventilation
• Peripheral chemoreceptors• Located in carotid and aortic arteries• Specialized glomus cells
• Sense changes in PO2, pH, and PCO2
central
chemoreceptors• Changes in CO2
Regulation of Ventilation
• Carotid body oxygen sensor releases neurotransmitter when PO2
decreases
Figure 18-19
7
6
54
3
21K+ channels closeLow PO2
Blood vessel
Voltage-gated Ca2+
channel opens
Ca2+
entry
Celldepolarizes
Exocytosis ofneurotransmitters
Receptor onsensory neuron
Glomus cellin carotid
body
Signal to medullarycenters to increaseventilation
Action potential
Low PO2
H+
CO2 + H2O
Cerebral capillary
Blood-brainbarrier
Cerebrospinalfluid
MedullaCentral chemoreceptor
PCO2
Respiratorycontrolcenters
Ventilation
CAH2CO3 H+ + HCO3
–
Regulation of Ventilation
• Central chemoreceptors monitor CO2 in cerebrospinal fluid
Figure 18-20
Regulation of Ventilation
• Chemoreceptor response to changes in plasma CO2
Figure 18-21
Plasma PO2
Stimulatescentral
chemoreceptor
PCO2 in CSF Arterial PCO2
inplasma
PlasmaPCO2
Stimulatesperipheral
chemoreceptorPlasma PO2
< 60 mm Hg
Ventilation
CO2in
CSF
HCO3–H+ + HCO3
–CO2 H+ +
Plasma PCO2
Negative feedback
Control of Ventilation
PLAY Interactive Physiology® Animation: Respiratory System: Control of Respiration
Regulation of Ventilation
• Protective reflexes• Irritant receptors • Bronchoconstriction• Sneezing• Coughing
• Hering-Breuer inflation reflex• Don’t over stretch and damage
Summary
• Diffusion and solubility of gases• Gas exchange• Gas transport• Transport of oxygen and carbon dioxide• Factors affecting oxygen-hemoglobin binding• Carbonic anhydrase and chloride shift
Summary
• Regulation of ventilation• Central pattern generator• Dorsal versus ventral respiratory groups• Peripheral versus central chemoreceptors