Neural and Chemical Control of Respiration

Question 1

homeostasis of blood gases

Answer 1

-nervous system interaction with the respiratory system is designed to maintain normal blood levels of oxygen, carbon dioxide, and hydrogens

Question 2

key points

Answer 2

• brainstem generates basic breathing rhythm and is influenced by ventilatory reflexes
• respiration rate and depth is controlled by blood gas concentrations and lung stretch receptors
• arterial Pco2 is most important factor for control of respiratory drive at rest
• central chemoreceptors detect changes in arterial Pco2- really changes in H concentration
• peripheral chemoreceptors detect changes in arterial Po2, PCo2, and pH

Question 3

inspiratory output

Answer 3

• ventral and dorsal respiratory group both active
• send out impulses to phrenic nerve and spinal nerves to external intercostals
• DRG and VRG connected via spinal respiratory motoneurons to the phrenic nerve

Question 4

central pattern generator

Answer 4

• breathing is neurogenic
• located in medullary respiratory center
• below the floor of the 4th ventricle of the brain
• has both dorsal and ventral respiratory groups
• CPG sends a rhythmic drive to the motorneurons controlling respiratory muscles and controls rate and tidal volume
• CPG receives input from higher brain centers and from peripheral and central chemoreceptors

Question 5

expiratory output

Answer 5

-the medullary VRG is connected via spinal respiratory motoneurons to spinal nerves that innervate the internal intercostals and abd muscles

Question 6

AP frequency

Answer 6

• phrenic/ external intercostal
• APs increase during inspiration for relaxed breathing
• expiration muscles not having much APs
• vigorous breathing increases the APs in abd/intercostal expiration muscles (hyperpnea)
• tidal volume increases as well as frequency

Question 7

Hering-Breuer Inflation Reflex

Answer 7

-during deep inspirations, lung inflation activates stretch receptors that inhibit further inflation via vagal afferents and phrenic efferents

Question 8

respiratory center

Answer 8

• just above the medulla
• pontine respiratory group controls center- in pons
• controlled by the hypothalamus
• brain stem is relay station
• has VRG and DRG (in NTS) and other controls

Question 9

BOT

Answer 9

• botzinger complex
• pacemaker of breathing
• pharmacological target
• expiratory neurons
• in venttrolateral medulla essential for pacemaker

Question 10

DRG

Answer 10

• bilaterally in the NTS
• inspiratory neurons
• initiator of activity of the phrenic nerves
• sends many collateral neurons to the VRG
• receives vagal afferents from chemoreceptors

Question 11

VRG

Answer 11

• located bilaterally in the retrofacial nucleus, nucleus ambiguous, and nucleus retroambifualis
• inspiratory and expiratory neurons
• contains BOT

Question 12

pontine respiratory group

Answer 12

• pneumotaxic center
• located in nucleus parabrachialis medialis and the KF nucleus of the pons
• fine tunes respiratory pattern and modulates pattern in response to vagal afferents responding to hypercapnea or hypoxia

Question 13

Level I transection

Answer 13

• with vagus has normal breathing

- without vagus has decreased frequency and increased tidal volume

Question 14

Level II transection

Answer 14

• with vagus has dec frequency and increased tidal volume

- without vagus has apneusis

Question 15

level III transection

Answer 15

• just below pons
• gasping with vagus
• more sporadic gasping without vagus

Question 16

Level IV transection

Answer 16

• below DRG
• apnea
• CPG above here

Question 17

Cheyne stokes respiration

Answer 17

• abnormal pattern characterized by alternating periods of hyperpnea and apnea, each cycle from 30s to 2 min
• altered arterial partial pressures of oxygen and carbon dioxide
• injuries to resp centers, chronic heart failure, CO, strokes, brain tumors

Question 18

cluster breathing

Answer 18

• stroke, head trauma, pressure, lesion in lower pontine region of brainstem
• closely groups series of shallow breaths similar in size separated by intervals of apnea and indicative of poor prognosis

Question 19

ataxic breathing

Answer 19

• lesion in medullary respiratory center

- completely irregular inspirations and expirations with irregular pauses and increasing periods of apnea

Question 20

kussmaul breathing

Answer 20

• abnormal form of deep and labored desperate and gasping breathing associated with severe metabolic acidosis, particularly diabetic
• shallow rapid hyperventilation becomes kissmaul as acidosis progresses

Question 21

central chemoreceptors

Answer 21

-activated primarily by hydrogen ions via blood CO2 crossing the blood brain barrier and generating hydrogen ions

Question 22

peripheral chemoreceptors

Answer 22

-activated by low blood partial pressures of oxygen, high partial pressures of co2, high H

Question 23

alveolar CO2

Answer 23

• major controller of respiration rate
• after intense hyperventilation, there is a period of apnea because CO2 is so low
• once CO2 levels reach normal, breathing starts
• also produces cheyne stokes rhythm

Question 24

increasing PACO2

Answer 24

• increases ventilation to get more out
• sensitivity to carbon dioxide increases with hypoxia
• shifts to left on ventilation vs PaCO2 graph
• smaller increase in co2 will cause increase in ventilation
• response to co2 also altered by sleep, drugs, metabolic acidosis. sleep and drugs make less sensitive, acidosis makes it more sensitive

Question 25

CO2 and O2

Answer 25

• plotting ventilation against line from CO2
• there is a set point at intersection between sensitivity curve and effector curve
• increasing levels of ventilation reduces CO2
• its a dynamic process
• drugs, acidosis move set point down and up respectively

Question 26

altering pH

Answer 26

• with constant CO2, low pH increases ventilation greatly
• with changing CO2, its dynamic again, ventilation increases with drop in pH and corrects it
• same effect on PO2 with constant CO2 and then not- first big changes then ventilation doesn’t allow for as big of a change

Question 27

blood brain barrier

Answer 27

-only CO2 crosses, central receptors respond to H dissociated

Question 28

peripheral chemoreceptors

Answer 28

-carotid and aortic bodies
-have glomus cells
low O2, closes K channel, cell depolarizes, Ca open, Ca stimulates IX which sends afferent signals to brain to change breathing
-if chemoreceptors are denervated, ventilation decreases, lack of O2