25. Respiratory System (30)

Cessation of Breathing in the Inspiratory Position

Apneusis

What is the effect of transection of the Brainstem in the Pons at Level II when the vagus nerve is left intact? -What does this indicate?

Apneusis Does Not Occur -Indicates that Vagus Nerves Inhibit the Apneustic Center

What is the effect of transection of the Brainstem at Level II between the apneustic center and the PRG along with the Transection of the Vagus Nerves?

Apneusis Occurs Because Inhibition from the PRG and Influence of Vagus Nerves is Eliminated

-Found in the Lower Pons -Promotes Inspiration and Has not been Actually Identified (Inferred from Physiological Studies on Experimental Animals)

Apneustic center

What is apneusis probably caused by?

Sustained Discharge of Medullary Inspiratory Neurons

What are the pontine respiratory groups under the influence of?

-The vagus nerve

What is the effect of transection of the Brainstem in the Pons at Level II along with the Transection of the Vagus Nerves (Now the Vagus Nerves have No Input into any Respiratory Centers)

-The Result is a Prolonged Inspiration Followed by Occasional Expirations (Apneusis)

What is the effect of transection of the Brainstem at Level I along with the Transection of the Vagus Nerves? -Does this create an abnormal balance between inspiration and expiration?

-VT Increases and Breathing Rate Decreases -No, this Results in Essentially a Normal Balance Between Inspiration and Expiration (Again No Vagal Input to the System)

What is the breathing pattern associated with transection at Level II between the apneustic center and PRG with intact vagus nerves?

-VT Increases and respiratory rate decreases

What would happen if the brain is transected at Level IV? -What does this indicate?

All Breathing Ceases -Strong Indication that Inspiratory Control is Located in Medullary Respiratory Centers

What is the effect of transection of the Brainstem at Level I when the vagus nerve is left intact?

No effect on breathing rate or depth

Where does the inspiratory group of the VRG send fibers?

One Group Sends Fibers to External Intercostals and the Other Sends Some Fibers to the Diaphragm

Does the ventral respiratory group (VRG) contain inspiratory or expiratory neurons? -What is the function of the VRG?

Contains Both Inspiratory and Expiratory Neurons -Increases breathing rate, causes active expiration

What respiratory center would function if the brain was transected at Level III? -What would breathing be like?

-Only the DRG would function (without any Input from Other Brain Centers) -Breathing would be Irregular and Gasping

What are the two parts of the respiratory-associated centers (pons)?

-Apneustic Center -Pontine Respiratory Groups (PRG)

Out of the DRG and VRG, which is superficial and which is deep?

-DRG is superficial -VRG is deep

What is the breathing pattern associated with transection at Level IV? Why?

-Death -Because the Medullary Centers Responsible for Initiating Respiration are not Able to Stimulate Breathing Movements

What are the two groups of diffuse neurons in the medullary respiratory centers? -Where are these groups located?

-Dorsal Respiratory Group (DRG): Located in Dorsomedial Region of Medulla -Ventral Respiratory Group (VRG): Located in Ventrolateral Region of Medulla

Where does the nucleus tractus solaris (NTS) region receive visceral afferent input from? -What does this input pertain to?

-Glossopharyngeal (IX) and Vagus (X) Nerves -PaO2 -PaCO2 -pH -Stretch Receptors Located in the Lungs and Baroreceptors in the Aorta and Carotid Sinuses

What are the overall functions of the respiratory centers?

-Initiate and Maintain Act of Breathing -Alter the Rate and Depth of Breathing

Where are the levels of the respiratory centers located?

-Level I: Above the Pons -Level II: In the Pons -Level III: In between the Pons and the Medulla -Level IV: In between the Medulla and Spinal Cord

What is the primary function of the neurons of the dorsal respiratory group (DRG)? -Where do they send impulses?

-Neurons Primarily involved with Inspiratory Actions -Neurons Send Nerve Impulses to the Diaphragm via Phrenic Nerves

What are the regions of the ventral respiratory group (VRG) -Which one Contains the pre-Bötzinger Complex (pre-BOT)?

-Nucleus Ambiguus (NA) -Rostral VRG -Caudal VRG: Contains the pre-Bötzinger Complex (pre-BOT)

What are other areas that transmit sensory signals to the medullary respiratory centers?

-Respiratory-Associated Centers (Pons) -Hypothalamus -Cerebral Cortex -Chemoreceptors: Peripheral and Medullary -Baroreceptors (Stretch) Associated with Lungs

What kind of activity is the dorsal respiratory group (DRG) associated with?

-Responsible for "Inherent Activity" Associated with Breathing -Initiating and Maintaining Breathing during Rest and Moderate Activity

Where does the expiratory group of the VRG send fibers?

-Sends Fibers to Other Inspiratory Neurons and to Expiratory Neurons within the Medulla

In which level is the apneustic center located?

Between Levels II and III

Where are the medullary respiratory centers located?

Bilaterally in the Reticular Formation of the Medulla Oblongata

What is the effect of transection of the Brainstem at Level III between the pons and medulla when the vagus nerve is left intact?

Breathing pattern is irregular and gasping

What types of cells is the dorsal respiratory group (DRG) made of? -What are their functions? What do they all effect?

Composed of Three Populations of Cells which affect the pattern of inspiration -Iα: Increase activity related to lung inflation -Iβ: Decrease activity related to lung inflation -P Cells: Pump cells

What are the effects of morphine and barbiturates on the medulla?

Depress Activity of Cells in the Medulla that Results in a Decrease in the Rate and Depth of Breathing

This medullary respiratory group is associated with the Nucleus Tractus Solitarius (NTS)

Dorsal Respiratory Group (DRG)

This Group is the Probable Site Responsible for Driving the Diaphragm and Integrating Cardiopulmonary Inputs that Reflexly Alter the Spontaneous Pattern of Inspiration and Expiration

Dorsal respiratory group (DRG)

What do expiratory neurons of the VRG innervate?

Expiratory Neurons Innervate Internal Intercostal and Abdominal Muscles and/or Auxillary Muscle Via the Vagus Nerves

What is the effect of transection of the Brainstem at Level III between the pons and medulla along with the Transection of the Vagus Nerves?

Irregularity Becomes Greater than with the vagus nerves because only the Medullary Centers are Intact

Modulate the action of the apneustic center (through inhibitory activity) by limiting duration of inspiration (primary function) and increasing the rate of respiration?

Pontine respiratory groups

Which region of the VRG acts as a pacemaker that establishes normal respiratory rhythm?

Pre-Bötzinger Region

What is the effect of a transection at level III between the pons and medulla?

This Prevents Nerve Impulses from the Apneustic Center and the PRG from Reaching the Medullary Respiratory Centers (DRG and VRG)

Can areas of the brain other than the respiratory centers have input to affect the respiratory centers?

Yes