Dr Archna Ghildiyal - PowerPoint Presentation

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Dr Archna Ghildiyal Associate Professor Department of PhysiologyKGMU

Respiratory SystemSlide2

LECTURE:8

Contents

Regulation of Respiration: Neural

Group of Neurons controlling Respiration

Breathing rhythm: Ramp Signals

Lung ReceptorsSlide3

Learning ObjectivesNeuralControl of Respiration : - Automatic -VoluntaryI & E

Neurones

Inspiratory

“Ramp” Signal

Pre-

Botzinger

Complex

Lung ReceptorsSlide4

Neural Control of RespirationBreathingAutomatic/Spontaneous

Voluntary Slide5

Neural control of RespirationSlide6

Groups of Neurons in the Respiratory CenterIn medullaDorsal respiratory group Ventral respiratory group

In Pons

Pneumotaxic

center

Apneustic

Center?Slide7

Dorsal Respiratory Group(DRG)Most neurons located within NTS, some in adjacent reticular substance of medullaNormal quiet breathing:

Repititive

Inspiratory

signals from DRG

Controls

Inspiration

Respiratory rhythmSlide8

Inspiratory “Ramp” SignalsRhythmical Inspiratory

discharge

from DRG

Nervous signal that is transmitted to the

inspiratory

muscles, mainly the

diaphragm

Begins weakly & increases steadily for about

2

secs

in normal respiration (inspiration)

Then ceases abruptly for approx next

3

secs

(expiration)Slide9

Control of Inspiratory Ramp1.Control of the rate of increase of the ramp signal  rate of ramp signal - ramp increases rapidly - fills the lungs rapidly

2.Control of the limiting point

at which the ramp suddenly ceases

Usual method for controlling the rate of respiration; shortens the duration of Inspiration & Expiration(



frequency of respiration )Slide10

Contd… Stopping the

Ramp



Shortens the rate of inspiration and

expiration



Increasing the

frequency of

respirationSlide11

Pneumotaxic center

(upper

pons

)

Located dorsally in upper

pons,in

N.parabrachialis

Sends continual inhibitory impulses to

inspiratory

center

Ramp controls stopping point of DRG

Inhibits I neurons

Switch breathing from inspiration to expirationSlide12

Contd…As impulse frequency rises: Faster and Shallower BreathingDamage to

Pneumotaxic

center : Results in increased depth of inspiration Slide13

Ventral respiratory group(VRG)Located in ventrolateral part of medulla,in

N.ambigues

&

N.retroambigues

Functions in both Inspiration & Expiration

Remain

inactive during normal quite respirationSlide14

Contd…Act as Overdrive mechanism

(as in heavy exercise)

Powerful

expiratory signals

to internal

intercostal

& abdominal muscles Slide15

Pre-Bötzinger ComplexCluster of interneurons  in the ventrolateral medulla  of the Brainstem

Contains Pace maker

Cells-Spontaneous BreathingSlide16

Apneustic Center (Lower Pons)

Role not clear

Stimulation causes

Apneusis

(

pause at full inspiration)

Integrates

inspiratory

cut-off informationSlide17

Mechanism of Rhythmic Ventilation

Medullary

respiratory center neurons are continuously active

(spontaneous/automatic breathing)

Combined input from all sources (

receptors,brain

) causes action potentials to stimulate respiratory musclesSlide18

To Increase Inspiration

More and more neurons get activated

To Stop Inspiration

Neurons receive input from

pontine

group and

stretch receptors in lungs

Inhibitory neurons activated , cause

Inspiratory

switch-off ,

Start of expiration

Effect: Relaxation of

Inspiratory

musclesSlide19

Voluntary controlProvided via the Cerebral Cortex Modulate the activity of controlling centers in the medulla and

pons

Allow the rate and depth of respiration to be controlled

During speaking, laughing, crying, eating, defecating, coughing, and sneezingSlide20

Contd… 

Chemoreceptor reflex

is capable of overriding it.

 Conscious control of respiratory neuronal networks in the

reticular formation

can effect other basic functions regulated by the brainstem(Yogic exercises)Slide21
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Contd…Stimulation of the reticular activating system of the brainstem (RAS):Stimulates Ventilation

Sleep:



VentilationSlide23

Peripheral receptorsChemoreceptorsPulmonary irritant receptors-on stimulation cause coughing,sneezing,bronchial

constriction

Lung “J Receptors”

Hering

-Breuer inflation reflexSlide24

Lung “J Receptors”Indian Physiologist Prof A S PaintalLocation:Sensory

nerve endings in alveolar walls in juxtaposition to pulmonary capillaries

Stimulus: Severe exercise, Engorged

capillaries,Pulmonary

oedema

Effect:Tachypnea,Hypotention,BradycardiaSlide25

J-ReflexStimulation (severe exercise) Inhibition of

gama

motor neurons supplying muscle spindle





Muscle Tone



Muscle Weakness & Stoppage of ExerciseSlide26

Hering- Breuer Inflation ReflexProtective reflexLung inflation signals limit inspirationStretch Receptors: In Muscular Walls Of Bronchi & Bronchioles Active when Tidal volume > 1.5 liters/breathInspiratory ramp :“Switches off” Slide27
Slide28

ReferencesJohn E. Hall.Guyton & Hall Text book of Medical Physiology. A south Asian ed

: New Delhi: Elsevier.2013.p. 364-373

Kim E. Barrett,

Heddwen

L. Brooks, Scott

Boitano

, Susan M. Barman.ed:23

rd

Ganong’s

Review of Medical

Physiology:Mc

Graw

Hill

http://meded.ucsd.edu/ifp/jwest/resp_phys/student_files.htmlSlide29

Question:1 Respiratory control centers are located in the :

A) Midbrain and Medulla 

B) Medulla and Pons 

C) Pons and Midbrain 

D) Upper Spinal Cord and MedullaSlide30

Question:2 Damage to Pneumotaxic center results in:A) Decreased depth of Inspiration

B) Increased depth of Inspiration

C) Increased depth of Expiration

D) Decreased depth of ExpirationSlide31

Question:3 Stimulation of the reticular activating system of the brainstem (RAS) plays what role in ventilation?

A) Stimulates ventilation 

B) Inhibits ventilation 

C) Stimulates inhalation but inhibits exhalation

(

apneustic

breathing)

D) Stimulates exhalation but inhibits inhalation Slide32

Question:4 Destruction of which part abolishes automatic respiration? A) Pre-Botzinger

complex

B) Ventral group of respiratory neurons

C) Dorsal group of respiratory neurons

D) Section at the inferior border of the

ponsSlide33

Question:5Which of the following statement is true?A) Hering

Breuer inflation reflex respond to lung distension by increasing frequency of respiration.

B) Irritant receptors respond to noxious gases by reflex

bronchodilatation

C) J receptors respond to pulmonary capillary congestion by rapid shallow breathing

D) DRG neurons initiate expirationSlide34

Answers1-B2-B

3-

A

4-

A

5-

CSlide35