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1

2

Where is the central pattern generator (CPG) located in the brainstem that controls the basic pattern (inspiration and expiration) of respiration?  

  1. pons
  2. medulla

3

What are the inputs to the central pattern generator (CPG) (also called the respiratory center)

  •   What input provides voluntary control of breathing?

 

Cortex-behavioral voluntary control

4

What are the inputs to the central pattern generator (CPG) (also called the respiratory center)

  •   Which inputs provide involuntary control of breathing? (7)

  1. peripheral chemoreceptors
  2. central chemoreceptors
  3. joint and muscle receptors
  4. pulmonary stretch receptors
  5. airway irritant receptors
  6. cerebellum
  7. hypothalamus

5

explain how each of these are involuntary ventilatory control mechanisms

  1. joint and muscle receptors
  2. pulmonary stretch receptors
  3. airway irritant receptors

  1. Joint and muscle receptors are the proprioceptors- know where body parts are in space
    • They will send signals to the brain when exercising to increase respiratory rate and cardiac output
  2. Lungs have pulmonary stretch receptors
    • Do not want the lung to inflate all the way, they will detect this
  3. Airway irritant receptors
    • Will detect noxious particles and you will cough

6

How does hypothalamus affect respiration?

  • temperature regulation
  • Hypothermic- RR will decrease
  • Hyperthermic- RR will increase

7

What are the major structures of the CPG (Central Pattern Generator)?

  1. PRG (Pontine respiratory group)
  2. Medulla oblongata- contains the inspiratory and expiratory nuclei

8

What happens in normal quiet breathing for inhalation and exhalation

9

What happens in forceful breathing

10

What is the normal rhythmic breathing times

  • Inspiration for 2 seconds
  • Expiration for 3 seconds

11

What are 4 things that can interrupt rhythmic breathing

  1. Vocalization
  2. swallowing
  3. parturition
  4. defecation

12

Describe the effect transection of the brain stem between the pons and the medulla would have on breathing

  •  able to breath normally
  • Medullary rhythmicity center is still intact

13

Describe the effect transection of the brain stem between the medulla and the spinal cord would have on breathing.

breathing will stop

14

What are the 3 elements of respiratory control

  1. Receptors (Sensors) that gather information (e.g. ↑ PaCO2) and send info via the afferents to
  2. Controller (Integration Center)- CPG (Central Pattern Generator) in the brainstem which coordinates the information and sends impulses via efferents to
  3. Effectors (respiratory muscles) which cause adjustments in ventilation and decrease the PaCO2 which decreases the sensor input (negative feedback)
     

15

What are the 2 nasal reflexes and what do they do?

  1. Sneeze reflex – strong inspiration – immediately followed by a vigorous exhalation – most of the gas exhaled through the nasal passages
  2. Dive reflex – water instilled into the nose or on the surface of the nose
    • Cessation of breathing, slowing of heart rate, bronchoconstriction

16

What are the 2 reflexes of the pharynx and what do they do

  1. Aspiration or sniff reflex – mechanical stimulation – series of brief, strong inspiratory efforts
  2. Swallowing – inhibition of breathing – closure of the larynx – complex coordinated muscle contractions to propel material into the esophagus
     

17

What are the 3 Laryngeal Reflexes and what do they do

  1. Mechanoreceptors – pressure and temperature
    • Negative pressure results in dilator (abductor) muscle contractions to open the airway
    • Direct pressure causes the larynx to close
  2. Irritant receptors – noxious gas – cough and apnea
  3. Water sensitive receptors – cause the larynx to close
     

18

Explain the function of slow adapting receptors in the lung

  • Slow adapting receptors – airway smooth muscle – impulses travel in vagus n.
    • Stretching of the airways is a stimulant
    • Monitoring lung volume
    • Involved in the Hering-Breuer reflexes

19

Explain the function of rapid adapting receptors in the lung

  • Rapid adapting receptors – airway epithelium – mechanoreceptors
    • Irritant receptors – dust, mucus, histamine, prostaglandins
    • Cough, bronchoconstriction, mucus secretion, rapid shallow breathing
       

20

What is the function of the C fibers- in the 1. juxtacapillary receptors/pulmonary interstitium

located in the pulmonary interstitium may monitor distention of the interstitium (e.g. edema)
 

21

What is the function of the C fibers in walls of the airways

stimulated by allergic or infectious diseases – results in tachypnea (increased respiratory rate)
 

22

What is the function of the muscle spindle strech receptors located in respiratory muscles


reflex control of muscle contraction strength
 

23

Hering-Breuer Inflation Reflex does what

  • The Hering-Breuer Inflation reflex begins in the proprioceptors of joints and muscles that activate the inspiratory centers of the medulla oblongata to increase ventilation prior to exercise induced oxygen requirements. 
  • The Hering-Breuer Inflation reflex detects lung expansion with stretch receptors, which limit the amount of lung tissue stretch. 
  • The amount of stretch is based on the metabolic/ventilatory requirements of the animal. 
  • If the lungs stay inflated --> expiration has been inhibited --> and the next inspiration will be inhibited. 
  • The lung has not deflated at this time and thus will inhibit the inspiratory areas from starting to fire for the next breath.  
  • Eventually, the animal will try to take a breath (inspire) due to the increase in [PCO2].
  • The Hering-Breuer Inflation reflex also prevents damage from over stretching the lung (Over-expansion --> potential visceral pleura membrane rupture --> positive air pressure into the thoracic cavity --> pneumothorax (positive air in the thorax) --> Collapsed lung (atelectasis).  

24

What does The Hering-Breuer Deflation Reflex do

  • You can visualize this in a normal animal- At the beginning of inspiration, press on the chest --> this will initiate this reflex to cause an immediate inspiration.
  • Also, you can clinically utilize this reflex if there is a patient that is experiencing apnea (cessation of breathing)- push on the animal’s chest and deflate the lung more in an attempt to stimulate an inspiration. 

25

What are the 2 peripheral chemoreceptors and where are they located and what innervated by

  1. Carotid bodies at the bifurcation of the carotid artery near innervated by CN IX
  2. Aortic bodies above and below the aortic arch near innervated by CN X

26

What do the peripheral chemoreceptors respond to

  • Decreases in PaO2
  • PaCO2 changes (very sensitive – 2 mmHg)
  • pH changes
     

27

  1. where are the central chemoreceptors located
  2. what do they respond to

  1. Ventral surface of the medulla oblongata –Retrotrapezoid nucleus (RTN)
  2. Respond to changes in
    • chemical composition of blood surrounding brain Interstitial Fluid (ISF) 
      • Including Cerebrospinal fluid
    • Respond to changes in [H+]
      • Increase [H+] stimulates ventilation
      • Decrease [H+] depresses ventilation
    • Indirectly responsive to PCO2

28

  1. Is the central chemoreceptor accessible by blood through the blood brain barrier (BBB) and associated H+ and HCO3-
  2. Is the central chemoreceptor accessible by cerebrospinal fluid (csf) and associated H+ and HCO3-?  

  1. yes
  2. yes

29

When __________ mm Hg is reached, the animal’s ventilation increases due to decrease in PaO2.

65 mmHg