lec 6 Control of respiration

Question 1

3 Components of neural control of respiration:

Answer 1

1) factors that generate alternating inspiration and expiration
2) Factors that control the magnitude of ventilation
3) factors that modify respiratory activity

Question 2

Medullary respiratory centers:

2 neuronal clusters:

Answer 2

Dorsal respiratory center:
controls quiet inspiration

Ventral respiratory group:
-inspiratory neurons and expiratory neurons.
-controls active expiration

Question 3

The primary respiratory control centre and other ones:

Answer 3

1) medulla respiratory center
2) the Pons- pneumotaxic (inhibits inspiration) and apneustic center (excitatory Inspiration)

Question 4

Dorsal group of neurons:

Answer 4

-Contain i neurons (inspiratory neurons)
-tractus solitarus is the sensory termination of afferent fibres in the **glossopharyngeal **nerve and Vagus nerve
-they receive impulses from chemoreceptors, aortic and carotid baroreceptors

Question 5

Ramp signal of dorsal group:

Answer 5

-Ramp allows inspiration process
-starts weak then becomes stronger then fades away
-2 sec + 3 sec= 5 sec cycle, so theres 12 cycles per minute

-Causes progreszive expansion of the lungs
- controlled by pneumotaxic center and Vagi impulses

Question 6

Ventral group of neurons:

Answer 6

-include ambigious and retroambiguous nucleus
-both I and E neurons.
-this group only stimulated during active expiration e.g exercise.

-isnt active during quiet inspiration

Question 7

Apneustic center:

Answer 7

in lower pons
-inhibits pneumotaxic center, has opposite effects to pneumotaxic center

Question 8

Neural control of PONS: pneumotaxic and apneustic

Answer 8

-Located in upper pons
-has 2 nuclei
-signals from pneumotaxic centre have inhibitory effects on the quiet inspiration aka Dorsal group of medulla

Stronger signals from pneumotaxic area, terminate Ramp signal early, therefore increasing respiratory rate

**weak signals mean ramp signals are longer and therefore slower respiratory rate **

Question 9

impulses from higher centers:

Answer 9

during emotional states, respiration is modified by cortex, limbic system, hypothalamus

Question 10

Impulses from proprioreceptros:

Answer 10

present in joints and deeper parts of skin, they respond to changes in position and movement.

active during exercise

Question 11

VERY IMPORTANT :

IMPULSES FROM STRETCH RECEPTROS IN LUNG: hering breuer reflex

Answer 11

Inhibits over inflation of lungs, when tidal volume reaches 1.5 liters

i.e inhbits the DGN, inhibiting respiration

Question 12

Impulses from irritant receptors:

Answer 12

involved in cough and sneezing reflex.

-irritate the epithelium in respiratory airways

Question 13

Impulses from J receptors:

Answer 13

these cause rapid breathing when theres and irritant chemical or edema.

i.e increase respiratory rate in DGN

Question 14

Visceral reflexes:

Answer 14

short apnea during swallowing, vomiting, defecation

Question 15

effect of temperature on respiratory centre:

Answer 15

direct: directly stimulate breathing
indirect: increase in PCO2, decrease PO2, H ions con increases, leading to hyperventilation

Question 16

Influence of chemical factors on respiration:

Answer 16

affect the ventilation indirectly

Question 17

central chemoreceptors:

Answer 17

present in medulla oblongata

Question 18

periphral chemoreceptors:

Answer 18

present in aortic and aortic bodies

-carotid bodies carried by glossopharygeal nerve

-aortic bodies impulses carried by afferent nerve fibres in vagi

Question 19

PCO2 on chemoreceptors:

Answer 19

-it dissociates into bicarbonate ions and H+ ions

-H+ ions are the most powerful stimuli to the central chemoreceptros, and have a weaker effect on the periphral chemoreceptors

-H+ ions in the CSF are much more potent stimulators than the H+ ions produced in the brain

Question 20

H ion concentration effect:

Answer 20

-H+ ions cant cross blood brain barrier like CO2
-the periphral chemoreceptors adjust H+ levels to monitor acidosis.
-as H+ stimulate hyperventilation to breathe out CO2

Question 21

Changes in PO2:

Answer 21

-via the periphral chemoreceptros
-stimulated when PO2 falls to low levels, below 60mmHg
- COPD patients and high altitude patients are susceptible

Question 22

regulation of respiration during exercise:

Answer 22

at the start of an exercise, impulses from proprioreceptors from the joints go to respiratory centre to stimulate ventilation.