Resp-Control Of Ventilation

Front 1

What are the respiratory centers?

Back 1

Respiratory centers: poorly defined collections of neurons in the brainstem that control the periodic nature of respiration. It consists of three areas:
1- the medullary respiratory center, 2- the apneustic center,
3-and the pneumotaxic center.

Front 2

Describe the Medullary respiratory center.

Back 2

found in the reticular formation of the medulla beneath the floor of the 4th ventricle. It has got two parts (different anatomically and functionally):
1-dorsal respiratory group: found in the dorsal region of the medulla(part of the nucleus tractus solitarius), chiefly associated with inspiration.
2- ventral respiratory group: found in the ventral area and associated with expiration.

Front 3

Describe the Apneustic center.

Back 3

one of the main groups of neurons involved in the control of respiration. Found in the lower pons. Transaction of the brains of experimental animals just above this area tends to produce a breathing pattern with a prolonged inspiratory phase.

Front 4

What is apneusis?

Back 4

An abnormal respiratory pattern consisting of a pause at full inspiration

Front 5

Describe the Pneumotaxic center.

Back 5

another group of neurons involved in the control of respiration. Found in the upper pons. Appears to 'switch off' inspiration, by sending inhibiting impulses to the to the dorsal respiratory group thus 'turning off' the inspiratory ramp prematurly.

Front 6

Where does the 'major output' of the respiratory centers go to?

Back 6

the phrenic nerves.

Front 7

Define Corpopedal spasms.

Back 7

: contraction of the muscles of fingers and toes, seen in tetany that can be caused secondary to alkalosis seen in hyperventilatory states.

Front 8

List some other parts of the brain (other than the respiratory centers) that can affect respiration?

Back 8

-cortex
-limbic system
-hypothalamus

Front 9

Define a Chemoreceptor.

Back 9

is a receptor that responds to changes in the chemical composition of the blood or other fluid around it.

Front 10

Where are the 'central' respiratory chemoreceptors located?

Back 10

in the ventral surface of the medulla, in the vicinity of the exits of the 9th and 10th cranial nerves

Front 11

Describe the Respiratory central chemoreceptors.

Back 11

are a group of neurons (separate from the respiratory center) which lie 200-400 micro.m below the ventral surface of the meducall, and stimulated by changes in the [H+] in the CSF, determined by the arterial PCO2

Front 12

Describe Glomus cells.

Back 12

the chemoreceptive cells in the carotid and aortic bodies. Of two types:
-type I which is round and high in dopamine content, thus giving it an intense flourescent stain. In close opposition to the afferent nerve fibers going to the medullary respiratory center (via the glossopharyngeal nerve, CN IX).
-type II cells
→ respond to low PO2, high PCO2, and high [H+]. changing oxygen tension causes a decrease in the intra-cellular production of ATP, leading to an increase in the release of neurotransmitters thus stimulating ventilation.

Front 13

At what oxygen tension does the sensitivity of the glomus cells begin?

Back 13

Pa O2 < 500 mmHg

Front 14

How does the carotid and aortic bodies differ?

Back 14

Carotid bodies are able to respond to changes in blood pH

Front 15

List the stimuli that can act upon the peripheral chemoreceptors.

Back 15

- rising PCO2
- hypoximia
-low pH

Front 16

What other receptors feed into the respiratory control center in the brainstem?

Back 16

1- pulmonary stretch receptors
2- Irritant receptors
3- J Receptors
4- Bronchial C receptors

Front 17

Where are the pulmonary stretch receptors found?

Back 17

within the airway smooth muscles.

Front 18

How are they stimulated?

Back 18

via lung inflation

Front 19

What is their afferent nerve?

Back 19

large myelinated fibers of the vagus nerve.

Front 20

What do they do when stimulated?

Back 20

they slow respiratory frequency by increasing the respiratory time

Front 21

Describe the Hering-Breuer inflation reflex.

Back 21

a reflex produced by the stretch receptors in the smooth muscles of the trachea and lower airways, causing an inhibitory effect on the pontine and medullary inspiratory centers leading to termination of inspiration. Important when TV is > 1 L.

Front 22

Describe the Lung deflation reflex.

Back 22

the opposite of the Hering-Breuer reflex that happens when the lungs are deflated, and that stimulates inspiration.

Front 23

List the receptors 'outside the lungs' that feed into the respiratory control center.

Back 23

1-nose and upper airway receptors
2-joint and muscle receptors
3-Gamma system
4-arterial baroreceptors
5-pain and temperature

Front 24

T/F increased blood pH stimulate central chemoreceptors

Back 24

False (except under very extreme conditions)
Increased hydrogen ion concentration in the blood stimulate the 'peripheral' chemoreceptors in the carotid bodies

Front 25

what causes the increase in ventilation during light to moderate exercise?

Back 25

1- receptors in the muscles and tendons that stretch stimulate ventilation

2-fine oscillation in PaO2 and PaCO2 affect peripheral chemoreceptors

3-servomechanism (like a thermostat) that holds CO2 constant in the central chemoreceptors

4-? the increase CO2 load in the lungs