A&p Ii Resp Exam Part V

Front 1

Control of Respiration

Back 1

Neural Control:

Front 2

Where are the dorsal resp. neurons (inspiratory area) located?

Back 2

in the dorsal portion of the medulla

Front 3

What neurons does it include?

Back 3

neurons in the nucleus tractus solitarius(NTS), or solitary tract nucleus, as well as surrounding reticular neurons in the brainstem

Front 4

The NTS is the _________point of sensory(afferent) activity in the _______and glossopharyngeal nerves to the brain

Back 4

terminal
vagus

Front 5

This is the same area that receives what type of activity?

Back 5

baroreceptor

Front 6

What group of neurons generates the basic rhythm of respiration?

Back 6

Dorsal respiratory neurons

Front 7

spont. periodic bursts of inspiratory action potential even in the absence of what?

Back 7

sensory input, even if grown in culture will generate action potentials

Front 8

What is sent to the primary inspirtory muscles(eg: diaphragm)

Back 8

Inspiratory ramp signal(crescendo of activity) rather than instantaneous burst of activity

Front 9

What does the ramp signal permit?

Back 9

1. a steady increase in insp. effort, rather than insp. gasp
2. Expiration occurs when the signal abruptly ceases
3. Rate of rise of the ramp signal is increased when respiration is incresed
4. the rate of respiration is determined by the cut off point of the ramp signal: the earlierthe ramp signal ceases, the shorter the time of inspiration

Front 10

Ramp signal from notes

Back 10

-

Front 11

Where is the pneumotaxic center located?

Back 11

nucleus parabrachialis of the upper pons

Front 12

What does the pneumotaxic center communicate with?

Back 12

dorsal resp. neurons

Front 13

The pneumotaxic trasmits signals to where?

Back 13

the inspiratory centers of the medulla

Front 14

What does the pneumotaxic center control?

Back 14

the cut off point of the inspiratory ramp signal, and thus is responsible for determining the respiratory rate

Front 15

Strong pneumotaxic activity can increase the resp. rate up to?

Back 15

30-40 breaths per minute

Front 16

Wher are the ventral respiratory neurons located?

Back 16

in the ventral medulla; includes neurons in the nucleus ambiguus and nucleus retroambiguus

Front 17

When are the ventral respiratory neurons activated

Back 17

in response to increased resp. drive, stimulation is received from the dorsal resp. neurons

Front 18

The ventral resp. neurons contain what type of neurons?

Back 18

both insp. and exp., the exp. neurons are particularly important in stimulating the expiratory muscles of the sbdomen during forceful expiration

Front 19

The apneustic center of the pons sends signals where?

Back 19

to the dorsal resp. neurons

Front 20

What signal do they send?

Back 20

to inhibit cutoff of the inspiratory ramp signal

Front 21

Physiological function is not clear but may work in association with what center?

Back 21

pneumotaxic center to regulate depth of respiration

Front 22

What is apneusis?

Back 22

an inspiration terminated at a lung volume near or equal to TLC

Front 23

Cerebral cortex

Back 23

-voluntary control of resp.-overriding of the brainstem; limited

Front 24

Examples of cerebral cortex control:

Back 24

voluntary breath-holding or hyperventilation

Front 25

Limbic system:

Back 25

stimulation of respiration in association with strong emotions eg: rage or fear

Front 26

What does the Hering-Breuer inflation reflex protect against?

Back 26

overinflation of the lung

Front 27

With the Hering-Breuer reflex, what sense lung expansion?

Back 27

stretch receptors in walls of the bronchi and bronchioles

Front 28

What turns off the inspiratory ramp signal?

Back 28

vagal afferent activity directed to the dorsal inspiratory neurons of the medulla

Front 29

In humans, the Hering-Breuer reflex becomes active when?

Back 29

when Vt exceeds about 1.5 liters
(almost 50% of the insp. capacity)

Front 30

So the Hering-Breuer reflex is primarily a protective reflex to prevent what?

Back 30

to prevent excess lung inflation, the importance of the reflex in humans has been questioned

Front 31

Chemical control of respiration

Back 31

central chemoreceptors
peripheral chemoreceptors

Front 32

Central chemoreceptors are located where?

Back 32

ventral medulla
near the point of exit of cranial nerves IX and X
anatomically distinct from the medullary respiratory centers

Front 33

What do the central chemoreceptors respond primarily to?

Back 33

changes in interstitial (H+)-that which is immediately surrounding these neurons in the brain, not plasma H+ ion concenration

Front 34

Increased interstitial H+ stimulates the chemoreceptors to do what?

Back 34

increase ventilation

Front 35

decreased interstitial H+ reduces activity in the chemoreceptors and what happens?

Back 35

decrease ventilation

Front 36

What is interstitial H+ surrounding the chemoreceptors determined by?

Back 36

local metabolism
local blood flow
PaCo2

Front 37

An increase in PaCo2(hypercapnia) causes elevation of what?

Back 37

interstitial Pco2 (blood-brain barrier is permeable to Co2)

Front 38

CO2 reacts with H2O in the interstitial fluid to generate what?

Back 38

H+

Front 39

H+ stimulates central chemoreceptors and what happens?

Back 39

ventilation increases

Front 40

What does compensatory hyperventilation do to PaCo2?

Back 40

decreases PaCo2 toward normal

Front 41

Interstitial pH returns toward normal as CO2 diffuses from _______tissue into the _______ and ventilation returns toward normal

Back 41

brain
blood

Front 42

Hypercapnia also causes what?

Back 42

cerebral vasodilation

Front 43

What does increased cerebral blood flow facilitate?

Back 43

CO2 delivery to the brain in order to stimulate blood flow

Front 44

Effects of arterial H+ and HCO3- on the central chemorecptors

Back 44

BUT much less sensative to acute changes

Front 45

Normally the blood-brain barrier is poorly permeable to what ions?

Back 45

H+
HCO3-

Front 46

The central chemoreceptors may sense this change but they are not very receptive to it

Back 46

True

Front 47

So, the central chemoreceptors are less sensative to acute changes in arterial H+ and HCO3- than to changes in what?

Back 47

PaCo2

Front 48

Changes in what have essentially NO DIRECT effect on the central chemoreceptors

Back 48

PaO2
ie: hypoxemia does NOT directly stimulate the central chemoreceptors

Front 49

What are the two types of peripheral chemoreceptors?

Back 49

Aortic bodies
Carotid bodies

Front 50

Where are the aortic bodies located?

Back 50

near the aortic arch(outside)

Front 51

What type of activity doe the aortic bodies send?

Back 51

afferent activity to the medulla via the vagus nerve

Front 52

Where are the carotid bodies located?

Back 52

at the bifurcation of the common carotid arteries

Front 53

What are the MOST important peripheral chemoreceptors in humans

Back 53

Carotid bodies

Front 54

Carotid bodies have what type of perfusion rate?

Back 54

High perfusion rate
20 mL/min/g tissue

Front 55

Arteriovenous O2 difference is essentially zero, thus the carotid bodies are very effective monitors of what?

Back 55

PaO2

Front 56

The carotid bodies send afferent activity where?

Back 56

medulla via the glossopharyngeal nerves

Front 57

Function of peripheral chemoreceptors:

Back 57

1. respond to hypercapnia, but much LESS important in this regard than are the chemoreceptors
(peripheral chemoreceptors are not primary monitors of PaCo2)
2. Respond to acidemia to stimulate ventialtion
3. respond to a decrese in PaO2 to stimulate ventilation

Front 58

So, the hypoxic drive is provided by what recepotors?

Back 58

peripheral chemoreceptors

Front 59

Peripheral chemoreceptors are _______responsible for hypoxic drive in humans

Back 59

solely
(remember that the central chemoreceptors are essentially unresponsive to changes in PaO2)

Front 60

When do the peripheral chemoreceptors become particularly sensitive?

Back 60

at a PaO2 below 60mmHg
but do have little response if falls below 100mmHg

Front 61

Peripheral chemoreceptors have no response to a decrease in what?

Back 61

decrease in arterial oxygen saturation or oxygen content alone-only respond to decrese in PaO2

Front 62

Peripher chemoreceptors
the hypoxic ventilatory response may be attenuated(reduced) somewhat by a concomitant decrease in what?

Back 62

PaCO2 caused by the increased ventilation; after a few days of hypocapnia, however, brainstem acclimitization to reduce PaCo2 occurs and ventilation increases if still chronic hypoxemia

Front 63

Peripheral chemoreceptors
Hypoxic response can be augmented by concomitant what?

Back 63

hypercapnia or acidemia

Front 64

What is normally the most important factor in the control of ventilation?

Back 64

PaCO2

Front 65

Ventilation changes proportionately with changes in what?

Back 65

PaCO2

Front 66

At normal PaO2 of 100mmHg, the slope of the minute ventilation-PaCO2 curve is what?

Back 66

0.5-0.7 L/min/mmHg

Front 67

Place graph here from notes

Back 67

-

Front 68

What is the apneic threshold in the normal adult?

Back 68

32mmHg
(extrapolation of the ventilation-PaCO2 curve to the x-axis yields the apneic threshold)

Front 69

What situations shift the ventilation-PaCO2 curve to the left?

Back 69

1. reduction in PaO2(also increases the sensitivity, or slope of the response)
2. acidemia
3. central etiologies, including drugs that stimulate the resp. centers, increased ICP, and emotional arousal

Front 70

What situations shift the ventilation-PaCO2 curve to the right?

Back 70

1. drugs that depress the resp. centers, eg: halogenated anesthetics, opioids, barbs
2. an increase in the work of breathing eg: airway obstruction
3. Metabolic alkalosis

Front 71

Hypoxic drive is NOT normally impotant for moment-to-moment control of ventilation but becomes important when?

Back 71

-residence at high altitude(where the Po2 is quite low, these individuals hypoxic drive can be the primary stimulus for ventilation)
-patients with severe lung disease and chronic hypercapnia(chronically elevated levels of Pco2)

Front 72

Normal CO2 stimulus for ventilation is suppressed with what?

Back 72

chronic hypercapnia(brain interstitial pH surrounding the central chemoreceptors is normal)

Front 73

What becomes the chief stimulus for ventilation in the chronic hypercapnic patient?

Back 73

PaO2

Front 74

-Response to arterial pH-
What acts on peripheral chemoreceptors?

Back 74

H+

Front 75

-Response to arterial pH-
stimulates ventilation independent of changes in what?

Back 75

PaCo2
eg: pt's with partly compensated metabolic acidosis demonstrate acidemia, hyperventilation and hypocapnia

Front 76

Ventilatory response to exercise

Back 76

-

Front 77

Ventilatory increases during exercise but the exact mechanism is not clear:

Back 77

PaCO2 DOES NOT increase
PaO2 may actually increase slightly
Arterial pH remains constant during moderate exercise, though pH typically decreses during heavy exercise due to lactate production

Front 78

Possible contributors to increased ventilation during exercise

Back 78

1. movement of the limbs
2. stimulation of peripheral chemoreceptors by oscillations in PaO2 and PaCO2
3. Central chemoreceptors may increase ventilation to maintain a constant PaCO2 (servo mechanism)
4. increased body temp

Front 79

Movement of limbs may:

Back 79

activate proprioceptors-sensory receptors in joint and muscles that monitor change in joint position

Front 80

Servo mechanism:

Back 80

you begin to exercise, tissue begins to increase rate of metabolism and rate of CO2 production, tends to raise the arterial Pco2, the central chemoreceptors respond by increasing ventilation and keeps arterial Pco2 from increasing