Respiratory Physiology #4

Front 1

Does oxygen or carbon dioxide diffuse more easily?

Back 1

CO2 diffuses 20x more easily than O2 so readily crosses cell membranes and physical barriers

Front 2

Two methods of oxygen transport in blood

Back 2

Dissolved in plasma (1%)

Bound to Hb (99%)

Front 3

Three methods of carbon dioxide transport in blood

Back 3

Dissolved in plasma - proportional to PaCO2

Bound to Hb

Bicarbonate ions in plasma (majority)

Front 4

Three forms of CO2 in plasma

Back 4

1. Dissolved in plasma - proportional to PaCO2

2. Combined with plasma proteins - carbamino compounds (small fraction)

3. Combined with water in plasma to form H2CO3

--Overall only about 10% of transport

Front 5

Transport of CO2 in red blood cells

Back 5

-Readily diffuses from plasma into RBCs

-RBCs have terminal protein groups that can react with CO2 to form carbamino compounds

-Major way: hydration reaction with water to form carbonic acid; uses carbonic anhydrase enzyme

Front 6

Chloride shift

Back 6

As more HCO3- is formed from hydration of CO2, it diffuses out of RBCs into plasma. Cl- diffuses into RBCs to maintain electrical neutrality.

-Water also diffuses into RBCs so blood cells in venous blood are larger

Front 7

Most CO2 produced is transported as...

Back 7

HCO3-

Front 8

CO2 in lungs

Back 8

-Diffuses out of blood plasma into alveoli (carbonic anhydrase reverses direction of rxn).

-Loss of CO2 from plasma pulls CO2 out of RBCs

-Ventilation removes CO2

-Dumping of CO2 change Hb conformation allowing O2 binding, O2 binding helps enhance CO2 dumping

Front 9

Normal levels of CO2

Back 9

~40 mmHg (35-45mmHg)

Front 10

If CO2 is increased...

Back 10

Stressor to body -- sympathetic response that inc HR, BP, ventilation (fight or flight)

-Fight or flight reflex to deliver more blood (and therefore more CO2) to lungs

Front 11

Two ways to measure COs levels

Back 11

1. CO2 in blood (artery, vein) with blood gas analyzer)

2. Expired air (end tidal) with a capnograph

Front 12

Three components of the respiratory control system

Back 12

1. Sensors (peripheral and central) gather info about CO2, O2, pH, movement...

2. Central controller in the brain coordinate info and determine what actions to take (4 parts of brain)

3. Effectors (muscles) induce response and ventilate animal

--together form feedback loop

Front 13

Central chemoreceptors

Back 13

Only respond to changes in H+ levels in interstitial fluid of brain - CO2 freely diffuses across BBB and stimulates respiration through altering H+ levels (delay b/c no carbonic anhydrase)

-Excitatory to inspiratory centre (DRG)

Front 14

What effect will an increase in PaCO2 have on ventilation?

Back 14

Increased tidal volume and resp rate b/c of inc H+ in brain from CO2 diffusion across BBB

-effects central chemoreceptors

Front 15

Peripheral chemoreceptors

Back 15

-Located in areas highly perfused with arterial blood (aortic bodies along aortic arch, carotid bodies at carotid bifurcation).

-Respond to changes in H+, PaCO2, PaO2

-Stimulate ventilation in response to low O2 or high CO2

-Excitatory to resp centre through vagus (aortic bodies) and glossopharyngeal (carotid)

Front 16

How much of ventilatory drive do peripheral chemoreceptors account for?

Back 16

~30% in response to CO2 (central for 70%)

Front 17

Peripheral responses to PaO2

Back 17

-Peripheral chemoreceptors normallyh respond to arterial CO2

-When arterial O2 decreases, activate and stimulate ventilation as a last ditch attempt to bring O2 in (euthanasia)

Front 18

Name two kinds of mechanoreceptors involved in controlling ventilation

Back 18

Lung stretch receptors

Muscle and joint receptors

Front 19

4 areas of the brain involved in respiration

Back 19

Dorsal respiratory group (DRG) - in medulla

Ventral Respiratory group (VRG) in medulla

Pneumotaxic Centre in rostral pons

Apneustic Centre (in caudal pons)

Front 20

Dorsal Respiratory Group

Back 20

-Generates the basic rhythm of breathing (main controller)

-Input from glossopharyngeal and vagal nerves (mechanoreceptors and peripheral chemoreceptors)

-Output via phrenic nerve to diaphragm (excitatory)

Front 21

Ventral Respiratory Group

Back 21

-Not active with normal respiration b/c expiration passive (elastic recoil of lungs and chest wall)

-responsible for expiration when needs to be active component (e.g., exercise, heaves)

Front 22

Pneumotaxic Centre

Back 22

-Inhibits inspiration by regulating inspiratory volume and rate (only one that inhibits)

-"fine-tuning" rhythm - remove these cells and ventilation still happens but looks a little different

Front 23

Apneustic Centre

Back 23

-believed to be involved in deep breathing (periods of no breathing, breathing with pause between) - called "apneustic breathing"

-Seen in Ketamine-based anesthesia, brain injury or tumours

Front 24

Muscles of respiration

Back 24

DIaphragm

Intercostals

Abdominal muscles

Accessory Muscles