7. Breathing Rate and Homeostasis

Question 1

what is the SOLE PURPOSE of the LUNGS

Answer 1

VENTILATION

• Inpiration: O2 enters
• Expiration: CO2 leaves
• altering respiratory rate and depth (unconsciously irrespective of activity)

Question 2

BREATHING feedback loop

Answer 2

Sensors -> Controller (brain) -> Effectors (respiratory muscles)

Question 3

components of the RHYTHM of VENTILATION

Answer 3

• RESPIRATORY CENTRE
• AUTONOMIC NERVOUS SYSTEM
• PHRENIC NERVE regulated inspiratory muscles
  Diaphragm, External Intercostals
• INTRATHORACIC CHNAGES (increase volume, decrease pressure)

Question 4

RHYTHM of the ACTION POTENTIALS in VENTILATION

Answer 4

Respiratory Centre in MEDULLA triggers Action Potentials via PHRENIC NERVE
- INSPIRATION
ACTIVE, pulses, muscle contractions, change thoracic cavity volume (increases)

EXPIRATION: Impulses STOP
muscles relax, decrease thoracic volume -> air IN

Question 5

what does the PONS in the brain regulate

Answer 5

MEDULLA

• APNEUSTIC CENTRE : GASP (sudden need for more O2)
• PNEUMOTAXIC CENTRE: ‘FINE-TUNING’

Question 6

what does the CORTEX in the brain regulate

Answer 6

VOLUNTARY OVERRIDE (Holding Breath)

Question 7

what does the HYPOTHALAMUS in the brain regulate

Answer 7

‘EMOTIONAL’ BREATHING

(when crying, laughing)

Question 8

EXTERNAL INTERCOSTAL MUSCLES are INNERVATED by which nerves and which spinal nerves derived from

Answer 8

INTERCOSTAL NERVES - T1-T11

Question 9

DIAPHRAGM is INNERVATED by which Nerve and which spinal nerves derived from

Answer 9

PHRENIC NERVE - C3,C4,C5

Question 10

what is the NAME of this equation

CO2 + H20 <-> H2CO3 <-> H+ + HCO3-

Answer 10

HANDERSON-HASSELBALCH equation

• KEY for blood maintaining steady state / pH

Question 11

in HANDERSON-HASSELBALCH equation what is the LUNG / RESPIRATORY Component and what is the KIDNEY / METABOLIC component

Answer 11

LUNG/RESPIRATORY: CO2 + H2O side

KIDNEY/METABOLIC: H+ + HCO3- side

Question 12

where is CO2 carried

Answer 12

either DISSOLVED in BLOOD
or
carried as HCO3-

Question 13

EQUILIBRIUM: what happens to the HANDERSON-HASSELBALCH equation when there is a RISE in CO2

Answer 13

moves to the RIGHT

• MORE H+ (ACID) / HCO3- (BASE) production

Question 14

WHERE is the CENTRAL CHEMORECEPTOR

Answer 14

VENTRAL LATERAL MEDULLA

Question 15

WHERE are the PERIPHERAL CHEMORECEPTORS MAINLY

Answer 15

mainly AROUND HEART

Question 16

what does CENTRAL CHEMORECEPTOR detect

Answer 16

Blood pH

• Exquisitely SENSITIVE to CO2
• detects CHANGES in H+ (pH) in CEREBROSPINAL FLUID (CSF)

Question 17

what do PERIPHERAL CHEMORECEPTORS MOSTLY respond to

Answer 17

O2 LEVELS

Question 18

why is CO2 MOST IMPORTANT

Answer 18

by CHANGING H+ in BRAIN

O2 only relevant when very low

Question 19

types of PERIPHERAL CHEMORECEPTORS

Answer 19

CAROTID bodies : detect changes PCO2, pO2, pH

AORTIC bodies: detect changes pCO2, pO2

Question 20

CHEMORECEPTORS DRIVE..

Answer 20

RESPIRATORY RATE

eg if high CO2, increased respiratory rate to remove

Question 21

name the OTHER RECEPTORS in the LUNG (back up systems)

Answer 21

• STRETCH Receptors (HERING-BRUER REFLEX)
  inhibit inspiration if excessive
• IRRITANT Receptors
  trigger to help cough
• J-Receptors
• BRONCHIAL C-FIBERS
  Constrict airways, Shallow breathing / Tachypnoea (rapid and shallow) (alter breathing pattern)

Question 22

how do KIDNEYS CONTROL ACID-BASE BALANCE

Answer 22

• HCO3- REABSORPTION
  85% in PCT (using carbonic anhydrase)
• H+ EXCRETION
  combined with buffers eg ammonia -> ammonium NH4+ (generates HCO3-)

Question 23

how can KIDNEYS GENERATE HCO3- (name)

Answer 23

DE NOVO

Question 24

HCO3- REABSORPTION in KIDNEYS takes place where

Answer 24

MAINLY PCT

Question 25

Why is BREATHING HOMEOSTASIS important in clinical practice

Answer 25

look at BLOOD GASES - use to quantify how sick patient is - use to Treat and Monitor Effectiveness of treatment

Question 26

which Blood Gas can you interpret O2 from

Answer 26

ARTERIAL (cannot interpret from Capillary

Question 27

when looking at ACID-BASE STATUS on a BLOOD GAS what 4 questions do you ask

Answer 27

1. is the pH normal, high, low? 2. is the pCO2 normal, high, low? 3. is the HCO3- normal, high, low? 4. has there been any COMPENSATION?

Question 28

EFFECT of CO2 on BLOOD

Answer 28

INCREASES ACIDITY (decrease pH) - H+

Question 29

when looking at ACID-BASE STATUS on a BLOOD GAS what 4 results can you get

Answer 29

1. ACIDOSIS or ALKALOSIS or Normal 2. RESPIRATORY (lungs ie if high CO2), METABOLIC (kidneys ie if high HCO3-) or MIXED (both high) 3. COMPENSATED or not 4. FULL or PARTIAL COMPENSATION

Question 30

what does it mean if the pH is NORMAL but CO2 or HCO3- is ABNORMAL

Answer 30

if pH NORMAL: FULLY COMPENSATED if high CO2, kidneys should compensate by high HCO3- (more reabsorption) if pH ABNORMAL, but some compensation shown then only PARTIAL

Question 31

how should LUNGS work to DECREASE high CO2 levels

Answer 31

INCREASE BREATHING RATE to expel CO2 eg panting if high CO2 then problem in Lungs - RESPIRATORY

Question 32

how should KIDNEYS work to DECREASE High HCO3- levels or INCREASE

Answer 32

LESS REABSORPTION of HCO3- so MORE EXCRETION in URINE INCREASE by MORE REABSORPTION into BLOOD (buffer H+) (i.e. if high CO2) secondary system - compensate for lungs

Question 33

when do LUNGS COMPENSATE for KIDNEYS

Answer 33

when LOW HCO3- and LOW pH (not due to high CO2 so must be kidneys) - LOW CO2 to compensate METABOLIC ACIDOSIS

Question 34

when is there both a RESPIRATORY and METABOLIC problem

Answer 34

when HIGH CO2 and LOW HCO3- - KIDNEYS NOT COMPENSATING for Lungs high CO2 -> low pH

Question 35

how are BLOOD GASES in ALTITUDE

Answer 35

- HIGH pH - LOW CO2 - NORMAL HCO3- UNCOMPENDATED RESPIRATORY ALKALOSIS

Question 36

what are the conditions in ALTITUDE

Answer 36

LOW OXYGEN (PaO2) (sensed by peripheral chemoreceptors) - HYPERVENTILATION : breathe faster to increase O2 -> more CO2 out so decrease CO2 -> detected by Central Chemoreceptors which try to stop breathing to increase CO2 -> low O2 (cycle)

Question 37

how the body RESPONDS to ALTITUDE

Answer 37

- HYPERVENTILATION : breathe faster to increase O2 -> more CO2 out so decrease CO2 -> detected by Central Chemoreceptors which try to stop breathing to increase CO2 -> low O2 (cycle) long-term: - KIDNEYS PRODUCE MORE ERYTHROPOEITIN so INCREASE RBC (try to hold more O2) - ANAEROBIC RESPIRATION INCREASE MITOCHONDIRA SIZE - Hb O2 DISSOCIATION CURVE shifts RIGHT for better UNLOADING O2

Question 38

how does HAEMOGLOBIN respond to OXYGEN LEVELS

Answer 38

OXYGEN DISSOCIATION CURVE shifts to the RIGHT - LOWER AFFINITY for O2 - BETTER UNLOADING of O2 for use in tissues (when high CO2 / acidosis) (when alkalosis) LEFT SHIFT : DECREASED AFFINITY Hb pick up MORE O2 but LESS AVAILABLE to CELLS

Question 39

what is the BREATHING FEEDBACK LOOP controlled by

Answer 39

CHEMORECEPTORS

Question 40

how should CO2 and HCO3- be

Answer 40

in EQUILIBRIUM

Question 41

in FULLY COMPENSATED ACIDOSIS how should pH, PCO2 and HCO3- levels be

Answer 41

pH : NORMAL (compensated) PCO2 : LOW (lungs compensating by increasing ventilation so more CO2 removed) HCO3- : HIGH (kidneys compensating by increasing HCO3- reabsorption which buffers H+)

Question 42

in FULLY COMPENSATED ALKALOSIS how should pH, PCO2 and HCO3- levels be

Answer 42

pH: NORMAL (compensated) PCO2: HIGH (Lungs compensating by slowing breathing rate so less CO2 is removed) HCO3-: LOW (Kidneys compensating, less HCO3- reabsorption as there is low H+ so no need to buffer)