WEEK 1: WEEK PHYSIOLOGY 2

Question 1

State the differences between partial pressure and gas content

Answer 1

1. PARTIAL PRESSURE: solution in in plasma affected by solubulityand PP of gaseous O2
2. GAS CONTENT: varies in form.

Question 2

Describe the role of haemoglobin in the transport of O2 in the blood

Answer 2

Binds 98%O2 in blood, 4 molecules. of O2 bound per Hb.

HbA: 2 alpha 2 beta

Question 3

HbA2

Answer 3

subtype of Hb in blood where beta chains replaced by delta

Question 4

HbF

Answer 4

beta chains replaced by gamma. Higher affinity. Extracts maternaal O2 from maternal.

Question 5

Myoglobin

Answer 5

cardiac, skel musc. exclusive

- O2 store greater affinity

Question 6

Explain why the shape of the oxyhaemoglobin dissociation curve is important to O2 loading in the lungs and unloading in the tissues.

Answer 6

• changes in PO2 favours oxygen loading/unloading directions at sites of respiration
• plateau ensures adequate Hb saturation at alveoli even if PP fluctuates
• venous PO2 AT. REST, 75% O2. reserve bound.

Question 7

Impact of pH on oxygen dissociation

Answer 7

ACIDOSIS - BOHR EFFECT SHIFTS “DROP” RIGHT = ↑O2 LEAVES AT 40mmHg+

BOHR = higher O2 required to unload at periphery

Question 8

Impact of CO2 on O2 dissociation

Answer 8

↑PCO2 = BOHR EFFECT

Question 9

Impact of temp on O2 dissociation

Answer 9

↑Temp = BOHR

↓ Temp = ↑Affinity therefore oxygen hoarded and ↓peripheral perfusion

Question 10

[DPG] impact on O2 dissociation

Answer 10

↑[DPG] = BOHR

HYPOXIA TRIGGERS DPG PRODUCTION

Question 11

What is the Bohr effect

Answer 11

Decreases affinity and increase in O2 dissociation, curve shifts to right, O2 leaves Hb to oxygenate at relatively higher pO2

Question 12

Compare oxyhaemoglobin dissociation for adult haemoglobin with that of foetal haemoglobin and myoglobin in relation to their physiological roles.

Answer 12

HbF higher affinity ensuring and “drop” at much lower pO2 ensuring effective extraction of O2 from maternal circulation.

Myoglobin much higher than Hb and HbF.

Question 13

Identify the forms in which CO2 is carried in the blood.

Answer 13

7% dissolved
95% RBC
23% oxyhaemoglobin
70% => co2+carbonic anhydrase = carbonic acid => bicarb buffer

Question 14

Explain the action of carbonic anhydrase in CO2 transport

Answer 14

co2+carbonic anhydrase = carbonic acid => bicarb buffer mainting blood pH

↓arterial CO2 = ALKALOSIS
CO2 + H2O <=> H2CO3 <=> HCO3- + H+
shifts reaction to left reducing H+ therefore alkalinity

Question 15

Identify the factors which favour CO2 unloading to the alveoli at the lungs.

Answer 15

• partial pressure gradient
• ventilation rate: hypervent. or hypovent?
• pH of blood; buffer status
• status of alveolar architecture

Question 16

Describe the relationship between ventilation and perfusion and its significance in health

Answer 16

V (alveolar, pulmonary) = Q (bloow flow) = optimal
Apex: ventilation (&alv pressure) > perfusion (&BP) , arterioles compressed VQ<1.0

Base: perfusion > ventilation d/t gravity pulling blood
= arterial pressure > alveolar pressure. VQ >1.0

EQUAL OUT AT RIB 3

Question 17

SHUNT

Answer 17

↓V=↑PCO2 ↓PO2, Q>V

1. surrounding arterioles CONSTRICT in response to HYPOXIA
2. bronchioles @ sites of relative ↑V DILATE
3. BLOOD redirected

alveolar compromise

Question 18

ALVEOLAR DEAD SPACE

Answer 18

V > Q (often at apex)

surrounding pulmonary vasodilation to increase and redirect blood flow to site to acquire extra O2

Question 19

Define the five different types of hypoxia

Answer 19

1. ANAEMIC HYPOXIA - pO2 normal but total O2 content reduced
2. HYPOXAEMIC HYPOXIA - atmos O2 or pathology = ↓o2 diffusion at lungs
3. HITOTOXIC HYPOXIA - poisoning e.g. CO
4. METABOLIC HYPOXIA - supply fails to meet demand
5. STAGNANT HYPOXIA - cardiac disease results in circulatory dysfunction. therefore delivery

Question 20

Explain how respiratory motor movements are affected by the central nervous system

Answer 20

BRAINSTEM: PONS + MEDULLA

DRG: INSPIRATORY via diaphragm, intercostals

VRG: EXPIRATORY via muscles of exp, maintain basal tone = PATENCY

Question 21

Factors that can override rhythm of respiration

Answer 21

1. EMOTION (limbic)
2. VOLUNTARY (higher centres)
3. MECHANOSENSORY THORAX (stretch receptors)
4. CHEMICAL COMPOSITION OF BLOOD (chemoreceptors)

Question 22

classes of chemoreceptors and identify the stimuli which activate them.

Answer 22

1. CENTRAL (medulla) 1º
   - CSF H+ (HYPERCAPNEA/HYPOCAPNEA)
   = ventilation response
2. PERIPHERAL (carotid, aortic bodies) 2º
   - pO2, plasma [H+]
   * d/t curve, greater reduction of O2 required to stimulaate ventilation. NOT O2 content but PO2
   * K+ influx and. dopamine depol.
   * responds to ↑[H+]

Question 23

factors involved in changing ‘respiratory drive’, rate and depth of breathing

Answer 23

• pCO2 in systemic circulation
• pH acidity of BBB
• overdrive inputs

Question 24

Explain how the peripheral chemoreceptors become important during hypoxia and acid-base imbalance.

Answer 24

• main stimulus is pO2
• indirect detection of CO2 d/t [H+] d/t aleration in H+ by any means (lactic acid e.g.)

↑[H+] = ↑ventilation vice versa (negative feedback)