2 - Respiratory System 2

Alveoli

Air filled pockets within lungs where all gas exchange takes place

Alveolar Organisation

Alveolus

1. Extensive capillary network

2. Surrounded by elastic fibres

3. Thin

4. Surface area vast (35x)

Alveolar Epithelium

1. Simple squamous

2. Type 1 Cells - thin, delicate

3. Patrolled by alvrolar macrophages

4. Type 2 Cells (Septal) - produce surfactant

Alveolar Macrophages (Dust Cells)

Engulf and digest foreign materials

Boyle’s Law

Henry’s Law

When gas under pressure comes in contact with liquid

1. Gas dissolves in liquid until equilibrium

2. Given temp - gas in solution proportional to PP of gas

Henry’s Law and Relationship between Solubility + Pressure

5 Reasons for Efficiency of Gas Exchange

1. Substantial differences in PP across the respiratory membrane

2. Distance involved in gas exchange are short

3. O2 + CO2 lipid soluble

4. Total surface area is large

5. Blood flow + airflow coordinated

Overview of Respiratory Process + Partial Pressure (External Respiration)

Overview of Respiratory Process + Partial Pressure (Internal Respiration)

Primary Gas Transport mechanisms

1. Blood plasma can’t transport enough o2/co2 to meet physiological needs

2. Red Blood Cells:

   • o2 + co2 - from peripheral

   • Remove o2/co2 - from plasma

Haemoglobin

1. Oxyhaemoglobin

2. Deoxyhaemoglobin

3. Carbaminohaeglonin

O2-Haemoglobin Saturation Curve

Temp + Hb Saturation

Haemoglobin + pH

1. Bohr effect = As the pH of the blood decreases (becomes more acidic), hemoglobin's ability to bind to oxygen decreases.

2. Caused by co2 - diffuse into RBC

3. Carbonic Anhydrase - catalyse reaction H2O

Bohr effect

Result of pH on hemoglobin-saturation curve

Metabolic Activity in RBC

1. 2,3 BPG:

   • RBCs generate ATP by glycolysis

   • Form lactic acid + BPG

   • More BPG - more o2 released by Hb

2. BPG Levels:

   • Rise - pH increase

   • Low - Hb not release o2

CO2 Transport

1. Generated by aerobic metabolism

2. 3 Pathway for CO2 molecule:

   • Dissolve in plasma

   • Bind to Hb

   • Converted to Carbonic acid

3. 3 Processes reversible

Key Note on Gas Transport

Control of Respiration

1. Normal Conditions - cellular rates of o2 absorption + co2 production = o2 absorption + co2 excretion at lungs

2. Normality Removed - cardiovascular + respiratory systems adjust

Local Control of Respiration (Tissues)

1. Increase preipheral tissue

2. Decrease PP o2

3. Increase PP co2

4. Changes in gas exchange

5. Increase blood flow

Local Control of Respiration (Alveoli)

Neural Control of Respiration

1. Respiratory Centres of Brain:

   • o2 Demand Rise - cardiac output + Respiratory rate increase

2. Involuntary:

   • Regulate respiratory muscle activity

   • Frequency + depth'

   • Respond to info from lung / respiratory tract

3. Voluntary:

   • Reflect activity in cerebral cortex

   • Affect respiratory centre + medulla oblongata

Respiratory Centre

Control of Respiratory in the Pons

Paired nuclei that adjust output of respiratory rhythmicity centres

1. Apneustic + Pneumotaxic centres

2. Regulate respiratory rate + depth of respiration

Respiratory Centre of Medulla Oblongata

Establish basic pace and depth of respiration

1. Dorsal Respiratory group (DRG):

   • Inspiratory center

   • Function - Quiet/Forced breathing

2. Ventral Respiratory Group (VRG):

   • Inspiratory/Expiratory center

   • Function - Forced breathing

Respiratory Centres + Reflex Controls

Basic Regulatory Patterns of Respiration

Respiratory Reflexes

1. Chemo - Pco2, Po2, Blood pH, CSF

2. Baro - changes in blood pressure

3. Stretch - changes in lung volume

Mechanoreceptors

1. Baroreceptors in aortic/carotid sinuses:

   • Changes in blood pressure

2. Stretch Receptors:

   • Changes in lung volume

Herong-Beur Reflexes

2 mechanoreceptor reflexes involved in forced breathing

1. Initiation Reflex - prevent overexpansion of lungs

   • Long vol increase DRG inhibited, VRG stimulated

2. Deflation Reflex - inhibit expiratory centres

   • Stimulates inspiratory centre during lung deflation

Chemoreceptor Reflexes

1. Cranial nerve IX - Carotid bodies

2. Cranial nerve X - Aortic bodies

3. Monitor CSF

Chemoreceptor Stimulation

Chemoreceptor Responses to Increase pCO2

Chemoreceptor Responses to Decrease pCO2

Control by Higher Centres

Control of Respiration

Respiration and Age