Respiration and Ventilation II Flashcards
Features of Alveoli Structure
Elastic Fibres around alveoli to aid passive recoil on exhalation
Capillary beds surround alveoli for high gas exchange
Smooth muscle around the terminal bronchiole to allow for bronchodilation/constriction
Thin cells walls for efficient gas exchange
Features of Alveolar Epithelium
Simple Squamous Epithelium
Consists of thin pneumocytes
Patrolled by dust cells (alveolar macrophages)
Contains septal cells that produce surfactant
Henry’s Law Definition
When gas under pressure comes in contact with liquid, gas dissolves in liquid until equilibrium is reached
Gas volume is proportional to partial pressure of gas
5 Reasons for Efficiency of Gas Exchange
Substantial Differences in partial pressure across respiratory membrane
Short exchange distances
O2/CO2 are lipid soluble
Total Surface Area = Large
Blood Flow and Airflow are coordinated
Partial Pressures in Alveolar Air/Capillaries
Blood arriving has Low PO2 (40) and High PCO2 (45)
Alveoli Air has High PO2 (100) and Low PCO2 (40)
Concentration gradient causes O2 to enter and CO2 to leave blood
Partial Pressures in Systemic Circuit
Oxygenated/Deoxygenated Blood mix from conducting pathways
Lowers the PO2 of blood entering systemic system (drops to 95)
Interstitial Fluid Partial Pressure
PO2 = 40
PCO2 = 45
Concentration gradient in peripheral capillaries is opposite to lungs
Function of Red Blood Cells
Transport O2 and CO2 to and from peripheral tissue
Remove O2 and CO2 from plasma, as plasma cant transport enough O2/CO2 to meet physiological needs
Features of RBC
No nucleus for more O2 storage
Concave structure for more efficient gas exchange
2 Types of Capillary
Pulmonary - O2 pickup away from alveoli
Systemic - O2 delivery towards alveoli
Haemoglobin Features
4 polypeptide structure
4 heme groups - bind to O2
Binding of O2 leads to conformational change in Hb to allow for more efficient O2 pickup
3 Types of Haemoglobin
Oxyhaemoglobin (HbO2)
Deoxyhaemoglobin (without O2)
Carbaminohaemoglobin (bound to CO2 after O2 dissociation)
Shape of Oxygen-Hb Saturation Curve
Sigmoid Curve
Higher PO2 results in greater Hb Saturation
Curve shown due to Hb changing shape each time O2 binds to it
Allows for Hb to bind to O2 at low O2 levels
Temperature and Hb Saturation Relationship
As Temp increases, Hb releases more O2, therefore lower O2 association
Significant in active tissues , e.g. active skeletal muscle
As Temp increases, sigmoid curve is shallower
pH and Hb Saturation Relationship
As pH increases, O2 association is higher
Due to Bohr Effect
Bohr Effect Definition
CO2 diffuses into RBC
CO2 reacts with H2O to produce H2CO3 (through the use of carbonic anhydrase)
H+ dissociates, lowering pH of blood
BPG and Hb
As BPG increases, more O2 released by Hb, therefore lower O2 association
BPG levels rise when pH increases
If BPG levels are too low, Hb won’t release O2
CO2 Transport Pathways
Generated by Aerobic Metabolism
1) Dissolve in plasma (7%)
2) Bind to Hb (23%)
3) Converted to H2CO3 (70%)
All reversible
Chloride Shift
HCO3- diffuses out of RBC, replaced by Cl-
Normal control of Respiration
Cellular O2 Absorption + CO2 production in cells = O2 absorption and CO2 excretion at lungs
Local Control of Respiration at tissues
High activity of peripheral tissue = Low PO2/High PCO2 = lower O2 association
Neural Control of Respiration
When O2 demand rises, Cardiac output and respiratory rates increase
Involuntary Neural Control of Respiration
Regulates respiratory muscle activity
Responding to info from lungs and respiratory tract
Voluntary Neural Control of Respiration
Reflects activity in the cerebral cortex
Affects output of respiratory centres and motor neurons (Medulla Oblongata, Pons)
Control of Respiration in the Pons
Apneustic and Pneumotaxic Centres used
Paired nuclei that adjust output of respiratory rhythmicity centres
Control of Respiration in Medulla Oblongata
Role is to establish basic pace and depth of respiration
Uses 2 groups (Dorsal/Ventral Respiratory Group)
Dorsal Respiratory Group (Type of Centre and Breathing)
Inspiratory Centre
Functions in Quiet and Forced Breathing
Ventral Respiratory Group (Type of Centre/Breathing)
Inspiratory/Expiratory Centre
Functions in Forced Breathing
Quiet Breathing Mechanism
Diaphragm/Intercostal muscles contract
Inhalation Occurs
DRG Inhibited
Diaphragm/Intercostal muscles relax
Exhalation occurs
DRG Activated
Forced Breathing Mechanism
Diaphragm/Intercostal muscles contract
Inhalation occurs
DRG + Inspiratory VRG Inhibited
Expiratory VRG activated
Diaphragm/Intercostal muscles relax
Exhalation occurs
DRG + Inspiratory VRC activated
Expiratory VRG inhibited
Types of Respiratory Reflexes
Chemoreceptors - PCO2, PO2 or blood pH changes
Baroreceptors - blood pressure changes
Stretch receptors - lung volume changes
Irritation in nasal cavity/larynx/bronchial tree
Hering-Breuer Reflexes
2 mechanoreceptor reflexes in forced breathing
Inflation/Deflation Reflex
Hering-Breuer Inflation Reflex
Prevents overexpansion of lungs
Hering Breuer Deflation Reflex
Inhibits expiratory centres
Stimulates inspiratory centres during lung deflation
Chemoreceptor Stimulation
Input from Cranial nerves IX + X
Subject to adaptation
Drop in PO2 to around 40 mmHg increases respiratory rate by 50-70%
10% Rise in PCO2 increases respiratory rate by 100%
Changes in Respiration at birth
Before birth, pulmonary vessels are collapsed, lungs contain no air
At birth, newborn overcomes force of surface tension to inflate bronchial tree and alveoli to take first breath
Changes in Respiration in elderly
Deterioration of elastic tissue
Arthritic changes and decreased flexibility
