DEN103 - Mechanics of Breathing

How does the dorsal respiratory group control inspiration

Sends signals to the inspiratory muscles

What Does The Ventral Respiratory Group Control

inspiration and expiration

What factors control the medullary centre

Ventral Respiration Group
Dorsal Respiration Group
Pons

How are the Pons invovled in Respiration

Contains 2 Centres that increase the rate and depth of respiration.
1)Pneumotaxic Centre
2)Apneustic Centre.

What does the pneumotaxic center do?

Increases The Rate of Respiration by Inhibiting Inspiration via shortening the breaths taken in

What does the Apneustic Centre do

Prolong Inspiration and Reduce the Rate of Respiration, increasing the depth of inspiration

Explain atmospheric pressure and alveolar pressure during inspiration and expiration

During Inspiration P atmos > P alv so air moves into the lungs

During Expiration P alv > P atmos so air moves out of the lungs

What are the primary muscles of Inspiration

external intercostals and diaphragm

What is Boyle's Law?

Increase in Volume leads to a reduction in pressure, air moves into the lungs down the pressure gradient

Pressure & Gas have an inverse relationship when temperature is constant

What is the Hering-Breuer reflex?

Stretch receptors in smooth muscle are activated due to extensive stretching on the lungs during inspiration. These receptors send impulses to the inspiratory centre in the medulla via Vagus Nerve. The medulla responds by inhibiting inspiration via Phrenic Nerve.

Which Accessory Muscles are used in forced Inspiration

Scalenes
Sternocleidomastoid
Neck & Back Muscles
Upper Respiratory Tract Muscles

What are the primary muscles of expiration

There aren't any, it's a passive process using elastic recoil and relaxation of the inspiration primary muscles

What muscles are used in forced expiration

Neck & Back Muscles
Internal Intercostals
Accessory Muscles
Abdominal Muscles

What is a pneumothorax?

collapsed lung - air in pleural space

What is Complience

Distensibility

Change in Volume / Change in Pressure

The ease at which the lungs expand during pressure changes

What produces Surfactant

Type II pneumocytes

What is surfactant?

chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing, composed of lipids and proteins

Prevents Alveolar Collapse
Regulates Alveolar Size
Prevents Oedema - Reduces Fluid entering Alveoli

The Pons send stimuli to the medulla to regulate rate and depth of breathing. True or False

True

What are the 2 centre of the Pons that regulate rate of breathing

Pnemotaxic Centre - increases the rate by shortening Inspiration

Apneustic Centre - increases the depth and reduces the rate by prolonging Inspiration

Where are Central Chemoreceptors located

Cerbro-spinal fluid

Where are peripheral chemoreceptors located?

carotid bodies and aortic arch

What does it mean to have a low Complience

More work required to inspire

What is Surfactant composed of

lipids and proteins

What are the factors that impact on airway resistance

Airway Diameter
Mucus Secretion
Oedema - increased fluid retention causing lung swelling and narrowing of airways
Airway Collapse

How is bronchial smooth muscle controlled

Autonomic Nervous System

Parasympathetic NS

Vagus nerve releases Acetylcholine which acts on Muscarinic Receptors leading to constriction

Sympathetic NS
norepinephrine leads to dilation

Which factors cause a right shift in the Dissociate Curve

Increased Temperature
Increased CO2
Decrease in pH
2,3 Diphosphoglycerate

What is Boyles law?

The relationship between the pressure and volume of a gas. The increase in volume leads to reduction in pressure. Air moves down the pressure gradient

What are the holes of the Diaphragm

Oesophageal Opening at T12
Aortic Opening at T12
Caval Opening at T8

What are the components of Elastic Recoil

Anatomical Component - Elastic nature of cells and ECM

Elastic recoil due to surface tension generated at air fluid interface

What is Anatomical Dead Space

volume of conducting airways, at rest approximatelt 30% of inspired air volume (150ml)

What is Physiological Dead Space

Volume of lungs not participating in gas exchange

What happens to volumes & Capacities during exercise

Increases

Residual Volume stays the same & Total Lung Capacity stays the same

ERV and IRV decreases

What is Poiseuille's Law?

Airway resistance is proportional to gas viscosity and length of the tube but inversely proportional to the fourth power of the radius

What is Airway Resistance

The resistance of the respiratory tract to airflow during inhalation and exhalation

What are the Humoral factors controlling bronchial smooth muscle

Epinephrine circulating in Blood - dilation

Histamine released during inflammatory response - constriction

What is Dalton's Law?

The total pressure of a mixture of gases is the sum of their individual partial pressures

Structure or Haemoglobin

Tetrameric Structure
4 subunits - 2alpha and 2 beta chains
Haem Unit contain single iron 2+ ion

Which enzyme helps convert Fe3+ back to Fe2+

Methaeglobin

Foetal haemoglobin

The beta chains are replaced by v chains, haemoglobin curve shifts to left, higher affinity for oxygen

What is the Ventilation Perfusion Ratio

ratio of alveolar ventilation to pulmonary blood flow

What is the Ventilation Perfusion Ratio used for

Determine whether there is a problem with gas ventilation or blood perfusion to that region of lung. Ratio varies down the lung.