This document describes an experiment to investigate various aspects of human breathing using a respiratory belt transducer. The experiment involves recording normal breathing and the effects of holding one's breath after inhaling and exhaling. It also examines the effects of hyperventilation, rebreathing exhaled gases, and how breathing affects heart rate. The setup uses a respiratory belt around the abdomen connected to a PowerLab device to record breathing movements and a finger pulse transducer to record heart rate.

1. Breathing

2. Learning Objectives
In this laboratory, you will
1. record breathing movements with a respiratory belt
transducer fastened around the abdomen.
2. investigate various aspects of breathing, including the
ability to hold the breath, hyperventilation, re-breathing,
and the relation between breathing and heart rate.

3. Four respiration processes
• Breathing (ventilation): air into and
out of the lung. 2 parts – inspiration
(breathing in ) and expiration
(breathing out).
• External respiration: gas exchange
between air and blood.
• Internal respiration: gas exchange
between blood and tissue.
• Cellular respiration: oxygen use to
produce ATP, carbon dioxide as
waste.

4. BREATHING INVOLVES TWO
PROCESSES
• Breathe out
•The diaphragm expand and
relax
•Volume in the thoracic cavity
decreased
•The lungs compress
•Air pressure in the lungs
increased
•Air rush out of the lungs
•Breathe in
•The diaphragm contracts and
flattens
Volume in the thoracic cavity
increased
•The lungs expand
•Air pressure in the lungs
decreased
•The difference in air pressure
causes air to rush into the lungs
INHALATION EXHALATION

5. Ventilation
External respiration: gas exchange
• Flow of gases between alveolar air and blood in pulmonary
circulation.
• Diffusion of O2 and CO2 in lungs depends on relative
concentrations or partial pressures of gases
• Movement of each gas always occurs from a high pressure area
to low-pressure area
• Partial pressure (PO2, PCO2) is the concentration of a gas in a
mixture.
• Partial pressure of O2 in arterial blood is expressed as PaO2

6. • Each gas in a mixture moves or diffuses according to its own
partial pressure gradient and independent of other gases
(Dalton’s law)
• O2 diffuses from alveolar air, an area of a high concentration of
O2, to the blood in pulmonary capillary, has low concentration of
O2 , until concentrations become equal
• CO2 diffuses out of pulmonary capillary into alveolar air
depending on its relative concentrations

7. RESPIRATORY MUSCLES
Diaphragm, intercostal muscles and the other accessory
respiratory muscles work in co-ordination for normal breathing
under central controller.

8. Respiratory areas in brainstem
Medullary respiratory center
• Dorsal groups stimulate the diaphragm
• Ventral groups stimulate the intercostal and
abdominal muscles
Pontine respiratory center
(pneumataxic) respiratory group
Involved with switching between inspiration
and expiration
Apneustic center
of the lower pons appears to promote inhalation
by a constant stimulation of the neurons in
the medulla oblongata.

10. Chemical Mechanism:
• Chemoreceptors:
• They are the receptors which give response to change in the
chemical constituents of blood like..
• A. Hypoxia O2
• B. Hypercapnea CO2
• C. Increased hydrogen ions concentration (decreased blood pH) •
Chemoreceptors are classified into two groups:
• 1. Central chemoreceptors
• 2. Peripheral chemoreceptors

11. Central chemoreceptors
• They are situated in deeper part of
medulla oblongata, close to the dorsal
group of neurons.
• This area is known as chemosensitive
area and neurons are called as
chemoreceptors.
• They are very sensitive to increase in
hydrogen ion concentration.
• Hydrogen ion cannot cross the blood
brain barrier and blood cerebrospinal
fluid barrier

12. Peripheral chemoreceptors
• The receptors are present in peripheral
portions of the body that’s why called
as peripheral chemoreceptors.
• They are very sensitive to reduction in
partial pressure of oxygen.
• Whenever, the partial pressure of
oxygen decreases these chemoreceptors
become activated and send impulses to
inspiratory center and stimulate them.
• Thereby increases rate and force of
respiration and rectifies the lack of
oxygen.

13. Setup
1. Fasten the respiratory belt around
the abdomen of a volunteer
2. Connect the plug on the respiratory
belt transducer cable to Input 1 on the
front of the PowerLab.

14. Exercise 1: Normal respiration
• In this exercise, you will record normal and rapid breathing, and
examine the effects of holding your breath after inhaling and after
exhaling.
2-3 minutes
2-3 minutes
M
M
cursor
cursor
Few seconds

15. Exercise 2: Hyperventilation
• In this exercise, you will record the effect of voluntary
hyperventilation on breath-holding and the recovery of normal
breathing rhythm.
2-3 minutes
as
long
as
possible.
30 seconds
2-3 minutes 2-3 minutes
2-3 minutes
30 seconds
select
Breath
Rate
breathing
select

16. Exercise 3: The effect of rebreathing
• In this exercise, you will observe the effect of rebreathing exhaled
gases. You will need to obtain a medium-sized paper bag. When re-
breathing, the volunteer should place this so that it covers the nose and
mouth and forms a tight seal.

17. 2-3 minutes
60 seconds
Continue recording for 60 seconds.

18. Exercise 4: Breathing and heart rate
• In this exercise, you will record and
examine the effect of breath-holding on
heart rate.
• Procedure
• Leave the respiratory belt fastened around the
abdomen of the volunteer.
• 2. Connect the finger pulse transducer to Input
2 on the PowerLab.
• 3. Place the pressure pad of the finger pulse
transducer against the tip of the middle finger
of either hand of the volunteer. Use the Velcro
strap to attach it firmly - neither loose nor tight.
• 4. Ensure that the person sits quietly with his or
her hands resting in their lap, or on a bench, to
minimize transducer movements.

19. Breathing
Pulse rate
pulse