Respiration Physiology

1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Respiratory system. Main
stages of respiration.
Regulation of respiration
PowerPoint® Lecture Slide Presentation by Robert J. Sullivan, Marist College

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
PowerPoint® Lecture Slide Presentation by Robert J. Sullivan, Marist College
System of respiration – complex of
structures and mechanisms of regulation,
the main aim of which is to supply
organism with oxygen and to remove
carbon dioxide out of the body.
Breathing - is a process of gas exchange
between cells of the organism and
external environment.

3.  External respiration: exchange of air
between the atmosphere and lungs
alveoli;
 Gas exchange between alveoli and blood
(diffusion);
 Transport of gases in blood;
 Gas exchange between blood and tissues;
 Cellular respiration: oxygen is used for
production of ATP.
STAGES OF RESPIRATION

4. Human Respiratory System

5. Upper Respiratory Tract
Functions
 Passageway for respiration
 Receptors for smell
 Filters incoming air to filter larger
foreign material
 Moistens and warms incoming air
 Resonating chambers for voice

6. Components of the Lower Respiratory
Tract

7. Lower Respiratory Tract
Functions
Transports air to and from lungs
Bronchi: branch into lungs (1-23
generations) (respiratory bronchi -
from 17 -23)
Lungs: transport air to alveoli for gas
exchange

8. Generations of bronchi

9. Alveoli
~ 300 million air
sacs (alveoli).
Large surface
area (60–80 m2).
2 types of cells:
1) Alveolar type I:
(Structural cells);
2) Alveolar type II:
(Secrete
surfactant).

10. Surfactant
 Phospholipid produced by alveolar type II cells and
forms layer between the air and water at the alveolar
surface.
 Supports form and sizes of alveoli: prevents collapse of
alveoli during expiration and superdystension of alveoli
during inspiration.
 Takes part in alveoli cleaning.
 Support dryness of alveoli.
 Its synthesis starts from 28-32
weeks of embryogenesis. Takes
part in the first breath of newborn.
The lack of it causes respiratory-
distress syndrome.

11. TYPES OF BREATHING
 costal, chest or shallow breathing (female);
 diaphragmatic, abdominal or deep breathing
(male);
 combined shallow and deep (optimal type).
Functionally, external breathing is provided by
breathing (respiratory) cycle. It is the rythmycal
changes of inspiration and expiration. Expiration is
longer than inspiration.
Normal respiratory rate 16-18 breathing
cycles per minute.

12. Respiratory Cycle
Figure 10.9

13. MUSCLES OF RESPIRATION
Respiratory muscles are of two types:
1. Inspiratory muscles
2. Expiratory muscles.
 However, respiratory muscles are generally
classified
into two types:
 1. Primary or major respiratory muscles, which are
responsible for change in size of thoracic cage
during normal quiet breathing
 2. Accessory respiratory muscles that help primary
respiratory muscles during forced respiration.

14. Respiratory Muscles
Primary inspiratory muscles are the diaphragm,
which is innervated by phrenic nerve (C3 to C5)
and external intercostal muscles, innervated by
intercostal nerves(T1 to T11).
Accessory inspiratory muscles:
sternocleidomastoid, scalene, anterior serrati,
elevators of scapulae and pectorals are the
accessory inspiratory muscles.
Primary expiratory muscles are the internal
intercostal muscles, which are innervated by
intercostal nerves.
Accessory expiratory muscles: muscles of
abdominal wall.

15. MECHANISM OF INSPIRATION
 It is active process, that arises due to the increasing of
thoracic cavity volume.
 Contraction of external intercostal muscles move ribs
upward and outward (increasing frontal and sagittal
directions of thoracic cavity).
 Diaphragm contracts and flattens, moving downward
(increasing vertical size of thoracic cavity) – main
force.
 These lead to increasing of thoracic cavity volume →
Intrapleural pressure decreases (-7 mm of water
column (-30 mm of water column during forced
inspiration)) → increasing lungs volume → decreasing
of pressure in lungs → air moves from higher pressure to
lower, from external environment to lungs.

16. MECHANISM OF EXSPIRATION
 It is passive process due to previous contractions
of inspiratory muscles.
 Diaphragm relaxes and return to its previous
position.
 Ribs also returns to resting position.
 Volume of thoracic cavity decreases →
intrapleural pressure increases (-4 mm of water
column) → decreasing lungs volume → increasing
of pressure in lungs → air moves from higher
pressure to lower, from lungs to external
environment.
 During forced expiration primary and accessory
expiratory muscles take part.

17. TRANSPULMONARY PRESSURE
 It is difference between alveoli and intrapleural
pressures.
 It is the measure of elastic forces in lungs, that try to
decrease lung’s volume during inspiration and
expiration.
Elastic recoil of lungs (lungs compliance)
Force, with what lungs try occupy the smallest volume.
It is caused by:
- Elastic tension of lungs;
- Surface tension of liquid, that is on alveoli;
- Tone of bronchial muscles.

18. Determinants of lungs compliance
 1. Stretch ability of the lungs tissues (particularly
connective tissue);
 Action of surfactant.
A pneumothorax is an abnormal collection of air
or gas in the pleural space that separates the lung
from the chest wall and which may interfere with
normal breathing.
Types of pneumothorax
1) closed
2) opened
3) valvular

20. Functional indexes of external
breathing
There are three groups of indexes:
1. Static:
1) Pulmonary (lung )volumes
2) Pulmonary (lung) capacities
2. Dynamic - indexes of alveolar
ventilation

21. Dead space
 There are three types of dead space: anatomic,
alveolar and physiologic. Anatomic dead space is the
space of conducting airways exclusive of alveoli
occupied by gas that does not exchange with blood.
It is about 150 ml. Alveolar dead space is the upper
parts of alveoli, that have normal ventilation, but lower
blood perfusion. The sum of anatomic and alveolar
dead space is called physiologic (total) dead space.
The functions of dead space are warming, cleaning,
moistening of air and providing of protective reflexes
(sneeze, cough).

22. Respiratory function of blood
The exchange of gases in lungs and tissues is
made by diffusion. The process of moving of
gas from a region of higher partial pressure to
one of lower partial pressure is called diffusion.
Partial pressure of gas is pressure of gas in
mixture of gases. Difference of partial pressure
of oxygen: in lungs it is 100 mmHg and in blood
it is 40 mmHg. The oxygen moves from lungs to
blood. Difference of partial pressure of carbon
dioxide: in the lungs it is 40 mmHg and in blood
it is 46 mmHg. The carbon dioxide moves from
blood into the lungs.

23. Respiratory function of blood
Diffusion of gases in the lungs takes place
across the alveolar-capillary membrane. The
alveolar-capillary membrane consists of
epithelium of alveoli, interstitial liquid,
endothelium of capillaries, plasma of blood,
membrane of erythrocytes, hemoglobin.
Velocity of diffusion of gases across the
alveolar-capillary membrane depends on
diffusion capacity of lungs and parameters of
gas.
O2 250-300 ml/min;
CO2 200-220 ml/min

24. The amount of gas that passes through the
alveolar-capillary membrane per minute of
time at gradient of partial pressure of 1 mmHg
is called the diffusion capacity of lungs.
DCL=S×k×L/P
Diffusion capacity of lungs depends on the
square of surface of membrane, the
coefficient of diffusion of gases, the coefficient
of solubility of gases and thickness of alveolar-
capillary membrane. The normal value of
diffusion capacity of lungs for oxygen is 25-30
ml/mmHg/min.
Respiratory function of blood

25. Gas Exchange Between the Blood
and Alveoli

26.  The oxygen is present in blood in two forms:
reversibly combined with hemoglobin
(oxyhemoglobin) – 95,5% and dissolved in the
plasma – 0,5%.
 The maximal amount of oxygen that can be
combined with hemoglobin in 100 ml of the blood is
called the oxygen-carrying capacity of the blood.
1 g of hemoglobin can combine 1,34 ml of oxygen.
The normal value of the oxygen-carrying capacity
of blood is 20 ml of oxygen in 100 ml of the blood.
 In the organism there is a dynamic equilibrium
between formation (oxygenation or association)
and splitting (deoxygenating or dissociation) of
oxyhemoglobin.
TRANSPORT OF OXYGEN IN BLOOD

27. Oxygen-Hemoglobin Dissociation
Curve
 The scheme of this equilibrium is called oxygen-
hemoglobin dissociation curve. It depends on partial
pressure of oxygen. Upper part of curve characterizes
conductions in the lungs and lower part – in tissues.
Velocity of dissociation of oxyhemoglobin depends on
the temperature of internal environment, рН of blood
(acidity), partial pressure of carbon dioxide,
concentration of 2,3-dyphosphoglycerate.
 Hyperthermia, acidosis, hypercapnea (increase of
partial pressure of carbon dioxide), increasing of 2,3-
DFG are reasons for increasing velocity of dissociation
of oxyhemoglobin (displacement curve to the right).

28. Oxygen-Hemoglobin Dissociation Curve
Hypothermia, alkalosis, hypocapnea
(decrease of partial pressure of carbon
dioxide), decreasing of 2,3-DFG are reasons
for decreasing velocity of dissociation of
oxyhemoglobin (displacement curve to the
left).

30. Transport of carbon dioxide in blood
Carbon dioxide appears in tissues at oxidizing
processes. Carbon dioxide is present in blood in
three forms:
1)bicarbonate (60-80%),
2) reversibly combined with hemoglobin
(carbamino form) – 15-30%
3) dissolved in the plasma 5-10%.
Hemoglobin combines carbon dioxide with the
help of enzyme carbonic anhydrase.

31. Gas exchange in tissues
 Difference of partial pressure of oxygen: in arterial end of
the capillary it is 100 mmHg, in tissues it is 15 mmHg. The
oxygen moves from blood to tissues.
 Difference of partial pressure of carbon dioxide: in
arterial end of capillary it is 50 mmHg and in tissues it is 70
mmHg. Carbon dioxide moves from tissues to blood.
 The amount of oxygen of arterial blood that passes from
blood to tissues (utilization) is called the coefficient of
utilization of oxygen(CUO).
 It is arterio-venous difference of oxygen.
 CUO=O2A-O2V/O2A

32. Gas exchange in tissues
The normal value in the state of rest is 30-45 %
(during physical activity -90 %).
The diminishing of supply of oxygen to tissues
is called tissue hypoxia. The reasons of tissue
hypoxia are: decreasing of partial pressure of
oxygen in arterial blood, diminishing of
oxygen-carrying capacity of blood and
diminishing of blood supply.

34. Functional system of regulation of respiration
Has three components:
1. Respiratory center;
2. Receptors;
3. Effector organs (respiratory muscles).

35. Control of respiration is done on the following levels:
 Higher nervous centres located in cerebral cortex and
hypothalamic-limbic system  these provide overall
regulation of respiratory system and voluntary control of
breathing (but accumulation of CO2 stimulates
chemoreceptors of respiratory center, and restoration of
breathing takes place).
 Medulla oblongata ( reticular formation) – here a
respiratory centre (bulbar center) itself is located.
Distinguish 2 parts of respiratory center: inspiratory
(dorsal) and expiratory (ventral). Bulbar center consists of
α and β respiratory neurons. α- neurons provide expiration
and β neurons – inspiration.
Nervous control of respiration

36. Nervous control of respiration
 Pons of brainstem – here a pneumotaxic centre (part of
respiratory centre) is located. Function of pneumotaxic
center is regulation of bulbar center. It provides rhythmic
changing of inspiration and expiration, regulates tidal
volume and RR due to physiological state of the organism.
 Lower part of pons – apneustic center: its stimulation can
cause deep and long inspiration.
 Spinal cord – here the nerve centres for diaphragm (C3 – C5
segment) and intercostal muscles (Th1-Th11 segments) are
located. Rhythmical impulses from medulla oblongata and
pons go to spinal centers of n. frenicus and thoracic part of
spinal cord by descending pathways (tractus
reticulospinalis). From spinal cord impulses go to respiratory
muscles and cause inspiration. When impulses are absent
passive expiration occurs.

37. Brain Stem Respiratory Centers
 Respiratory centre is a primary regulator . It consists of such
3 collections of neurons:
Dorsal respiratory group (D.R.G.) – extends most of the
length of the medulla on both sides. Most of its neurons are
located within the nucleus of the tractus solitarius. The main
function of this part of respiratory centre is to provide
inspiration. Neurons of which D.R.G. is composed have
rhythmical pacemaker activity. The action potentials that
arise in them are transmitted via nervous pathways firstly
into spinal cord (neurons in segments C3-5, Th1-Th11) and
then via phrenic and intercostal nerves to the diaphragm
and external intercostal muscles.

38. Brain Stem Respiratory Centers
 Ventral respiratory group (V.R.G.) – is located 5
millimeters anterior and lateral to D.R.G. in the nucleus
ambiguus rostrally and the nucleus retroambiguus
caudally. Features: 1) neurons of the ventral respiratory
group remain almost totally inactive during normal quiet
respiration; 2) two types of neurons exist in V.R.G.: one
cause inspiration and the other cause expiration (!). In
general V.R.G. is important in providing control of
respiration when high levels of pulmonary ventilation are
required, especially during heavy exercise.

39. Brain Stem Respiratory Centers
 Pneumotaxic centre or pontine respiratory group
(P.R.G.) – located dorsally in the nucleus parabrachialis of
the upper pons, transmits signals to the D.R.G. The primary
function of this centre is to decrease the activity of D.R.G.
neurons thus making the inspiration act shorter in time.
When the pneumotaxic signal is strong, inspiration might last
for as little as 0.5 second, thus filling the lungs only slightly;
when the pneumotaxic signal is weak, inspiration might
continue for 5 or more seconds, thus filling the lungs with a
great excess of air.
 Activity of P.R.G. has a secondary effect of increasing the
rate of breathing, because limitation of inspiration also
shortens expiration and the entire period of each respiration .

40. Role of different receptors in breathing
 pulmonary stretch receptors – are located in
muscular walls of the bronchi and bronchioles
throughout the lungs. Irritation of these receptors
causes Hering-Breuer inflation reflex: when
the lungs become overstretched the information
from stretch receptors is transmitted via the vagal
nerves to the neurons of D.R.G. and cause their
inhibition, so the inspiration stops. It’s a protective
reflex and in humans it is not activated until the
tidal volume increases to more than three times
normal (greater than 1.5 l of air per breath).

41. Role of different receptors in breathing
 irritant receptors – are located in the epithelium
of air ways - in nasal cavity (irritation causes
sneezing reflex) and in trachea, bronchi, and
bronchioles (irritation causes cough reflex and
spasm of bronchi). They are stimulated by
mechanical and chemical irritants
 pulmonary “J receptors” – are located in alveolar
walls near the pulmonary capillaries. They are
stimulated especially when the pulmonary capillaries
become overfilled with blood, when pulmonary
edema occurs, when the blood pressure in small
cycle increases, by biologically active substances .
Their excitation leads to reflexive spasm of bronchi
and larynx, dyspnea or apnea.

42. Chemoreceptors
 Monitor changes in
blood PC02, P02, and pH.
 Central:
 Medulla.
 Peripheral:
 Carotid and aortic
bodies.
 Control breathing
indirectly.
Insert fig. 16.27

43.  Pleural receptors: mechanoreceptors, that are
stimulated when features of pleura are violated.
 Receptors of air ways: provide protective reflexes.
 Receptors of respiratory muscles.
 Proprioceptors of joins and not respiratory
muscles: activate during movements, are
important during physical activity.
 Extero- and interoceptors : pain, changes of skin
temperature can cause hyperventilation.

45. Mechanism of the fist
inspiration
Birth is very big stress for
newborn. First of all
bandaging and suddenly
cutting of umbilical cord
causes stopping of changing
of gases and then increasing
of blood CO2 tension and
concentration of H-ions,
decreasing of O2 tension.
CO2 is irritant for central
chemoreceptors and causes
inspiration.

46. Mechanism of the first inspiration
 Secondly narrow maternal passages are irritant for tactile
receptors of skin.
 Changing of temperature of external environment for
newborn (from 37-38ºC to 22-24ºC) – irritation of
thermoreceptors.
 Irritation of receptors of vestibule of inner ear.
 These intensive irritants cause increasing of excitation of
respiratory center.
 In newborn first inspiration and expiration are active.

47. Regulation of respiration in conditions of
lower partial pressure of oxygen
 Appeared in mountains, pressure chamber.
 Lower partial pressure of oxygen causes hypoxemia.
 It stimulates chemoreceptors of carotid sinus, that
leads to hyperventilation, hypocapnia and
respiratory alkalosis.
 Hypoxemia stimulates synthesis of erythropoietins in
kidneys (stimulates erythropoesis).
 At the height 4-5 km mountain disease occurs
(decreasing HR, AP, RR, headache).
 Prolonged stay in such conditions leads to
compensatory reactions (increasing RBC, Hb, OBC,
hyperventilation…).

48. Regulation of respiration in conditions of
higher partial pressure of oxygen
 In case of diving (each 10 m increase PO2 on
1 atm.).
 In case of rapid decompression, gases, that
are dissolved in the blood can’t so quickly be
removed from the body, bubbles are formed
(Nitrogen). Aeroembolism (diving disease)
occurs.

49. Thank you for attention