Control of Breathing - PowerPoint PPT Presentation

1 / 29
About This Presentation
Title:

Control of Breathing

Description:

Located in the tracheal and bronchial smooth muscle ... Which includes the conducting airways and alveoli that ventilated but do not perfuse ... – PowerPoint PPT presentation

Number of Views:290
Avg rating:3.0/5.0
Slides: 30
Provided by: drjeffspe
Category:

less

Transcript and Presenter's Notes

Title: Control of Breathing


1
Control of Breathing
2
Control of Breathing
  • Central control
  • Breathing is controlled by neurons located in the
    pons and the medulla.
  • Sensors
  • They are located in
  • Respiratory and Cardio vascular systems
  • Muscles and tendons
  • Skin
  • Viscera and brain
  • Pulmonary receptors
  • Sensors in the respiratory system.
  • 3 groups
  • Pulmonary stretch receptors
  • Pulmonary irritant receptors
  • Type-J receptors

3
Control of Breathing
  • 1. Pulmonary stretch receptors
  • Inflation of lung stimulates
  • Located in the tracheal and bronchial smooth
    muscle
  • Response results in decrease of Rf and
    bronchodilation
  • 2. Irritant Receptors
  • Located in the epithelium of the larynx and URT.
  • Chemical or mechanical irritation of airways can
    stimulate
  • coughing,
  • hypernea, and
  • bronchoconstriction.

4
Control of Breathing
  • 3. Type-J Receptors are thought to be responsible
    for the hypernea that accompanies pulmonary
    embolism or pulmonary vascular congestion.
  • It is thought that these receptors are located in
    the walls of the pulmonary capillaries.

5
Control of Breathing
  • Chemoreceptors
  • Are sensors that detect changes in arterial blood
    gases or chemical composition.
  • Two types
  • Peripheral located in the carotid bodies of the
    bifurcation of the common carotid arties and
    aortic body.
  • They are sensitive to changes in arterial O2 PP.
  • Central located near the ventral aspect of the
    medulla.
  • Responds to changes in the interstitial tissue
    fluid pH.

6
Lung Volumes and Ventilation
7
Respiratory System
  • Ultimate importance of the pulmonary ventilatory
    system is to continually renew the air in the gas
    exchange areas of the lungs
  • where the air is in the proximity to the
    pulmonary blood.
  • These areas include
  • alveoli, alveolar sacs, alveolar ducts, and
    respiratory bronchioles.

8
Respiratory System
  • Main respiratory processes involved in gas
    exchange are
  • Ventilation movement of gas(es) into and out of
    the lungs
  • Perfusion flow of blood per unit volume of
    tissue
  • Ventilation/perfusion ratio (V/Q) how matching
    of air and blood in the lung influences gas
    exchange.

9
Respiratory System
  • Diffusion how gas gets across the air- blood
    barrier.
  • Gas transport how gases are moved from lungs
    to the tissues.
  • Mechanics of breathing how the lungs are
    moved.
  • Control of breathing how the supply of gas
    exchange is adjusted to the demand.

10
Ventilation
  • How much air goes in and out?
  • Lung Volumes
  • The volume of air inhaled or exhaled during a
    normal breath is termed tidal volume (VT).
  • Also known as the depth of a breath
  • In a healthy resting athletic horse its about 12
    ml/kg of body weight (5-6 liters).
  • Respiratory frequencies (Rf) the number of
    complete breaths taken per minute
  • Expired minute volume (VE)
  • tidal volume x respiratory frequency

11
Ventilation
  • Exercise imposes a potent stress on the
    ventilatory pump
  • Minute ventilation (MV) increases almost
    linearly.
  • Which is the volume of gas that enters or leaves
    the airways in any minute.
  • The expired minute ventilation (VE), which
    averages 80 l/min at rest may reach values in the
    vicinity of 1800 l/min during heavy exercise.

12
Ventilation
  • To accommodate the change in minute ventilation,
    a horse can alter its
  • tidal volume (VT),
  • respiratory frequency (Rf),
  • or both
  • In Trotter horses, increase in MV is achieved by
    both (VT and Rf) at low exercise, and increase
    respiratory frequency at high exercise
    intensities.
  • Values as high as 133 breaths/ min have been
    reported on treadmills.

13
Ventilation
  • In galloping horses, respiratory and the
    locomotion are coupled.
  • Step and respiratory frequencies average 110 to
    130 per minute with max. values of 148 per
    minute.
  • Therefore, increase ventilation with increasing
    speeds is due mainly to the increase in tidal
    volume (12 - 15 liters).

14
Ventilation

VO2max
15
Ventilation
liters
VT
16
Ventilation
  • Alveolar and Dead Space Ventilation
  • Only a part of the inspired volume reaches the
    area of the lung where gas exchange takes place
    Alveolar ventilation (VA).
  • The remaining part of the minute ventilation is
    wasted in the regions of lung where no gas
    exchange occurs Physiologic dead space
    ventilation (VD).
  • Which includes the conducting airways and alveoli
    that ventilated but do not perfuse

17
Alveolar Ventilation
  • Rate of Alveolar Ventilation
  • Alveolar ventilation per minute is the total
    volume of new air entering the alveoli each
    minute.
  • Its equal to the respiratory rate (Rf) times the
    amount of new air that enters the alveoli with
    each breath.

18
Ventilation
  • On expiration, the air in the dead space is
    expired first, before any of the air from the
    alveoli reaches the atmosphere.
  • The dead space is equally disadvantageous for
    removal of the expiratory gases from the lungs.

19
Ventilation
liters
Value
20
Ventilation
  • Exercise-induced changes in VA and VD to VT ratio
    in horses depend on the type of exercise.
  • During mild to moderate exercise
  • The dead space volume does not change
    significantly
  • If exercise is prolonged at a constant rate
  • The dead space ventilation will increase by a
    simultaneous increase in Rf and in VD to VT ratio
  • During intense efforts
  • There is a decrease in the same ratio from 60 to
    20
  • In absolute terms, the physiologic dead space is
    reduced from 3.5 liters at rest to 2.5 liters
    during heavy exercise.

21
Ventilation
  • The dead space to tidal volume ratio averages 50
    to 60 in the resting horse.
  • Studies have shown evidence that adequate gas
    exchange is maintained with very low tidal volume
    and very high respiratory frequency.

22
Ventilation

23
Ventilation
  • For a given minute ventilation, the lower the
    physiologic dead space ventilation,
  • The higher the alveolar ventilation and the
    better the gas exchange.

24
Respiratory System
  • From a functional standpoint the respiratory
    system can be divided into two major components
  • Upper or extrathoracic respiratory tract
  • URT
  • Lower or intrathoracic respiratory tract
  • LRT

25
Respiratory System
  • Distinction can be made by the neg. and pos.
    pressure experienced by the airways during
    breathing.
  • Exercise magnifies these pressures and
  • Enhances detrimental effects when disease and
    malfunction is present

26
Respiratory System
  • Elastic properties of the lung.
  • The normal lung is a network of elastin and
    collagen fibers.
  • Pressure-volume
  • curve

27
Elastic properties of the lung
  • Compliance
  • Measure of the distensibility of the lung.
  • A measure of the ease w/ which a hollow viscus
    may be distended.
  • Can be illustrated in the
  • slope of either the inflation
  • or deflation curve of the
  • pressure-volume diagram.

28
Elastic properties of the lung
  • Surface tension
  • Is responsible for helping to determine the
    elasticity and thus the compliance of the lung.
  • If to high atelectasis may occur.
  • Absence of gas from a part or the whole of the
    lungs,
  • Due to failure of expansion or resorption of gas
    from the alveoli

29
Elastic properties of the lung
  • Interdependence
  • Is the phenomenon whereby alveoli are held open
    from support offered by neighboring lung units.
  • Helps prevent atelectasis
  • Also may play a role in exercise-induced
    pulmonary hemorrhage.
Write a Comment
User Comments (0)
About PowerShow.com