UNIT B: Human Body Systems

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UNIT B Human Body Systems

• Chapter 8 Human Organization
• Chapter 9 Digestive System
• Chapter 10 Circulatory System and Lymphatic
  System
• Chapter 11 Respiratory System
• Section 11.2
• Chapter 12 Nervous System
• Chapter 13 Urinary System
• Chapter 14 Reproductive System

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Chapter 11 Respiratory System
UNIT B
Chapter 11 Respiratory System

• In this chapter, you will learn about the
  structure and function of the respiratory system.

How would a narrowing and swelling of the airways
affect the respiratory volumes? How do the
typical treatments for asthma work to reduce the
symptoms? Why is it so difficult to develop a
cure for asthma? What are some of the normal
defence mechanisms of the respiratory tract?
Asthma is a disease in which the airways become
constricted (narrowed) and inflamed (swollen),
both of which can result in difficulty breathing.
It is one of the most common chronic diseases in
children. It is estimated that 10 to 15 percent
of children in Canada have asthma.
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11.2 Mechanism of Breathing
UNIT B
Section 11.2
Chapter 11 Respiratory System

• A free flow of air is vitally important during
  ventilation (breathing).
• A spirometer is a device used to record the
  volume of air inhaled and exhaled with each
  breath.

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UNIT B
Section 11.2
Chapter 11 Respiratory System
Figure 11.7 Measuring ventilation. A spirometer
measures the air inhaled and exhaled with each
breath. During inspiration, the pen moves up.
During expiration, the pen moves down. Vital
capacity (red) is the maximum amount of air a
person can exhale after taking the deepest
inhalation possible.
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Respiratory Volumes
UNIT B
Section 11.2
Chapter 11 Respiratory System

• Tidal volume the amount of air that is inhaled
  and exhaled at rest

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UNIT B
Section 11.2
Chapter 11 Respiratory System

• Inspiratory reserve volume the additional volume
  of air that can be inhaled beyond the tidal
  volume (e.g., during deep breathing)
• Expiratory reserve volume the addition volume of
  air that can be exhaled beyond the tidal volume

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UNIT B
Section 11.2
Chapter 11 Respiratory System

• Vital capacity the maximum volume of air that
  can moved in and out during a single breath
• Vital capacity tidal inspiratory reserve
  expiratory reserve

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UNIT B
Section 11.2
Chapter 11 Respiratory System

• Residual volume amount of air that remains in
  the lungs and airways after a full exhalation
• During normal breathing, only 70 of tidal volume
  reaches the alveoli about 30 remains in the
  airways. This air is not useful for gas exchange
  because it has been depleted of oxygen.

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UNIT B
Section 11.2
Chapter 11 Respiratory System

• Respiratory volumes depend on various factors.
• Age (decreasing after age 30)
• Gender (10-20 lower in women)
• Physical activity (20-30 higher in conditioned
  athletes)
• Respiratory disorders
• Some disorders decrease vital capacity or can
  increase residual volumes because the individual
  has difficulty emptying the lungs

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Inspiration and Expiration
UNIT B
Section 11.2
Chapter 11 Respiratory System

• To understand ventilation, the following facts
  should be remembered
• There is a continuous column of air from the
  pharynx to the alveoli in the lungs.
• The lungs lie within the sealed-off thoracic
  cavity.
• Rib cage top and sides of the thoracic cavity
• Intercostal muscles lie between the ribs
• Diaphragm and connective tissue floor of the
  thoracic cavity
• The lungs adhere to the thoracic wall through the
  pleura.
• Space between the two pleurae is minimal due to
  surface tension of the fluid between them

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Inspiration
UNIT B
Section 11.2
Chapter 11 Respiratory System

• Inspiration is the active phase of ventilation.
• Diaphragm contracts and lowers
• Intercostal muscles contract
• Rib cage moves up and out
• As the thoracic volume increases, the lung volume
  increases, and air pressure in alveoli decreases
• Alveolar pressure is lower than atmospheric
  pressure outside lungs, causing air to flow into
  airways

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Expiration
UNIT B
Section 11.2
Chapter 11 Respiratory System

• Expiration is the passive phase of ventilation.
• Diaphragm relaxes and moves up
• Intercostal muscles relax
• Rib cage moves down and in
• As the thoracic volume decreases, the lung volume
  decreases, and air pressure in alveoli increases
• Alveolar pressure is higher than atmospheric
  pressure outside lungs, causing air to be pushed
  out

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UNIT B
Section 11.2
Chapter 11 Respiratory System
Figure 11.8 Inspiration and expiration compared.
a. During inspiration, the thoracic cavity and
lungs expand so that air is drawn in. b. During
expiration, the thoracic cavity and lungs resume
their original positions and pressures. Now, air
is forced out.
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Control of Breathing
UNIT B
Section 11.2
Chapter 11 Respiratory System

• Ventilation is controlled by a respiratory centre
  in the medulla oblongata of the brain.
• Stimulates inspiration by automatically sending
  impulses to the diaphragm through the phrenic
  nerve, and to the intercostal muscles through the
  intercostal nerve

Figure 11.9 Nervous control of breathing. The
respiratory centre automatically stimulates the
external intercostal (rib) muscles and diaphragm
to contract via the phrenic nerve. After forced
inhalation, stretch receptors send inhibitory
nerve impulses to the respiratory centre via the
vagus nerve. Usually, expiration automatically
occurs because of the lack of stimulation from
the respiratory centre to the diaphragm and
intercostal muscles.
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Control of Breathing
UNIT B
Section 11.2
Chapter 11 Respiratory System

• When the respiratory centre stops sending signals
  to the diaphragm and rib cage, the diaphragm
  relaxes and expiration occurs
• Following inhalation, stretch receptors in the
  alveolar walls send inhibitory nerve impulses via
  the vagus nerve to the respiratory centre, which
  inhibits the respiratory centre from sending
  impulses

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Control of Breathing
UNIT B
Section 11.2
Chapter 11 Respiratory System

• Chemical Input
• The respiratory centre is also sensitive to
  levels of carbon dioxide and hydrogen ions in the
  blood
• When carbon dioxide or hydrogen ion
  concentrations increase, the respiratory centre
  increases rate and depth of breathing
• Respiration rate is also influenced by cells
  called carotid bodies and aortic bodies
• When concentration of blood oxygen decreases,
  these bodies signal the respiratory centre to
  increase rate and depth of breathing

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Check Your Progress
UNIT B
Section 11.2
Chapter 11 Respiratory System

1. Compare tidal volume and vital capacity.
2. Explain why inspiration is considered the active
   phase of ventilation, and expiration the passive
   phase.

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UNIT B
Section 11.2
Chapter 11 Respiratory System
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UNIT B
Section 11.2
Chapter 11 Respiratory System
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