Download Plants and Pollinators

The Respiratory System
Chapter 11
Respiration
• Physiological process by which oxygen
moves into internal environment and
carbon dioxide moves out
• Oxygen is needed for aerobic
respiration
• Carbon dioxide is produced by same
Respiratory System
• Acts in concert with the circulatory
system to deliver oxygen and remove
carbon dioxide
• Also helps regulate acid-base balance
Human Respiratory System
pharynx (throat)
epiglottis
larynx (voice box)
trachea (windpipe)
pleural membrane
bronchiole
alveoli
intercostal muscle
diaphragm
Airways
• Air enters through nose
• Moves through pharynx and larynx to
trachea
• Trachea branches into two bronchi
• Each bronchus branches into
bronchioles
• Bronchioles end in alveoli where gas
exchange occurs
Speech Production
• Vocal cords stretch
across laryngeal
opening; opening
between them is
glottis
• Position of cords is
varied to create
different sounds
Glottis closed
Glottis open
Pressure Gradients
• Concentration gradients for gases
• Gases diffuse down their pressure
gradients
• Gases enter and leave the body by
diffusing down pressure gradients
across respiratory membranes
Atmospheric Pressure
• Pressure exerted by the weight of the
air on objects on Earth’s surface
• At sea level = 760 mm Hg
• Oxygen is 21% of air; its partial
pressure is about 160 mm Hg
Fick’s Law
• Describes the rate at which a substance
(such as oxygen) will diffuse across a
membrane (such as a respiratory
surface)
• Rate is proportional to the pressure
gradient across the membrane and to
the surface area of the membrane
Altitude Sickness
• Humans are adapted to lower elevations
where oxygen levels are relatively high
• At high altitude
– Hyperventilation leads to ion
imbalances in cerebrospinal fluid
– Increased capillary permeability can
cause edema
Decompression Sickness
• Pressure increases with water depth
• While diving, pressurized air keeps
lungs from collapsing
• During ascent, pressure decreases
• Bubbles of gaseous nitrogen can form
in blood and block flow
Carbon Monoxide Poisoning
• Colorless, odorless gas
• Binds to hemoglobin 200 times more
tightly than oxygen does
• Even tiny amounts can tie up
hemoglobin and prevent oxygen
delivery
Bronchitis
• Irritation of the ciliated epithelium that
lines the bronchiole walls
• Air pollutants, smoking, or allergies can
be the cause
• Excess mucus causes coughing, can
harbor bacteria
• Chronic bronchitis scars and constricts
airways
Emphysema
• An irreversible breakdown in alveolar
walls
• Lungs become inelastic
• May be caused by a genetic defect
• Most often caused by smoking
Asthma
• Can be triggered by allergens
• Smooth muscle ringing bronchi
contracts
• Mucus is produced by bronchial
epithelium
• Result is reduced air flow
• Can be treated with aerosol inhalers
Breathing
• Moves air into and out of lungs
• Occurs in a cyclic pattern called
the respiratory cycle
• One respiratory cycle consists of
inhalation and exhalation
Changes in Pressure
Atmospheric pressure:
Intrapleural
pressure:
Intrapulmonary
pressure:
760
760
760
754
756
756
759
760
761
Before
inhalation
During inhalation
(lungs expanded)
During
exhalation
Inhalation
• Diaphragm flattens
• External intercostal
muscles contract
• Volume of thoracic
cavity increases
• Lungs expand
• Air flows down pressure
gradient into lungs
Normal (Passive) Exhalation
• Muscles of
inhalation relax
• Thoracic cavity
recoils
• Lung volume
decreases
• Air flows down
pressure gradient
and out of lungs
Active Exhalation
• Muscles in the abdomen and the
internal intercostal muscles contract
• This decreases thoracic cavity volume
more than passive exhalation
• A greater volume of air must flow out to
equalize intrapulmonary pressure with
atmospheric pressure
Lung Volume
• Tidal volume is 500ml of air
• Vital capacity is tidal volume, plus inspiratory
reserve and expiratory reserve
• This is still less than total lung capacity
• Lungs are never fully deflated
Respiratory Membrane
• Area between an
alveolus and a
pulmonary capillary
• Oxygen and
carbon dioxide
diffuse across
easily
alveolar
epithelium
capillary
endothelium
fused
basement
membranes
of both
epithelial
tissues
Oxygen Transport
• Most oxygen is carried bound to
hemoglobin in red blood cells
• Hemoglobin has a great affinity for
oxygen when it is at high partial
pressure (in pulmonary capillaries)
• Lower affinity for oxygen in tissues,
where partial pressure is low
Carbon Dioxide Transport
• Most carbon dioxide is transported as
bicarbonate
• Bicarbonate formation is enhanced by
the action of carbonic anhydrase inside
red blood cells
• Smaller amounts are transported
dissolved in blood and bound to
hemoglobin
Bicarbonate Formation:
A Two-Step Reaction
• Carbon dioxide combines with water to
form carbonic acid
CO2 + H2O ---> H2CO3
(catalyzed by carbonic anhydrase)
• Carbonic acid releases a hydrogen ion
to form bicarbonate
H2CO3 ---> H+ + HCO3-
Breathing Rhythm
• Diaphragm and intercostal muscles
under control of reticular formation
• One cell cluster controls inspiration, the
other expiration
• Resulting rhythm is fine tuned by
centers in the brain stem
Magnitude of Breathing
• Receptors in medulla detect H+
• Signal increase in rate and depth of
breathing
• Carotid bodies and aortic bodies detect
CO2, oxygen, and pH
• Signal increase in rate of breathing
Chemical Controls
• Increase in CO2 causes smooth muscle
of bronchioles to dilate
• Decrease in CO2 causes smooth
muscle of bronchioles to constrict
• Local controls also work on lung
capillaries
Apnea
• Breathing that stops and starts
• Sleep apnea is common in elderly
Effects of Smoking
• Shortened life expectancy
• Increased rates of cancers
• Increased rate of heart disease
• Impaired immune function and healing
• Detrimental to fetus