Transcript The Respiratory System Part 4: Regulation & Maintenance

The Respiratory
System
Part 4: Regulation &
Maintenance
The Respiratory System

Respiratory System: The system of the
body primarily concerned with gas
exchange, namely carbon dioxide &
oxygen.
 Oxygen
is essential for metabolic reactions
that produce the energy required for all life
processes.
 Carbon Dioxide is the waste product of the
metabolic reactions that must be removed
from the body. Excessive buildup can lead to
acidity that can be toxic to cells.
Respiration

Respiration: 3 meanings…
 Ventilation
of the lungs (breathing)
 Exchange of gases between air & blood and
blood & tissue fluid
 Use of oxygen in cellular metabolism
Functions of the Respiratory
System
Provides gas exchange by in taking
oxygen & delivering it to the body cells &
eliminating carbon dioxide waste products
produced in the body cells.
 Helps to regulate the blood pH.
 Contains receptors for the sense of smell,
filters inspired air, and produces sound for
vocalization.

Respiratory Anatomy

6 Principle Organs of the Respiratory
System:
 Nose
 Pharynx
 Larynx
 Trachea
 Bronchi
 Lungs
Respiratory Anatomy
Conducting Division: Organs that enable
the passage of airflow.
 Respiratory Division: Any tissue where
gas-exchange occurs.

 Alveoli:
Sacs in the lungs that exchange gas.
Respiratory Anatomy
Upper Respiratory Tract: The airway
from the nose through the larynx.
 Lower Respiratory Tract: The airway
from the trachea through the lungs.

Respiratory Path

Air flows from the… nasal or oral cavity 
pharynx  trachea  primary bronchi 
secondary bronchi  tertiary bronchi 
bronchioles  alveoli.
Nose

Nose: The organ responsible for detecting
odors, cleansing & humidifying the air we breath,
adding resonance to the voice.
by bones & cartilage – alar, septal, &
lateral cartilages.
 External Nares: The two openings commonly known
as the nostrils.
 Nasal Cavity: The cavity that extends from the
external nares to the back of the internal nares aka
the choanae.
 Vestibule: The anterior portion of the cavity.
 Nasal Fossae: The two halves of the nasal cavity.
 Supported

Nasal Septum: Divides the nasal cavity into the nasal
fossae.
Nose
Superior, Middle & Inferior Conchae:
The projections or shelves along the walls
of the chambers.
 Superior, Middle & Meatuses: The
narrow nature of the passages helps trap
moisture during exhalation & insures that
incoming air is moist as well.

 Cilia
(hair) & mucus in the cavity traps debris
and sweeps it up & out of the pharynx to be
swallowed & digested (or spit out).
Pharynx

Pharynx: The portion we think of as the
“throat”. Funnel-shaped, muscular tube
above 5 inches long.
 Extends
from the internal nares to the cricoid
cartilage of the larynx.
 Main function is a passageway for food or air.
 Also serves as a resonating chamber for our
voices & houses the tonsils.
Pharynx

3 Regions of the Pharynx:
 Nasopharynx:
Lies just beneath the nasal cavity &
extends to the soft palate.

Opens to the internal nares & the auditory tubes/eustachian
tubes. Leads directly to the…
 Oropharynx:
Lies between the soft palate & hyoid
bone. Houses both the lingual & palatine tonsils.


Fauces: The opening to the mouth!
Leads directly to the…
 Laryngopharynx:
Begins at the hyoid bone & opens
into both the esophagus & larynx.


Esophagus leads to the stomach for food.
Larynx leads to the lungs for air.
Larynx

Larynx: Connects the pharynx with the trachea.
 Called
the “voicebox”
 Important for keeping foods & liquids out of the
airway.
 9 Cartilages make up the wall of the larynx.

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
1 Epiglottis
1 Thyroid Cartilage
1 Cricoid
2 Arytenoids
2 Corniculate
2 Cuneiform
Larynx

Glottis: The superior opening of the
larynx.
 Epiglottis:
The guarded flap of tissue that
keeps food from the airway.

Extrinsic Muscles: Cause the larynx &
pharynx to rise when swallowing takes
place – this causes the epiglottis to close
downward like a lid & prevent food from
entering the airway.
Larynx

Mucus Membranes: Membranes line the larynx
with two pairs of folds.
 Ventricular
Folds aka False Vocal Cords:
 True Vocal Cords: Inferior to the false vocal cords,
which produces sound via elastic ligaments stretched
between the cartilage.
 Intrinsic Muscles create tension to pull on the
corniculate and arytenoid cartilages which causes the
sound of the air passing through the larynx to change
in pitch.



When the cords are pulled tight, the pitch produced is higher.
When the cords are relaxed, the pitch produced is lower.
Volume is adjusted via the force of the air through the larynx.
Trachea


Trachea: Known as the windpipe – about 5 inches long,
connecting the larynx to the right & left pulmonary
bronchi.
Mucus Layers: From deepest to superficial…






Mucosa
Submucosa
Hyaline Cartilage
Adventitia
Primary Function of the Mucus Layers: Keep dust &
small particles out of the lungs.
C-Shaped Cartilage Rings: Keep the trachea from
collapsing when we inhale, & ciliated epithelial cells help
to sweep mucus upwards & outwards to keep debris out
of the lungs.
When Things Go Wrong with the
Trachea…
Tracheotomy: An operation where an
opening is made in the trachea to bypass
any obstruction.
 Intubation: A procedure in which a tube is
inserted into the mouth or nose & guided
down the respiratory tract to the lungs.

Bronchi

Carina: An internal ridge where the trachea
separates into the right & left primary bronchus.
 The
mucous membrane of the carina is the most
sensitive area of the entire laryns for initiating a cough
reflex.

Bronchi: The paths that divide off into the lungs
from the trachea.
 Right
Primary Bronchus: Goes to the right lung.
 Left Primary Bronchus: Goes to the left lung.

The primary bronchi further divide into the
smaller bronchi.
Bronchi

Secondary (Lobar) Bronchi: The branch of the brinchi
that supply each lobe of the lung.



Tertiary (Segmental) Bronchi: Further branches of the
secondary bronchi.
Bronchioles: The smallest branches of the bronchi,
lacking cartilage, but have smooth muscle in the walls.


2 go to the left lung, 3 to the right.
Primary Lobule: The portion of lung that is supplied by each
bronchiole.
Terminal Bronchioles: Bronchioles are divided into 5080 terminal bronchioles.

These further divide into small respiratory bronchioles which
divide into alveolar ducts & end in the alveolar sacs (where gas
exchange occurs).
The Lungs
Lungs: The paired, cone-shaped organs
that are located in the thoracic cavity to
rapidly exchange gas.
 Hilun: The depression point at which each
lung receives the bronchus, blood vessels,
lymphatic vessels, & nerves.

The Lungs


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Pleural Membranes: Two layers of serous
membranes which enclose & protect each lung.
Parietal Pleura: The superficial layer that lines
the wall of the thoracic cavity.
Visceral Pleura: Covers the lungs.
Pleural Cavity: The small space between the
visceral & parietal pleurae.
 Pleural
Fluid: The lubricating fluid that allows the
membranes to move easily over one another during
breathing, & causes the membranes to have surface
tension (stick together).
The Lungs

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Base: The broad, inferior portion of the lungs.
Apex: The narrow, superior portion of the lungs.
Costal Surface: The surface of the lungs that
lies against the ribs.
Mediastinal (Medial) Surface: Contains the
hilus (where the bronchi, blood vessels, &
nerves enter & exit).
 Root:
Formed by the pulmonary artery & veins,
bronchus, bronchial arteries & veins, pulmonary
plexuses of nerves, lymphatic vessels, bronchial
lymph glands, & areolar tissue all enclosed in the
pleura.
The Lungs

Cardiac Notch: The indentation in the
anterior border of the left lung.
 The
left lung is about 10% smaller than the
right lung.
 The right lung is thicker & broader than the
left lung because the diaphragm is higher on
the right side.
Alveoli

Alveoli: Microscopic functional units of the
lungs, where gas exchange takes place.
 Alveolus:
The cup shaped structure lined
with simple squamous epitheliun &
surrounded by a basement membrane.
 Alveolar Sacs: Made up of two or more
alveoli that share a common opening.
Alveoli

Alveolar Epithelial Cells: Two types of cells
that line the walls of the epithelial cells.
 Type
1 Alveolar Cells: Most prevalent type - the
mane sites of gas exchange.
 Type 2 Alveolar Cells aka Septal Cells: Secrete
alveolar fluid, which keeps the surface between the
cells and the air moist & produces surfactant. Found
between the Type 1 Alveolar Cells

Surfactant: An element of alveolar fluid that lowers its
surface tension & reduces the tendency of alveoli to collapse.
Alveoli

Respiratory Membrane: Exchanges oxygen &
carbon dioxide by diffusion across the alveolar &
capillary walls.
 Extends
from the alveolar air space to the blood
plasma.
 Consists of 4 layers:
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
Alveolar Wall: Consists of Type 1 & 2 Alveolar Cells &
Alveolar macrophages (wandering macrophages that remove
dust particles & other debris from the lungs.
Epithelial Basement Membrane: Underlies the alveolar
wall.
Capillary Basement Membrane: Fuse to the basement
membrane.
Endothelial Cells: Cells of the capillaries.
Blood Supply to the Lungs


Pulmonary Arteries aka Bronchial Arteries:
Main arteries that supply blood to the lungs.
Pulmonary Trunks: Deoxygenated blood
travels through the pulmonary trunk to the lungs
to become oxygenated.
 Divides
into the left pulmonary artery (serves the left
lung) & right pulmonary artery (serves the right lung).

Oxygenated blood then returns to the heart
through one of the four pulmonary veins that
drain into the left atrium.
Blood Supply to the Lungs


Ventilation-Perfusion Coupling: The
phenomenon of the blood vessels in the lungs
undergoing vasoconstruction as a result of
hypoxia to divert the blood from poorly ventilated
areas to well ventilated areas to optimize
oxygenation.
Bronchial Arteries: Branch from the aorta to
deliver oxygenated blood to nourish the lungs.
 Most
blood then returns to the heart through the
pulmonary veins.
 Superior vena cava returns any blood that drains
into the bronchial veins or branches of the azygos
systems.
Respiration

Respiration: The process of gas exchange. 3 steps…

Pulmonary Ventilation: The mechanical flow of air into & out of
the lungs – breathing!


External Respiration: The exchange of gases between the
alveoli of the lungs & the blood in the pulmonary capillaries,
aided by the thin walls of the capillaries & alveoli.


Blood in the pulmonary capillaries loses carbon dioxide & gains
oxygen.
Internal Respiration: The exchange of gases between the
blood in the systemic capillaries & tissue cells.


Air flow is due to the alternating pressure differences caused by the
contraction & relaxation of the respiratory muscles.
Blood in the systemic capillaries loses oxygen to the tissue cells &
gains carbon dioxide.
Cellular Respiration: The metabolic reactions within all
cells that consume oxygen & give off carbon dioxide
while producing ATP for energy.
Inhalation

Inhalation aka Inspiration: The act of
breathing in – considered active due to
muscular contractions involved.
 Phrenic
nerves stimulate the diaphragm to
cause a downward contraction.
 The external intercostal muscles are
stimulated by this and raise the ribs.
 The chest cavity and the lungs expand to fill
the space, increasing the volume and
decreasing the pressure.
Inhalation: Atmospheric Pressure

Air pressure inside the lungs is equal to the
atmospheric pressure (1 atmosphere or 760
mm).
 Pressure
inside the alveoli is lower than atmospheric
pressure when the volume of the lungs increases
(inhalation).
 This causes air to be forced into the lungs!
 The air in the lungs is now higher in atmospheric
pressure than the air outside the body, which leads to
expiration.

Boyle’s Law: The pressure of a gas in a closed
container is inversely proportional to the volume
of the container – as the volume increases, the
pressure decreases!
Inhalation: Pressure


Intrapleural Pressure: The level of pressure
between the two pleural lining layers, which is
always lower than atmospheric pressure.
Alveolar (Intrapulmonic) Pressure: The
pressure inside the lungs that decreases as the
volume of the lungs & thoracic cavity increases.
 Causes
a pressure difference between the alveoli &
atmosphere, forcing air to flow from the area of high
pressure (outside) to low pressure (inside lungs).

Compliance: The amount of effort that is
required to expand the lungs & the chest wall.
 High
compliance means the chest wall & lungs will
expand easily.
Muscles of Respiration

Diaphragm: The dome-shaped skeletal
muscle that forms the floor of the thoracic
cavity.
 Contraction
causes the ribs & sternum to
elevate, increasing the front-to-back
dimension of the thoracic cavity.
 Contraction causes the air pressure decrease
in the lungs that forces air into the body.
 Contraction accounts for 75% of air entering
the body!
 The most important muscle in inhalation!
Muscles of Respiration

External Intercostals: The muscles
running between the ribs.
 Contraction
leads to elevation of the ribs.
 Contraction accounts for 24% of the air
entering the body!
 Second most important muscle for inhalation.
Exhalation

Exhalation aka Expiration: The act of
breathing out - considered passive unless
forced.
 Elastic
Recoil helps to force the air back from the
area of high pressure (inside the lungs) to the area of
low pressure (outside the body).

Elastic Recoil: The returning of the chest wall &
lungs to normal shape after the stretching that
occurs during inhalation. This is aided by….
 The
recoil of elastic fibers within the tissue that had
been stretched during inhalation.
 The inward pull of the surface tension of the lungs,
caused by the alveolar fluid.
Let’s Review – Breathing!
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Diaphragm & External Intercostal muscles
contract, causing the diaphragm to move
downward and the ribs & sternum to lift.
Movement causes the vertical dimensions of the
thoracic cavity to increase, causing the air
pressure in the lungs to decrease.
Decrease in air pressure causes air to flow
from the area of high atmospheric pressure
(outside the body) to the area of low
atmospheric pressure (inside the lungs).
Let’s Review – Breathing!
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Relaxation of the inspiratory muscles causes
exhalation to start!
Elastic recoil occurs in the diaphragm &
external intercostal muscles, decreasing the
dimensions of the thoracic cavity.
This decreases the volume of the lungs, causing
the pressure to increase.
Air is forced from the area of high atmospheric
pressure (inside the lungs) to the area of low
atmospheric pressure (outside the body).
When Respiration Goes Wrong…

Chronic Obstructive
Pulmonary Disease
(COPD): Any disorder
causing a long-term
obstruction of airflow,
which reduces
pulmonary ventilation.
When Respiration Goes Wrong…

Asthma: Allergens
trigger the release of
inflammatory
chemicals, causing
bronchoconstriction
and thick mucus
production.
 Can
lead to death from
suffocation!
When Respiration Goes Wrong…

Chronic Bronchitis:
The inflation of the
bronchi &
immobilization of the
cilia – causes a
chronic cough to help
bring up sputum.
When Respiration Goes Wrong…

Emphysema: The break
down of the alveolar
walls, leading to
enlargement of the
remaining alveolar sacks.

Much less respiratory
membrane is then available
for gas exchange, requiring
3-4 times the normal
amount of energy to help
breathe.
When Respiration Goes Wrong…
Smoking!
When Respiration Goes Wrong…
Smoking!
Chronic Bronchitis
Emphysema X 2
Lung Volume & Capacity

Respiration Rate: The average number of
breaths taken per minute.
 Healthy
minute.
adults average 12 breaths per
Lung Volume & Capacity

Tidal Volume (Vt): The amount (volume) of air moved
with each breath.

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
Varies from one person to the next.
Approximately 70% of tidal volume (350mL) moves into the
functional sections of the respiratory system.
Approximately 30% (150mL) remains in the conducting airways
– the anatomic dead space.
Alveolar Ventillation Rate: The volume of air per
minute that reaches the alveoli & respiratory portions of
the lungs – measured as the functional tidal volume
multiplied by the respiratory rate.

AVR = 350mL/breath X 12 breaths/min = 4200 mL/minute.
Lung Volume & Capacity

Minute Ventilation (MV): The total
volume of air inhaled & exhaled each
minute – calculated as the respiratory rate
multiplied by the tidal volume.
 MV
= 12 breaths/min X 500mL/breath = 6
liters/minute.
 If this is lower than normal it can be a sign of
pulmonary malfunctioning!
Lung Volume & Capacity

Inspiratory Reserve Volume: The
difference in inhaled air volume between
normal tidal volume and the tidal volume
of a deep breath.
 Normal
tidal volume = 500mL
 Normal inspiratory reserve volume = 3100mL

3100mL is the amount that is more than normal –
you actually take in 3600mL.
Lung Volume & Capacity

Expiratory Reserve Volume: The amount of air typically left in the
lungs after a normal exhalation.


Forced Expiratory Volume (FEV1.0): The volume of air that can be
forcefully exhaled from the lungs in one second, after a maximum
inhalation & using maximum effort.


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Approximately 1200mL in healthy adults.
In English: The amount of air you can exhale during 1 second if you
take the deepest breath possible and blow as hard as you can!
Residual Volume: The amount of air still remaining in the lungs in
the noncollapsible airways even after the expiratory reserve volume
is exhaled.
Minimal Volume: The amount of residual volume remaining should
the thoracic cavity open.

The change in pressure causes some residual volume to be lost as the
pressures of the cavity & the outside world attempt to equalize.
Lung Volume & Capacity

Lung Capacity: The combinations of specific
lung volumes.
 Inspiratory
Capacity: The sum of tidal volume &
inspiratory reserve volume.

500mL + 3100 mL = 3600 mL
 Functional
Residual Capacity: The sum of residual
volume & expiratory reserve volume.

1200mL + 1200mL = 2400mL
 Vital
Capacity: The sum of inspiratory reserve
volume & expiratory reserve volume.

3600mL + 1200mL = 4800mL
 Total
Lung Capacity: The sum of vital capacity &
residual volume

4800mL + 1200mL = 6000mL
Lung Volume & Capacity

Spirometer (Respirometer): An
instrument used to measure the
respiratory rate & the tidal volume.
 Spirogram:
The graph of the spirometer
readout.
 Upward Deflection shows inhalation.
 Downward Deflection shows exhalation.
Gas Exchange Laws
– Dalton’s Law

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Dalton’s Law: Each gas in a mixture of gases exerts its
own pressure as if no other gases were present.
Partial Pressure (Px): The pressure on a specific gas
(x) in a mixture – this controls the movement of oxygen &
carbon dioxide from the atmosphere to the lungs, to the
blood, & to the tissue.



Determined by multiplying the percentage of each gas in the
mixture by the total pressure of the mixture.
The greater the partial pressure, the faster the diffusion of the
gases across a permeable membrane from the area of higher
pressure to the area of lower pressure.
Total Pressure: The sum of all the partial pressures in a
gas mixture.
Gas Exchange Laws
- Henry’s Law

Henry’s Law: The quantity of gas that will
dissolve in a liquid is proportional to the partial
pressure of the gas & its solubility coefficient.
 The
higher the partial pressure & the higher the
solubility in the solution, the easier it is for the gas to
stay within the fluid.

Example: Soda!
 While
the bottle is closed, the partial pressure is high,
causing the CO2 to stay within the liquid.
 When the bottle is opened, the pressure drops,
allowing the CO2 to escape!
Gas Exchange Laws
- Charles’ Law

Charles’ Law: At a constant pressure, the
volume of a given quantity of gas is
directly proportional to the absolute
temperature.
 As
the temperature rises, the volume rises the
same “percentage”.
 Example: If the temperature doubles, the
volume doubles.
Oxygen

Oxyhemoglobin: A binding of oxygen with the
heme portion of hemoglobin (4 iron atoms)
found within the blood.
+ O2   Hb- O2
 This allows oxygen to be transmitted by the blood!
 98.5% of blood oxygen is bound to hemoglobin.
 1.5% of oxygen is dissolved in blood plasma itself –
this is the oxygen that gets transported into tissue
cells.
 Hb

Deoxyhemoglobin: Oxyhemoglobin that has
unloaded its oxygen.
 This
occurs when blood oxygen reaches a tissue area
with lower partial pressure.
Oxygen

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Partial Pressure of Oxygen: The higher the partial
pressure of oxygen, the more it can combine with
hemoglobin.
Fully Saturated: The term given to deoxyhemoglobin
that is completely converted to oxyhemoglobin –
hemoglobin that is full of oxygen!
Partially Saturated: The term given to hemoglobin
that’s a mix of deoxyhemoglobin & oxyhemoglobin –
hemoglobin mixes that are oxygenated & deoxygenated.
Percent Saturation of Hemoglobin: The average
saturation of hemoglobin with oxygen.

Can be almost 100% when the oxygen’s partial pressure is high
(fully saturated) or low (partially saturated) if the partial pressure
is low.
Oxygen
Affinity: The tightness of the bond
between the Hb (hemoglobin) & oxygen.
 Oxygen-Hemoglobin Dissociation
(Saturation) Curve: The measure of the
level between oxygen levels & hemoglobin
saturation.

 Can
be shifted left for a higher affinity or right
for a lower affinity via 4 main factors…
Oxygen

Factors Affecting Oxygen-Hemoglobin Dissociation
(Saturation) Curve:

Acidity: As acidity increase, pH decreases, causing a decrease
in the Hb/O2 affinity.





Bohr Effect: The shift in the curve to the right, allowing O2 to
dissociate from Hb readily.
If acidity lowers, pH increases, and we see a left shift as the Hb/O2
affinity increases.
Partial Pressure of the O2- CO2: Can cause a right curve,
increasing the affinity, due to a resulting increase in acidity.
Temperature: The higher the temperature, the more O2 is
released from the Hb.
2,3-bisphosphoglycerate (BPG): A substance found in the red
blood cells that decreases the affinity & helps unload oxygen
from the Hb.
Carbon Monoxide Poisoning

Carbon Monoxide: A colorless, odorless gas
with a VERY high affinity for hemoglobin!
 Elevated
levels of carbon monoxide can cause
carbon monoxide poisoning!
 Carbon monoxide binds to hemoglobin at 200 times
the strength of oxygen’s bond!
 Pure oxygen can help… sometimes.

Symptoms: Lips & oral mucosa appear bright
cherry red, flu-like symptoms of headache &
nausea, etc.
Carbon Dioxide

Carbon Dioxide: Normal waste product of cellular
respiration.


53mL of gaseous carbon dioxide (CO2) present every 100mL of
deoxygenated blood in normal resting conditions.
3 Methods of CO2 Transport:



Dissolved: Approximately 9% dissolved in blood plasma – once
this reaches the lungs, it diffuses into the alveolar air & is
exhaled.
Carbamino Compounds: 13% combines with amino acid
groups & proteins in the blood to form carbamino compounds.
Bicarbonate Ions: 78% of CO2 transported in the blood plasma
this way.


CO2 diffuses into systemic capillaries, enters the red blood cells,
reacts with water & carbonic anhydrase (CA) enzymes, & forms
carbnic acid.
Carbonic acid then dissociates into hydrogen & bicarbonate ions.
Carbon Dioxide

Haldane Effect: The lower the amount of
oxyhemoglobin, the higher the CO2
carrying capacity of the blood.
 Basically,
the more oxygen the blood is
carrying, the less carbon dioxide it can pick
up, and visa versa.
Gas Exchange in Tissue


Diffusion: The movement of particles from an
area of high concentration to an area of low
concentration.
For gas exchange:
 The
blood supply in the alveolar capillaries has a high
concentration of CO2 while the outside air does not,
causing CO2 to move out of the blood & into the air to
be exhaled.
 The outside air has a high concentration of O2 while
the blood supply in the alveolar capillaries has a low
concentration of O2, causing O2 to move from the
outside air into the blood supply.
Control of Respiration

Respiratory Center: The group of neurons in the brainstem that
controls the respiratory muscles – connected to the cortex to allow
conscious control.. 3 areas:

Medullary Rhythmicity Area: Controls the basic rhythm of respiration located in the medulla oblongata.



Pneumotaxic Area: Helps coordinate the transition between inhalation
& exhalation –



Inspiratory Area: Stimulates the muscles of inspiration.
Expiratory Area: Stimulates the internal intercostal & abdominal muscles to
allow deeper respiration when needed.
Baroreceptors: “Stretch” receptors in the lungs that ensure the lungs don’t
become overinflated.
Inflation Reflex aka Hering-Breur Reflex: The stimulation of the
baroreceptors when the lungs reach capacity triggers the start of exhalation
while the lack of stimulation during deflation triggers a new round of
inhalation.
Apneustic Area: Area in the pons that also contributes to the transition
between inhalation & exhalation – stimulates the inspiratory area to
prlong inhalation when a long, deep breath is needed.

The pneumotaxic region overrides the apneustic region when activated,
Control of Respiration


Voluntary control of breathing: Allows us to
hold out breath when needed.
Involuntary control of breathing: Once the
carbon dioxide & hydrogen waste products build
up in the body, the inspiratory center will be
strongly stimulated and breathing will be forced
to resume.
 Hypothalamus
& limbic systems can alter breathing
patterns during emotional reactions as well, e.g.
laughing or crying.

Air Movements that aren’t breathing:
Yawning, sneezing, coughing, laughing, & crying
– reflexes!
Control of Respiration

Chemoreceptors: Sensory neurons that
respond to chemicals.
 Central
Chemoreceptors: Respond to changes in
the concentration of H+ (hydrogen) & PCO2 (partial
pressure of carbon dioxide) in the cerebrospinal fluid.

Located in the medulla oblongata.
 Peripheral
Chemoreceptors: Respond to changes
in the concentration of H+ (hydrogen) & PCO2 (partial
pressure of carbon dioxide) in the blood stream.

Located in the aortic bodies as clusters along the wall of the
arch of the aorta, & in the carotid bodies along the walls of
the left & right common carotid arteries.
Control of Respiration

Negative Feedback System: System that
attempts to keep the level of some given
molecule as close to homeostasis as possible.
 As
PCO2 increases, pH decreases, triggering the
peripheral chemoreceptors.
 The peripheral chemoreceptors trigger the inspiratory
area to increase the rate & depth of breathing.
 Hyperventilation: The inhalation of more O2 and
exhalation of more CO2 that occurs via deep, rapid
breathing until the PO2 and pH return to normal.

Typically triggered by panic or anxiety.
Control of Respiration

Hypercapnia aka Hypercarbia: When
arterial PCO2 is lower than normal.
 When
this occurs, the chemoreceptors are not
stimulated, so the inspiratory area is not
triggered until CO2 accumulates.
Other Factors Influencing Breathing






Limbic System Stimulation: Anticipation of activities or emotional
anxiety will stimulate the limbic system, which in turn stimulates the
inspiratory center.
Temperature: An increase in body temperature increases the
respiration rate, while a drop in body temperature decreases the
respiratory rate.
Pain: Visceral pain (abdominal) will slow breathing, somatic pain
(limbs) will increase breathing, and sudden, severe pain will cause
brief apnea (halting the breathing process).
Stretching of the Anal Sphincter Muscle: Increases the rate of
respiration, particularly in newborns.
Irritation of the Airways: Can cause the cessation of breathing,
followed by a cough or sneeze to reduce the irritant.
Blood Pressure: A rise in blood pressure will decrease the
breathing rate, while a drop in blood pressure will increase the
breathing rate.