# exercise & the respiratory system

## 65 terms

### why do we need the respiratory system?

bring good air in
-need O2; brings O2 into body, CV system gets it to the tissues & tissues use O2 plus nutrients to make energy in the form of ATP --- no O2 to tissues = no energy = death
-as humans make energy from O2 they create CO2 which MUST be removed from the body. an accumulation of CO2 creates an acidic internal environment, crippling the tissues ability to make energy --- too much CO2 in tissues = no energy = death

### respiratory gas transport

the transport of oxygen and carbon dioxide via the bloodstream

### pulmonary or external respiration

ventilation (breathing) and the exchange of gases (O2 & CO2) in the lungs between alveoli and blood

### cellular or internal respiration

the gas exchange between blood and tissue cells and relates to O2 utilization and CO2 production by the tissues

### ventilation

the mechanical process of moving air into and out of lungs

### diffusion

the random movement of molecules from an area of high concentration to an area of low concentration

### Boyle's Law

states that the pressure of a gas sample is indirectly proportional to the volume of the sample
-an inverse relationship
-as volume increases, pressure decreases
(high volume = low pressure; low volume = high pressure)
-air will typically go to where there is a greater volume, lower pressure

P1V1 = P2V2

### Dalton's Law

the total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently
-sum of Partial Pressures

### Partial Pressure

= total pressure x fraction of gas
(in mm Hg)

*think of it as "pushing pressure" - an amount of force that pushes a gas across a membrane... higher [this] = higher diffusion of gas

### Fick's Law of Diffusion

the rate of gas transfer (V gas) is proportional to the tissue area (A), the diffusion coefficient of gas(D), and the difference in the partial pressure of the gas on the two sides of the tissue, and inversely proportional to the thickness (T)

Vgas = (A/T) x D x (P1-P2)

### function of the respiratory system

-brings the atmospheric gases into and waste gases out of the body
-oversees gas exchanges between the blood and external environment
-exchange of gasses takes place w/i the lungs in the alveoli
-passageways to the lunges filter/purify, warm, and humidify the incoming air thereby protecting the delicate alveoli

### parts of the respiratory system

conducting zone = the air passageways or tubes
-nose, pharynx, larynx, trachea, bronchi & bronchioles ending at the terminal bronchiole

respiratory zone = functional lung tissue - the lungs
-respiratory bronchiole, alveolar ducts, alveoli

### nose & mouth

-entrances into the body lined with mucus membrane
-the nose and nasal cavity serves to filer, humidify, and warm the air as it comes in
-the mouth is recruited as the demand for larger volumes of air occurs

### pharynx

-lined with mucus membrane
-connects the nasal and oral cavities
-used by food, liquid & air

### larynx

-voicebox, contains vocal chords
-directs the food and liquid down the esophagus
-directs air into the trachea

### bronchial trees

consists of:
-trachea
-primary bronchi
-secondary bronchi
-tertiary bronchi
-bronchioles
-terminal bronchiole

### trachea (windpipe)

-fairly rigid walls reinforced with C-shaped rings of hyaline catrilage to prevent collapse of the "tube" during strong, rapid inhalation. also allows neck to bend
-lined with a ciliated mucus membrane which traps inhaled dust and particulate matter and then sweeps it up to the larynx to be swallowed to spit out

### bronchi

-the initial large tubes that branch off the trachea
-total of 23 branches
-as branches increase, the amounts of cartilage decreases

### bronchioles

-bronchi under 1 mm in diameter
-no cartilage or ciliated mucus membrane
-increase in elastic tissue and smooth muscle
-terminal bronchiole = last air passageway

### end of air passageways and beginning of functional lung tissue

-the last of the tubes bringing air to the lungs is the terminal bronchiole
--it is not the last bronchiole, only the last one which is NOT able to exchange gas
-the last bronchiole is the respiratory bronchiole which marks the beginning of the functional lung tissue & where gases are exchanged with the bloodstream

### lungs

-serve as an interface b/w air and the blood w/i the CV system -- site of gas exchange
-occupy most of the thoracic cavity
--apex is near the clavicle
--base rests on the diaphragm
-each one is divided into lobes by fissures
--left = two lobes (only 2 b/c <3 is taking up part of the room in left side of thor. cavity)
--right = 3 lobes
-covered by a fluid filled sac - the pleura

### alveoli

-thin, squashed or flat cells ( squamous epithelial layer) form the wall
-pulmonary capillaries cover the surface
-thin walls of both [this] and the capillaries allow for the easy diffusion of gases
-over 300 million; spreading them all out in a thin layer would cover half a tennis court ~ 70m^2
- when you smoke, this is what you are killing

### pleura

-coverings of the lungs
-pulmonary (visceral) pleura covers the lungs surface
-parietal pleura lines the walls of the thoracic cavity
--b/w the two layers is the pleural space
--pleural fluid fills the area b/w the laters
---allows for sliding or gliding of lung tissue over thoracic wall
--- critical in allowing the expansion of the lungs so air can move in

### pulmonary ventilation

-completely mechanical process
-depends on volume changes in the thoracic cavity - Boyle's law
-volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure
-two phases to breathing -- inspiration (flow into lungs) & expiration (air leaving lung)

### inspiration

-when a person is at rest, the diaphragm and external intercostal muscles contract
--disphragm contracts and moves down
--ext. intercostal muscles contract and lift rib cage up
-both actions increase the size of the thoracic cavity therefore, by Boyle's Law, as volume goes up pressure goes up
-lower pressure in the lungs compared to outside the mouth and nose, so external air is pulled into the lungs due to an increase in intrapulmonary volume and pressure gradient created (ext air pulled into lungs b/c pressure inside the lungs < outside moth/nose)
-with exs or resp. distress, the scalene and sternocleidomastoid muscles are recruited to further lift the rib cage
-[this] is "active", meaning muscles contract and energy is used

### expiration

-at rest, largely a passive process which depends on natural lung elasticity and the relaxing of the inspiratory muscles
-diaphragm relaxes and moves upward; rib cage sinks downward
-as muscles relax, volume decreases so by Boyle's Law, pressure goes up and air is pushed out of the lungs

### forced expiration

- occurs by contracting internal intercostal muscles to depress the rib cage
-abdominal muscles also contract to push the contents of the abdominal cavity up, thereby pushing the diaphragm up further
--both actions increase the size of the thoracic cavity. therefore, by Boyle's law, as volume goes down pressure goes up
-higher pressure in the lungs compared to outside the mouth/nose causes air to move out of lungs

### pressure difference in thoracic cavity

-normal pressure within the pleural space is always negative
-pressure within the pleural space is called intrapleural pressure
-differences in lung and pleural space pressures keep lungs form collapsing
-a collapsed lung is due to the loss of the negative intrapleural pressure

### input to the resp. contol centers

-central chemoreceptors
- peripheral chemoreceptors
-neural input -- from motor cortex or skeletal muscle

### central chemoreceptors

-located in medulla
-sensitive to PCO2 & H+ concentration in cerebrospinal fluid

### peripheral chemoreceptors

-found in the aortic and carotid bodies
-sensitive to PO2, PCO2, H+, and K+ in blood

### factors influencing respiratory rate and depth

-physical factors
-volition (conscious control)
-emotional factors
-chemical factors

### physical factors influencing resp. rate & depth

-increased body temp
-talking
-exercise
-coughing

### chemical factors influencing resp. rate & depth

oxygen levels
-changes in O2 concentration in the blood are detected by chemoreceptors in the aorta and carotid artery
-information is sent to the medulla oblongata

Carbon dioxide levels
-level of CO2 in the blood is the main regulatory chemical for respiration
-increased carbon dioxide increases respiration
-changes in CO2 act directly on the medulla oblongata

CO2 levels are a strong stimulus to breath than O2 levels

### neural regulation of respiration

-activity of respiratory muscles is transmitted to the brain by the phrenic and intercostal nerves
-neural centers that control rate and depth are located in the medulla
-the pons appears to smooth out respiratory rate

### eupnea

normal respiratory rate
12-15 respirations per minute

### hypernea

increased respiratory rate often due to demand for extra oxygen

### respiratory volume and capacities

-many factors that affect it:
--a person's size, age, sex, physical condition
-measured by spirometry
-normal resting breathing moves about 500 to 1000 ml of air with each breath

### tidal volume (TD or Vt)

the air moved in and out wit each breath
-will vary

### vital capacity (VC)

the maximum amount of air that can be expired following a maximum inspiration
total volume of air one can move in and out of te lungs
-will always be te same
=TV + IRV +ERV

### Residual Volume (RV)

the air remaining in the lungs after a maximum expiration
-after exhalation, about 1200 ml of air remains in lungs

### inspiratory reserve volume (IRV)

the amount of air that can be taken in forcibly over the tidal volume
-as TV increases, [this] decreases because it is a volume held in reserve to increase inspiratory volume
-usually between 2100 & 3200 ml

### expiratory reserve volume (ERV)

the amount of air tat can be forcibly exhaled
-as TV increases [this] decreases because it is a volume held in reserve to increase expiratory volume
-approx. 1200 ml

### total lung capacity (TLC)

the total amount of air the lungs can hold and equals the sum of VC & RV

### functional residual capacity (FRC)

the amount of air left in the lungs after a normal tidal volume expiration
-an important diagnostic tool

### respiratory cycle

one inhalation and one expiration

### pulmonary ventilation

-the amount of air moved in or out of the lungs per minute
-can be found by multiplying the frequency or rate of breathing (f) over one minute by the volume of air in or out of the lungs per breath (Vt)
=Vt x f

air that remains in conduction zone and never reaches alveoli

"unused" ventilation
-does not participate in gas exchange

### functional volume

-air that actually reaches the respiratory zone
--if Vt is 500 ml and Vd is 150 then about 350 ml is [this]. this increases with increased tidal volume or decreases if dead space increases

### alveolar ventilation (Va)

volume of inspired gas tat reaches the respiratory zone
-the functional volume

### pulmonary diffusion

-the process by which gases are exchanged across the respiratory membrane in the alveoli to the blood and vice-versa
--aka external respiration
-amount of gas exchange depends on the partial pressure of each gas
-gases diffuse along a pressure gradient, moving from an area of higher pressure to lower pressure following the Law of Diffusion

### respiratory membrane (air-blood barrier)

-thin squamous epithelial layer lining alveolar walls
-pulmonary capillaries cover external surfaces of alveoli

### external respiration

oxygen movement into the blood
-the alveoli always has more O2 than the blood
-O2 moves by diffusion towards the area of lower concentration
-pulmonary capillary blood gains oxygen
carbon dioxide movement out of blood
-blood returning from tissues as higher concentrations of CO2 than air in the alveoli
-pulmonary capillary blood gives up CO2
blood leaving the lungs is oxygen-rich and carbon dioxide-poor

### internal respiration

exchange of gases b/w blood and body's cells

an opposite reaction to what occurs in the lungs
-CO2 diffuses out of tissues to blood
-O2 diffuses from blood into tissues
-both do so down their concentration gradient

### oxygen transport in the blood

inside red blood cells attached to hemoglobin (oxyhemoglobin [HbO2]
~97% of oxygen carried in the blood this way
a small amount is carried dissolved in the plasma
~3% of oxygen is carried this way

### carbon dioxide transport in the blood

most is transported in the plasma as bicarbonate ion (HCO3-)
~67% is transported in this manner
chemically bound to Hb
~25% but at different binding sites than O2
a small amount is carried dissolved is plasma
~8%

### factors affecting oxygen uptake and delivery

-oxygen content of blood
-amount of blood flow
-local conditions within the muscle

-hemoglobin concentration largely determines the oxygen-carrying capacity of blood
-training affects oxygen transport in muscle

### oxygen transport with exercise

-Co2 levels increase
-temperature increases
-lactic acidic levels increase = increased [H+] = decreased pH
-more ATP is needed and made anaerobically resulting in more 2,3 DPG

-any or all of these scenariors allow more oxygen to be unloaded at the tissues. this is the Bohr effect
-if the reverse happens, one or all of them decreases then there would be less unloading at the tissues. this is Haldene effect

### O2-Hb dissociation curve: 2-3 DPG

-RBC must rely on anaerobic glycolysis to meet the cells energy demands
- a by-product is 2-3 DPG, which can combine with hemoglobin and reduce Hb's affinity of O2
- 2-3 DPG increase during exposure to altitude
-at sea level, right shift of curve no to changes in 2-3 DPg, but to degree of acidosis and blood temp

### O2 transport in muscle

-myoglobin (Mb) shuttles O2 from the cell membrane to the mitochondrira
-high affinity for O2 than Hb
--even at low PO2
-- Allows Mb to store O2

### arterial - venous oxygen difference

-the increase in (a-v)O2 difference during strenuous exercise reflects increased O2 use by muscle cells., this use increases O2 removal from arterial blood, resulting in a decreased venous oxygen concentration
-if blood flow through the tissues is already at max, then this is the only way to get more O2 delivered to the tissue
-for people with a compromised heart, they rely on a-v O2 difference to allow them to move

### blood flow to the lungs

-when standing, most of the blood flow is to the base of the lung
--due to gravitational force

### ventilatory breakpoint

-the point during intense exercise at which ventilation increases disproportionately to the oxygen consumption
-when work rate exceeds 70% VO2max, energy must be derived from glycolysis
-glycolysis increases CO2 levels, which triggers a respiratory response and increased ventilation

### ventilatory threshold

-point during intense exercise at which metabolism becomes anaerobic
-reflects the lactate threshold under most conditions, though the relationship is not always exact
-identified by nothing an increase in Ve/VO2 without a concomitant increase in the ventilatory equivalent for carbon dioxide