Lab 8: The Respiratory System

sequence of inhalation

1. inspiratory muscles contract (diaphragm descends; rib cage rises)

2. thoracic cavity volume increases

3. lungs are stretched; intrapulmonary volume increases

4. intrapulmonary pressure drops

5. air flows into lungs down its pressure gradients until intrapulmonary pressure is 0 (= to atmospheric pressure)

during inhalation (ribs + sternum)

ribs are elevated and sternum flares as external intercostals contract

during inspiration (diaphragm)

diaphragm moves inferiorly during contraction

during inspiration (external intercostals)

external intercostals contract

pressure and volume relationship

pressure is inversely proportional to volume

bucket handle effect

1. ribs and sternum elevate due to contraction of external intercostal muscles

2. increases both width and depth of thoracic cavity

3. effect is to increase volume of thoracic cavity

inhalation is…

active

exhalation is…

passive, but can become active during exercise

sequence of events in exhalation

1. inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages)

2. thoracic cavity volume decreases

3. elastic lungs recoil passively; intrapulmonary volume decreases

4. intrapulmonary pressure rises

5. air flows out of lungs down its pressure gradient until intrapulmonary pressure is 0

during exhalation (ribs + sternum)

ribs and sternum are depressed as external intercostals relax

during exhalation (diaphragm)

diaphragm moves superiorly as it relaxes

during exhalation (external intercostals)

external intercostals relax

exhalation during exercise

becomes active; abdominal muscles and internal intercostals contract and force air out of lungs

bainbridge effect

1. during inhalation, thoracic pressure decreases (because volume increases)

2. venous blood return to heart increases as abdominal pressure is greater than thoracic pressure

3. pressure in right atria increases due to more blood

4. atrial stretch receptors signal this to SA node and medulla oblongata

5. increased efferent sympathetic signals to SA node increase HR during inhalation

tidal volume (TV)

amount of air inspired during normal released breathing

Inspiratory Reserve Volume (IRV)

the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume

Expiratory Reserve Volume (ERV)

the additional air that can be forcibly exhaled after the expiration of a normal tidal volume

Residual Volume (RV)

the volume of air still remaining in the lungs after the expiratory reserve volume is exhaled

Total Lung Capacity (TLC)

the maximum amount of air that can fill the lungs

TLC equation

TV+IRV+ERV+RV

Vital Capacity (VC)

the total amount of air that can be expired after fully inhaling

VC equation

TV+IRV+ERV

basic respiratory waveforms =

volumes

respiratory capacities =

sum of 2 or more respiratory volumes

functional residual capacity (FRC)

the amount of air remaining in the lungs after a normal expiration

FRC equation

RV + ERV

inspiratory capacity (IC)

the maximum amount of air that can be inspired

IC equation

TV + IRV

minute ventilation

total volume of gas that flows into our out of respiratory tract in 1 minute to give you a flow rate

normal MVV at rest

6 L/min eupnea

eupnea

normal breathing

normal MVV with exercise

up to 200 L/min

cellular respiration

produces CO2

bicarbonate buffering system characteristics

1. occurs in RBCs

2. maintains blood pH level

3. enzyme carbonic anhydrase

bicarbonate buffering system—pH too high

1. HCO3- is created in systemic capillaries

2. HCO3- diffuses from RBCs into plasma

3. HCO3- combines with H+ to form H2CO3

bicarbonate buffering system—pH too low

H2CO3 dissociates to release H+

hyperventilation

increased depth and rate of breathing that exceeds body’s need to remove CO2

effects of hyperventilation

1. hypocapnia + alkalosis

2. cerebral vasoconstriction + ischemia

hypocapnia

decreased blood CO2 levels

alkalosis

increased blood plasma pH

treatment for hyperventilation

breathing into paper bag increases CO2 levels

why does hyperventilating not increase O2 levels?

O2 levels do not change much as RBCs are saturated

composition of air inhaled

1. 21% O2

2. 0.04% CO2

3. 78-79% N2

4. Other gases (argon, etc) less than 1%

composition of air exhaled

1. 16% O2

2. 4-5% CO2

3. 78-79% N2

4. Other gases (argon, etc) less than 1%

hypoventilation

decreased depth and rate of breathing that does not meet the body’s need to remove CO2

effects of hypoventilation

1. hypercapnia

2. acidosis

3. hypoxia

4. stimulate respiratory control centers

hypercapnia

increased blood CO2

acidosis

decrease in blood plasma pH

hypoxia

drop in O2 levels

increase in H+, CO2, and/or big decrease in O2…

stimulate central and peripheral chemoreceptors that send afferent signals to DRG to increase minute ventilation

decrease in H+, CO2, and/or increase in O2…

silences chemoreceptors. DRG influence on VRG is lessened and minute ventilation decreases

pontine respiratory centers

interact with the medulla respiratory centers to smooth the respiratory pattern

ventral respiratory group (VRG)

contains rhythm generators whose output drives respiration

dorsal respiratory group (DRG)

integrates peripheral sensory input and modifies the rhythms generated by the VRGs

phrenic nerves (C3, C4, C5)

innervates the diaphragm

spirometry/forced expiratory volume tests distinguish between…

1. obstructive pulmonary diseases

2. restrictive lung diseases

obstructive pulmonary diseases

1. increased airway resistance

2. traps air

3. asthma, bronchitis

4. FRC and RV increase due to hyperinflation of lungs

5. normal overall volume

6. reduced flow rate

restrictive lung diseases

1. reduced total lung capacity

2. due to disease (tuberculosis), posture (kyphosis), or damage from lung toxins (fibrosis)

3. thoracic cavity small or lungs unable to expand

4. VC, TLC, FRC, RV decline

5. reduced volume

6. normal or increased flow rate

diameter of airways affects…

flow rates, not the volume of air you can fit in your lungs

pulmonary ventilation

1. air is inhaled through the nasal and oral cavities

2. air moves through pharynx, larynx, and trachea into lungs

3. then it is exhaled, flowing back through the same pathway

internal respiration

bloodstream delivers O2 to cells and removes CO2

respiratory system anatomy

nasal cavity

composed of the chambers of the internal nose that are apart of upper respiratory system

laryngopharynx

1. most posterior part of pharynx

2. shared by respiratory + digestive systems

3. front merges with larynx

trachea

conveys air between upper and lower respiratory structures

nasopharynx

1. airway of upper respiratory system

2. always open

lungs

two organs responsible for gas exchange

primary bronchi

major airways of the lower respiratory system

alveoli

major sites of gas exchange, where O2 is brought into the bloodstream and CO2 is removed

oropharynx

1. shared by respiratory + digestive

2. airway in upper respiratory

bronchi

1. major airways in lower respiratory system

2. link trachea with R and L lungs

3. wrapped in rings of hyaline cartilage

4. interiors lined with mucous membrane

minute ventilation equation

tidal volume x respiratory rate

forced expiratory volume

measures the max amount of air you can forcefully exhale in the 1st second of a full breath

tidal volume and exercise

increases significantly

reserve volume (IRV and ERV) and exercise

decrease

vital capacity and exercise

stays the same

which lung volume remains in the lungs after someone has exhaled all the air they can exhale?

residual volume