Respiratory System Chapter 21

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Respiratory gas equilibrium

- PO2 and PCO2 are stable in the alveoli and tissues - Equilibrium disrupted when tissue oxygen demand increases •Respiratory rate and tidal volume must increase •Without that increase, alveolar PO2 levels decrease, and alveolar, blood, and tissue PCO2 levels increase -Can lead to hypoxia and dangerous drop in pH

Level 1: Respiratory rhythmicity centers

-most basic control -pacemaker cells in medulla oblongata generate cycles of contractions in diaphragm -paired respiratory rhythmicity centers establish pace of respiration by adjusting pacemaker cells and coordinating other respiratory muscles • Each center subdivided into two groups: 1. Dorsal respiratory group (DRG): • Chemoreceptors detecting O2, CO2, and pH levels in blood/CSF • Baroreceptors - stretch receptors; monitor stretch of lung wall • Mainly concerned with inspiration • Inspiratory center of DRG controls lower motor neurons to primary inspiratory muscles (external intercostals, diaphragm) 2. Ventral respiratory group (VRG) • Mainly associated with expiration • Functions only when breathing demands increase and accessory respiratory muscles are involved

Carbon dioxide transport in blood

1. Dissolved in plasma (~7%) 2. Enters RBCs and is bound to Hb (~23%) • HbCO2 or carbaminohemoglobin 3. Enters RBCs and is converted to bicarbonate ion (~70%) • Reversible reaction catalyzed by carbonic anhydrase • CO2 + H2O → H2CO3 → HCO3- + H+ • HCO3- exchanged out of cell with Cl- (chloride shift) • H+ binds to Hb, forming HbH+ (which acts as pH buffer)

During quiet breathing...

Active inhalation via inspiratory muscles, Passive exhalation—done by elastic recoil of tissues and gravity, NO EXPIRATORY MUSCLES

stimuli that trigger respiratory reflexes

Chemoreceptors, baroreceptors, stretch receptors, irritating physical or chemical stimuli

Lower respiratory system does....

Conducts air to and from gas exchange surfaces

When are Accessory inspiratory muscles activated to assist primary inspiratory muscles?

EX. Running, to increase speed/amount of rib movement to move more air when needed

What is external respiration?

Exchange of gases between interstitial fluids and external environment, Includes pulmonary ventilation (breathing), alveolar ventilation (movement of air into and out of alveoli)

upper respiratory system does....

Filters, warms, and humidifies incoming air Protects delicate lower tract Reabsorbs heat and water in outgoing air

Temperature affects hemoglobin saturation

Higher temp: Hb to release oxygen more readily Especially important in active tissues (generate heat)

Superior movement of the rib cage

Increases the depth and width of the thoracic cavity, increasing its volume and decreasing pressure within it

Vital Capacity (VC)

Maximum amount of air you can move in or out of lungs per cycle, ERV + VT + IRV

Pulmonary ventilation must be closely regulated to....

Meet tissue oxygen demands

upper repsiratory system consists of

Nose, nasal cavity, paranasal sinuses, pharynx

What is internal respiration?

Oxygen absorption and carbon dioxide production by tissue cells

Which of the following events would you predict as carbon dioxide is released from your muscles into the surrounding capillary bed?

Oxygen delivery to muscle is increased when more carbon dioxide is produced by the muscle.

What is the relationship between the pressures at label "8"?

P outside < P inside

In internal respiration, in arriving oxygenated blood, CARBON DIOXIDE...

PCO2 - 40 In normal interstitial fluid: PCO2 = 45 Carbon dioxide diffuses into blood from tissues

In external respiration, In arriving deoxygenated blood, CARBON DIOXIDE...

PCO2 = 45 In alveoli : PCO2 = 40 Carbon dioxide diffuses into alveoli from blood

In external respiration, In arriving deoxygenated blood, OXYGEN....

PO2 = 40 In alveoli: pCO2 = 100 Oxygen diffuses into the blood from alveoli

In internal repsiration, in arriving oxygenated blood, OXYGEN..

PO2 = 95 In normal interstitial fluid: PO2 = 40 oxygen diffuses into the tissues from blood

Blood pH directly affects hemoglobin saturation (Bohr effect)

Ph decrease: saturation curve shifts right Ph increase: saturation curve shifts left

During start of a breath, no air movement occurs

Pressure outside = Pressure inside

The following is a list of some airways. 1. secondary bronchus 2. bronchioles 3. alveolar ducts 4. primary bronchus 5. respiratory bronchiole 6. alveoli 7. terminal bronchiole The order in which air passes through is

Primary bronchus, Secondary Bronchus, Bronchioles, Terminal Bronchiole, respiratory bronchiole, alveolar ducts, alveoli (4, 1, 2, 7, 5, 3, 6.)

Bronchioles have....

Thick layers of smooth muscle that allow for bronchoconstriction (asthma) and bronchodiliation

During exhalation

Thoracic cavity decreases (dec volume) Pressure outside < Pressure inside Air is forced out from an area of high pressure to low pressure Intrapulmonary pressure > atmospheric pressure

During inhalation

Thoracic cavity enlarges (inc volume) Pressure outside > pressure inside Air moves in from an area of high pressure to low pressure Intrapulmonary pressure < atmospheric pressure

Total Lung Capacity (TLC)

Total volume of lungs, averages 6000ml in adult males and 4200ml in adult females, VC + RV

What are the characteristics of Pneumocytes Type I in alveolar structure and what is their primary function? a) Thick and robust, involved in gas exchange b) Thin and delicate, sites of gas diffusion c) Secretory cells producing surfactant d) Immune cells responsible for phagocytosis

b) Thin and delicate, sites of gas diffusion

Most of the carbon dioxide in the blood is transported as

bicarbonate ions in the plasma

Boyle's Law of Gases states that

if the volume goes up, the pressure goes down.

Dalton law

in a mixed gas, each individual gas contributes its individual pressure (partial pressure) toward total pressure of the gas mixture

In quiet breathing,

inspiration involves muscular contractions and expiration is passive

When the diaphragm contracts and moves inferiorly

it increases the volume of the thoracic cavity, decreasing pressure within (change in volume= change in pressure)

lower respiratory system consists of

larynx, trachea, bronchus, bronchioles, respiratory bronchioles, alveoli

Respirator mucosa does..

lines nasal cavity through large bronchioles

Blood arriving in pulmonary arteries has:

low PO2 and high PCO2 than in alveolar air

What is Anoxia?

no oxygen, Much of damage caused by heart attacks and strokes is is due to this

Respiratory Rate (RR)

number of breaths per minute ~12-18 for resting adults

The glottis is

opening to the larynx

Exhalation is usually a _____ process done by___________ and ______

passive process done by elastic recoil and gravity

pulmonary ventilation is driven by

pressure changes within the pleural cavities

The respiratory mucosa consists of

pseudostratified ciliated columnar epithelium and underlying areolar tissue called LAMINA PROPRIA

The process of respiration that moves air into and out of the lungs is __________.

pulmonary ventilation

Respiratory reflexes provide...

rapid automatic adjustments in pulmonary ventilation

During exhalation, the mucosa....

reabsorbs heat and water; reduces heat loss and water loss to environment

In nasal cavity, veins do what?

release heat to warm inhaled air

2,3-bisphosphoglycerate (BPG)

released by RBCs as they break down glucose for energy Binds to hemoglobin and increases release of oxygen

Terminal bronchioles branch to

respiratory bronchioles

Which of the following can be calculated if the tidal volume and respiratory rate are known?

respiratory minute volume

Henry law

the amount of a particular gas in a solution is directly proportional to its partial pressure (at set temperature)

Inspiratory Capacity (IC)

the volume of air inhaled after a normal exhale (TV+IRV)

If a patient being tested inhales as deeply as possible and then exhales as much as possible, the volume of air expelled would be the patient's

vital capacity

The glottis is made of

vocal folds and rima glottidis

What is the tidal volume of the lungs?

volume of air moved into and out of lungs in normal breath

Functional residual capacity (FRC)

volume of air remaining in the lungs after complete quiet cycle, ERV + RV

Accessory expiratory muscles are used

when need to force exhalation (EX blowing up a balloon), Decrease thoracic cavity volume quickly

oxygen-hemoglobin saturation curve

• Graph showing hemoglobin saturation (percentage of heme units bound to oxygen at a given moment) at different partial pressures of oxygen • Has an "S-shape" due the increased hemoglobin affinity for oxygen with each oxygen molecule bound • Areas of the curve with a steep slope have large changes in Hb saturation with small changes in plasma PO2

areolar ventilation (Va)

• Is amount of air reaching alveoli/minute • Some air never reaches alveoli; remains in conducting portion of lungs (= anatomic dead space VD) • At rest, VD averages ~ 150 mL • Is calculated as breaths per minute multiplied by volume of air in the alveoli (tidal volume minus anatomic dead space • VA = f × (VT - VD) • Air reaching alveoli is a mix of "used" air and freshly inhaled air • = Less oxygen in alveolar air compared to atmospheric air

Level 3: Higher Centers

• Located in hypothalamus, limbic system, and cerebral cortex • Can alter activity of pneumotaxic centers • Normal breathing can occur without higher input

The left lung has how many lobes?

2 (superior and inferior) created by oblique fissure

The right lung has how many lobes?

3 lobes (superior, middle, inferior) created by horizontal and oblique figures

Ends of C-shaped tracheal cartilage connected by ELASTIC LIGAMENT and TRACHEALIS MUSCLE do....

Allows expansion of esophagus during swallowing, Allows tracheal constriction (parasympathetic stimulation) or dilation (sympathetic stimulation)

Minimal Volume (MV)

Amount of air in the lungs if they were allowed to collapse, Included in residual volume, Cannot be measured in a healthy person

Residual Volume (RV)

Amount of air remaining in the lungs after a forced exhalation

Expiratory Reserve Volume (ERV)

Amount of air that can be forcefully exhaled after a normal tidal volume exhalation

Inspiratory Reserve Volume (IRV)

Amount of air that can be forcefully inhaled after a normal tidal volume inhalation

Each terminal bronchiole supplies air directly to

a single pulmonary lobule

paranasal sinuses are and do...

air-filled cavities lined with mucous membrane, located in the bones of the skull. Mucus secreted by sinuses helps to moisturize and clean nasal cavity surfaces

Respiratory bronchioles lead to

alveolar ducts, then to alveolar sacs composed of alveoli

What are the three layers of the blood air barrier?

alveolar epithelium, fused basement membrane (alveolar and capillary), capillary epithelium

What is the function of alveolar macrophages in the alveolar structure, and how do they contribute to maintaining lung health? a) They produce oxygen for cellular respiration b) They regulate blood pH levels c) They locate and phagocytize particles that could clog the alveoli d) They secrete surfactant to prevent alveolar collapse

c) They locate and phagocytize particles that could clog the alveoli

Describe the role of Pneumocytes Type II in the alveolar structure, including the substance they secrete and its function. a) They secrete mucus to trap pathogens b) They produce antibodies to fight infections c) They secrete surfactant to reduce surface tension d) They facilitate gas exchange through their thin membranes

c) They secrete surfactant to reduce surface tension

During most daily activities, the human respiration rate is most closely linked to the blood levels of ________.

carbon dioxide

Bronchioles lack what?

cartilaginous support

vestibular folds

close glottis during swallowing, prevent foreign objects

When gas is contained

collisions with container wall cause pressure, More collisions = more pressure, decreasing container volume = even more collisions (pressure)

Two divisions of the respiratory system

conducting (nasal cavity to larger bronchioles) and respiratory (smallest bronchioles to alveoli)

What is hypoxia?

deficiency in the amount of oxygen reaching the tissues, Severely limits metabolic activities

Which of the following is not a function of the nasal mucosa?

dehumidify the incoming air

The hilium

depression in an organ where blood vessels and nerves enter and leave

primary inspiratory muscles include:

diaphragm (~75% of movement & flattens floor of thoracic cavity) and external intercostals (~25% of movement & elevate ribs)

Water from mucus....

evaporates to humidify inhaled air

Bowles Law

for a gas in a closed container and at a constant temperature, pressure (P) is inversely proportional to volume (V); it determines direction of air movement during pulmonary ventilation.

The vocal folds (contain vocal ligaments)

function in voice production (speech); also called the true vocal cords.

A decrease of blood pH from 7.4 to 7.2 causes hemoglobin to ________.

give up more of its oxygen molecules

Hemoglobin (Hb)

• Molecule with four protein subunits that transports 98.5% of oxygen in blood (remaining 1.5% dissolved in plasma) • Each subunit contains one heme unit (containing iron) that can reversibly bind one oxygen molecule • With bound oxygen, is called oxyhemoglobin (HbO2) • Carbon monoxide (CO) is dangerous because it can also irreversibly bind to heme units, making them unavailable for O2 transport

chemorecptor reflexes

• PCO2 is the most important factor influencing respiration • Small changes in PCO2 levels cause large changes in respiratory rate - rise of only 10% in arterial PCO2 doubles respiratory rate; in contrast, PO2 levels have to drop below 60 mm Hg before triggering respiratory centers • Hypercapnia (increased arterial PCO2) • Most commonly caused by hypoventilation • Hypocapnia (decreased arterial PCO2) • Most commonly caused by hyperventilation • Snorkelers sometimes hyperventilate to increase dive time • Oxygen starvation may occur while underwater (= shallow water blackout)

Level 2 Pneumotaxic and Apneustic centers

• Paired nuclei in pons • Adjust the output of the respiratory rhythmicity centers 1. Apneustic centers • Promote inhalation by stimulating DRG • Degree of stimulation adjusted based on sensory information from the vagus nerve about lung inflation 2. Pneumotaxic centers • Inhibit apneustic centers • Promote passive or active exhalation • Increased pneumotaxic output shortens inhalation duration (= faster respiratory rate) • Decreased output slows pace and increases depth of respiration

Respiratory minute volume (Ve)

• Volume of air moved per minute • Equals breaths per minute multiplied by tidal volume • VE = f × VT • Variation in either factor will affect VE and also can affect alveolar ventilation

3 levels of regulation

➢ Level 1: Respiratory rhythmicity centers ➢ Level 2: Apneustic and pneumotaxic centers ➢ Level 3: Higher centers


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