Human Physiology Exam 3

Respiration and Renal

Ventilation

Transport of gases

Diffusion (1)

across a barrier due to partial pressures (between lungs and blood)

Circulation

transport of blood between tissues and lungs

Diffusion (2)

of gases between blood and tissues

How do gases diffuse?

By differences in partial pressures

What is true about the delivery of blood and oxygen?

They are delivered at the same rate

What gases are exchanged by the capillaries and the alveoli?

Oxygen is passed to the blood, and Carbon Dioxide is passed to the alveoli by diffusion

Where else does Carbon dioxide get exchanged with oxygen?

In cells, oxygen diffuses from the blood and is exchanged with the carbon dioxide produced by cell metabolism

What holds open the largest airways?

The skeleton

What is the airway in your throat?

The larynx

What is the larynx held open by?

C-shaped cartilages connected by ligaments and smooth muscle

What is the opening of the larynx called and what is it protected by?

The glottis and it is protected by the epiglottis

What airway follows the larynx?

The trachea

What does the trachea split into?

The left and right bronchus

What do the bronchus turn into and what is different at this level?

The bronchioles and they have no cartilage structure

What type of bronchiole does the most gas exchange occur?

The terminal bronchioles, and the exchange occurs in the alveoli

What is the shape of alveoli?

NOT spherical, they are polyhedral shapes

What is true about all alveoli even of different origin?

They are all interconnected, so if one stretches they all stretch.

Losing what aspect of alveoli makes deep breathing difficult?

The elasticity (decreases the amount of stretch, and therefore cannot increase volume as much)

What is true about the membrane of the lung?

It is a plural membrane

What is the outer plural membrane called?

The parietal plural membrane

What is the inner plural membrane called?

The visceral plural membrane

What is the space between the plural membranes called?

The intraplural space (filled with intraplural liquid)

What are the ribs constantly doing?

They are always pulling out on the lungs (expanding)

What are the alveoli always doing?

They are always pulling in on the lungs

What constantly keeps the tension between the two membranes so that the lungs keep its shape?

The intraplural fluid (think wet dish analogy)

What are the muscles between the ribs?

The intercostals

On what basis does gas does air move in an out?

Gas Laws (Boyle’s Law: P1V1=P2V2)

What is the first step of inhalation mechanics

The diaphragm contracts, pulling down (intercostals contract as well in deep breaths)

What is the second step of inhalation mechanics

increase of thoracic volume (increase of alveolar volume and the pressure in the alveoli becomes sub atmospheric)

What is the third step of inhalation mechanics

Air rushes in because of pressure difference (Palv < Patm)

What is the first step of exhalation mechanics?

Relaxation of the diaphragm (usually all thats needed)
Abdominals will also contract during exercise to further push diaphragm up

What is the second step of exhalation mechanics?

A decrease in alveolar volume, increasing alveolar pressure to supra atmospheric

What is the third step of exhalation mechanics?

Air rushes out due to pressure difference (Palv>Patm)

Airflow Equation

V= ∆P(atm-alv)r^4pi/(viscosity)L8

What is true about Patm and Palv at the ebnd of wither inhalation or exhalatian

Patm=Palv

What do obstructive pathologies do?

Reduce radius of airways, increasing resistance
Breathing work is increased
Lung volumes are normal but the rate of breathing is not, CO2 builds up

What do restrictive pathologies do?

Reduce ability to produce a change in pressure (elasticity of alveoli decreases)
Lung volume decreases

How many mL of air in in a tidal volume?

450mL

How much air actually enters the lungs?

350mL

What is the leftover air called?

dead space

What is there always some of in the lungs?

CO2

Ventilation equation

V=f(breath/min) x Vt(liters/breath) (Vt=tidal volume)

Ventilation Equation in Alveoli

Va= f x (Vt-Vd) (Vd=dead space)

Compliance of lungs Equation

Compliance= ∆lung volume/∆presssure (Palv-Pip)

What lines all alveoli?

Pneumocyte I

Why can water be present in alveoli?

Pneumocyte II produces surfactant which interferes with the hydrogen binding of water, not allowing it to form droplets.

What occurs in drowning?

The surfactant in the lungs is washed out and water fills the alveoli
When this is done by freshwater, the pneumocytes explode due to the lack of salt

The partial pressure of a gas is determined by:

Barometric Pressure (BP) x percentage of the gas in the air (Fx)

As atmospheric pressure drops:

So does PO2 (high altitudes)

Gas Exchange Equation

Mgas=-DA(∆Pgas/L)

Mgas

Flux of gas

D

Diffusion Constant

A

Surface Area

∆Pgas

Pgas(alv)-Pgas(capillary)

L

Path length gas travels

∆Pgas/L

Diffusion gradient

PO2 in alveoli

100mmHg

PO2 in capillary

40mmHg

How does Illness affect gas exchange?

Bacteria makes the body react allowing capillaries to diffuse more, filling alveoli with liquid

L increases, SA decreases, D decreases, O2 to the blood decreases

Medicines or an increases in PO2 entering the body can fix this

Alveolar Gas Equation

PO2(alv)=FlO2(BP-PH2O)-(PCO2(alv)/R)

PO2(alv)

Alveolar Oxygen Partial Pressure

FlO2

Fractional Concentration of inspired oxygen

BP

Barometric Pressure

PH2O

Vapor Pressure of water at 37ºC

PCO2(alv)

Alveolar Partial Pressure of CO2

R

Respiratory Exchange ratio (VCO2/VO2)

Arterial Blood Partial Pressures

PO2= 100mmHg

PCO2= 40mmHg

Veinous Blood Partial Pressures

PO2= 40mmHg

PCO2= 46mmHg

(same in skeletal muscle)

Why do we need hemoglobin?

O2 has poor solubility in water, so it can not be transported by plasma, but hemoglobin can reversibly bind to O2

Hematocrit

55-63% plasma
1% white blood cells (when healthy)
37-45% red blood cells

What should hemoglobin content always be above?

10mg/dl

What is true about hemoglobin content at higher altittudes?

There is more present in the blood in order to transport more oxygen (20mg/dl)

What happens when hemoglobin content starts to drop towards 10mg/dl?

The kidney releases EPO, increasing red blood cell synthesis (athletes use this to their advantage by training at higher altitudes)

What does CO2 levels direct affect in blood?

pH levels (CO2+H2O—> H2CO3—→H+ + HCO3- —> H+ + CO3(2-))

How is CO2 found in blood?

60-80% as HCO3-

11-30% as CO3(2-)

7-10% as CO2(aq)

Polycythemia

More red blood cells/hemoglobin found than expected (normal at high altitudes)

Anemia

Less red blood cells/hemoglobin found than expected (feel faint and exercise intolerant)

Peripheral Chemoreceptors (in corroded artery)

Manage PO2 (if it goes below 60mmHg)

Manages PCO2 (If it is ±5 from 40mmHg)

Manages pH (if out of range of 7.35-7.45)

Central Chemoreceptors (in brain)

Manages PCO2 (becasue of its affect on pH)

If PO2 < 60mmHg

Chemoreceptor signals to brain, which then signals to the diaphragm to increase tidal volume and breath rate, decreasing CO2

If PCO2 is ±5 from 40

Brain signals for a deep breath (there are many receptors for this to keep pH under control because our body always has CO2)

How much of total body water is intracellular fluid?

2/3

How much of the extracellular fluid is interstitial fluid?

75%

How much of the extracellular fluid is interstitial fluid?

75%

Why do IV drugs impact everywhere almost instantaneously but not the brain?

The plasma is carrying the drug and the brain is resistant to excess fluid, so where the plasma has already rushed the drug everywhere else, the brain is receiving it slowly

What manages body fluid?

The renal system

What are the four symptoms in an inflammatory response? (caused because of fluid flowing in)

Red, heat, pain and swelling

What are the primary roles of the renal system?

Regulate body water concentration

Regulate inorganic ion concentrations

Long-term management of acid/base levels

What are the less primary roles of the renal system?

Excrete water soluble wastes and xenobiotics

Gluconeogenesis
Endocrine: Long term MAP management, hematocrit management

What are “The Players” of the renal system?

Paired kidneys

Paired ureters

Urinary bladder

Urethra

How do fluids enter the body?

Drinking, eating

How does fluid release from the body?

Breathing
Urine (managed)
Sweat
Vomit
Hemorrhage
Stool
Crying

What does the bladder do when full?

Contracts rhythmically (done by the detrusor muscle) and the internal sphincter dilates (controlled by sympathetic)

What has to be voluntarily dilated in order to release urine?

The external sphincter (controlled by a somatic nerve)

What is the relationship between the strength of detrusor contractions and the volume of the bladder?

The fuller the bladder, the harder the contractions

Urine Contents

WATER (Na+, Cl-, K+, HCO-, H+, Ca2+)

Urea

Uric acid

NH3

Creatinine

Xenobiotics

How do the kidneys get their blood?

Renal Artery feeds it 1L/min (also has a direct veinous connection)