physiology test 3

what are the different types of respiration

1. external respiration

2. cellular respiration

describe external respiration

the movement of gases between the environment and the body’s cells

describe cellular respiration

• what is going on in the mitochondria

• intracellular reactions with oxygen (final electron acceptor) to produce energy in the form of ATP

what are the fundamental requirements for gas exchange

1. moist surface

2. thin barrier

3. large surface area

4. partial pressure gradients

5. ventilation and perfusion

describe a moist surface as a fundamental requirement for gas exchange

• gases must dissolve in water before they can diffuse across membranes

• solubility and how moist the surfaces are

• gas particles have to dissolve into a liquid

describe a thin barrier as a fundamental requirement for gas exchange

• the respiratory surface must be thin to minimize diffusion distance

• fick’s law of diffusion

• easy to pass through and increase rate of diffusion to supply oxygen into the bloodstream at the rate it is needed

describe large surface area as a fundamental requirement for gas exchange

• a greater surface area allows for more efficient gas exchange

• fick’s law of diffusion

describe partial pressure gradients as a fundamental requirement for gas exchange

• gases move from an area of higher partial pressure to lower partial pressure

• pressure dictates diffusion

• Henry’s Law is the actual law behind this

describe ventilation and perfusion as a fundamental requirement for gas exchange

• mechanisms to maintain gradients (e.g. breathing, blood flow)

• bulk flow when brining in air from the atmosphere into our conducting system and then getting it into our bloodstream

what are the four processes in vertebrates that comprise external respiration

1. bulk flow of atmospheric air into and out of the lungs (i.e. ventilation)

2. diffusion of molecules between the air in the lungs and dissolved in the blood

3. CV transport of gases dissolved in the blood using bulk flow

4. diffusion of molecules between those dissolved in the blood and those dissolved in the interstitial fluid and cytosol

describe what is happening in this diagram

1. Oxygen is being inspired from the atmosphere

2. oxygen fills the aveoli

3. oxygen diffuse into the blood stream down a pressure gradient as there is more oxygen in the atmosphere than in the blood stream

4. higher pressure of oxygen in the blood than in the tissues (tissues constantly using up oxygen in the process of respiration)

5. oxygen diffuses into tissues

6. CO2 is produced as a biproduct of respiration

7. CO2 diffuses into the blood stream following the pressure gradient and then into the aveoli

describe the conducting system

• part of the respiratory system not involved in the gas exchange (everything but the alveoli)

• provides a low-resistance pathway for airflow and conditions inspired air

• thick cartilage rings keep the structure fixed and open (so non-collapsible)

• air gets warmed to the temperature of the body, humidified, and filtered here

• total cross-sectional area increases with each division (even though the diameter of the airways gets smaller, they get exponentially more numerous); reduces the velocity of airflow

describe the diameter of the conducting system as it traveled to the aveoli

gets smaller as you go down the conducting zone

describe the cross-sectional area of the conducting system as it travels to the aveoli

• total cross-sectional area increases as the amount increases, with more of the smaller parts

• velocity of air flow allows more time for exchange

describe the aveoli

• microscopic, thin-walled air sacs that are the primary site of gas exchange within the lungs, which facilitate the rapid and efficient exchange of O2 from inhaled air into the blood and CO2 from the blood into the alveolar air for exhalation

• where gas exchange occurs

• want to have a thin membrane for oxygen to enter the bloodstream and CO2 to exit the bloodstream

• capillary beds surround in order to facilitate gas exchange

• lots of moisture and high humidity surrounding the membrane sacs

what are the three important factors of the aveoli

1. large surface area (about the area of a tennis court if you unravel all of it)

2. short diffusion distance (only 1 epithelial cell thick and 80-90% of the external surface is surrounded by capillaries)

3. large concentration gradient (always replenished)

describe type I alveolar cells

involved in gas exchange

describe type II alveolar cell

• aka surfactant cells

• synthesize and secrete surfactant

• decreases surface tension and allows for the expansion

describe how surfactant reduces the surface tension inside alveoli so they require less effort to inflate

• Law of LaPlace: P = 2T/r

• if two bubbles have the same surface tension, the smaller bubble will have the higher pressure according to the law of LaPlace

• surfactant reduces surface tension by H-bonding with surrounding moist areas to help break up the surface tension

• equalize the pressure between the two sizes and make i easy to inflate for gas exchange to occur

describe why premature infants are susceptible to respiratory distress syndrome

• can’t produce surfactant, so everytime they go to exhale, their aveoli collapse and cannot open up again

• surfactant isn’t produced until about 34 weeks when type II alveolar cells become fully mature

• leads to high alveolar surface tension leading to their collapse

• treatment is to use a nebulizer to administer an aerosolized surfactant and ventilation support

describe how lungs expand since they cannot expand on their own

• plueral sac surrounds the lungs and keeps them compartmentalized to a certain extent

• moisture creates a surface tension (negative pressure) because of the liquid nature of the sac that holds the chest wall and lungs together

• anchors the lung to the chest wall because of the moist liquid nature of this sac, it makes it easier to stick to that chest wall

• when the chest wall expands, it’s going to take the lung with it

describe the pleural sac

a two-layered membranous sac that surrounds the lungs and lines the chest cavity which allows the lungs to move easily and inflate when breathing

describe the role of skeletal muscles in ventilation

• change the volume of the thoracic cavity, which alters the pressure in the lungs and creates the pressure gradients for airflow

• skeletal muscles do the work to expand the chest wall and because the pleural sac is stuck to it, it just follows

• the lungs and muscles have opposing forces as the tension is in opposite direction as the chest wall expands outward, the elasticity of the lungs wants to go inward

• external and internal intercostals help expand and contract

how are volume and pressure related

• inversely proportional

• boyle’s law: P1V1=P2V2

• decreasing volume increases collisions and increases pressure (and vice versa)

describe inspiration

• thoracic volume increase (needs to make room so the diaphragm contracts and moves down)

• diaphragm contracts down (give a mechanical boost to the lungs)

• ribs contract outward

• space inside lungs increases

• pressure inside lungs decreases

• pressure inside lungs is less than atmospheric pressure

• air rushes into lungs

describe expiration

• diaphragm relaxes, thoracic volume decreases (diaphragm relaxes and pushes up on the lungs and helping to force out the air)

• diaphragm relaxes up

• ribs relax downward

• elastin causes lungs to shrink

• space inside lungs decreases

• pressure inside lungs increases

• pressure inside lungs is greater than atmospheric pressure

• air rushes out of the lungs

describe the functions of the pleural sac

1. creates a moist slippery surface that reduces friction during ventilation

2. holds lungs tight to the thoracic wall so that when it expands the lungs expand with it

3. uses cohesive forces to hold membranes together so hey move as one

describe intrapleural pressure

• negative pressure inside pleural sac is due to:

  • developmentally created in utero

  • chest wall elasticity

  • elastic recoil of lungs

  • resistance of pleural fluid to being “stretched”

• pressure is opposing direction because of the lungs’ elasticity

• when the rib cage expands, the lungs are going to go with it because its anchored o that pleural sac, but the elasticity of the lungs wants to snap back so that the pressure is the opposing direction

what would happen if the pleural sac were punctured and you tried to breathe

• the lungs cannot properly work and there is a loss of compliance

• the lung will collapse

describe a pneumothorax

• if the sealed pleural cavity is opened to the atmosphere, air flows in

• the bond holding the lung to the chest wall is broken, and the lung collapses, creating air in the thorax

• positive atmospheric pressure enters through the muscles

• lost of compliance

describe anatomical dead space (ADS)

• portions of the conducting zone that have some remainder of fresh or stale air

• important in understanding the pressure gradient and how pressure is going to decrease when it gets to the alveoli

describe what is happening in this diagram

• at the end of inspiration, there is 150 mL of fresh air left over in the conducting zone and 2700 mL of stale air in the alveoli due to gas exchange

• when the body exhales 500 mL, the first 150 mL is the fresh air left over in the conducting zone and the final 350 is stale air from the alveoli

• at the end of expiration, 150 mL of stale air remains in the conducting zone

• when the body inhales 500 ml of fresh air, the first 150 mL is the stale air from the conducting zone and the second 350 mL is fresh air; there is 150 mL of fresh air that remains in the conducting zone

what is tidal volume

the amount of air that is going to be expelled

what does stale air refer to

air that has been mined of its oxygen by the oxygen diffusing into the blood stream

why is there always 150 mL of air in the conducting zone

conducting airways are reinforced with cartilage and do not collapse during ventilation

how much of your total blood volume does the pulmonary circulatory system contain at any given time

10 percent

what occurs as a result of the flow rate being high due to the extensive number of capillaries in the alveoli

• it has a slower velocity than it does in the rest of your body

• the blood pressure in the pulmonary circuit remains low (25/8 mm Hg rather than 120/80 mm Hg)

what are the steps for gas exchange with the blood in the capillaries

1. Ventilation leads to the bulk flow of atmospheric air into and out of alveoli

2. diffusion of gas molecules between air in the alveoli and the blood

3. transport of dissolved gases using bulk flow of blood in the CVS

4. diffusion of gas molecules between the blood and the ECF/cytosol of the cells

describe hypercapnia

• elevated levels of CO2 in the blood

• respiratory acidosis

• pH decreases and in a more acidic state

• not blowing off as much CO2

• consumption of O2 out paces the amount coming in so O2 levels starkly decrease

describe hypoxia

too little O2 in the blood

describe respiratory alkalosis

• due to hyperventilation (breathing at a faster rate than normal)

• increase pH, causing basic conditions

• increase in O2 partial pressure and concentration

• breathing off all the CO2

what is the physiological pH of blood

7.35-7.45

describe Dalton’s law

• the total pressure of air is the sum of the partial pressures exerted by the individual gases

• 760 mmHg at sea level, decreases with elevation

describe partial pressure

the partial pressure of an individual gas can by calculated by multiplying the fractional concentration of a gas by the total air pressure

how does the presence of water vapor impact the partial pressures of other gases

• the presence of water vapor contributes to the total air pressure, and therefore negatively impacts the partial pressures of other gases in the air

• lowers the partial pressures

why is there a difference between atmosphere and alveolar gas composition

• atmospheric air traveling through the conducting system is warmed to 37ºC and becomes 100% saturated with H2O (P_H2O = 47 mmHg

  • PO2 of air entering the alveoli is already down to 150 mm Hg

• anatomical dead space leaves stagnant air (air that doesn’t have O2 that mixes in) behind in the conducting system on exhalation

• alveoli not completely emptied on exhalation (i.e. residual volume)

what law dictates that gases diffuse down partial pressure gradients

Henry’s Law

describe Henry’s Law

• states that partial pressure and particle solubility determine diffusion of gas particles into a fluid, NOT particle concentration

• the amount of gas that dissolves into a liquid is proportional tot he partial pressure of that gas in the gaseous phase and the solubility of that gas in a particular liquid

which has a higher solubility: O2 or CO2

CO2

what is the role of hemoglobin in the blood

• O2 transport in the blood

• increases the amount of O2 that the blood can hold

• without it, the blood can hold minimal O2

describe hemoglobin (Hb)

• a molecule composed of four protein globin chains, each surrounding a central heme group

• each heme group consists of a porphyrin ring with an iron atom in the center

• each hemoglobin molecule can reversibly bind to four oxygen molecules

• when hemoglobin is bound to oxygen, it is referred to as oxyhemoglobin (HbO2)

• with each O2 that binds, there becomes a stronger affinity for the next O2 to bind

describe hemoglobin in arterial blood

• when O2 leaves the alveoli, <2% is dissolved in the plasma and the rest (>98%) is in the form of oxyhemoglobin

• when the oxyhemoglobin comes into contact with tissues that need it, the O2 separates from the hemoglobin, is dissolved in the plasma, and diffuses into the cell for cellular respiration

what does the amount of oxygen bound to Hb depend on

• plasma O2 which determines the percent saturation of hemoglobin

• amount of hemoglobin which determines the total number of Hb binding sites and is calculated from Hb content per RBC and number of RBCs

what is the equation to calculate the percent saturation of Hb

(amount of O2 bound to Hb) / (the maximum amount that could be bound) x 100

what is the percent of O2 unloaded by hemoglobin to tissues

25%

describe the oxyhemoglobin saturation curve

• relationship is S-shaped

• if atmospheric P_O2 levels fall, Hb is still mostly saturated, so blood leaving alveoli is still largely oxygenated

• as tissues become more active and use more O2, Hb can deliver increasing quantities of O2

• chemoreceptors kick in to adjust the curve when it drops below 60

describe O2 delivery during exercise

• as O2 use increases in active tissues (increased metabolism), P_O2 in those tissues can drop to 20 mm Hg

• percent oxygen saturation of hemoglobin drops

• percent of oxygen unloaded drops

what are the different factors affecting O2-Hb Binding

• traits of the internal environment impact the affinity of Hb to bind to O2 and help to intrinsically meet the body’s changing O2 demand

  • increasing affinity means higher %HbO2 at a given P_O2

  • decreasing affinity means lower % HbO2 at a given P_O2

what are factors that affect the percent saturation of Hb

• P_CO2

• pH

• temperature

• 2,3-BPG (metabolism biproduct)

describe the effect of pH in the blood with regard to the Bohr Effect

• causes for low pH

• increase in muscle activity forces muscles to use anaerobic respiration, which results in an increase in lactic acid, H+, and C2

• decrease in pH due to increased metabolism causes a right shift for the saturation of a P_O2, meaning that at a given pressure, there is less hemoglobin saturation

describe the effect of temperature in the blood

• causes for increased temperature come from increased muscle activity, warming muscles up, and signals to body that they need more O2

• there is more hemoglobin saturation (more O2) at lower temps

• there is less O2 (hemoglobin saturation) at higher temps due to increased activity and increased heat/acidity

describe the effect of CO2 in the blood with the carbamino effect

• at high P_CO2, CO2 binds reversibly to Hb to form a carbaminohemoglobin molecule

• causes for increased CO2 come from increased muscle activity that forces muscle respiration to increase which results in an increased CO2; or problems with ventilation

describe the effect of 2,3-BPG (DPG) in the blood

• 2,3-bisphosphoglycerate (an intermediary of the glycolysis pathway)

• causes for an increase in BPG

• chronic hypoxia from living at high altitudes

describe fetal vs maternal Hb

the fetal hemoglobin has a higher hemoglobin saturation which is why it is able to get O2 from the mom

describe CO2 transport from the tissues to the blood

1. CO2 diffuses out of the cells into systemic capillaries

2. only 7% of the CO2 remains dissolved in plasma

3. nearly a fourth of the CO2 binds to hemoglobin, forming carbaminohemoglobin

4. 70% of the CO2 load is converted to bicarbonate and H+ (hemoglobin buffers H+)

5. HCO3- enters the plasma in exchange for Cl- (the chloride shift)

what is HbH

hemoglobin bound to H+ that acts as a buffer to changes in pH

what is HbCO2

carbaminohemoglobin; hemoglobin bound to CO2

MEMORIZE this equation and know what to use it

• when the solution is basic, right shift to free up H+

• when the solution is acidic, left shift to convert to CO2

describe CO2 transport from blood to lungs

1. CO2 diffuses out of cells into systemic capillaries

2. only 7% of the CO2 remains dissolved in the plasma

3. nearly a fourth of the CO2 binds to hemoglobin, forming carbaminohemoglobin

4. 70% of the CO2 load is converted to bicarbonate and H+ (hemoglobin buffers H+)

5. HCO3- enters the plasma in exchange for Cl- (the chloride shift)

6. at the lungs, dissolved CO2 diffuses out of the plasma

7. by the law of mass action, CO2 unbinds from hemoglobin and diffuses out of the RBC

8. the carbonic acid reaction reverses, pulling HCO3- back into the RBC and converting it to CO2

memorize this chart for the neural control of respiration

memorize this diagram for the chemoreceptor control of ventilation

what do central chemoreceptors monitor

CO2 in the cerebrospinal fluid

what do carotid and aortic chemoreceptors monitor

CO2, O2, and H+

describe the hypoxic drive and the O2-Hb curve

• when the P_O2 is less than 60, it stimulates an increase in ventilation

• this is important because it is right before the large drop in hemoglobin saturation at lower P_O2

• this is when the peripheral chemoreceptors kick in

describe lung compliance

the ability of the lung tissue to stretch and expand

describe lung elasticity

ability of the lung to shrink down and empty of air

what two factors affect the total arterial O2 content

• oxygen dissolved in plasma

• oxygen bound to Hb

what factors influence oxygen dissolved in plasma

• composition of inspired air

• alveolar ventilation

• oxygen diffusion between alveoli and blood

• adequate perfusion of alveoli

what factors influence alveolar ventilation

• rate and depth of breathing

• airway resistance

• lung compliance

what factors influence the oxygen diffusion between alveoli and blood

• surface area

• diffusion distance (membrane thickness and the amount of interstitial fluid)

what are the different pathologies that cause hypoxia

• emphysema (destruction of alveoli means less surface area for gas exchange)

• fibrotic lung disease (thickened alveolar membrane slows gas exchange and loss of lung compliance may decrease alveolar ventilation)

• pulmonary edema ( fluid in the interstitial space increases diffusion distance and arterial P_CO2 may be normal due to higher CO2 solubility in water)

• asthma (increased airway resistance decreases alveolar ventilation)

what are the parts of the urinary tract

• paired ureters (carry urine from kidneys to bladder)

• bladder (temporarily stores urine)

• urethra (carries urine from bladder to the outside of the body)

describe the paired kidneys

• remove metabolic wastes and toxins (constantly filtering the blood in homeostatic range)

• long term regulation of pH of the plasma

• regulate osmolarity of solutes in body fluids (alter concentration and water composition to regulate blood pressure by adding/removing liquid)

• regulate plasma volume

• stimulate red blood cell production (sythesize and release a hormone called EPO that stimulates the production of more RBCs)

• activate viatamin D3

• synthesize glucouse from non-carbohydrates (gucogenesis)

• release/degrade hormones (renin that is an enzyme that activates a hormone cascade)

describe how the kidneys maintain homeostasis

• through a massive filtration rate

• filter ~200 liters of blood daily

  • total plasma volume in an adult is 3-5 liters

  • filters entire plasma volume ~60x per day

  • this high filtration rate (glomerular filtration rate [GFR]) is essential for rapidly clearing wastes and precisely regulating bodily fluids (can be used to assess kidney function as a common clinical marker)

how can an individual survive with only 1/3 of one kidney being functional

• not all of the kidneys work at the same time

• illustrates the functional reserve of the kidney itself as they don’t work at 100% capacity all of the time and have the ability to ramp up the function

describe how the kidneys control blood volume and regulate plasma volume

• add or remove the solute content to regulate the blood volume

• add or remove water content of the blood to regulate the plasma volume

• primary mechanism for long-term control of mean arterial blood pressure

• through regulation of Na+ and water

describe how the kidneys regulate osmolarity

• the kidneys maintain plasma osmolarity in a tight range (290-300 mOsm)

• through regulation of water excretion, primarily through the action of antidiuretic hormone (ADH)

describe how the kidneys regulate the plasma pH

• primary organ for long-term acid-base balance

  • excretion of H+ (fixed acids)

  • reabsorbtion and synthesis of HCO3- (can either pick up a proton or give up a proton depending on the direction of the pH disruption)

describe how the kidneys regulate ion balance

• controls plasma concentration of key electrolytes

  • Na+, K+, Ca2+

describe the metabolic waste that is excreted by the kidneys

• urea (nitrogenous waste from amino acid metabolism)

• uric acid (from nucleic acids

• creatinine (from phosphocreatine metabolism in skeletal muscles)

  • more muscles, more creatine

  • if high, it means that the kidneys are not filtering out at the rate that they are supposed to)

  • plasma creatine is a common clinical marker for estimating GFR but it is not the most accurate because someone who works out a lot or has more muscle mass is going to have higher amounts of creatine

describe the xenobiotics that the kidneys excrete

• drugs

• environmental toxins

• food additives (food dye)

what are the different endocrine and metabolic functions of the kidneys

• stimulation of red blood cell production

• activation of vitamin D3

• release/degrade hormones

• gluconeogensis

• ammonia synthesis

describe stimulation of RBC production as an endocrine and metabolic function of the kidneys

the kidneys synthesize and secrete the hormone erythropoietin (EPO) that makes more RBCs in response to low oxygen levels

describe the activation of vitamin D3 as an endocrine and metabolic function of the kidneys

carries out final hydroxylation step to convert inactive vitamin D into clacitriol

describe the release/degrade of hormones as an endocrine and metabolic function of the kidneys

• major site for hormone degradation

• releases the enzyme Renin, which activates the RAS system to raise blood pressure

describe gluconeogenesis as an endocrine and metabolic function of the kidneys

makes glucose from non-carbohydrate sources (amino acids) during prolonged fasting

describe ammonia synthesis as an endocrine and metabolic function of the kidnesy

kidneys synthesize ammonia (NH3) from glutamine, which acts as a urinary buffer to trap and excrete H+

give a description of the kidneys

• about the size of your clenched fist

• posterior to the abdominal wall (behind ribs to back)

• partially protected by ribcage (bottom floating ribs)

• surrounded by perirenal fat to absorb mechanical shocks

• receive 20-25% of CO but are only 0.4% of body mass (very high rate of blood flow!!)

what is the morphology of the kidneys

• cortex

• nephrons

  • cortical nephrons in the cortex and have the most expression

  • Juxtamedullary nephrons in the medulla are fewer but play an important role

• medulla (high salt content that help with purification, concentration, or very dilute urine)

• renal pelvis where urine exits the collecting duct

• ureter that sends the urine to the bladder

what are the four processes that urine forms through

1. filtration

2. reabsorption

3. secretion

4. excretion