Physiology Respiratory and Kidneys

Define the term “bulk flow” in the context of the respiratory system.

the large-scale movement of air caused by pressure differences that happens during breathing

Explain the relationship between pressure and flow within the respiratory system.

Describe how the muscular pump creates pressure gradients for ventilation.

increased pressure = restricted flow

Distinguish between cellular respiration and external respiration.

external respiration includes ventilation

Define ventilation.

exchange of air between atmosphere and lungs, aka inspiration and expiration

Explain the exchange and transport processes of O₂ and CO₂ between the atmosphere, lungs, blood, and cells.

1. Exchange of air between atmosphere and lungs

2. Exchange of O₂ and CO₂ between lungs and blood

3. Exchange of O₂ and CO₂ between blood and cells

Which structures are in the upper and lower respiratory tracts?

Upper:

Oral cavity

Pharynx

Larynx 

Lower:

Trachea

Two primary bronchi

Lungs

What are alveoli, and what is their function in the respiratory sytem?

What are the two types of alveoli?

site of gas exchange

type 1 cells: gas exchange

type 2 cells: produce surfactant

Describe the components of the thoracic cage and their roles in breathing. Please focus on the role of muscles and how they change the dimensions of the thoracic cage.

Diaphragm: as it flattens during inhalation, directly increases the thoracic volume

during exhalation, it expands and thoracic volume decreases

Internal intercostals: function in forced exhalation

External intercostals: function in forced inhalation

Explain the function of pleural sacs and the importance of pleural fluid.

lines the lungs and inner surface of the chest cavity

pleural fluid lowers the friction between membranes and holds lungs tight against thoracic wall

Discuss how airways connect the lungs to the external environment and their functions in air preparation.

functions in air preparation:

1. warm air to body temperature

2. adding water vapor

3. filter out foreign material

Define the respiratory cycle.

1 inspiration + 1 expiration

What causes inspiration and expiration in terms of alveolar pressure changes?

inspiration: alveolar pressure decreases

expiration: alveolar pressure increases

Discuss the changes in intrapleural pressure during the respiratory cycle and their significance.

intrapleural pressure usually kept at -3 mm Hg

During inspiration, pressure drops

During expiration, returns to normal value

Define lung compliance and elastance.

What is high and low compliance?

compliance: ability to stretch

high compliance: stretches easily

low compliance: requires more force

elastance: ability to return to resting volume when stretching force release

ability to return from stretch

How might these change in disease states (obstructive and restrictive lung disease)?

obstructive lung disease: increased airway resistance

restrictive lung disease: reduced lung compliance

Explain the role of surfactants in breathing and the Law of LaPlace.

surfactants: surface active agents

contains proteins and phospholipids

reduces surface tension

disrupt cohesive force of water

Law of LaPlace: as pressure goes up, resistance must also go up or lung can stretch or rupture

What is Newborn Respiratory Distress Syndrome (NRDS)? What are its clinical signs?

harder for babies to breath, harder to get oxygen in and carbon dioxide out

clinical signs:

grunting

use of accessory muscles

nasal flaring

How does airway diameter affect airway resistance?

wider airways = less resistance

How do other factors affect airway resistance?

viscosity of air: humidity and altitude may alter

upper airways: mucus can cause physical obstruction

bronchioles: bronchoconstriction and bronchodilation

Review the different types and patterns of ventilation (Table 17.3) as presented in the lecture.

eupnea: normal breathing

hyperpnea: increased respiratory in response to increased metabolism (exercise)

hyperventilation: increased respiratory rate without increased metabolism (emotional hyperventilation)

hypoventilation: decreased alveolar ventilation (asthma)

dyspnea: difficulty breathing (pathologies or hard exercise)

apnea: cessation of breathing (voluntary breath holding)

How does PO2 and PCO2 vary with hypo- and hyperventilation?

hypoventilation: decreased alveolar ventilation

lower PO2 and higher PCO2

hyperventilation: increased alveolar ventilation

higher PO2 and lower PCO2

What are auscultation and spirometry?

auscultation: listening to breath sounds

spirometry: pulmonary function test

Differentiate between obstructive and restrictive lung diseases.

Provide examples of diseases that increase airway resistance and those that reduce lung compliance.

Obstructive lung disease: increased airway resistance

asthma

obstructive sleep apnea

COPD
Restrictive lung disease: reduced lung compliance

pulmonary fibrosis

Why does the body need oxygen, and why must carbon dioxide be removed?

oxygen is essential for producing ATP

carbon dioxide is a waste product produced during cellular respiration

too much CO₂ can harm the body

Define hypoxia and hypercapnia.

hypoxia: too little oxygen

hypercapnia: increased concentrations of CO₂

List the three regulated variables the body monitors to avoid hypoxia and hypercapnia

1. oxygen

2. carbon dioxide

3. blood pH

Describe the process of gas exchange between the alveoli and blood, and between blood and tissues

Between alveoli and blood

partial pressure of oxygen in alveoli is higher than blood, so it will diffuse to blood

opposite for CO₂

partial pressure of oxygen in blood is higher than in tissues, so it will diffuse to tissues

opposite for CO₂

Explain how individual gases (PCO2) diffuse along partial pressure gradients (Figure 18.1)

@ the lungs

@ the tissues

after oxygen diffuses into cells and is used for energy, CO₂ diffuses out of cells

CO₂ is transported through the blood and enters the capillaries

enters alveoli and is exhaled through the lungs

How does the composition of inspired air (alveolar PO2) vary with altitude?

Higher altitude decreases P_O2

Identify factors that can lead to hypoventilation and discuss their effects on oxygen uptake

Decreased lung compliance

Increased airway resistance

CNS depression

• alcohol poisoning

• drug overdose

Define the diffusion rate and list the factors that affect it

Diffusion rate is roughly proportional to:

surface area*concentration gradient*barrier permeability/distance²

primary factor is concentration gradient

Discuss how pathological changes can affect gas exchange in terms of surface area, diffusion barrier permeability, and diffusion distance

surface area:

decrease in amount of alveolar surface area

diffusion barrier permeability:

increase in thickness of alveolar membrane

diffusion distance:

increase in diffusion distance between alveoli and blood

How do each of the below impact diffusion rate:

emphysema

fibrotic lung disease

pulmonary edema

asthma

emphysema: destruction of alveoli means less surface area for gas exchange

fibrotic lung disease: having scar tissue in your lungs gives lower compliance and increases thickness of alveolar membranes

pulmonary edema: fluid in interstitial space increases diffusion time

asthma: increased airway resistance decreases ventilation

Define the Fick equation

Fick’s equation: estimates oxygen consumption

explain the law of mass action as it pertains to oxygen binding (how does the concentration of PO₂ shift reactions with hemoglobin)

More PO2 means oxygen binds to hemoglobin better

Less PO2 means oxygen lets go of hemoglobin more easily

How do physiological changes (changes in metabolic activity) affect O₂-Hb binding affinity?

Increased metabolic activity means decreased oxygen affinity

Can you predict how affinity changes with each of the following: pH, temperature, and PCO₂

decreased affinity:

decrease pH

increased temperature

increased P_CO2

What is the role of the dorsal respiratory group (DRG)?

communicates with the muscles of inspiration via the phrenic nerve

How do chemo- and mechanoreceptors regulate the respiratory rate?

sensory input to pons via glossopharyngeal and vagus nerves

Explain the functions of the pontine respiratory groups (PRG)

pneumotaxic center: “off switch”

controls the rate and depth of breathing

apneustic center: “stimulator” for inspiration

How do pneumotaxic and apneustic centers of the pons interact with the medulla?

Describe the ventral respiratory group (VRG) and its role in breathing.

• pre-Botzinger complex: basic pacemaker activity

has areas for:

• active expiration

• > normal inspiration

• innervate muscles of:

  • larynx

  • pharynx

  • tongue

What does the Pre-Botzinger complex do?

The VRG has areas for what?

What muscles are innervated by the VRG?

Discuss the role of peripheral chemoreceptors in ventilation.

Where are they located?

How do each of these change ventilation?

located in carotid bodies

initiate increase in ventilation if:

oxygen is too low

pH is too low

carbon dioxide is too high

How do central chemoreceptors in the CNS respond to changes in CO2 and pH?

Where are they located?

Located in central nervous system

As CO2 increases, it is converted to bicarbonate and H⁺

increased H⁺ affects pH, which affects blood pH

What three things to protective reflexes of the lung respond to?

What is bronchoconstriction responding to?

Explain the Hering-Breuer inflation reflex and how it is activated

physical injury, irritation, and over inflation

bronchoconstriction is responding to irritants

Hering-Breuer reflex prevents over-inflation of lungs

activated by pulmonary stretch receptors

travels via vagus nerve to brainstem

List the components of the urinary tract

ureters

urinary bladder

urethra

Define the nephron

smallest functional unit of kidney

Where are nephrons found?

What are cortical nephrons, and where are they found?

What are juxtamedullary nephrons, and where are they located?

In cortex and medulla

cortical nephrons make up 80%, found in outer cortex

juxtamedullary nephrons make up 20%, found in inner medulla

Which is the site of filtration?

Define renal corpuscle.

Bowman’s capsule

renal corpuscle = glomerulus + bowman’s capsule

What is the juxtaglomerular apparatus?

where the ascending limb passes between the afferent and efferent arterioles

Define filtration as it occurs in the kidneys.

What is the filtrate, and what happens to it?

filtrate is filtered plasma that passes through the glomerulus

it is excreted unless reabsorbed

99% is reabsorbed

Describe reabsorption and secretion and their relation to the peritubular capillaries.

reabsorption is materials in filtrate passed back into the blood

reabsorption and secretion occurs within peritubular capillaries

How does the filtrate composition at the renal corpuscle compare to plasma?

filtrate composition is identical to plasma at renal corpuscle

What changes occur in the filtrate as it moves through the:

Proximal tubule

Loop of Henle

Distal tubule

Collecting duct

proximal tubules: 70% of filtrate is reabsorbed

composed of solutes and water

300 mOsm

Loop of Henle:

descending limb: H₂O reabsorbed

1200 mOsm

ascending limb: solutes reabsorbed

100 mOsm

Distal tubule and collecting duct: some reabsorption and secretion

100-1200 mOsm, depending on hydration state

Define filtration fraction.

% renal flow that filters into tubule

What are the three pressures that influence glomerular filtration?

Briefly describe each of the three pressures (which way does each push or pull fluid).

How is the net filtration pressure computed?

1. capillary blood pressure

biggest driving pressure

2. capillary colloid osmotic pressure

opposes filtration, pulls fluid back to plasma

3. capsule fluid pressure

opposes filtration

net filtration is 1 - 2 and 3

What is the glomerular filtration rate?

How does net filtration pressure and filtration coefficient influence it?

GFR = volume filtered per unit time

net filtration pressure influences by blood pressure

filtration coefficent influences by permeability of filtration slits

How is the glomerular filtration rate (GFR) maintained relatively constant?

How does changing resistance at the afferent and efferent arterioles modify GFR?

(exam question)

maintained by regulating blood flow through renal arterioles

increased resistance in afferent arteriole = decreased GFR

decreased resistance in afferent arteriole = increased GFR

increased resistance in efferent arteriole = increased GFR

decreased resistance in efferent arteriole = decreased GFR

Differentiate between active and passive reabsorption.

active uses ATP, passive doesn’t

What is the role of sodium in active transport within the nephron?

What molecules symport with sodium?

primary active transport of Na⁺ causes electrical gradient

anions follow it, causes osmotic gradient

secondary active transport with symport system

glucose

amino acids

other organic molecules

Discuss the concept of saturation and the transport maximum in renal transport.

saturation: all carriers occupied by substrate

transport maximum: transport rate at saturation

Define renal threshold and glucosuria.

renal threshold:

glucosuria: glucose in urine

What is secretion in the context of kidney function, and what substances are commonly secreted?

secretion: active movement of molecules from extracellular fluid into nephron lumen

How does the proximal tubule, Loop of Henle, distal tubule, and collecting ducts contribute to reabsorption and secretion?

Proximal tubule: secretes H⁺ into filtrate

Reabsorbs:

Na⁺

Cl^-

K⁺

H₂O

HCO_3-

Nutrients

Loop of Henle:

Descending limb: reabsorbs water by osmosis

Ascending limb: reabsorbs Na⁺ and Cl^-

Distal tubule: Balances H⁺ and salt concentrations between urine and interstitial fluid surrounding nephron

Collecting duct:

additional H⁺ is secreted into urine

water is reabsorbed

some urea is reabsorbed at bottom of ducts

Describe the micturition process and the sphincters’ role in urine flow control.

Micturition: process of urinaiton

two sphincters control urine flow

Explain the simple spinal reflex involved in micturition.

1. stretch receptors in bladder walls send signal to spinal cord

2. parasympathetic fibers induce bladder smooth muscle contraction

3. somatic neurons to external sphincter inhibited

Identify the primary route for excreting water and ions.

kidneys

What are secondary routes for excreting:

water and ions

water and bicarbonate

water and ions: feces and sweat

water and bicarbonate: lungs

What are examples of behavioral mechanisms that contribute to homeostasis?

thirst

salt craving

For the systems that integrate fluid and electrolyte balance, which is rapid and which is slow?

How is each controlled?

rapid responses:

respiratory and cardiovascular systems

under neural control

slow responses:

renal system

under endocrine/neuroendocrine control

If given a scenario, such as a decrease (or increase) in blood volume, can you predict how the body would respond in the following examples:

cardiac output

thirst and water intake

ECF and ICF

blood pressure

kidneys (conserve or excrete)

decrease in blood volume:

increase cardiac output, vasoconstriction

increase thirst, water intake

increase ECF and ICF

raise blood pressure

kidneys conserve salt and water

everything is flipped for increase in blood volume

List the sources of water intake and the routes through which water is lost from the body.

Water intake:

ingestion

normal metabolism

IV fluids

Loss of water:

urine

feces

insensible water loss (skin and exhalation)

diarrhea

vomiting

excessive sweating

Explain how osmolarity represents urine concentration

Low osmolarity = high water (100 mOsm)

High osmolarity = low water (1200 mOsm)

Describe the processes that occur in the descending and ascending loops of Henle and how they contribute to urine concentration.

Descending limb: loses water by osmosis

Ascending limb: impermeable to water and actively transports Na⁺ out

Define the role of vasopressin in water reabsorption. For example, how does vasopressin influence the permeability of the collecting ducts?

vasopressin causes the insertion of aquaporins

aquaporin: puts a hole that is specifically permeable to water in the cell membrane of the collecting duct epithelium and reabsorbs the water back into the peritubular capillaries

Describe how extra NaCl in the body influences vasopressin release and thirst.

Extra NaCl leads to vasopressin release, water conservation

thirst increases

(Figure 20.8) How does:

Vasopressin secretion impact water reabsorption

Thirst impact water intake and ECF volume

How does ECF impact blood pressure

vasopressin secretion causes more water reabsorption

thirst increases water intake, results in increase in ECF volume

increase in ECF volume causes increase in blood pressure

Explain how aldosterone and angiotensin II production are stimulated and their effects on sodium balance.

aldosterone controls sodium balance

Detail the renin-angiotensin (RAS) function and its response to decreased blood pressure.

RAS has juxtaglomerular cells secrete renin if blood pressure decreases

Describe the renin-angiotensin pathway.

What is being produced by the juxtaglomerular cells?

What are the enzymes that convert angiotensinogen to angiotensin I and angiotensin II?

renin converts angiotensinogen to angiotensin I

angiotensin converting enzyme (ACE) converts:

angiotensin I to angiotensin II

List how angiotensin II (ANG II) increases blood pressure.

1. increases vasopressin secretion (puts in aquaporin in your kidneys, helps conserve water)

2. stimulates thirst

3. is potent

4. increases sympathetic output to heart and blood vessels

5. increase proximal tubule Na⁺ reabsorption

Differentiate between respiratory and metabolic acidosis and alkalosis.

How does respiratory rate relate to P_CO2 and pH?

respiratory acidosis:

hypoventilation = P_CO2 increases = pH decreases

respiratory alkalosis:

hyperventilation = P_CO2 decreases = pH increases

metabolic acidosis:

dietary and metabolic input of H⁺ exceeds excretion = pH decreases

metabolic alkalosis:

loss of H⁺ through excessive vomiting or excessive ingestion of bicarbonate-containing antacids

= pH increases