Unit 3 Study Guide

1.    What are the four general functions of the respiratory system?

The four general functions of the respiratory system are to provide an

1. air passageway

2. serve as a site for oxygen and carbon dioxide exchange

3. allow for detection of odors

4. enable sound production.

Describe the structural and functional differences between the conducting zone and respiratory zone.

The conducting zone transports air and includes all structures from the nasal cavity to the terminal bronchioles (Nasal cavity, Pharynx, Larynx, Trachea, Bronchus, Bronchiole, Terminal Bronchiole)

While the respiratory zone participates in gas exchange and includes the respiratory bronchioles, alveolar ducts, and alveoli.

 What is the primary function of the nasal cavity?

The primary function of the nasal cavity is to warm, cleanse, and humidify the air as it enters the respiratory tract.

 Describe the locations within the nasal cavity of the olfactory and respiratory regions along with the nasal vestibule.

Olfactory region is the most superior portion of the nasal cavity and contains olfactory epithelium.

Respiratory region has an extensive vascular network in the lamina propria

Nasal vestibule is immediately internal to the nostrils and contains vibrissae.

Within which region of the nasal cavity do nosebleeds occur most commonly and why? What is the clinical term for nosebleeds?

Nosebleeds most commonly occur in the respiratory region because of the superficial blood vessels found there. The clinical term for a nosebleed is epistaxis.

Where would you find vibrissae in the nasal cavity, what are they and what is their function?

Vibrissae are coarse hairs found in the nasal vestibule, and they function to trap large particulates from the air.

 What are the major functions of the larynx?

The major functions of the larynx are to produce sound, serve as a passageway for air, prevent ingested materials from entering the respiratory tract, assist in increasing abdominal pressure for urination and defecation, and to participate in sneeze and cough reflexes.

  Describe the location of the vocal cords within the larynx.

The vocal cords extend from the inner surface of the thyroid cartilage to the arytenoid cartilages within the larynx.

Which muscles are necessary to create sound? Describe how sound is produced when these muscles are stimulated.

The intrinsic laryngeal muscles are necessary to create sound. When they pivot the arytenoid cartilages, the vocal cords move, and when air is forced past them during expiration, they vibrate to produce sound.

What causes someone to have a higher or lower range of sound production? How do we influence the volume of sound production?

The range of sound depends on the length and thickness of the vocal folds (men have longer and thicker folds, producing lower ranges), while the loudness/volume is determined by the force of air passing between the vocal cords.

Describe the 4 processes of respiration.

The four processes of respiration are:

Pulmonary Ventilation (movement of air between atmosphere and alveoli)

Alveolar Respiration (exchange of gases between alveoli and pulmonary capillaries)

Gas Transport (movement of gases within the blood between pulmonary and systemic capillaries),

Systemic Respiration (exchange of gases between systemic blood and body tissues)

 When the thoracic cavity expands, what causes the lungs to expand as well? When the thoracic cavity depresses, what causes the lungs to also shrink in size?

The lungs expand when the thoracic cage expands because of surface tension from serous fluid in the pleural cavity, and the lungs shrink when the thoracic cage depresses because of the elastic recoil of the lungs.

How does the diaphragm contracting/relaxing affect the volume of the thoracic cavity? (be sure to include what type if dimensional change has occurred)

When the diaphragm contracts, it moves inferiorly into the abdominal cavity, increasing the vertical dimension of the thoracic cavity; when it relaxes, the vertical dimension decreases.

How does the ribcage widening or narrowing affect the volume of the thoracic cavity? (include dimension change)

When the ribcage widens it increases the lateral dimension of the thoracic cavity, and when it narrows, the lateral dimension decreases.

How does the movement of the sternum affect the volume of the thoracic cavity?

Movement of the sternum anteriorly increases the anterior-posterior dimension, while posterior movement decreases it.

  What is the relationship between the volume of the thoracic cavity and the pressure within it?

According to Boyle’s Law, there is an inverse relationship between thoracic volume and pressure: when volume increases, pressure decreases, and when volume decreases, pressure increases.

Why do we need to change the volume of the thoracic cavity to breath?

We need to change the volume of the thoracic cavity to generate pressure gradients that allow air to move into and out of the lungs

To move air there needs to be a pressure gradient between two connected compartments. What is a gradient (define it)? How does a pressure gradient affect the movement of air?

A gradient is a difference between two connected areas. A pressure gradient causes air to move from high pressure to low pressure.

What two pressures within the thoracic cavity are affected when the volume of the thoracic cavity changes? (be sure to describe what causes each of these pressures and where they can be found) Which of these two pressures is connected to the atmosphere and helps create the pressure gradients needed for breathing?

The two pressures are intrapulmonary pressure (air pressure within the alveoli connected to the atmosphere through the conducting zone) and intrapleural pressure (fluid pressure in the pleural cavity created by surface tension). Intrapulmonary pressure is the one directly connected to the atmosphere and creates the pressure gradients needed for breathing

   Why does the intrapleural pressure always need to be lower than the intrapulmonary pressure? If these two pressures are equal, what would happen to the lungs?

Intrapleural pressure must always remain lower than intrapulmonary pressure to keep the lungs adhered to the thoracic wall. If they become equal, the lungs collapse (pneumothorax)

 Describe the process of inhalation (inspiration). Be sure to include the muscles involved and whether they are contracting or relaxing, the pressures involved, how the changing of the thoracic volume affects these pressures and how the gradient generated affects the movement of the air.

During inhalation, the diaphragm and external intercostals contract, expanding the thoracic cavity. This decreases intrapleural pressure (to about 754 mmHg) and lowers intrapulmonary pressure (to 759 mmHg). Because atmospheric pressure remains 760 mmHg, air flows into the lungs down its pressure gradient

  Describe the process of exhalation (expiration). Be sure to include the muscles involved and whether they are contracting or relaxing, the pressures involved, how the changing of the thoracic volume affects these pressures and how the gradient generated affects the movement of the air.

During exhalation, the diaphragm and external intercostals relax, decreasing thoracic volume. Intrapleural pressure rises back to 756 mmHg, and intrapulmonary pressure increases to 761 mmHg. Because this is higher than atmospheric pressure, air flows out of the lungs.

 When moving only a Tidal volume of air in or out of the lungs, is a large pressure gradient needed between the atmosphere and the alveoli? Why or why not?

No, a large pressure gradient is not needed for tidal volume breathing, because only about 500 mL of air moves in and out, and small pressure changes are sufficient

  If a larger pressure gradient is generated between the atmosphere and the alveoli, what will happen to the volume of air moving in/out of the lungs?

A larger pressure gradient causes a greater volume of air to move in and out of the lungs

  Describe eupnea. Why is eupnea important to body function?

Eupnea is rhythmic breathing at rest with about 12 breaths per minute, requiring only 5% of total energy expenditure, and it ensures a constant supply of oxygen and removal of carbon dioxide.

What is apnea? When might someone be in apnea?

Apnea is the absence of breathing, and it may occur during swallowing, breath holding, drug-induced anesthesia, or neurologic disease/trauma.

Compare and contrast hyper- versus hypo- ventilation.

Hyperventilation is breathing faster or deeper than the body’s needs, causing excessive loss of CO₂ and pH imbalance, while hypoventilation is breathing slower or shallower than needed, leading to CO₂ retention and pH imbalance.

What is airflow and what three things affect it?

Airflow is the amount of air moving in and out with each breath, and it is affected by pressure gradients, resistance, and compliance.

  Describe the difference between resistance and compliance.

Resistance refers to factors making airflow more difficult, like bronchoconstriction or mucus buildup, while compliance is the ease with which the lungs and chest wall expand

What is pulmonary ventilation and alveolar ventilation. Why are they not the same?

Pulmonary ventilation is the total amount of air inhaled per minute, while alveolar ventilation is the portion that reaches the alveoli for gas exchange. They are not the same because some air remains in dead space

  Describe the two types of dead space that affect alveolar ventilation.

Anatomic dead space is the air left in the conducting zone that never reaches alveoli (about 150 mL), and physiologic dead space is caused by respiratory disorders that reduce alveoli available for exchange.

 How do the two divisions of the ANS affect the bronchi/bronchioles and which nerves do they use?

The sympathetic division (T1–T5 spinal nerves) causes bronchodilation, and the parasympathetic division (via the vagus nerve, CN X) causes bronchoconstriction.

Where can we find the three respiratory centers within the brain?

The three respiratory centers are in the medulla oblongata (ventral respiratory group and dorsal respiratory group) and in the pons (pneumotaxic center).

  What is the function of the pneumotaxic center?

 The pneumotaxic center regulates respiratory muscles to limit the depth of inhalation and is important in sneezing and coughing.

  Describe the two types of chemoreceptors that can stimulate the DRG. Include where these chemoreceptors can be found, what type of fluid they are monitoring and what chemical changes can stimulate them.

Central chemoreceptors are located in the medulla oblongata, monitor CSF pH, and respond to CO₂ changes. Peripheral chemoreceptors are in the aortic bodies (CN X) and carotid bodies (CN IX), detect changes in H⁺, PCO₂, and also large drops in PO₂.

What other types of receptors can stimulate the DRG? (be sure to describe each of them with where they can be found and what stimulates them)

Proprioceptors in joints and muscles detect body movement and increase breathing rate and depth. Baroreceptors in the visceral pleura and bronchiole smooth muscle detect stretching and inhibit inspiration. Irritant receptors in respiratory passageways detect dust and particulates, triggering sneezing and coughing

Once the DRG is stimulated, it then stimulates the VRG. What nerves are stimulated by the VRG to change respiration? Be sure to include which muscles are innervated by each nerve.

Once the DRG is stimulated, it activates the VRG, which sends impulses through the phrenic nerves to the diaphragm, the intercostal nerves to the intercostal muscles, and other somatic nerves to accessory muscles to adjust breathing.

 Compare and contrast the pulmonary and bronchial circulations.

The pulmonary circulation carries oxygen-poor blood from the right ventricle to the lungs for gas exchange and returns oxygen-rich blood to the left atrium, while the bronchial circulation delivers oxygen-rich blood from the aorta to nourish the tissues of the respiratory system.

Describe how the bronchial and pulmonary circuits are connected and how this affects the oxygenation of the blood returning to the heart.

Some deoxygenated blood from bronchial veins drains into the pulmonary veins, slightly reducing oxygen levels in the blood entering the left atrium.

What does the respiratory membrane consist of?

The respiratory membrane consists of the alveolar epithelium, capillary endothelium, and their fused basement membranes.

 Describe the two types of alveolar epithelium found in the lungs.

Type I cells are squamous and form the thin walls for gas exchange, while Type II (septal) cells secrete surfactant to prevent alveolar collapse.

  What is the function of surfactant?

Surfactant reduces surface tension inside alveoli, keeping them from collapsing during expiration.

  What are dust cells?

Dust cells (alveolar macrophages) engulf microorganisms and debris within alveoli.

 What is the partial pressure of a gas?

A partial pressure is the pressure exerted by one gas in a mixture; it drives diffusion from high to low pressure areas

What is a gas’s solubility coefficient and how does it affect carbon dioxide differently than oxygen?

A solubility coefficient measures how much gas dissolves in a liquid; CO₂ has a higher solubility than O₂, so it diffuses more easily.

Why are the partial pressure within the alveoli different than the partial pressures in the atmosphere?

Alveolar partial pressures differ because of air mixing, gas exchange, and water vapor, making PO₂ lower and PCO₂ higher than in the atmosphere

 What would happen to the partial pressure of oxygen within the alveoli if the partial pressure of water vapor increased (such as on a humid day)? How would this affect the ability of oxygen to diffuse into the blood?

Increased water vapor would lower PO₂ in alveoli, reducing oxygen diffusion into the blood.

   Bio 168 refresher (do not skip this!) Oxygen and carbon dioxide will simply diffuse across the respiratory membrane. What does this mean, to simply diffuse? Why can the respiratory gasses do this (what is it about their chemical nature)?

To simply diffuse means that oxygen and carbon dioxide move from areas of higher partial pressure to areas of lower partial pressure without the use of energy (passive transport).
They can do this because they are small, nonpolar gases, allowing them to pass easily through the thin lipid membranes of the respiratory membrane.

  Describe alveolar respiration (include the two respiratory gases and their specific movements)

Alveolar respiration (external respiration) is the exchange of gases between the alveoli and the blood in the pulmonary capillaries.

• Oxygen (PO₂) is greater in the alveoli (104 mm Hg) than in the blood (40 mm Hg), so it diffuses into the blood.

• Carbon dioxide (PCO₂) is greater in the blood (45 mm Hg) than in the alveoli (40 mm Hg), so it diffuses into the alveoli to be exhaled

1.    What anatomic features of the respiratory membrane make it so efficient for gas diffusion?

a.    What would happen to the amount of diffusion if someone had mucus built up in their lungs from an infection? (would this affect the surface area or thickness of the membrane)

b.    What would happen to the amount of diffusion if someone had cancer and needed to have part of their lung removed? (would this affect the surface area or thickness)

The respiratory membrane is efficient for gas diffusion because it has a large surface area (about half a tennis court) and is extremely thin (0.5 micrometers).

a. If someone has mucus buildup from an infection, it increases the thickness of the membrane, decreasing diffusion efficiency.

b. If someone has part of a lung removed, it decreases the surface area, which also reduces diffusion efficiency.

1.    Describe ventilation-perfusion coupling. What would stimulate both vasodilation and bronchodilation?

Ventilation-perfusion coupling is the process of matching airflow (ventilation) with blood flow (perfusion) in the lungs.

• Increased PCO₂ in blood → causes vasodilation of pulmonary arterioles, increasing blood flow to alveoli.

• Increased PCO₂ in bronchioles → causes bronchodilation, increasing airflow to remove CO₂.

1.    Describe systemic respiration (include the two respiratory gases and their specific movements)

Systemic respiration (internal respiration) is the exchange of gases between systemic capillaries and body cells.

• Oxygen diffuses from blood (PO₂ = 95 mm Hg) into systemic cells (PO₂ = 40 mm Hg).

• Carbon dioxide diffuses from systemic cells (PCO₂ = 45 mm Hg) into the blood (PCO₂ = 40 mm Hg).

1  What do the cells use oxygen for? How is carbon dioxide related to this?

Cells use oxygen for cellular respiration to make energy (ATP).
Carbon dioxide is a waste product of this process and must be transported to the lungs for removal

1.    Describe the transport of oxygen in the blood. Be sure to include how much oxygen can be transported using each method.

Oxygen transport in blood:

• < 2% dissolved in plasma (low solubility).

• ~98% transported by binding to iron (Fe²⁺) in hemoglobin → forming oxyhemoglobin (HbO₂).

1.    Describe the transport of carbon dioxide in the blood. Be sure to include how much carbon dioxide can be transported using each method.

a.    Why can 7% of carbon dioxide dissolve into the plasma but only 2% of oxygen?

Carbon dioxide transport in blood:

• 7% dissolved in plasma.

• 23% bound to globin proteins of hemoglobin → forming carbaminohemoglobin (HbCO₂).

• 70% converted to bicarbonate (HCO₃⁻) in plasma after being formed in RBCs.

a. CO₂ is more soluble (has a higher solubility coefficient) than O₂, allowing 7% of CO₂ to dissolve in plasma versus only 2% of O₂.

1.    Within which capillaries will carbon dioxide be converted into bicarbonate? Describe the process.

Carbon dioxide is converted into bicarbonate within systemic capillaries.

• CO₂ enters the RBC and combines with H₂O → forms carbonic acid (H₂CO₃) via carbonic anhydrase.

• H₂CO₃ then splits into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺).

• HCO₃⁻ leaves the RBC and enters the plasma.

  What is the function of carbonic anhydrase? (be specific, which part of the conversion does this enzyme function in)

Carbonic anhydrase is the enzyme that catalyzes the conversion of CO₂ and H₂O into carbonic acid (H₂CO₃) inside RBCs.
It speeds up this reaction so it can occur at the rate required by the body.

  Within which capillaries with bicarbonate be converted into carbon dioxide? Describe the process.

Bicarbonate is converted back into carbon dioxide within pulmonary capillaries.

• HCO₃⁻ re-enters the RBC (as Cl⁻ leaves via the reverse chloride shift).

• HCO₃⁻ combines with H⁺ → forms H₂CO₃, which is broken down by carbonic anhydrase into CO₂ + H₂O.

• CO₂ then diffuses out of the RBC into the alveoli to be exhaled.

What is the chloride shift?

The chloride shift is the exchange of ions that maintains electrical neutrality in the RBC.

• In systemic capillaries, bicarbonate leaves the RBC and chloride (Cl⁻) enters.

• In pulmonary capillaries, the process reverses: bicarbonate enters and chloride leaves.

What three substances can be transported by hemoglobin? What part of the hemoglobin does each of these substances bind to?

Hemoglobin can transport three substances:

1. Oxygen – binds to the iron (Fe²⁺) of the heme group.

2. Carbon dioxide – binds to the globin proteins.

3. Hydrogen ions (H⁺) – also bind to the globin proteins.

  How does the binding or releasing of these substances affect the hemoglobin’s structure and thus the ability to bind the other substances?

When any of these substances bind or are released, the shape of hemoglobin changes (conformational change).
This shape change alters hemoglobin’s ability to bind the other two substances, influencing oxygen, CO₂, and H⁺ transport.

  What is the cooperative binding effect of oxygen?

The cooperative binding effect means that each O₂ molecule that binds to hemoglobin makes it easier for the next one to bind.
This creates a steep rise in saturation as PO₂ increases.

What are we talking about when we talk about ‘hemoglobin saturation’? What is the most important variable that affects hemoglobin saturation?

Hemoglobin saturation is the percentage of heme binding sites occupied by oxygen molecules.
The most important variable affecting it is the partial pressure of oxygen (PO₂)

The Oxygen hemoglobin saturation curve relates what two things?

The oxygen-hemoglobin saturation curve (OHSC) relates PO₂ (partial pressure of oxygen) to the percent O₂ saturation of hemoglobin.

Why is the curve not linear?

The curve is not linear because of the cooperative binding effect .The first oxygen binds with difficulty, but each successive one binds more easily until saturation levels off

As blood moves through the pulmonary capillaries, what happens to hemoglobin saturation? How saturated will the hemoglobin become?

As blood moves through pulmonary capillaries, hemoglobin becomes more saturated.
At alveolar PO₂ of 104 mm Hg, hemoglobin reaches about 98% saturation.

   If a person is at a higher altitude and there is a lower partial pressure of oxygen in the atmosphere, how would hemoglobin saturation be affected? Why would a lower hemoglobin saturation of the blood going to our tissues matter?

At high altitude, atmospheric PO₂ decreases, so alveolar PO₂ and hemoglobin saturation both decrease.
Lower saturation means less oxygen delivered to tissues, which can cause altitude sickness and reduced tissue oxygenation.

As blood moves through the systemic capillaries, what happens to hemoglobin saturation? During rest, how low does’ hemoglobin saturation usually become?

As blood moves through systemic capillaries, hemoglobin releases oxygen, causing saturation to drop.
During rest, it drops to about 75% saturation, meaning 25% of oxygen is released to tissues.

What is oxygen reserve?

The oxygen reserve is the amount of oxygen still bound to hemoglobin (about 75%) after passing through systemic capillaries.
It ensures that extra oxygen is available during increased metabolic demand.

If a person was physically active and the partial pressure of oxygen was lower in the tissues than normal, what would happen to hemoglobin saturation? Does is matter how low hemoglobin saturation is in the veins? Why or why not?

During physical activity, tissue PO₂ decreases, causing more oxygen to be released from hemoglobin (lower saturation).
It doesn’t matter if venous hemoglobin saturation is low, because this shows that oxygen is being effectively delivered to tissues.

Besides partial pressure, what other four things can influence the amount of oxygen released from hemoglobin? Describe how they each affect hemoglobin saturation.

Four other factors that influence oxygen release from hemoglobin:

1. Temperature – ↑ temp = ↓ hemoglobin affinity, more oxygen released.

2. H⁺ (Bohr effect) – ↓ pH or ↑ H⁺ = more oxygen released.

3. 2,3-BPG – ↑ 2,3-BPG (from hormones like epinephrine, thyroid hormone) = more oxygen released.

4. CO₂ binding – ↑ CO₂ = more oxygen released, and vice versa (Haldane effect).

  When the OHSC shifts to the right, how does this affect the movement of oxygen (more oxygen released from hemoglobin or less)? What three things would cause a shift right in the graph?

A right shift in the OHSC means decreased oxygen affinity → more oxygen released from hemoglobin.
Caused by:

1. ↑ temperature

2. ↑ H⁺ (↓ pH)

3. ↑ CO₂ (and increased 2,3-BPG)

When the OHSC shifts to the left, how does this affect the movement of oxygen? What three things would cause a shift left in the graph?

A left shift means increased oxygen affinity → less oxygen released from hemoglobin.
Caused by:

1. ↓ temperature

2. ↓ H⁺ (↑ pH)

3. ↓ CO₂

   List the functions of the kidney (both primary and secondary). Be sure to be specific about what is being eliminated, regulated, formed, etc.

The primary functions of the kidney are filtration of blood, elimination of wastes (urea, uric acid), regulation of ion levels (Na⁺, K⁺, Ca²⁺, PO₄³⁻), acid-base balance (H⁺, HCO₃⁻), blood pressure (fluid balance, renin), and removal of hormones/drugs.

Secondary functions are formation of calcitiol, production of erythropoietin (EPO), and gluconeogenesis during starvation.

   Compare and contrast the three processes of urine production. Be sure to include whether the process is passive, active, or both and what is moving (water, nutrient, etc) and ‘from _______ to ________’.

Glomerular filtration is passive, moving water and solutes from blood in glomerulus → capsular space.

Tubular reabsorption is active and passive, moving useful substances from tubular fluid → blood.

Tubular secretion is active, moving wastes/ions from blood → tubular fluid.

Describe the filtration membrane (what it is composed of).

The filtration membrane is composed of fenestrated endothelium, a basement membrane, and podocytes with filtration slits.

  Where can mesangial cells be found and what are their functions?

Mesangial cells are found within capillary loops of the glomerulus; they are phagocytic and contractile, helping regulate filtration rate.

  What types of substances will freely filter through the filtration membrane out of the blood? What types of substances will NOT filter through the filtration membrane and why not?

Freely filtered substances are small like water, glucose, ions, urea, vitamins, amino acids. Not filtered are formed elements and large proteins due to size and negative charge

Describe the three pressures that affect glomerular filtration. Be sure to include whether the pressure is promoting or inhibiting filtration.

Glomerular hydrostatic pressure (HPg) promotes filtration, while blood colloid osmotic pressure (OPg) and capsular hydrostatic pressure (HPc) oppose filtration.

Why is the pressure inside the glomerulus greater than other capillaries of the body? Why does this make these capillaries more vulnerable to damage?

The afferent arteriole is larger than the efferent arteriole, increasing pressure inside the glomerulus, which promotes filtration but makes capillaries more vulnerable to damage.

How would we calculate net filtration pressure within the glomerulus? How does NFP relate to glomerular filtration rate?

NFP = HPg – (OPg + HPc). A higher NFP leads to a higher GFR.

If both NFP and GFR increase, how does this affect the ability of the kidneys to reabsorb important substances?

When NFP and GFR increase, less time for reabsorption occurs, so more substances remain in urine

Why can Inulin be used to measure GFR?

Inulin is used to measure GFR because it is freely filtered, not reabsorbed, and not secreted.

   What is a ‘normal’ GFR? If someone’s GFR is low, what does this tell us about their kidney function?

A normal GFR is 125 mL/min; a low GFR means decreased kidney function.

What two physiological processes influence GFR?

GFR is influenced by diameter of the afferent arteriole and surface area of the filtration membrane.

Intrinsic control of the kidney functions to _________ GFR while extrinsic control of the kidney is used to ____________ or _______________ GFR based on _____________ ______________.

Intrinsic control functions to maintain GFR, while extrinsic control is used to increase or decrease GFR based on physiologic need

  Describe the two mechanisms of renal autoregulation. Be sure to include what stimulates each response, how the kidney responds to each stimulus and how the kidney’s response helps to maintain homeostasis.

The myogenic response reacts to blood pressure changes by vasoconstricting or dilating the afferent arteriole.

The tubuloglomerular feedback uses macula densa cells to sense Na⁺ levels, adjusting afferent arteriole diameter and filtration surface area to stabilize GFR.

  Why does renal autoregulation have limitations? What are they?

Renal autoregulation fails when MAP < 80 or > 180 mmHg because arterioles are already maximally dilated or constricted.

  Describe the two extrinsic controls of GFR. Be sure to include what stimulates each, how the kidney is affected by each (change in surface area of filtration membrane and affect on afferent arteriole) and how the kidneys response helps to bring about the change required by each control.

Sympathetic stimulation (via renin → angiotensin II) causes afferent arteriole constriction and mesangial cell contraction, decreasing GFR.

ANP is released from the heart, causing afferent arteriole dilation and mesangial relaxation, increasing GFR.

What is micturition? Which divisions of the nervous system are involved in this process?

Micturition is urine expulsion controlled by the sympathetic, parasympathetic, and somatic divisions of the nervous system.

    Describe the storage reflex of the bladder. Be sure to include the division of the ANS responsible, the muscles/sphincters involved, and what those muscles/sphincters do (contract, relax)

The storage reflex (sympathetic) causes detrusor muscle relaxation and internal sphincter contraction, allowing the bladder to fill.

Describe the micturition reflex of the bladder. Be sure to include the division of the ANS responsible, the receptors, nerves, muscles, and sphincters involved, as well as the response of the muscles/sphincter (contract, relax).

The micturition reflex (parasympathetic) is triggered by baroreceptors when bladder volume is 200–300 mL; it causes detrusor contraction and internal sphincter relaxation via the splanchnic nerve.

  Describe our voluntary control of micturition. Be sure to include which part of the brain controls this control and any nerves/sphincters involved.

Voluntary control is by the cerebral cortex, sending signals through the pudendal nerve to relax the external urethral sphincter

  How does the stress-relaxation response of the bladder allow us to delay micturition if necessary?

The stress-relaxation response lets the detrusor muscle relax as the bladder fills, allowing delayed urination until reflexes override voluntary control.

  What is the difference between paracellular and transcellular transport?

Paracellular transport occurs between epithelial cells, while transcellular transport occurs through the epithelial cells, requiring substances to cross the luminal and basolateral membranes.

  What are the luminal and basolateral membranes of a cell?

The luminal membrane faces the tubular fluid, while the basolateral membrane faces the basement membrane and interstitial fluid.

  Peritubular capillaries have low hydrostatic and high osmotic pressures. Why? (think about where the blood comes from that moves into the peritubular capillaries)

Peritubular capillaries have low hydrostatic pressure and high osmotic pressure because the blood entering them has just been filtered by the glomerulus, losing fluid but retaining proteins, creating a strong osmotic pull for reabsorption.

Describe the difference between transport maximum and renal threshold. Which one is a rate? Which one is dependent upon transport proteins? Which one is a chemical gradient that inhibits reabsorption of a substance?

Transport maximum (Tm) is the maximum rate of reabsorption based on the number of transport proteins. Renal threshold is the maximum plasma concentration before a substance begins to appear in urine. Thus, Tm is a rate and dependent on transport proteins, while renal threshold represents a chemical gradient that limits reabsorption.

   Within which part of the renal tubule does the reabsorption of nutrients occur? What percentage of nutrients are reabsorbed?

Reabsorption of nutrients occurs in the proximal convoluted tubule (PCT), and 100% of nutrients are reabsorbed there

  Describe the process of glucose reabsorption. Be sure to include the ion movement glucose is dependent upon and the type of membrane transport that is occurring (passive or active or both).

Glucose reabsorption uses secondary active transport with Na+/glucose symporters across the luminal membrane (using Na+ gradient for energy). Then, glucose exits the basolateral membrane via facilitated diffusion through a glucose uniporter, entering the peritubular capillaries.