Description
Chapter 22: Physiology of the Respiratory System
Respiratory System: Physiology
Pressure
Intrapulmonary Pressure: pressure in the lungs (aka Intra-alveolar pressure)
o Equals the Atmospheric Pressure: 760 mm Hg
Intrapleural Pressure: pressure in the pleural cavity
o Less than Atmospheric Pressure: 756 mm Hg (–4 mm Hg)
∙ Fluid in pleural cavity is the reason the membranes can slide across one another (need a big force to separate them) Don't forget about the age old question of What is a mosque?
Surface Tension
∙ Kept negative
If more than atmospheric pressure alveoli would collapse lungs collapse
Lymphatics drain the fluid in pleural space
Pulmonary Ventilation (breathing process)
↳ ventilating the alveoli
Breathing Process:
o Volume Change Pressure Changes Facilitate Breathing (pressure gradient)
2 Major Phases
1) Inspiration (inhalation)
∙ Active Process – consuming energy (ATP)
Contraction of skeletal muscles
Diaphragm
o Location: separates the Thoracic Cavity from the
Abdominal Cavity
o Activated by nerve impulses form the somatic NS
o Becomes flat; moves downward
∙ Increases the height (or vertical dimension) of the
If you want to learn more check out What is the meaning of adjacent nodes?
Thoracic Cavity
↳ Keep in mind: Diaphragm during relaxation ⇒
dome-shaped
External Intercostal Muscles
o Location: between (individual) ribs
o Ribcage moves outward
∙ Increases the diameter (width)
∙ Promotes the ↑ of volume in the Thoracic Cavity; ↑ of
volume in Lungs If you want to learn more check out What is the purpose of the treasury dept in the federal government?
∙ ↳ Lungs will be stretched due to the surface tension
between the
pleural membranes ⇒ cause the clinging on lungs
to thoracic
cavity wall
Pressure (intra-alveoli) in lungs decreases less than atmospheric pressure in a short-time
Air enters from area of high pressure
o Air from outside the lungs move inside
∙ Lasts for about 2 seconds
2) Expiration (exhalation)
∙ Passive Process
Relaxation (elastic recoiling of lung) + recoiling of skeletal
muscles
Diaphragm returns to dome-shape; ↓ height of lungs
Intercostal Muscles ↓ diameter of lungs
Automatic recoiling of the lungs:
Promotes ↓ volume in lungs and ↑ in pressure
o Generates Pressure Gradient
∙ High pressure in lungs moves outside to the
environment
Factors Influencing Breathing Process
1. Airway Resistance
NOT a significant factor!
o There are only certain points at which there are problems in airway resistance
∙ Trachea and the Primary + Secondary Bronchi If you want to learn more check out What is the meaning of equality in economics?
No resistance due to cartilage rings around the airways
∙ Tertiary Bronchi ⇒ ONLY point where airway resistance could occur; irregular plates in the wall
∙ Bronchioles ⇒ smooth muscle layer; no cartilage = should have resistance, WRONG!
Airway resistance (< 1 ml in diameter)
Branches out so extensively; makes up for small diameter
o Surface Area is huge ⇒ NO resistance
∙ Terminal Bronchioles
Extensive branches provide a huge cross-sectional area which makes up for the small diameter = No resistance
∙ Respiratory Bronchioles or Alveoli Ducts
Gas exchange occurs here
Resistance is not the driving force; diffusion is
2. Compliance of Lung
Degree of stretch-ability (↑ stretch = ↑ compliance)
o Under Healthy Conditions ⇒ very high stretch-ability
o Under Disease
∙ Chronic Inflammation: inflammation that may have a rapid or slow onset but is persistent and resistant to leaveWe also discuss several other topics like What are the standard integration formulas?
Occurs when the tissues are unable to overcome the effects of the injuring agent
∙ Fibrosis: changing elastic tissue of lungs into fibrous tissue
Formation of scar tissue
Fibrous is made of tough fibrous connective tissue (dense
collagen replacing elastic)
Influencing the stretch ability leads to ↓ in compliance of
lungs
Compliance of the lung also depends on Compliance of the Thoracic Cavity
o Abnormality in bone of ribcage leads to ↓ in compliance of thoracic cavity = ↓ in compliance of lungs
3. Surface Tension of Fluid in Alveoli
Assumption Case!
o If the fluid on the internal wall of alveolus was pure water it would collapse due to hydrogen bonding of water molecules (makes alveolus assume the smallest size)
∙ This condition doesn’t happen due to the synthesis and release of Surfactant (lipo-protein)
Fluid is partly water, other particles, and surfactant
Synthesized by Type II Alveolar Cells (cuboidal) which prevents cohesiveness of water molecules We also discuss several other topics like How do we perceive speech accurately?
∙ Occurs in premature babies
Babies born before the end of pregnancy (8 weeks before)
Placed on ventilators because they have Infant Respiratory
Distress Syndrome (IRDS)
o Have the complete respiratory system but synthesis of
surfactant takes place after 7 months
∙ Babies are exposed to the collapse of alveoli due to
surface tension
External + Internal Respiration
Both are gas exchange process; meaning diffusions of O2 and CO2 External Respiration: process in which gas exchange at the level of the lungs (pulmonary gas exchange)
o Called external due to exchange of gases when source of O2 is from the external environment + exhalation of CO2 into environment
o Diffusion of O2: From alveolus through respiratory membrane into capillaries
o Diffusion of CO2: From blood of capillaries into alveolus goes outward during exhalation
Internal Respiration: process of capillary gas exchange at the level of the tissue
o Partial pressures and diffusion gradients are reversed from external respiration
∙ Diffusion of O2: from blood into tissues
∙ Diffusion of CO2: from tissue into blood
Factors Influencing External + Internal Respiration
1. Partial Pressure Gradient (concentration gradient for gases) o Relative amount of the gases
∙ External Resp.
Oxygen
O2 in Alveoli = 104 mm Hg
O2 in Blood Returning from Tissue = 40 mm Hg
o Creates a partial pressure gradient
∙ About 64 mm Hg
∙ O2 in alveolus is higher; it moves from alveolus into
blood in capillary
Carbon Dioxide
In Alveoli = 40 mm Hg
In blood returning from Tissue = 45 mm Hg
o Partial pressure is only about 5 mm Hg
Although the difference of PP is drastic between O2 and CO2 the same amount of gases are exchanged
CO2 seems less, but the is that CO2 is 20x more soluble in plasma and alveolar fluid than O2
∙ Internal Resp.
Oxygen
In Blood Entering Tissue = 100 mm Hg
In Tissue = less than 40 mm Hg
o PP is about of less than 60 mm Hg
∙ O2 moves rapidly from blood into tissues; at the same
time CO2 moves quickly from tissues into blood
∙ Gas exchange between blood and tissue takes place
by simple diffusion
2. Thickness + Surface Area of Respiratory Membrane
o Resp. Membrane is extremely thin; efficient in gas exchange ∙ Inflammation due to Ammonia formation of edema increases thickness of surface membrane
o Surface Area
∙ Huge # of Alveoli = Huge amount of Surface Area
Emphysema: complete destruction of alveoli wall
No respiratory membrane ⇒ promotes problem in gas
exchange
In healthy people = 90 m2 (40x greater than surface area of skin) 3. Transport of Gases
o Transport of Oxygen
∙ Oxygen: gas binding to hemoglobin
Not soluble in plasma; 1.5% of dissolved oxygen travels in hemoglobin
∙ Hemoglobin: made of 4 polypeptide chains, each with a heme group which has one iron atom (area where O2 binds; MAX = 4)
Binding is reversible! Unbinds when O2 is needed
First O2 Bind ⇒ promotes the change of shape to allow the other O2 molecules to bind to the hemoglobin at a fast rate First O2 Unbind ⇒ promotes change of shape to allow the rest of O2 to unbind as well
∙ Association between Oxygen + Hemoglobin
Partially Saturated: Hemoglobin < 4 O2 molecules binded Fully Saturated: Hemoglobin has all 4 O2 binded
∙ Percent O2 Saturation of Hemoglobin
Local Partial Pressure
In the Lungs
o PP= 100 – 104 mm Hg
∙ 98% O2 saturation
In the Tissue
o PP = 40 mm Hg (After one complete systemic circulation) ∙ 75% saturation
o Blood in the veins to the heart
∙ Still has O2 in case it is needed anywhere else
∙ ↳ Even at high altitude there is still 95% O2 saturation ↳ Important to note! Oxygen-hemoglobin Dissociation Curve ⇒ how much O2 is going to unbind from the hemoglobin; how much oxygen will be used/released
Partial Pressure of CO2
Increase in CO2 = ↑ Hydrogen Ion = ↓ pH (Acidosis)
o Promotes the change in shape of hemoglobin
∙ Facilitating the unbinding of O2 = ↓ Saturation
► At 40 mm Hg (level of tissue) there is now 60% O2
saturation,
instead of the usual 75% at the level of tissue
↳ More O2 is being released
o Bohr Effect: the phenomena that O2is released where it is needed
∙ ↑ in CO2 occurs at the level of the tissue which is were more O2 is needed (for exercise and such)
Decrease in CO2 = ↓Hydrogen Ion = ↑ pH
o More O2 in being binded; less O2 is being released
Temperature
Increase of body temperature at Tissues
o PP = 40 mm Hg
∙ Almost 50% (normal conditions = 75%)
► ↑ Release of O2
Production of Organic Compound = 2,3-bisphosphoglycerate Occurs during the rise of body tempt.
Influences the affinity of O2 and hemoglobin
o Transport of Carbon Dioxide
∙ More routes are available for the transport of CO2
Through Plasma (7-10%)
CO2 is more soluble in the plasma = ↑ percentage will be dissolved during transport
Carbamino-hemoglobin (20%)
CO2 binded to hemoglobin
Bicarbonate Ion (70%)
∙ At the Level of the Tissues
CO2 moves from the tissues into the blood
Once in blood, CO2 moves to RBC where it will be hydrated (by water present in RBC)
o Takes place at a fast rate; catalyzed by Carbonic
Anhydrase
∙ Leads to production od Carbonic Acid (weak acid)
► Breaks into Bicarbonate ion and Hydrogen ion
↳ BC ion leaves RBC to plasma (to get to the lungs)
↳ Cl- enters RBC through Chloride Shift to keep
medium of RBC in
normal conditions
↳ Hydrogen ion (in RBC) influences the shape of
hemoglobin
(which contains O2)
↳ Promotes the release of O2 (Bohr Effect!)
∙ At the Level of the Lungs
CO2 moves from blood into lungs to be exhaled out of the body Returns Bicarbonate back to the plasma ⇒ Reverse Chloride Shift
Hydrogen releases from the hemoglobin because of the entrance of O2
o Hydrogen + Bicarbonate ions will react together to turn back into Carbonic Acid
∙ Carbonic Anhydrase is used to reverse the Carbonic
Acid back into CO2 and water (H2O in RBC)
∙ ► CO2 can now be pushed into alveolus to be exhaled
out of body
4. Neural Mechanisms (for control of breathing) – Summary o Medullary Centers
∙ Located in the Medulla Oblagata + Pons
∙ Consists of 2 Groups
Ventral Respiratory Group (VRG)
Cluster of nerves
o Contains rhythm generators whose output drives
respiration
∙ No pacemakers!
Made of Expiratory and Inspiratory Neurons
o Work to together in Mutual Inhibition ⇒ one is activated while the other is inhibited
∙ Sends impulses to the inspiratory muscles (external
intercostals and diaphragm)
Dorsal Respiratory Group (DRG)
Cluster of nerves
o Integrates peripheral sensory input
o Modifies the rhythms generated by the VRG
Posterior to ventral
o Pontine Respiratory Center
∙ Located in the Pons of the brainstem
Superior to Medullary Centers
∙ Interact with the Medullary Respiratory Centers to smoothen the respiratory pattern
Control of Breathing by Neural Mechanisms – Further Explained Ventral Respiratory Group
Contains inspiratory + expiratory neuronal networks
Impulses sent by the Phrenic Nerve (to Diaphragm) and the Intercostal Nerve
o Activation of Intercostal Nerve promotes the inspiration phase ∙ Activates contraction of inspiratory muscles
Inhalation takes place for 2 secs.
Impulses stop from inspiratory + Activation of expiration
neurons occur
o Intercostal + diaphragm go into relaxation ⇒ Expiratory
Phase (3 secs.)
∙ Impulses through Phrenic + Intercostal activate once
again causing activation of inspiration + inhibition of
expiration
>> Leads to 12 -16 sec. cycle
Dorsal Respiration Group
Responsible for integrating information
o Receives information form chemoreceptors
o Relays info to the VRG
Located a bit posterior to the VRG
Pontine Respiratory Center
Similar to DRG
o Integrates info relaying into DRG and VRG
Responsible for smooth transition between inspiration + expiration Controls breathing during sleep + exercise
Neural + Chemical Influences on Brain Stem Respiratory Centers Control of breathing rate
Control of Gases
Negative Feedback Mechanism
o Receptors senses a change of gases in arterial blood (blood going to the brain/out of left ventricle and into tissues)
∙ Chemoreceptors
Central Chemoreceptors
In brain, mainly the brainstem
Peripheral Chemoreceptors
Located in arteries
o Close to baroreceptors which sense change in BP
o Close to the Aortic Arch
Located in the Ceratoid Artery
o Blood entering the brain
∙ CO2 ⇒ most important stimulus that promotes a change in breathing rate
Hypercapnia: Increase of CO2 in Arterial Blood (Normal CO2 = 40 mm Hg) o Change in breathing rate occurs once CO2 goes up 5 mm Hg ∙ Almost doubles the breathing rate
∙ Blood goes into the brain where the Blood Brain Barrier is (continuous capillary with no intercellular clefts)
CO2 will be able to diffuse through the BBB into the
cerebrospinal fluid (aka fluid of the brain)
CO2 will react with water to produce Carbonic Acid, leading to Bicarbonate + Hydrogen Ion
o Hydrogen Ion ⇒ Acidosis ⇒ disturbance of metabolic
activity
∙ No buffer in the brain like the hemoglobin in RBCs
∙ Influences Central Chemoreceptors
>>Breathing rate is increased to get rid of H+
(therefore CO20
>>Impulses is sent to the Medullary Center →
Muscles →
Increase in Breathing Rate
>Expels more CO2, getting rid of H+
Hypoxia: O2 Deprivation
o O2 saturation should go way below 60 mm Hg
∙ At the tissue (40 mm Hg) there is still 75% O2 saturation Change in breathing rate will NOT change until way under 60 mm Hg
o Negative Mechanism = Same as Hypercapnia
∙ Only difference is that the Peripheral Chemoreceptors receive the impulse instead of the Central Chemoreceptors
Brain goes numb due to O2 deprivation, therefore the central chemoreceptors are numb
Acidosis: Increase of Hydrogen Ions (↓ pH)
o Influences Peripheral Chemoreceptors
o ↑ H+ in blood and reaches the BBB but does NOT diffuse ∙ The BBB is not permeable to Hydrogen (not lipid-soluble) Not going to be a major factor in changing the Breathing Rate o Conditions such as Diabetes could also increase H+ ⇒ increasing CO2
Chapter 25: The Urinary System
Organs
Kidneys
Bean-shaped organs
Functions:
o Formation of Urine
o Control of blood pressure (in long term mechanism)
Right Kidney is a bit lower/inferior to the Left Kidney
o The liver is right above/superior the right kidney
In the presence of endocrine glands
o Adrenal Glands (hats, sit atop the kidneys)
3 Major Regions
o Cortex
∙ Outer region
∙ Consists of the nephrons
Functional & structural units of kidney
Responsible for the formation of urine
1 million nephrons are found here
o Renal Medulla
∙ Made of triangular-shaped structures called Renal Pyramids
Base of pyramid faces the cortex
Tip faces the Renal Pelvis
Each has a striped appearance due to permeable collecting ducts that drain the nephrons
Papilla of Pyramid: finger-like projecting structures
o Where all collecting ducts fuse together
o Urine goes from Papilla to Renal Pelvis
∙ Papilla of Renal Medulla → Minor Calyx (cup-shape) →
Major Calyx → Renal Pelvis → Ureter → Urethra → Out
of Body
o Renal Pelvis
∙ Broadened top part of the ureter
Funnel shaped
Where the kidney tubules drain
Renal Column = extends from cortex into all 3 regions
Renal Lobe = 2 renal columns surrounded by renal pyramid
o Average of 7-8 lobes in each kidney
Ureters
Tubes from kidneys to Urethra
Urethra
Expels urine to outside the body
Functional + Structural Unit of Kidney: The Nephron
Made of 2 Major Portions
Renal Corpuscle
o Made of Glomerulus and Glomerular Capsule
∙ Glomerulus:
Network of fenestrated capillaries
Allows fluid to pass; prevents plasma proteins from exiting
Responsible for filtration of blood
∙ Glomerular Capsule
Aka “Bowman’s Capsule”
Beginning part of the renal corpuscle
Surrounds Glomerulus
Leads to the Renal Tubule
Renal Tubule
o 3 Areas
∙ Proximal Convoluted Tubule
∙ Loop of Henle or the Nephron Loop
∙ Distal Convoluted Tubule
Distal & Proximal describes their position to the Renal Corpuscle Leads to the Collecting Ducts which is not part of the Renal Tubule
Physiology of Nephron
Renal Corpuscle
Located in the Cortex
Part of Nephron Loop is located in the Medulla
o Glomerulus Capsule
∙ Double-layered Membrane
Parietal Layer of Glomerulus Capsule
External + single layer of simple squamous
o Does NOT have to do with filtration
Visceral Layer of Glomerulus Capsule
The parietal layer when it turns inferiorly
Adheres to the Glomerulus
Internal layer made of modified epithelial cells called
Podocytes
o Contain cytoplasmic extensions to cling to Glomerular
Capillaries called Foot Processes
∙ Foot Processes interdigitate ⇒ they leave gaps or
Filtration Slits
∙ Extremely important in formation of urine
Renal Tubule
Made of single layer of epithelial but changes in accordance to the different regions
o Proximal Convoluted Tubule
∙ Simple Cuboidal epithelial cells
Abundances in microvilli on the epical surface of the epithelial cells
Epical Surface = surface facing the lumen (or inside of the cell)
o Region where reclaiming of the material from lumen
through the cells back into the blood occurs (Reabsorbing
occurs)
∙ Huge # of microvilli = increases the surface area
Makes up the Brush Border
o Increases absorption
o Loop of Henle
∙ Descending Limb
Cuboidal epithelial cells with microvilli (Thick Descending Limb) Lower portion turns into Simple Squamous epithelial cells (Thin Descending Limb)
o Same epithelial in the actual loop
∙ Ascending Limb
1st Portion (turning up) = Simple Squamous epithelial (Thin Ascending Limb)
2nd Portion (going up) = Cuboidal epithelial (Thick Ascending Limb)
o Distal Convoluted Tubule
∙ Cuboidal epithelial
∙ Not abundant in microvilli
∙ Region that secretes material from blood into urine to be able to excrete wastes
Collecting Ducts
Contains 2 Types of Cells
o Principal Cell
∙ More abundant of the two
∙ Simple Squamous
∙ Contains NO microvilli
∙ Associated with Sodium-Water Balance
o Intercalated Cell
∙ Simple Cuboidal
∙ Abundant in microvilli
∙ Associated with Acid-Base Balance
Nephron Capillary Beds
2 Types
o Glomerulus Capillary
∙ Anatomical + Psychological exception
∙ Drained by efferent arteriole
Makes it an exception ⇒ arterioles are usually drained by venules!
Arterioles have high pressure; meaning high resistance;
therefore, high blood pressure
Average BP is 26 mm Hg; in the Glomerulus Capillary BP is 55 mm Hg
o Higher BP ables it to push the fluid out to the Glomerulus
to produce urine
Efferent arteriole has a smaller diameter than the afferent
arteriole
o Increases the resistance ⇒ ability to push fluid out
Leads to generation of other capillary bed
o Peritubular Capillary
∙ Tiny capillaries that travel alongside nephrons
Allows reabsorption and secretion between blood and the inner lumen of the nephron
∙ Branched off of efferent arteriole
Leads to the Cortical Nephron
85% of kidney nephrons
Nephron Loop is shorter
Glomerulus is further away from the Corticormedullary
Junction
Leads to the Juxtamedullary Nephron
Vasa Recta = the long capillaries running vertical + parallel to Henle’s Loop
o Part of the Juxtaglomerular Complex
Juxtaglomerular Complex
Region/contact between Ascending Limb of the Nephron + the Afferent Arteriole of the Peritubular Capillary
Involved in blood pressure regulation via the release of Renin and the autoregulation of Glomerular Filtration Rate
o Contains different types of cells
∙ Macula Densa Cells
Modified (tall) Cuboidal epithelial cells from the Ascending Limb Chemoreceptors = senses chemicals in the filtrate
Mainly senses sodium chloride present in the filtrate
∙ Granular Cells
Aka Juxtaglomerular Cells
Belong to the Afferent Arteriole
Smooth muscle cells; modified to be larger
Contain granules
Contains the enzyme Renin
o Promotes vasoconstriction
Mechanoreceptors!
∙ Extra-glomerular Mesangial Cells
Located between Macula Densa cells + Granular Cells
Contain gap junctions
Provides the ability to communicate signals between the
Macula + Granular cells
Physiology of the Kidney
3 Processes + the excretion of urine
Glomerular Filtration
o Filtration of fluid derived from the plasma (except blood cells + plasma proteins)
Reabsorption
o In Proximal Convoluted Tubule (all over the Renal Tubule)
o Selective reclaiming of certain substances from filtrate back into blood; back to venous blood
Tubular Secretion
o Selective secretion of material
∙ From blood through epithelial cell to urine to be excreted
Filtrate is not the same as urine
Filtrate: plasma without blood cells or plasma proteins
Urine: everything not needed in filtrate; waste
Filtration
Passive process
Increase of blood pressure in the glomerulus leads to movement of filtrate 3 Layered Filtration Membrane (in glomerulus)
Glomerular Capillary Endothelium (epithelial)
o Fenestrated
∙ Allows passage of all material except blood cells through the Filtration Slit that provides a place of exchange between the
podocytes and glomerular capillary
Basement Membrane
o Fused membranes of the podocyte and glomerular capillary
o Physical barrier
∙ No proteins present here!
o Made of negatively charged glycoproteins
∙ Electrically repels the negatively charged plasma proteins in the capillary
Electrical Repulsion occurs!
Major reason for maintaining plasma proteins
Foot Processes of Podocyte of Glomerular Capsule
o Finger-like projections of Podocytes that wrap around the glomerular capillaries
o Contain filtration slits between the foot processes
∙ Slit Diaphragm
Thin membranes that extend across the filtration slits
Catch and stop any macromolecules that manage to get by
the basement membrane
Made of Mesangial Cells
o Modified smooth muscle cells
∙ Can contract + controls surface area
o Engulf proteins that escape the filtration membrane
∙ Substances < 3 mm can pass
∙ Substances > 5 mm cannot pass
Factors Affecting Glomerulus Filtration Rate
Outward + Inward Pressures
Outward Pressure
o Promotes filtration
∙ Hydrostatic Pressure of Glomerulus (HPGC) = Blood Pressure in Glomerulus = 55 mm Hg
Extremely high because its drained by arterioles
The efferent arteriole is also smaller in diameter compared to the afferent arteriole
Reabsorption does not occur in Glomerular Capillary!
(Glomerulus)
Filtration occurs across (unlike blood capillaries)
HP is the single force responsible for filtration
There are no proteins present
o No Colloid Osmotic Pressure in the Glomerulus (OPGC)
o Outward Pressure = HP in Glomerulus + OP in Glomerulus = 55 mm Hg Inward Pressure
o Opposes filtration
∙ Colloid Osmotic Pressure in Glomerular Capsule (OPCS) = 30 mm Hg Proteins are present in the blood of the glomerulus
Provides opposing force because proteins attract water
∙ Capsular Hydrostatic Pressure
Fluid in the glomerular capsule, not the blood
Confined to a small space; HP in capsule (HPCS) = 15 mm Hg o Inward Pressure = HP in Glomer. Capsule + OP in Glomer. Capsule = 45 mm Hg
NFP: Winning Force
Net-Filtration Pressure (NFP) = Outward Pressure – Inward Pressure = HPGC – (HPCS + OPGC)
= 55 – (15 + 30)
= 10 mm Hg
Due to the blood in the Glomerulus (capillary)
o ↑ BP in Glomerulus = ↑ Net Filtration Pressure
∙ Filtration rate is dependent on the NFP
Glomerular Filtration Rate (GFR)
Amount/volume of filtrate formed in a minute = 120 mm per min. (180 L per day)
o Directly proportional to:
∙ Surface Area for filtration
Surface area is almost = to the surface area of your skin!
∙ Permeability of filtration membrane
About 1000x more permeable than blood capillaries
Due to the fenestrations
∙ NFP
Most controllable + Most important factor
Dependent on blood pressure
Adjustment in diameter of Afferent arteriole helps control the blood pressure
o Changes the HP in Glomer. Capillary = changes in NFP =
change in GFR
Vasoconstriction
↓
↓ Diameter
↓
↓ Blood Flow
↓
↓ Blood Pressure in the Glomerulus (HP)
↓
↓ Net Filtration Rate (NFP)
↓
↓ Glomerular Filtration Rate (GFR)
∙ Therefore, a decrease in urine output = the
conservation of water
↳ Maintains the blood volume and blood pressure
o Extreme changes in blood pressure leads to Extrinsic
Mechanisms
Extrinsic Mechanisms
Occurs when BP is < 80 mm Hg and > 180 mm Hg
o EX: Hypovolemic Shock
∙ Extrinsic takes over Intrinsic
Drastic decrease in systemic pressure is sensed by the
baroreceptors
Activates the Cardio-Exhibitory Center which leads to
Vasoconstriction
o Activates Granular cells of Juxtaglomerular Apparatus to
release Renin
o Activates Sympathetic NS to release Renin as well
∙ Renin: enzyme that catalyzes plasma proteins to
create Angiotensinogen and Angiotensin II
↳ Which promote further vasoconstriction
∙ Renin also activates the Adrenal Glands
↳ Releases Aldosterone to promote the reabsorption
of Sodium of
urine back to the blood
↳ Sodium attracts water
↳ ↑BV = ↑SV = ↑CO = ↑BP = ↑NFR =
↑GFR