Exam 3 LO Flashcards
What are the two kinds of nephrons?
- Cortical= 80%, short loops of henle (reabsorption)
- Juxtamedullary= 20%, long loops of Henley ( control urine concentration)
Renal cortex and renal medulla: iso-osmotic or hyper osmotic
Cortex= iso-osmotic and medulla= hyper-osmotic
Describe bowman’s capsule
Encloses glomerular fenestrated capillaries
The proximal convoluted tubule within the
Loop of henle within the
Distal tubule within the
Renal cortex
Extends into medulla then to cortex
Renal cortex
Fluid from renal corpuscle enters ___
Proximal tubule
Contains the ascending and descending loops
Loop of henle
Fluid enters __ from loop of henle
Distal tubule
The distal tubule contains what cells? What do those cells do?
Macula densa cells, sense ions
Forms ducts that drain into major calyces
Collection duct
Carries blood to the glomerulus, entering the capillary
Afferent arteriole
Capillary network, positioned between 2 arterioles
Glomerulus
Carries blood away from the glomerulus (leaving capillary)
Efferent arteriole
What cells do the afferent arteriole contain? Function of cells?
Juxtaglomerular cells, sense mean arterial pressure
Short loops of henle of cortical nephrons that extend from cortex to medulla
Peritubular capillaries
What is the juxtaglomerular apparatus?
Coordinates ions and blood pressure; macula densa cells plus juxtaglomerular cells
Explain the slits of podocytes
Surrounded by glomerular capillaries, contain pedicels and wrap around capillaries (spaces between pedicels are filtration slits)
Describe the fenestrated endothelium (glomerular endothelial cells) of the filtering membrane
allows for filtration of ions, water, small molecules, single amino acids, and drugs
What is the GFR?
Measure of kidney function, amount of filtrate formed per minute (120-125 mL/min)
What is the major determinant of GFR
Glomerular capillary hydrostatic pressure (P gc)
What is the GFR regulated by
Auto regulation of intrinsic factors, tubuloglomerular feedback, and extrinsic factors (neural and hormones)
Extrinsic factors regulate what
Blood pressure
What is RAAS
Renin, angiotensin, aldosterone, system
Ways to increase the GFR?
- Vasoconstrict efferent arteriole
- Vasodilator afferent arteriole
(Increase filtration: increase Pgc)
Ways to decrease GFR?
- Vasoconstrict afferent arteriole
- Vasodilate efferent arteriole (blood flowing out of capillary increases)
Promote filtration - oppose filtration=
Net filtration pressure
What starling forces promote filtration? What values?
Glomerular capillary hydrostatic pressure (55 mmHg) and bowman’s space protein/oncotic pressure (0 mmHg)
What starling forces oppose filtration?
Blood plasma protein pressure (in capillary- 30 mmHg) & bowman’s space hydrostatic pressure (15 mmHg)
Describe basement membrane of filtering membrane. Consists of? What passes through?
consists of collagen fibers and negatively charged glycoproteins and podocytes
- allows only water and small solutes to pass through
-negative charge repels plasma proteins and prevents them from entering bowman’s space
Autoregulation keeps the GFR constant as mean arterial pressure changes by:
If the MAP increases…
afferent arteriole vasoconstricts
Autoregulation keeps the GFR constant as mean arterial pressure changes by:
If the MAP decreases…
afferent arteriole vasodilates
Tubuloglomerular feedback is what kind of feedback
negative
Pathway of tubuloglomerular feedback to regulate GFR…
- Stimulus: Change in the GFR- increase in GFR
- Receptor: Sensed by the macula densa in the distal tubule
- Input: Increase in sodium, chloride, and water
- Control center: Juxtaglomerular apparatus
- Ouput: NO decreases (because it is a vasodilator)
- Effector: afferent arteriole vasoconstricts
- Response: Opposes stimulus- decrease in GFR
Extrinsic factors regulate….
What’s an example of a hormone?
blood pressure; RAAS
Increase in blood pressure= increase GFR — which results in what action
to get rid of fluid
If an increase in BP, this causes an increase stretch in the atria, which…
secretes ANP from the atria and increases GFR
Decrease in blood pressure= decrease in GFR—which results in what action
to save fluid
If there’s a decrease in BP, this causes an increase in…
sympathetics (NE) and angiotension II until BP returns to normal
Increase in sympathetics and angiotension effects the afferent arteriole how?
Vasoconstricts
What is not found in the filtrate?
cells, large proteins
Describe the body compartments, specifically the intracellular and extracellular fluid…
Intracellular fluid (inside the cell)= Na+: 15 mM
K+: 150 mM
Cl-: 7 mM
Extracellular fluid (blood plasma + interstitial fluid)=
Na+: 145 mM
K+: 5 mM
Cl-: 100 mM
What are the different functions of kidneys?
excretion of waste products (urine), regulate blood, and produce hormones
What hormones are produced in the kidneys?
- Erythropoetin (EPO)
- Active vitamin D
- Renin
Function of erythropoetin?
increase RBC count
Function of active vitamin D?
regulates calcium
Describe the RAAS production and pathway:
- Decreased BP in capillaries is sensed by juxtaglomerular cells in the kidney (less stretch in afferent arteriole walls)
- Juxtaglomerular cells secrete renin
- Angiotensinogen (inactive) is secreted from liver
- Renin removes -inogen from angiotensinogen, forming angiotension I
- In blood vessel, angiotensin I is converted into angiotension II by ACE (angiotension converting enzyme)
- Angiotension II effects the cardiovascular system by vasoconstricting (decrease radius, increase resistance)
AND
Angiotension II effects the kidney, causing the adrenal gland to secrete aldosterone, sensed by macula densa cells which increase sodium reabsorption and blood volume (water retension) - Increases the blood pressure in #6
Describe how the distal tubule participates in homeostasis of H+ (pH regulation secretion) and K+ (aldosterone regulation secretion)
If there’s an increase in K+ in the plasma, it is sensed by the adrenal gland which secretes aldosterone
Aldosterone enters the kidneys/collecting ducts
K+ secreted into the urine
Role of aldosterone
Secrete more K+ and reabsorb more Na+
Relationship between blood and urine pH
If the blood is too acidic, urine will be acidic & vice versa
When H+ levels in the blood are high, what happens in the body?
Body secretes H+ and reabsorbs K+
When H+ levels in the blood are low, what happens in the body?
Body reabsorbs H+ and secretes K+
Compare and contrast the luminal and basolateral side of the cell (what is on each side?)
Luminal side= aquaporins, secondary active transport between Na+ and glucose or amino acids (co-transporter), and sodium/hydrogen exchanger
Basolateral sode= aquaporins, K+ leak channels, primary active transport (Na/K ATPase), glucose or amino acid transporters in reabsorption, bicarbonate transporter
What kind of reabsorption: solutes/water in tubular fluid return to bloodstream by passing through the cell through aquaporins
Transcellular reabsorption
What kind of reabsorption: solutes/water in tubular fluid returns to bloodstream by moving between cells (fluid leaking)
Paracellular reabsorption
What is the direction of tubular reabsorption vs secretion?
Reabsorption= lumen to peritubular capillary (blood)
Secretion= peritubular capillary(blood) to lumen
What is tubular reabsorption? What is commonly reabsorbed?
Taking the substances out of the filtrate in Bowman’s capsule and moved back into the bloodstream
Glucose, amino acods, ions, bicarbonate
What is tubular secretion? What is commonly secreted?
removing substances the body doesn’t need
H+, toxins, drugs
Secreting H+ into the urine and reabsorbing bicarbonate is driven by
Na/K ATPase
A measure of the volume of plasma over time that’s filtered of a particular substance
Clearance
Clearance is defined in terms of __ not __; clearance is __
plasma, urine; substance specific
How is clearance a measure of GFR?
Substance is reabsorbed when clearance of substance is less than GFR (back into the blood)
Substance is secreted when clearance of substance is more than the GFR (into urine)
What type of substances have a clearance less than GFR
Amino acids, glucose, things we want! (lower clearance)
What type of substances have a clearance more than GFR
toxins, drugs (have higher clearance)
Compare inulin and creatinine?
Free filtered
How does the body clear inulin
filtration
How is inulin a measure of GFR
clearance of inlulin is the same as GFR
Characteristics of inulin?
- Not endogenous (not reabsorbed or secreted)
- All of inulin in bowman’s capsule is excreted
- Some of inulin of afferent arteriole is filtered
Characteristics of creatinine?
endogenous substance but not reabsorbed; slightly secreted at proximal tubule
What is creatinine?
breakdown of creatine phosphate in muscle
How is creatinine a measure of GFR
Best clinical measure of GFR
The largest amount of solute and reabsorption is where
Proximal tubule
100% of organic solutes (glucose or amino acids) are…
reabsorbed
H secretion and bicarbonate reabsorption uses what system
carbonic anhydrase
What is the effect of H on the pH
decreases the pH
what is the effect of bicarbonate on the pH
increases pH
How are acids (H+) and drugs secreted?
through secondary active transport coupled to Na co transport (NHE)
Describe the reabsorption of Na+, glucose, amino acids, and water in the proximal tubule
Water: water moves from the lumen to the cell to the peritubular capillary by aquaporins (transcellular reabsorption) or through paracellular reabsorption
Glucose and amino acids: glucose or amino acids are reabsorbed from lumen to the cell by secondary active transporters with sodium, then enter the peritubular capillary through glucose or amino acid transporters on the basolateral side.
Sodium ion: moves from lumen to the cell by secondary active transporter with glucose or amino acids, then enter the peritubular capillary through a primary active transporter Na+/K+ ATPase.
Describe the secretion of the hydrogen ion in the proximal tubule
Hydrogen ion secreted from the cell to the lumen by secondary active transporter (Na+/H+ exchanger) in exchange for Na+.
The process of secreting H+ into the urine and reabsorbing the bicarbonate ion back into the blood is driven by
Na+/K+ ATPase
__ combine in a cell through carbonic anhydrase to form bicarbonate and H+
Co2 from blood and water from lumen
Describe water reabsorption and osmolarity
As fluid moves along, solute reabsorption is followed by water—osmolarity remains constant
Describe the basics of water and balance
Major homeostatic function
Water gains=water loss (water gains are 60% liquid and water loss is 60% urine)
Juxtaglomerular nephrons are most involved in…
Water balance
Describe the osmolarity of cortex?
ISO-osmotic, 300 mOSM
- fluid becomes more concentrated as it enters descending loop in medulla
Describe the osmolarity of medulla
Hyper-osmotic, concentration of solutes increase as you move further into the medulla towards bottom of loop
Water flows out in __ loop through aquaporins, and the filtrate becomes more __
Out, concentrated
Urine becomes less concentrated in what loop?
Ascending
What occurs in the thick ascending loop?
A Na/K/Cl symporter, the ions move into the cell by the symporter at the same time in same direction
- nacl is pumped into the vasa recta capillaries and K is recycled through leak channels
Sodium and K enter the capillary by the symport through
Cl enters the capillary from symport by the
Sodium potassium ATPase
Cl channel
__osmolarity as we go down the medulla
High
Water travels by osmosis in what part of loop of henle
Descending loop
As filtrate travels up ascending limb near cortex, it becomes…
Less concentrated as Na, K, Cl is pumped out of lumen into capillaries
What is a diuretic
Chemical that makes urine, blocks na/Cl/k symporter so that water remains in urine
What is the countercurrent multiplier?
Trapped NaCl in medulla causes a high osmotic environment
As blood enters vasa recta capillaries, the capillary becomes
Hyperosmotic
In vasa recta capillary, water leaves the capillaries and plasma becomes more __ causing __
Concentrated, NaCl to move back into capillary to maintain high osmolarity
Makes the loop of henle a water circulator
Countercurrent exchange
Concentration gradients in the medulla are due to….
different transport characteristics
__ uses concentration gradients to (re)circulate salts and urea
Vasa recta
Concentrated medulla is used to…
save water, involving ADH
Loop of Henle helps save water by ___ and gets rid of water by __
concentrating urine, diluting urine
Dehydrations leads to an…
increase in ADH, increasing aquaporins
Why is urine diluted? Concentrated?
No aquaporins, no ADH; aquaporins present
ADH partakes in
water reabsorption
Acts on principal cell in collecting duct
ADH
How does ADH act on the principal cell?
- ADH (from blood) binds to ADH receptor (GPCR) in principal cell, causing aquaporins to move to luminal side.
- Water leaves the urine and enters aquaporins on the luminal side
- Water leaves luminal side and travels to aquaporins on the basolateral side into capillary
Describe the negative feedback regulation of ADH secretion from posterior pituitary:
If there’s an increase in plasma volume=
If there’s a decrease in plasma volume=
Increase in plasma volume= increase in water, decrease in ADH= increase in diluted urine
Decrease in plasma volume= decrease in water, increase in ADH= increase in concentrated urine
Describe how the distal tubule participates in pH homeostasis of H+ and K+
Some H secreted by primary active transport in intercalated discs. The H that is secreted gets exchanged for K+ by K+/H+ ATPase pump
In the proximal tubule, H+ is secreted and gets exchanged for __ by __
Na+, NHE (secondary active transporter)
If the urine and the blood are too acidic=
If the urine and the blood are too basiac=
more H+ secreted and more bicarbonate reabsorbed
less H+ secreted and less bicarbonate reabsorbed
Neural vs hormonal reflexes
Neural: baroreceptors, fast acting, subject to position change
Hormonal: RAAS, slow acting, blood volume and sodium changes
Compare and contrast the proximal tubule as a work horse and distal tubule as a fine tuner
Proximal tubule:
- Does the most reabsorption and secretion (2/3 water and ions reabsorbed, all drugs and toxins secreted, all glucose and AA reabsorbed)
- Little hormone regulation
Distal tubule:
- Maintains homeostasis
- Small Na amounts reabsorbed and K secreted
- Regulated by hormones (ADH, aldosterone)
What occurs in the early distal tubule?
Helps with calcium homeostasis in blood plasma
What occurs in the LATE distal tubule? What is in the distal tubule?
Principal cells and intercalated discs, acid base and water balance
Principal cells reabsorb and secrete what?
reabsorb Na and secrete K
Intercalated cells reabsorb and secrete what?
reabsorb bicarbonate and secrete H+
Aldosterone characteristics
Steroid hormone, can be long lasting when bound to albumin, slow acting
Aldosterone is slow acting because it is involved in
gene transcription
Aldosterone receptor binds to __ and regulates __
DNA, Na and K channels and Na/K ATPase pump
What happens after aldosterone in the blood enters the principal cell?
- Aldosterone binds to aldosterone receptor and DNA
- Na, K, and Na/K ATPase are transcribed from binding
- Na reabsorbed entering capillary by Na/K ATPase and K is secreted
The ability to stretch, the change in pressure needed to inflate the lung
Compliance
What is surfactant’s effect on surface tension and compliance
Lowers the surface tension, increases compliance of the lung
How does surfactant affect surface area and compliance
Decreases h bond formation to inflate the lung
Example of high compliance in the lung and work of breathing
Emphysema, easy to inflate the lungs but hard to deflate
High compliance requires what kind of change in pressure to inflate the lung? Low compliance?
Low pressure; higher pressure
__ compliance = stretches easily
__ compliance= increased stiffness
High
Low
Example of low compliance in the lung? Effect on work of breathing?
Restrictive lung disease (fibrosis), easy to deflate but harder to inflate
Ability to return back to resting state once the force is released
Elastance
What increases elastance (elastic recoil in the lung)
Elastin and collagen
Relationship between compliance and elastance
If high compliance, low elastance
Inversely proportional
Pressure inside a bubble (alveoli) formed by a fluid film is the function of 2 factors….
Surface tension and the radius
Apply the law of laplace to alveoli in the pulmonary system…(surface tension, pressure, and radius)
If the radius increases, pressure decreases (inversely Proportional)
If surface tension increases, pressure increases (directly proportional)
In the Law of LaPlace, of 2 bubbles have the same surface tension, the smaller bubble will have a…
Higher pressure and more surfactant
Describe the characteristics of surfactant and explain how surfactant reduces surface tension and equalizes inflation pressures in the lung
Surfactant sticks polar head in between h bonds and disrupts h bonding at the air water interface, lowering surface tension in the alveoli
__ surface tension= compliance __= __ pressure
Decrease, increase, decrease
When bronchioles contract what happens to airflow and resistance
Decrease air flow and increase in resistance
Apply the principals of airway resistance to the radius of airways
-Length and viscosity of air entering lung are constant
- radius matters the most in determining resistance
In the upper airways, if affected by a physical obstruction what happens to resistance
Increases
Bronchodilation vs bronchoconstriction: resistance? Mediated by?
Bronchoconstriction= increase resistance, mediates by parasympathetic neurons (muscarinic receptors), histamine, leukotrienes
Bronchodilation= decrease resistance, mediated by co2 and epinephrine (b2 receptors)
What is ventilation perfusion matching
Match areas of lung receiving oxygen with blood flow to lung
What happens in ventilation perfusion mismatch?
Ventilation decreases in alveoli, co2 increases, and o2 decreases leading to too much constriction and no diffusion
- can’t remove co2 and oxygenate blood
How to prevent hypoxic vasoconstriction
Blood vessels constrict and divert blood flow to a better ventilated alveoli
What’s the danger of hypoxic vasoconstriction?
If there’s too much vasoconstriction in the pulmonary artery, pressure and after-load increases on right side of heart (heart failure)
What does boyles law say about pressure and volume
Inversely proportional
Describe the atm and alveolar pressure at rest and the pressure gradient?
ATM pressure and alveolar pressure are equal, no pressure gradient, no volume or pressure change
Describe the atm and alveolar pressure during inhalation and the pressure gradient?
Alveolar pressure is less than atmospheric pressure; air moves down gradient inward; lung volume increases and alveolar pressure decreases
At the end of inhalation or exhalation: what happens to atmospheric pressure and alveolar pressure
They equalize
Describe the atm and alveolar pressure at exhalation and the pressure gradient?
Alveolar pressure increases above atm pressure, mechanical event of relaxation decreases lung volume; increase in pressure provides gradient for air to move out of lungs
What lung volume or capacities can’t be measured with a simple spirometer
Residual volume
Volume of air inspired or expired during a single breathing cycle
Tidal volume
Max volume of air inspired during inhalation
Inspiratory reserve volume
Max volume of air expired during exhalation
Expiratory reserve volume
Volume of air that remains in the lungs (dead space) after maximum expiration
Residual volume
Volume of air in the lungs at the end of a normal expiration
Function residual capacity
Functional capacity=
ERV + RV
Max volume of air that can be inspired after a normal expiration
Inspiratory capacity
Inspiratory capacity=
TV + IRV
Maximum volume of air that can be expired after a maximum inspiration
Vital capacity (forced vital capacity)
Vital capacity=
IRV + TV + ERV
Total volume of air in the lungs after a max inspiration
Total lung capacity
Total lung capacity=
Vital capacity plus residual volume (VC + RV)
Formula for minute volume
Tidal volume times respiratory rate
Average minute volume
5-6 l/min
Formula for alveolar ventilation
(Tidal volume- dead space air) x respiratory rate
Amount of air available for gas exchange
alveolar ventilation
At rest, what happens to the intrapleural pressure?
Diaphragm is released, intrapleural pressure is less than atmosphere
During inspiration, what happens to the intrapleural pressure?
Thoracic volume increases, intrapleural pressure decreases even more than at rest
During expiration, what happens to the intrapleural pressure?
Diaphragm relaxed and volume decreases, intrapleural pressure increases and returns to baseline (still negative compared to atm pressure)
Why is the intrapleural pressure negative?
Because atm pressure is set to 0, intrapleural pressure is sub atmospheric, under normal conditions it has negative pressure
Normally, the pressure in the intrapleural space is
Below atmospheric pressure (increase volume, decrease pressure)
During forced expiration, what happens to the pressure in the intrapleural space
Increases above atmospheric (increase pressure, decrease volume)
Pressure an individual gas exerts on a given space
Partial pressure
Partial pressure of oxygen in the atmosphere
160
Partial pressure of oxygen in the alveoli
100 mmHg
Partial pressure of oxygen in the artery (arterial pressure)
100
Partial pressure of oxygen in the venous capillary (venous pressure)
40 mmHg
Partial pressure of carbon dioxide in the atmosphere
Less than 1 mmHg
Partial pressure of carbon dioxide in the alveoli
40 mmHg
Partial pressure of carbon dioxide in the artery (arterial pressure)
40 mmHg
Partial pressure of carbon dioxide in the venous capillaries (venous pressure)
46 mmHg
Oxygen is high in the __ and low in the ___
Carbon dioxide is high in __ and low in the ___
Alveoli, venous capillaries
Venous capillaries, alveoli
Alveolar partial pressures or oxygen and carbon dioxide closely resemble venous blood in
Hypo ventilation
During hypoventilation, what’s the relationship between oxygen and carbon dioxide
Low oxygen and high carbon dioxide partial pressures
Alveolar partial pressures of carbon dioxide and oxygen levels more closely resemble the atmosphere
Hyperventilation
Normal ventilation is
4.2 L/min
During hyperventilation, what’s the relationship between oxygen and carbon dioxide
Low carbon dioxide and high oxygen partial pressures
Explain the steps of oxygen released at the tissues
- At rest, cellular o2 levels are 40 mmHg.
- O2 moves from dissolved down pressure gradient (100 mmHg to 40 mmHg)
- Drop in oxygen pressure allows some oxygen to unbind hemoglobin and move into the plasma (increasing partial pressure)
- O2 continues to move down its gradient and oxygen unbinds hemoglobin increasing partial pressure until hemoglobin reaches 75% saturation. (25% released to tissues)
- Once RBC saturation reaches 75% , no more oxygen can be released and oxygen in plasma moves into the cell until cell PO2 equals PO2 dissolved in plasma (40 mmHg)
Each hemoglobin binds
4 oxygen molecules
If partial pressure of plasma increases, what happens to hemoglobin percent saturation?
Increase (more oxygen can bind hemoglobin)
Using the oxygen hemoglobin binding curve…
Describe a resting cell, what’s the partial pressure of oxygen?
40 mmHg, once hemoglobin reaches the cell it begins releasing oxygen into the tissues to make atp
In a resting cell, when does hemoglobin go back to the lung to get more oxygen
When 25% oxygen is released
In the alveoli what percent of hemoglobin is bound to oxygen in the lung?
98%
What happens during exercise in relation to the oxygen hemoglobin binding curve?
Hemoglobin releases more oxygen into tissues than in resting cell to meet demands of the tissue based on environment
What is the main parameter that affects affinity of hemoglobin with oxygen
Metabolism
Increase in metabolism= __ tissue demand for oxygen
Increase
In a __ ward shift…..
As percent saturation of oxygen __, more oxygen is released into tissues
right, Decreases
Examples of rightward shifts
Low blood ph, high temperature, high blood co2 partial pressure, and added BPG
A higher blood pco2 allows more…
Oxygen to diffuse off RBC
Inserts itself into hemoglobin and traps it into a state of release (found in smokers)
2-3 BPG
In a __ shift…
Release less oxygen, hold onto more oxygen (tightly bound)
Left
To get hemoglobin to let go of oxygen, need a….
Lower pressure
Examples of leftward shifts
High blood ph, low temperature, low blood PCO2, no BPG
LOWER METABOLISM
Describe the transport of oxygen into the blood….
- When you breathe oxygen, it enters the alveoli ( p alveoli= 100 mmHg)
- Oxygen moves down pressure gradient out of alveoli into plasma (60 mmHg) until the gradient has equalized 100 mmHg (p alveoli=p plasma o2)
- Once oxygen is in the plasma, it binds hemoglobin in RBC (decreasing the pO2 in plasma hack to 60 mmHg)
- Oxygen continues to move down pressure gradient into plasma and bind hemoglobin until the hemoglobin reaches 98% saturation
- Once the last oxygen molecule fills the last binding site of hemoglobin, more oxygen than replaces the oxygen bound to hemoglobin
Bound content is dependent on the
Oxygen in plasma: number of binding sites and percent saturation of hemoglobin
All of the oxygen content in the blood
Total oxygen content
Available hemoglobin bound to oxygen
Percent saturation
directly proportional to the number of hemoglobin molecules and number of binding sites on hemoglobin occupied by oxygen
Bound content
Bound content formula
Number of hemoglobin molecules x percent saturation
Mary has 12% of hemoglobin
Frank had 13% of hemoglobin
Both have an alveolar pO2 of 100 mmHG:
- Who is more saturated?
- Who has a higher total content?
- Who has a higher dissolved content?
- Who has high bound content?
- Both, because when pO2= 100 mmHg, both have 98% saturation
- Frank, he has more hemoglobin percentage
- Both, because alveolar pO2 is proportional to dissolved content pO2
- Frank because has more hemoglobin, more bound oxygen
Co2 highest concentration is in the ___ , with a pressure of ___
Cell, 46 mmHg
As co2 increases, it favors the production of
H and bicarbonate
What are the steps for the transport of CO2
- Co2 diffuses out of cells into capillaries-plasma(46 to 40 mmHg)
- Some (7%) of co2 remains dissolved in plasma and some (23%) binds hemoglobin
- Most co2 is converted into bicarbonate and H through carbonic anhydrase
- Hemoglobin buffers H
- Bicarbonate enters the plasma in exchange for Cl entering the RBC (chloride shift) by secondary active transport.
- At lungs, dissolved co2 diffuses out of plasma (46 mmHg) into lungs (40 mmHg) until co2 levels equal 40 mmHg
- Co2 unbinds from hemoglobin and diffuses out of RBC
- Carbonic acid reaction reverses, pulling bicarbonate back into RBC and Cl back out- converting bicarbonate back to co2
Major control center for breathing ___
Responsible for fine tuning control of breathing ___
Medulla, pons
When the medulla and pons are activated by the chemoreceptors, they innervate…
Somatic motor neurons for inspiration and expiration
Inspiration somatic motor neurons innervate…..
Whereas
Expiration somatic motor neurons innervate…
External intercostals and diaphragm
Internal intercostals and abdominal muscles
Three parts of medulla
dorsal and ventral respiratory group and pre bot complex
What part of the medulla is in charge of inspiratory ventilation (regular respiration)
DRG
What part of the medulla is responsible for expiratory ventilation (often when forced)
VRG
What part of the medulla is an intrinsic pattern generator (pacemaker), cells set respiration rate
Pre bot complex
Discuss the mechanism of plasma levels of oxygen in the control of ventilation…
- Low oxygen in plasma allows less oxygen to diffuse into chemoreceptors (below 60)
- K channels close in response to low oxygen
- Cell depolarizes
- Depolarization opens VG Calcium channels and calcium enters the cell.
- Calcium in cell triggers the exocytosis is of neurotransmitters
- Neurotransmitters bind receptor on sensory neuron, triggering an action potential
- AP signals medullary centers to increase ventilation
Describe the location & function of central chemoreceptors
Respond to changes in Co2 only, in medulla, activated by H+
When co2 levels are high, __ levels are high
H+
When there’s an increase in co2 in the plasma, there more ___ in the CSF
H and bicarbonate
In cerebral capillary (blood brain barrier), some H ions cannot go into the CSF. Why?
There’s no transporter for diffusion of H ion, h found in CSF is only from co2
Describe the location & function of peripheral chemoreceptors
Respond to changes in o2, co2, and ph (H+) in arterial side
-located in aortic arch and carotid bodies
-Sends signals to afferent sensory neurons, then to medulla and pons
