Renal 5 Flashcards
Regulation of Tubular
Reabsorption
Essential to maintain a precise balance between
GFR and tubular reabsorption.
Tubular reabsorption controlled by (3)
Local Control
Mechanisms, Nervous System, and Endocrine
System
Reabsorption of some solutes can be individually
—.
adjusted
Local Control Mechanisms (3)
Tubuloglomerular Feedback Response (TGF)
Glomerulotubular Balance (GTB)
Arterial Pressure (pressure natriuresis/diuresis)
Systemic Control Mechanisms (2)
Hormones
Sympathetic Nervous System
Hormones (5)
- aldosterone
- angiotensin II
- antidiuretic hormone (ADH)
- atrial natriuetic peptide (ANP or ANF)
₋ parathyroid hormone
TGF Response: Autoregulation of GFR. (3)
Keeps GFR constant
Afferent and Efferent arteriolar resistance related to flow rate of NaCl by macula
densa
Example: GFR increase-increased NaCl to macula densa- TGF response decreases
GFR
Glomerular Tubule Balance (GTB): Autoregulation
of PT reabsorption rate (4)
PT reabsorption rate related to tubular load
As tubular LOAD increases, rate of
REABSORPTION increases.
Depends on changes in peritubular capillary and
renal interstitial fluid Starling’s forces.
Example: GFR increase-GT balance increases PT
Na+/H20 reabsorption to maintain Na+/H20
balance
Together these two mechanisms help to
prevent overloading of the distal tubule
segment when GFR increases due to pressure changes or other disturbances
Assures — may be maintained
Homeostasis
Small increases in MAP can cause marked increases in urinary (2)
Na+ and H2O excretion.
Mechanisms not understood
Normal kidney function and pressure natriuresis mechanisms assure that
large changes in salt and water intake accommodated with only minor changes in ECF volume, CO, and MAP
Aldosterone: Cellular Mechanism
Stimulates
Na+ reabsorption and
K+ Secretion
Aldosterone: Cellular Mechanism
onest and duration
slow onset
long duration
Aldosterone: Cellular Mechanism
increases (2)
number and activity
activity
Control of Aldosterone Secretion
increase (2)
Increased plasma K+
Angiotensin II
Increase
Increased plasma K+
Angiotensin II
(changes associated with
Na+
and volume depletion or low
blood pressure)
Control of Aldosterone Secretion
Decrease (2)
Atrial natriuretic peptide
(ANP/ANF)
Increased Na+ concentration
(osmolarity; weak)
Decrease Atrial natriuretic peptide (ANP/ANF) Increased Na+ concentration (osmolarity; weak) (changes associated with
increased Na+ and volume or
high blood pressure)
Other Effects of Aldosterone (3)
Increases H+ secretion by intercalated cells of late distal & cortical
collecting tubule membrane: excess aldosterone levels may cause
metabolic alkalosis.
Increases Na+ reabsorption and K+ secretion by sweat and salivary
glands.
Increases Na+ absorption by intestinal (colon) mucosa.
Angiotensin II:
Cellular Mechanism
major regulator of (2)
na and water reabsorption
Angiotensin II:
Cellular Mechanism
occurs in most
nephron segments
Angiotensin II:
Cellular Mechanism
stimulus (2)
decreased MAP
decreased ECFvol
Angiotensin II: Cellular Mechanism effector responses (6)
Stimulates aldosterone production.
Directly increases Na+ reabsorption (proximal, loop, distal,
collecting tubules).
Increases H+ secretion
Constricts efferent arterioles and increases GFR
Constricts systemic arterioles, increasing TPR and MAP
Increases Aldosterone secretion from Zona Glomerulosa
ADH: Cellular
Mechanisms
increases
water reabsorption
ADH: Cellular
Mechanisms
location
late DT and CD
ADH: Cellular
Mechanisms
Stimulus (2)
increased ECFosm
decreased MAP
ADH: Mechanisms of Action (3)
Increases H2O permeability via activation of Gαs Protein linked receptor Activates cAMP Increases the synthesis and insertion of AQP-2 into luminal membrane.
Atrial Natriuretic Peptide (ANP)
increase
decrease
increase GFR
decrease na reabsorption (increase na excretion)
ANP
Stimulus
Secreted by cardiac atria in
response to stretch (increased
blood volume).
ANP: Effector Responses (4)
Effector Responses Directly inhibits Na+ and H2O reabsorption in PT Increases GFR (dilates afferent, constricts efferent arterioles). Inhibits renin release and aldosterone formation. Helps to minimize blood volume expansion (CHF).
hormone:
site of action:
effect:
hormone:
site of action:
effect:
hormone:
site of action:
effect:
hormone:
site of action:
effect:
SNS Decreases (2) Excretion
Na+ and H2O
SNS Decreases Na+ and H2O Excretion: (4)
Constricts arterioles. Stimulates renin release. Decreases GFR and renal blood flow. Directly stimulates Na+ reabsorption via α receptors on tubule epithelial cells in PT and TAL.
Total Ca++ amount in body
1100 g, 99% stored in bones
Total Body Ca++ (3)
- 0.1% ECF
- 1% ICF/IC compartment
- Majority in bone
ECF — tightly regulated
Ca++
Ca
Critical for: (6)
⁻ Normal cell function ⁻ Neural transmission ⁻ Membrane excitability ⁻ Bone structure ⁻ Blood Coagulation ⁻ Intracellular signaling
— Ca++ is form most
important for functions in body
ionized
–% of Plasma
Ca++ Filtered
60
–% of Filtered Ca++
Reabsorbed in PCT
65
—%
Reabsorbed in
Loop of Henle
25-30
—% Reabsorbed
in Distal and
Collecting Tubule
4-9
–% Excreted
1
PTH Regulates Ca++ Reabsorption in (2)
TAL and DT
Luminal
Absorption (3)
50% by para- cellular bulk flow; passive Favored by +8 mV luminal charge 50% transcellular; entry passive
