Midterm Chapter 20

Question 1

The amount of water in the body is regulated mainly by balancing water intake by __________________, and water excretion by the _____________________.

Answer 1

intake by drink

excretion by renal excretion (pee out)

Question 2

The part of the uriniferous tubule that creates a concentrated medullary interstitium is the ______________________. The substance most important for concentrating the interstitial fluid is ______________. What is the maximum concentration of the interstitium? ____________ (include units).

Answer 2

1. DCT & cortical collecting duct
2. Na+
3. 1400 mOsm

Question 3

Without hormonal influence the collecting duct is ( permeable / impermeable) to water. Without hormonal influence the collecting duct ( will / will not ) absorb water from the filtrate.

Answer 3

default = impermeable to H2O

will not absorb water

Question 4

The hormone that adjusts the permeability of the collecting duct is _______________________________ (full name). It is secreted from the _________________________ _______________ (be specific). It affects collecting duct cells by causing ______________________ (a protein) to be inserted into the membrane, causing the permeability to be (higher / lower) and resulting in (increased / decreased) water reabsorption. The urine produced will have a (higher / lower) concentration and a ( higher / lower ) volume.

Answer 4

1. hormone - ADH (antidiuretic hormone)
2. secreted from the posterior pituitary
3. protein - aquaporine
4. permeability to be higher resulting in higher water reabsorption
5. Urine will have a higher concentration and lower volume

Question 5

The primary sensors for the negative feedback system that regulates urine concentration are called _____________ and they are located in the _______________________ (be specific).

Answer 5

Osmoreceptors in the the thirst center in the hypothalamus

Question 6

Normally the osmotic concentration of the blood is about ________________ (includes units). When dehydrated it might be about ________________. The levels of circulating ADH should be (higher / lower) than normal. The urine produced will have a (high / low) concentration and a ( high / low ) volume.

Answer 6

Normal osmotic concentration = ~300mOsm
Dehydrated = ~310mOsm
ADH levels should be higher than normal
Urine produced will have a high concentration and low volume

Question 7

Normally the osmotic concentration of the blood is about ________________ (includes units). When overly-hydrated it might be about ________________. The levels of circulating ADH should be (higher / lower) than normal. The urine produced will have a (high / low) concentration and a ( high / low ) volume.

Answer 7

Normal osmotic concentration = ~300mOsm
Overly hydrated = ~290mOsm
ADH levels should be lower than normal
Urine produced will have a low concentration and high volume

Question 8

Based on its molecular structure what kind of hormone is aldosterone? The receptors that bond aldosterone will be located where in a cell? What general effect does aldosterone have on its target cells. What specific effects does it have?

Answer 8

Steroid hormone
Binding receptors are located inside a cell
General effect - alters gene expression
Specific effect - Increase Na+ transporters in DCT and cortical collecting duct, Increase Na+ reabsorption, Increase BV = increase BP

Question 9

The sections of a uriniferous tubule that are sensitive to aldosterone are____________________________ and the ____________________________ (be very specific).

Answer 9

DCT and Cortical collectind duct

Question 10

From where is aldosterone secreted?

Answer 10

from the adrenal cortex

Question 11

With respect to sodium balance _______________ stimulates aldosterone secretion.

Answer 11

low BP (low Na+)

Question 12

Complete the following statement about the RAS. _____________________ is produced by the liver. _________________________ is released in the kidneys by __________________ ______, which converts ___________________________ to __________________________. Finally _________________________ is converted to Angiotensin II by the enzyme ______________________ found in the endothelium of blood vessels.

Answer 12

Angiotensinogen is produced by the liver.
Renin enzyme is released in the kidneys by granular cells, which converts Angiotensinogen to Angiotension I. Finally Angiotensin I is converted to Angiotensin II by the enzyme ACE (angiotensin converting enzyme) found in the endothelium of blood vessels.

Question 13

Renin is secreted by _____________________________ (be a specific as possible). These cells are sensors and detect ______________________________ . When would these cells release renin?

Answer 13

Secreted by the granular cells in the juxtoglumerula.
Detect low BP
Would release renin when blood pressure drops

Question 14

Renin is secreted by _______________________ (be a specific as possible). These cells are innervated by _____________________________________________ which release _________________________onto them (a neurotransmitter).

Answer 14

Secreted by the granular cells in the JG.

innervated by sympathetic neurons which release epi/norepi

Question 15

Renin is secreted by ______________________________ (be a specific as possible). These cells receive signals from the macula densa when GFR is ( high / low). This is most likely to occur when blood pressure is (high / low).

Answer 15

Secreted by the granular cells in the JG.
receive signals from macula densa when GFR is low
most likely to occure when BP is low

Question 16

Angiotensin II has a number of powerful effects. List the effects (5 of them) and explain how they each effect maintains homeostasis.

Answer 16

1. Stimulates ADH secretion - if BP decreases due to decrease in BV then ADH secretion is stimulated = increase water reabsorption
2. Powerful vasoconstrictor which targets afferent arterioles of renal corpuscle - If decrease in BP then vasoconstrict = increase BP
3. Stimulates thirst = drink = increase BV
4. Stimulates Aldosterone release which increases Na+ reabsorption (good for low Na+ diets) = increase H2O reabsorption
5. Stimulates cardiac and vasomotor centers in medulla - Cardiac centers increase HR and contractility and Vasomotor increases vasoconstriction and resistance in arteries (Increase BP = Increase CO x Increase R arteries)
   * all help keep you alive if you’re dehydrated or bleeding to death.

Question 17

ANP is a hormone released from the what? What is the stimulus?

Answer 17

ANP = Atrial Natriuretic Peptide
Secreted by atrial cardiac muscle cells
Stimulus = stretch in atria

Question 18

ANP (stimulates / inhibits) renin release, thereby indirectly influencing secretion of 2 separate hormones. Explain in detail how this helps maintain homeostasis (two ways, one for each hormone).

Answer 18

ANP inhibits renin release influencing the release of ADH and Aldosterone

1. Decreases ADH which decreases water reabsorption
2. Decrease aldosterone which decreases Na+ reabsorption

Question 19

ANP causes (vasoconstriction / vasodilation) of the afferent arteriole. Explain in detail how this helps maintain homeostasis.

Answer 19

ANP causes vasodilation of the afferent arteriole

Causes an increase in GFR which increases water excretion

Question 20

The levels of K+ in the ECF must be regulated within very narrow limits. Explain why K+ is so important? What would happen if its levels were to rise or fall to non-homeostatic levels?

Answer 20

K+ is so important because it dictates the resting membrane potential. If levels rise too much you’ll have a hyperexcitable CNS, if they drop you’ll have a depressed CNS

Question 21

With respect to potassium balance, what is the primary hormone for K+ regulation? What is the stimulus for its release (in this context). What is the primary target? What effect does it have on the target.

Answer 21

Primary hormone - aldosterone
Stimulus - increased K+ in ECF
Primary target - DCT and cortical CD
Effect - increase K+ secretion

Question 22

Predict the effect of the following on 1) osmolarity of the blood and 2) blood volume. Bleeding events (hemorrhage). Dehydration. Over-hydration (drinking a lot of water).

Answer 22

Bleeding event (hemorrhage): normal osmolarity/decreased BV
Dehydration: increased osmolarity/decreased BV
Over-hydration: decreased osmolarity/increased BV

Question 23

Outline the compensatory responses activated during a bleeding event. Be sure to note the sensors, hormones, effectors and effects.

Answer 23

1. Stimulus: Decrease BP
Sensor: Granular Cells of the JG detect low BP
Release: renin
2. Stimulus: Low Na+ in filtrate due to:
Low GFR, low Pglom, low BP
Sensor: Macula densa
Release: renin
3. sympathetic stimulation = renin release

Renin uses angiotensinogen to make angiotension 1 which uses ACE (angiotensinogen converting enzyme) to make angiotension 2.
Angiotension 2:
1. increase ADH secretion which increases H2O reaborption
2. stimulates aldosterone which increases Na+ and H2O reabsorption
3. powerful vasoconstrictor = increase BP
4. stimulates thirst = increase BV
5. Stimulates cardiac and vasomotor centers in medulla - Cardiac centers increase HR and contractility and Vasomotor increases vasoconstriction and resistance in arteries

Question 24

Outline the compensatory responses activated during dehydration. Be sure to note the sensors, hormones, effectors and effects.

Answer 24

Same responses as in a bleeding event plus:
Osmoreceptors detect ECF concentration.
increase ADH = increase H2O = 310 mOsm =
Reabsorption in CD

Question 25

Outline the compensatory responses activated during excessive water drinking. Be sure to note the sensors, hormones, effectors and effects.

Answer 25

Stimulus: stretch in atria from increase in BV
sensor: atrial cardiac muscle cells
Release: ANP (Atrial Natriuretic Peptide)
Effects: 1. dilate afferent arteriole
2. decrease renin release which decreases aldosterone (less Na+ reabsorption) and ADH (less water reabsorption = more Na+ in urine and increase in Na+ loss)

Question 26

Explain why changes in pH are incompatible with normal cellular function.

Answer 26

If the pH deviates too far in either direction, cells become poisoned by their own toxic waste and die.
pH changes can denature proteins - extra H+ can run into the H+ bonds (H+-O) and take the H+ away breaking the bond and creating H2O.

Question 27

`what does the term pH mean?

Answer 27

potentials of hydrogen

Question 28

List the major sources of H+ in the body. Describe a scenario for each one (when do these sources contribute to body [H+]?

Answer 28

1. CO2 (most common) - source: your cells
2. Food - acetic acid, malic acid, ethanol, amino acids, fatty acids
3. lactic acid - excessive exercising
4. ketone bodies - fasting, type 1 diabetes

Question 29

List the primary buffer input to the body from outside sources. Where does it come from? (2 sources)

Answer 29

1. Antacids (most common)

2. Very minimal from food

Question 30

List the primary buffer in the blood. Where does it come from? (2 sources)

Answer 30

HCO-3 of the bicarbonate/carbonic acid buffer system
Source:1. RBC’s, 2. Kidney Cells (PCT)
(Add lactic acid because it can react with hydrogen to form carbonic acid -> bicarbonate