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Anatomy and Physiology > Chapter 24 > Flashcards

Chapter 24 Flashcards

1
Q

Fluid Compartments

A

Areas separated by selectively permeable membranes and differing from each other in chemical composition

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2
Q

Major Fluid Comparments

A
  1. 65% ICF

2. 35% ECF - divided into 25% Tissue fluid, 8% blood plasma and lymph, and 2% transcellular fluid

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3
Q

Water moves by osmosis from…

A

The digestive tract to the bloodstream

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4
Q

Water moves by capillary filtration from…

A

The blood to the tissue fluid

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5
Q

Osmosis from one fluid compartment to another is determined by the…

A

Relative concentration of solutes in each compartment.

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6
Q

Electrolytes play the principal role in…

A

Governing the body’s water distribution and total water content.

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7
Q

A person is in a state of fluid balance when…

A

Daily gains and losses are equal

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8
Q

2 sources the gains come from

A
  1. Metabolic Water

2. Preformed Water

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9
Q

Metabolic Water

A

Produced as by-product of dehydration synthesis reactions and aerobic respiration

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10
Q

Preformed Water

A

Ingested in food and drink

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11
Q

Routes of water loss

A
  1. 1,500 mL as urine
  2. 200 mL in feces
  3. 300 mL in expired breath
  4. 100 mL in sweat

5 400 mL as cutaneous transpiration

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12
Q

Cutaneous Transpiration

A

Water that diffuses through the epidermis and evaporates. (Not same as sweat)

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13
Q

Insensible water loss

A

Output through the breath and cutaneous transpiration. (we are usually not aware of this)

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14
Q

Sensible water loss

A

Noticeable output, particularly through the urine and sweating

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15
Q

Obligatory water loss

A

Output that is relatively unavoidable: expired air, cutaneous transpiration, sweat, fecal moisture, and the minimum urine output

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16
Q

Fluid intake is mainly governed by

A

Thirst

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17
Q

Dehydration

A

Reduces BV and BP and raises blood osmolarity

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18
Q

Hypothalamus has at least 3 groups of neurons called

A

Osmoreceptors

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19
Q

Osmoreceptors

A
  • respond to angiotensin II and to rising osmolarity of the ECF
  • Communicate with other hypothalamic neurons that produce antidiuretic hormone thus, promoting water conservation
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20
Q

2 reasons why we salivate less when we are thirsty

A
  1. The osmoreceptor leads to sympathetic output from the hypothalamus that inhibits the salivary glands
  2. In dehydrated person, there is lower capillary BP and higher osmolarity of the blood so saliva is not produced that well.
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21
Q

The only way to control water output is through

A

Variations in urine volume

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22
Q

The kidneys..

A
  • Cannot completely prevent water loss nor can they replace lost water or electrolytes
  • They never restore fluid volume or osmolarity
  • But in dehydration, they can support existing fluid levels and slow down the rate of loss until water and electrolytes are ingested
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23
Q

Changes in urine volume are usually linked to

A

adjustments in sodium reabsorption

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24
Q

The total volume of fluid remaining in the body may change but

A

its osmolarity remains stable

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25
Q

What is best understood in the context of electrolyte balance?

A

Controlling water balance by controlling sodium excretion

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26
Q

Antidiuretic hormone provides a

A

Means of controlling water output independently of sodium

27
Q

What stimulates the posterior pituitary to release ADH?

A

The increased osmolarity of the blood

28
Q

Aquaporins

A

when installed in the plasma membrane, they serve as channels that allow water to diffuse out of the duct into hypertonic tissue fluid

29
Q

By helping the kidneys retain water, ADH…

A

slows down the decline in BV and the rise in its osmolarity thus, forming negative feedback loop

30
Q

Conversely, if BV and BP are too high or blood osmolarity is too low, ADH…

A

is inhibited

31
Q

What is an effective way of compensating for hypertension?

A

The renal tubules reabsorb less water, urine output increases, and total body water declines.

32
Q

Lack of ADH increase the ratio of water to sodium in the urine and it…

A

raises the sodium concentration and osmolarity of the blood

33
Q

Electrolytes are important for multiple reasons:

A
  1. Chemically reactive
  2. Participate in metabolism
  3. Determine the electrical potential across cell membranes
  4. Strongly affect the osmolarity of the body fluids and the body’s water content and distribution
34
Q

Electrolyte balance includes

A

All salts, acids, and bases

35
Q

Salts provide:

A
  1. Neuromuscular excitability
  2. Secretory activity
  3. Membrane permeability
36
Q

Sodium (Functions)

A
  • One of the principal ions responsible for the resting membrane potentials of cells
  • Inflow of sodium is an essential event in the depolarization that underlies nerve and muscle function.
  • The principal cation of the ECF
  • Account for 90% to 95% of its osmolarity
  • Most significant solute in determining total body water and the distribution of water among fluid compartments
  • Na-K pump is an important mechanism for generating body heat
  • Sodium bicarbonate plays a major role in buffering the pH of the ECF
37
Q

Sodium (Homeostasis)

A
  • There are multiple mechanisms for controlling sodium concentration, tied to its effects on BP and osmolarity and coordinated by aldosterone, antidiuretic hormone, and the natriuretic peptides
  • Aldosterone plays the primary role in adjustment of sodium excretion
  • Hyponatremia and hyperkalemia directly stimulate the adrenal cortex to secret aldosterone
  • Hypotension stimulates it by the way of the renin-angiotensin-aldosterone mechanism
  • As more sodium ions are reabsorbed, more potassium ions are secreted
  • The reabsorption of sodium ions causes the secretion of potassium or hydrogen ions
  • Progesterone reduces sodium reabsorption and has diuretic effect
38
Q

Potassium (Functions)

A
  • Most abundant cation of the ICF
  • The greatest determinant of intracellular osmolarity and cell volume
  • Produces the resting membrane potentials and action potentials of nerve and muscle cells
  • Essential cofactor for protein synthesis and some other metabolic processes
39
Q

Potassium (Homeostasis)

A
  • Closely linked to sodium
  • 90% is filtered by the glomerulus and reabsorbed by the PCT and rest is into the urine.
  • Its excretion is controlled in the nephron by changing the amount of potassium returned to the tubular fluid by the DCT and CD.
  • When its concentration is high, they secrete more K
  • When its concentration is low, the CD secretes less
  • Aldosterone regulates potassium balance
  • The more sodium there is in the urine, the less K and vice versa
40
Q

Potassium imbalances are the…

A

most dangerous of all electrolyte imbalances

41
Q

Normokalemia

A
  • K concentrations in equilibrium
  • Equal diffusion into and out of cell
  • Normal resting membrane potential
42
Q

Hyperkalemia

A
  • Elevated extracellular K concentration
  • Less diffusion of K out of cell
  • Elevated RMP (cells partially depolarized)
  • Cells more excitable
43
Q

Hypokalemia

A
  • Reduced extracellular K Concentration
  • Greater diffusion of K out of cell
  • Reduced RMP (cells hyperpolarized)
  • Cells less excitable
44
Q

Calcium (Functions)

A
  • Lends strength to the skeleton
  • Activates the sliding filament mechanism of muscle contraction
  • serves as a second messenger for some hormones and neurotransmitters
  • Activates exocytosis of neurotransmitters and other cellular secretions
  • Essential factor in blood clotting
  • must be kept at low concentration in order to keep high concentration of phosphate ions
45
Q

Calcium (Homeostasis)

A
  • Regulated by parathyroid hormone and calcitriol
  • Parathyroid hormone enhances reabsorption from filtrate
  • Calcitonin removes Ca from plasma via osteoblasts
46
Q

The pH of a solution is determined solely by its

A

Hydrogen ions

47
Q

Strong Acid

A

Gives up most of its hydrogen ions and lower the pH of a solution

48
Q

Weak Acid

A

Ionizes only slightly and keeps most hydrogen in a chemically bound form that does not affect pH

49
Q

Base

A

Any chemical that accepts H

50
Q

Strong Base

A

Has a strong tendency to bind H and raise the pH

51
Q

Weak Base

A

Binds less of the available H and has less effect on pH

52
Q

Buffer

A

Any mechanism that resists changes in pH by converting a strong acid or base to a weak one

53
Q

Physiological Buffer

A

A system that stabilizes pH by controlling the body’s output of acids, bases, or CO2.

  • Urinary System buffers the greatest quantity of acid or base but slow
  • Respiratory system exerts is fast but cannot alter the pH as much as the urinary system
54
Q

Chemical Buffer

A

A substance that binds H and removes it from solution as its concentration begins to rise or releases H into solution as its concentration falls

  • Can restore normal pH within a fraction of a second
55
Q

Major challenges of Acid-Base Balance

A
  • Maintaining H concentration of body fluids
  • Optimal pH differs in various fluids
  • H produced via metabolic reactions
56
Q

Buffer Systems

A
  • Composed of weak acid and a weak base

- 3 major chemical buffers are Bicarbonate, Phosphate, and Protein

57
Q

The amount of acid or base that can be neutralized by a chemical buffer system depends on 2 factors:

A
  1. The concentration of the buffers

2. and the pH of their working environment

58
Q

Bicarbonate Buffer System

A
  • A solution of carbonic acid and bicarbonate ions
  • Reversible reaction
  • Lungs and Kidneys constantly remove CO2 which keeps the reaction moving to the left, and more H is neutralized
  • If there is a need to lower the pH, the kidneys excrete HCO3 which keeps the reaction to the right and elevate the H concentration of the ECF
59
Q

Phosphate Buffer System

A
  • A solution of HPO4 and H2PO4
  • Works much like the bicarbonate system
  • The reaction can move right to lower pH or move left to raise pH
  • Optimal PH is 6.8
  • Has stronger buffering effect than an equal amount of bicarbonate buffer
  • Much less concentrated in the ECF so they are less important in buffering the ECF
60
Q

Protein Buffer System

A
  • More concentrated than either bicarbonate or phosphate buffers
  • Accounts for about 3-quarters of all chemical buffering in the body fluids
  • Carboxyl releases H when pH begins to rise and lowers pH
  • Amino binds H when pH falls too low, rasing pH to normal
61
Q

Respiratory Control of pH

A
  • Adding CO2 to the body fluid riases H concentration and lowers pH and vice versa
  • Relates to bicarbonate buffering system
  • Rising CO2 concentration and falling pH stimulate chemoreceptors which increases pulmonary ventilation
  • This expels excess CO2 and reduces H concentration
  • A drop in H concentration raises pH and reduces pulmonary ventilation which expels CO2 faster, lowering pH to normal
62
Q

Renal Control of pH

A
  • Neutralize more acid and base than respiratory system and chemical buffers
  • Secretes H into tubular fluid
63
Q

Secretion and neutralization of Hydrogen ions in the kidneys

A
  1. H in blood reacts with HCO3 to form H2CO3
  2. H2CO3 decomposes into H2o and CO2, which enter the tubule cell
  3. Tubule cells acquire CO2 from blood, tubular fluid, and their own aerobic respiration
  4. Carbonic anhydrase (CAH) combines H2O and CO2 to re-form H2CO3
  5. H2CO3 ionizes to form HCO3 (which returns to the blood) and H
  6. Na-H antiport exchanges H fo Na
  7. NaHCO3 from glomerular filtrate decomposes into Na and HCO3-NA is pumped into tubule cell
  8. Na is removed by Na-K pump at the base of the cell
  9. HCO3 reacts with H from tubule cell to form H2CO3
  10. CAH on brush border decomposes H2CO3 to H2O and CO2 again
  11. CO2 enters the tubular cell and H2O passes in the urine (carrying the H that was originally in the blood)

Anatomy and Physiology (13 decks)

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