M11 and M12 anat and Phy 235

What is TRUE regarding maintenance of the extracellular fluid (ECF) osmolarity within homeostatic limits?

Changes in ECF osmolarity impact cell volume (via swelling or shrinkage)

Which chemical directly causes the formation of Angiotensin I?

Renin

The plasma concentration of which of these chemicals is not homeostatically regulated in the RAAS pathway?

Angiotensinogen

If the concentration of renin in the plasma decreases, how will the clearance of Na+ change?

 CNa will increase

Which is the primary hormone responsible for regulating the potassium levels of the extracellular fluid (ECF)?

 aldosterone

Which of the following stimulates a decrease in the frequency of action potentials in hypothalamic neurons with axonal projections to the posterior pituitary? Select all that apply

edema in the tissues

increased blood pressure

Which of the following would occur due to high levels of ADH secretion?

Select ALL that apply.

An increase in water reabsorption

High collecting duct water permeability

Renin and aldosterone are part of the renin-angiotensisn-aldosterone system. Renin is a i that ii , and aldosterone is a iii with a iv receptor.

 i. enzyme; ii. Converts angiotensinogen to angiotensin I; iii. steroid; iv. intracellular

Which of the following will happen following the ingestion of a large amount of water?

 The osmolarity of the extracellular fluid (ECF) will decrease.

During hemorrhage:

Select all that apply.

 

aldosterone secretion increases, sympathetic activity increases, and arteriolar constriction in blood vessels going to the stomach increases

Plasma levels of atriuretic peptide (ANP) are increased in patients with heart failure because:

 Venous pressure is increased.

Edema in systemic tissues often occurs  in patients with chronic heart failure. Why?

Hydrostatic pressure in the systemic capillaries increases due to an increase in venous pressure.

In which region of the mammalian nephron is the majority of the water and salt reabsorbed?

 Proximal tubule

In which region(s) of the mammalian nephron is the reabsorption of water and salt regulated to determine final urine osmolarity and volume? Select all that apply.

collecting duct

distal tubule

Neural reflexes regulate the reabsorption of water in the distal tubule and collecting duct of the nephron.

False

Which are avenues for NaCl input or generation in humans? Select all that apply.

 Ingesting food

The primary hormone system that regulates ECF volume is ____, while the ____ hormone(s) play(s) a supportive role.

 RAAS ; ADH

The primary hormone system that regulates ECF osmolarity is ____, while the ____ hormone(s) play(s) a supportive role.

 ADH ; RAAS

Diuresis

Increased production of urine, helping the body eliminate excess water.

Natriuresis

Excretion of sodium in the urine. Often linked with diuresis because sodium pulls water with it.

Renin

An enzyme secreted by the kidneys in response to low blood pressure or low sodium. It starts the RAAS cascade

Angiotensinogen

A protein produced by the liver that is the inactive precursor to angiotensin I. Renin converts it into angiotensin I.

Angiotensin I

An inactive molecule formed from angiotensinogen. It’s converted into angiotensin II by ACE.

Angiotensin II

A powerful vasoconstrictor (narrows blood vessels), raises blood pressure, and stimulates aldosterone release.

Aldosterone

A steroid hormone from the adrenal glands that promotes sodium (and water) reabsorption and potassium excretion in the kidneys, raising blood volume and pressure.

Angiotensin Converting Enzyme (ACE)

The enzyme that converts angiotensin I into active angiotensin II. It's found mostly in the lungs.

Atrial Natriuretic Peptide (ANP)

Released by the heart’s atria in response to stretch (from too much blood volume); promotes natriuresis and diuresis, reducing blood pressure.

Brain Natriuretic Peptide (BNP)

Released mainly by the ventricles of the heart in response to high pressure; has similar effects as ANP and is also used as a clinical marker for heart failure.

Medullary Interstitial Osmotic Gradient

The concentration gradient in the kidney’s medulla that helps draw water out of the collecting duct, concentrating urine

Antidiuretic Hormone (ADH) / Vasopressin

Released by the posterior pituitary; makes the kidneys reabsorb more water by increasing water channels (aquaporins) in the collecting ducts.

Aquaporin

A type of protein channel in kidney cells that allows water to move across the membrane. ADH increases their presence to reabsorb water and concentrate urine.

Maintenance of which variable regulated by the kidney is most important for the optimal function of enzymes?

ECF Ph

Which are avenues for NaCl output or loss in humans? Select all that apply.

urine, feces, and evaporation from skin

Changes in ECF K⁺ concentrations can have a major impact on resting membrane potential and the excitability of cells.

True

Angiotensin Converting Enzyme (ACE) is an enzyme that is found in the luminal membranes of endothelial cells lining blood vessels and converts angiotensin I to angiotensin II.

True

In which region of the mammalian nephron does the reabsorption of water and salt coupled with the flow of blood through the vasa recta lead to the generation and maintenance of the renal medullary osmotic gradient?

Loop of Henle

In which region of the mammalian nephron is the reabsorption of water and salt regulated to determine final urine osmolarity and volume?

Distal tubule and collecting duct

The kidneys contribute to homeostatic regulation of several variables in the extracellular fluid (ECF), including volume, osmolarity, ion concentrations and pH. Why is maintaining each of these variables within a homeostatic range important to survival in humans? In other words, what would be the consequences if each variable were not maintained within homeostatic limits? ECF ion concentrations

Many functions of cells are dependent on ion concentrations and concentration gradients (excitability, exocytosis, intracellular signaling, muscle contraction, bone formation, blood clotting).

The kidneys contribute to homeostatic regulation of several variables in the extracellular fluid (ECF), including volume, osmolarity, ion concentrations and pH. Why is maintaining each of these variables within a homeostatic range important to survival in humans? In other words, what would be the consequences if each variable were not maintained within homeostatic limits? ECF pH

Enzymes operate optimally within narrow pH ranges and hydrogen bonding plays an important role in the structure of molecules.

The kidneys contribute to homeostatic regulation of several variables in the extracellular fluid (ECF), including volume, osmolarity, ion concentrations and pH. Why is maintaining each of these variables within a homeostatic range important to survival in humans? In other words, what would be the consequences if each variable were not maintained within homeostatic limits? ECF osmolarity

ECF osmolarity impacts cell volume because H₂O, but not solutes are freely permeable across the cell membrane

The kidneys contribute to homeostatic regulation of several variables in the extracellular fluid (ECF), including volume, osmolarity, ion concentrations and pH. Why is maintaining each of these variables within a homeostatic range important to survival in humans? In other words, what would be the consequences if each variable were not maintained within homeostatic limits? ECF volume

Mean Arterial Blood Pressure (MAP) depends on volume over time

What are the avenues of H₂O input and output in humans?

Input: food, drink, metabolism

Output: skin, lungs, urine, feces

In which part of the nephron is the permeability to H₂O regulated? What hormone is primarily responsible for this regulation? What is the chemical class of the hormone? Which variable, ECF volume or ECF osmolarity, does this hormone maintain at homeostatic levels?

H₂O reabsorption is regulated in the DT & CD by ADH (vasopressin), a peptide hormone that maintains ECF osmolarity at homeostatic levels.

What are the avenues of NaCl input and output in humans?

Input: food, drink

Output: skin, urine, feces

In which part of the nephron is the permeability to Na⁺ regulated? What hormone is primarily responsible for this regulation? What is the chemical class of the hormone? Which variable, ECF volume or ECF osmolarity, does this hormone maintain at homeostatic levels?

Na⁺ reabsorption is regulated in the DT & CD by aldosterone, a steroid hormone that maintains ECF volume at homeostatic levels.

How do the natriuretic peptides regulate renal function and what triggers their secretion?

These are “anti-aldosterone” hormones that increase Na⁺ excretion by reducing Na⁺ reabsorption in the distal tubule and collecting duct through inhibition of the RAAS and ADH systems. Increased myocardial stretch (blood volume) triggers their secretion.

Why is maintaining ECF K⁺ concentrations at homeostatic levels so important? What hormone is responsible for regulating K⁺ secretion in the nephron? How is this related to Na⁺ reabsorption?

Extracellular K⁺ concentrations have a major impact on resting membrane potential and excitability of cells. Aldosterone is the hormone that regulates K⁺ secretion in the DT of the nephron. It is inversely related to Na⁺ reabsorption because synthesis of Na-K-ATPase pumps is the mechanism by which regulation is achieved.

The primary hormone system that regulates ECF osmolarity

ADH

The primary hormone system that regulates ECF volume is

RAAS

Gastrointestinal system endocrine secretions include:

Gastrin, Motilin, and gastric inhibitory peptide (GIP)

Pancreatic enzymes do not digest the pancreas before they are secreted into the small intestine because:

they require proteolytic activation at the small intestine to become active.

The primary function of the stomach is to:

mechanically digest food materials.

Where in the GI tract does carbohydrate digestion begin?

mouth

Intrinsic factor:

is necessary for the absorption of vitamin B12.

Ingested fats are absorbed:

into lacteals in the small intestine villi.

In the gastrointestinal (GI) system, i and ii are maximized by regulating the activity of iii and iv.

i. digestion; ii absorption; iii motility; iv secretion

In dumping syndrome, the rate of gastric emptying from the stomach to the small intestine is faster than normal. Which of the following will happen as a consequence of this?

The probability of gastric reflux (heartburn) will increase.

The loss of intestinal tissue that occurs with an intestinal atresia specifically at the duodenum can cause which of the following Select ALL the apply: 

Decrease in absorption of carbohydrates, Decrease in GIP secretion, and a decrease in levels of intrinsic factor

Long reflexes in the GI tract:

can be stimulated by the smell of food.

During the cephalic phase of digestion:

secretion of gastrin increases.

Which of the following would INCREASE the strength of intestinal smooth muscle contractions? Select all the apply.

Distension/stretch of the intestine, the pH inside the duodenum becoming more acidic, and tasting/chewing food

i stimulates motility of ii, which aids in the iii_ fats.

i. gastrin; ii. the stomach; iii. mechanical breakdown