Exam 3 Flashcards
(80 cards)
Briefly explain the difference between osmolarity and tonicity
- Osmolarity: depends on the concentration of an osmotically active solute. penetrating and non-penetrating doesn’t matter
- Tonicity: the flow of water. the outcome of osmolarity with respect to the environment of the cell
What anatomically distinguishes cortical and juxtamedullary nephrons? How do they differ in function?
- cortical: Short loop of henle, located shallow in the renal cortex. it is good at producing urine and moving urea but bad at water reabsorption
- Juxtamedullary: Long loop of henle, located deep in renal medulla. good at water reabsorption but bad at moving waste (Urea)
Many Substances are found at higher concentrations in the urine than they are in the blood. Briefly discuss two different mechanisms that allow this to happen.
- secretion: Substances will use active transport to go into the urine from blood stream. This will lead to higher concentration of substances in the urine
- reabsorption: Water reabsorption will leave a higher concentration of substances in the urine automatically.
In a normal kidney, which of the following conditions would cause an increase in the glomerular filtration rate (GFR)?
a decrease in concentration of colloid proteins in the blood
Dan has been lost in the desert for two days with very little water. As a result, you would expect to observe what?
elevated ADH levels
Snake venoms are generally hydrophilic and protein-based. Assuming there is not a way to enter the blood stream (such as wound or ulcer in the upper GI tract), they ca be ingested without harm. why? Explain how proteins are digested and absorbed.
proteins are broken down into:
- Amino- acids: used sodium linked co-transport for absorption
- Di & tripeptides: Uses co-transport with H+ for absorption
- Babies use receptor mediated endocytosis for full proteins
What is the role of sodium in absorption of glucose by enterocytes?
Glucose is absorbed through sodium linked co-transport to extract 100% of glucose into the bloodstream via enterocytes.
Distinguish segmental and peristaltic contractions
Peristaltic: Smooth muscle contracts behind a bolus pushing it forwards
Segmental: mixes food in place by alternating contractions in sections
what is the main function of bile salts in digestion?
they emulsify fats
Salivary ___ is an enzyme that begins digestion of starches liberating glucose molecules.
Amylase
What are the major functions of the urinary system?
- Filter blood and remove waste products
- regulate blood volume and blood pressure
- balance electrolytes and pH
- Regulate osmolarity
- produce hormones
- activate vitamin D
List and describe 4 processes involved in urine production.
Filtration: at the glomerulus; movement of fluid and solutes into the Bowman’s capsule.
Reabsorption: Movement of substances from filtrate back into the blood
secretion: Active transport of substances from blood into the filtrate
Excretion: removal of final urine from the body via ureters, bladder, and urethra
How is glomerular filtration rate controlled? there is a lot to this. think about local and global control mechanisms.
Local (autoregulation):
- Myogenic mechanism: Afferent arteriole constricts/dilates in response to BP changes.
- Tubuloglomerular feedback: Macula densa senses NaCl and signals changes in afferent arteriole diameter.
Systemic (global):
- Sympathetic nervous system: Can reduce GFR during stress.
- Hormonal control: RAAS increases GFR indirectly through vasoconstriction and aldosterone; ANP increases GFR by dilating afferent arteriole.
How are the following substances reabsorbed: sodium, water, small anions, glucose?
- Sodium (Na⁺): Actively transported via Na⁺/K⁺-ATPase pumps.
- Water: Follows Na⁺ passively by osmosis (especially via aquaporins).
- Small anions (e.g., Cl⁻): Follow electrochemical gradients.
- Glucose: Co-transported with Na⁺ via SGLT (sodium-glucose linked transporter), then facilitated diffusion into capillaries.
How are organic anions secreted into the urine? why is secretion considered to be a competitive process?
- Secreted by proximal tubule cells using organic anion transporters (OATs).
- Competitive process because multiple compounds may use the same transporter—if transporters are saturated, secretion of one drug can inhibit another.
How do ADH and RAAS pathway regulate urine osmolarity/pressure? when are each of these pathways used respectively?
ADH (vasopressin): Released in response to high blood osmolarity; increases water reabsorption via aquaporins in collecting ducts. use when dehydration or high blood osmolarity.
RAAS pathway: Activated by low BP; increases Na⁺ and water reabsorption, vasoconstriction, and aldosterone release. Use when low blood volume of blood pressure.
How does the urinary system help regulate blood pH?
- Kidneys secrete H⁺ and reabsorb HCO₃⁻ (bicarbonate).
- This maintains acid-base balance over hours to days.
What are the 4 components/activities of the digestive system?
- Ingestion
- digestion
- absorption
- elimination
What is the function of saliva? what enzymes are present in saliva and what are their functions in digestion?
- Lubricates food, begins carbohydrate digestion, contains antimicrobial agents.
Enzymes present:
- Salivary amylase: Begins starch digestion.
- Lingual lipase (minor role in lipid digestion).
List the secretory cells of the stomach and their major products
- Parietal cells: Secrete HCl and intrinsic factor.
- Chief cells: Secrete pepsinogen (converted to pepsin by HCl).
- Mucous cells: Secrete mucus to protect the stomach lining.
Where in the digestive system do muscles undergo tonic contractions? why?
In sphincters and parts of the stomach; prevent back flow and maintain compartmentalization
What are slow wave potentials? how do they help set up patterns of peristaltic contractions in the intestine?
- Cyclical depolarizations in smooth muscle.
- Don’t always reach threshold but help coordinate peristalsis by timing contractions.
List and describe the two major forms of peristalsis.
- Propulsive peristalsis: Moves contents forward.
- Segmental peristalsis: Mixes contents and improves absorption
What is the main digestive secretion of the liver? What is its function and how does it work?
Bile: Emulsifies fats; bile salts surround fats to form micelles, increasing surface area for lipase action.
