BIOG 1440 Prelim 3

What are the two compartments where fluid is found in the body?

Intracellular fluid and extracellular fluid (interstitial fluid & plasma)

What is intracellular fluid?

Fluid found inside of the cells

What is interstitial fluid?

Fluid found outside & surrounding the cells

What is plasma?

Fluid found in vessels of organisms with closed circulatory systems

What is extracellular fluid made of?

Water + electrolytes + nonelectrolytes

What are electrolytes?

Substances that DO dissociate into ions (salts, acids, bases, some proteins)

What are nonelectrolytes?

Organic molecules that DON'T dissociate, no electric charge (sugars)

What is the major cation and anion found in extracellular fluid?

Na+ and Cl-

What are the functions of extracellular fluid?

Cell function, cell structure, and a vehicle for nutrients & chemicals

What does extracellular fluid contribute to cell function?

Helps maintain electrical gradients across membranes (Na+ outside the cell & K+ inside the cell)

What does extracellular fluid contribute to cell structure?

Water/ions alter the volume of cells (osmosis) & hydrostatic pressure maintains tissue and organ position

How does extracellular fluid act as a vehicle for nutrients & chemicals?

The fluid volume and concentration of solutes is important to maintain

What is a conforming organism (conformer)?

- "no" homeostasis

- cells are iso-osmotic with env (solute concentrations are equal)

- typically in marine environments (invertebrates)

What is a regulating organism (regulator)?

- able to reach homeostasis

- tissues maintain relatively stable internal conditions (changing to be the same when env changes, costs energy)

- typically in unstable or constantly inhospitable environments (estuaries/salty)

What organisms are examples of conformers?

Musscles and barnacles

What organisms are examples of regulators?

Shrimp

What organisms can be both conformers and regulators?

Green crab

What parameters do regulators need to regulate?

- Vol of water in the ECF (volume regulation)

- Concentration of ions available (ionic regulation)

- Osmotic pressure (osmotic regulation)

What is the problem for osmoregulators in freshwater?

Salt loss by diffusion and water gain by osmosis

What is the issue with freshwater bass?

- Tissues are hyperosmostic (higher concentration of solute than env) which drives osmotic water gain through gills and other surfaces

- Uptake of water and some ions in food

How do freshwater bass solve their issue?

- Gills actively uptake Na+ and Cl-

- Excretion of large volumes of water in dilute urine from the kidney

What is the problem for osmoregulators in seawater?

They face desiccation (drying out) and inward salt diffusion

What is the issue with bony fish?

- Tissues are hypoosmotic (lower concentration of solute than env) which drives osmotic water loss through gills and other surfaces

- Gains salt ions from food by drinking seawater

How do bony fish solve their issue?

- Gills actively secrete Cl- and Na+ follows actively/passively

- Excretion of salt ions and small volumes of water in scanty urine

What is the issue for cartilaginous fish (sharks) in seawater?

- Osmotic water gain through gills & surfaces and food

How do cartilaginous fish solve their issue?

- Active transport of salt out through rectal gland

- Kidney produces urine (H2O & salt)

- Does not drink seawater

What is thirst?

A response to true (hypertonic) dehydration and hypovolemia

What is hypertonic dehydration?

- Intracellular thirst

- Triggered by high electrolyte levels (hypernatremic dehydration)

- Solute concentration is higher outside the cell, water diffuses out

What is hypovolemia (isotonic dehydration)?

- Extracellular thirst

- Triggered by the loss of fluid without changing concentration (decrease in blood plasma)

- Solute concentration is equal and water volume is low in the body

What is the thirst pathway for hypertonic dehydration?

1. Electrolyte concentration is too high

2. Osmolarity increases

3. Osmoreceptors pick up & signal intracellular thirst

4. Intracellular thirst

5. Drink water

What is the thirst pathway for hypovolemia?

1. Fluid volume is too low

2. Decrease in plasma volume

3. Baroreceptors activate (close to the heart)

4. Extracellular thirst

5. Drink water AND eat salt

What can occur in the blood during extraceullar thirst?

- Risk of heart function (HR increases to maintain output)

- Induces blood vessel constriction

What are the functions of sodium?

- Cell uptake of nutrients and water

- Muscle contraction

- Helps nerves carry messages between brain and body

- Balance bodies fluids and regulate blood pressure

What is excretion?

The elimination of the waste products of metabolism

Where does nitrogenous waste come from and what does it consist of?

Nitrogenous waste is produced from the metabolism of protein & nucleic acids, it consists of ammonia, urea, and uric acid

Rank the toxicity of ammonia, urea, and uric acid

Ammonia > Urea > Uric Acid

Rank the water volume required to produce ammonia, urea, and uric acid

Ammonia > Urea > Uric Acid

Rank the energy requirement for the production of ammonia, urea, and uric acid

Uric Acid > Urea > Ammonia

Where are the three nitrogenous waste products released in the body?

- Ammonia is released through whole-body surface (in aquatic environment)

- Urea is released in urine, through kidney (lost H2O from ECF)

- Uric acid is secreted as a paste (little water loss)

How does the kidney eliminate waste effectively?

The kidney eliminates urea while limiting ion and water loss via selection reabsorption, which can be adjusted (osmoregulation)

What is the excretory system used by flat worms?

Protonephridia, a network of dead-end tubes

How does protonephridia occur?

Interstitial fluid filters through membrane (flame bulb) and the filtrate empties to the external environment

What is the excretory system used by earthworms?

Metanephridia, a series of segments with tubes

How does Metanephridia occur?

Urine is dilute and solute reabsorption along with nitrogenous waste excretion occurs

What is the excretory system used by insects?

Malpighian tubules, tubes open on the hingut

What occurs within the malpighian tubules?

Nitrogenous waste from hemolymph into the tubule

How is urine produced?

The progressive refining of a filtrate along a tube

What are the functions of the "excretion tubes"?

1. Filter extracellular fluids

2. Reclaim valuable solutes & water

3. Secrete toxins & other waste

What is the "equation" for excretion?

Excretion = filtration - reabsorption + secretion

What is the anatomy of the kidney?

- Retroperitoneal organ, 11-15 cm

- Bean shaped, connected to renal artery & vein (20-30% cardiac output)

- Feeds using into the bladder through ureter

- Blood enters, some is reabsorbed, some urine is formed

What is a nephron?

The basic unit of the kidney

What are the steps a filtrate follows in the nephron?

1. Generate a filtrate from Blood in Bowmans Capsule

2. Filtrate progresses from proximal tube

3. Filtrate transferred to the loop of Henle

4. Filtrate transferred to the distal tubule

5. To the collecting duct

How is water reabsorption regulated throughout the process of urine formation?

There is constant reabsorption of most water in the proximal tubule and loop of henle but water reabsorption is hormonally regulated (based on dehydration) in the distal tubule and collecting duct

What occurs in Bowmans Capsule?

- Goal: generate the primary urine

- Energy comes from circulation (hydrostatic blood pressure)

- Colloid (protein) oncotic pressure and Capsule pressure contradict filtration

What occurs in the proximal tubule?

- Goal: reabsorption of water, solutes, nutrients + selective secretion

- pH regulation: secretes hydrogen ions, uptakes bicarbonate

- Active and passive transport from filtrate to interstitial fluid and capillaries (Na+/K+ pump, nutrients)

- Toxic material secreted

- Filtrate volume decreases but remains iso-osmotic to the blood

What occurs in the loop of Henle?

- Goal: reabsorb MOST water and solutes (NaCl)

- Water is reabsorbed based on the high osmolarity of the interstitial fluid (ECF hyperosmotic compared to urine)

What is countercurrent multiplication?

Process by which energy is used to generate an osmotic gradient that allows for water to be reabsorbed and to produced a concentrated urine

How does osmolarity change surrounding the loop of henle?

In the descending portion, the osmolarity increases, and in the ascending portion, the osmolarity decreases

What are the three segments of the loop of henle?

thin descending limb, thin ascending limb, thick ascending limb

What are the characteristics of the descending limb of the loop of henle?

Permeable to water and less to ions, water is reabsorbed via osmosis

What are the characteristics of the ascending limb of the loop of henle?

Impermeable to water and permeable to ions, ions are reabsorbed by diffusion passively

What are the characteristics of the thick ascending limb of the loop of henle?

Actively pumps NaCl out, ions reabsorb actively (Na+, K+, Cl-)

How does reabsorption through a concentration gradient work in the descending loop?

Increasing concentration of salt, salt flows into the tube and water flows out, kidney reabsorbs water and loses some salt

How does reabsorption through a concentration gradient work in the ascending loop?

Decreasing concentration of salt, salt flows out of the tube, kidney reabsorbs salt but does not lose the water that has been reabsorbed in descending loop

What occurs in the distal tubule?

- Dilute urine enters

- The distal tubule regulates the K+, Ca2+, and NaCl concentrations of body fluids

- Contributes to pH regulation

- Na+ reabsorption is stimulated by mineralocorticoids (aldosterone)

What occurs in the collecting duct?

- 5% of kidneys water and salt reabsorption only

- Due to hyperosmotic interstitial fluid established by the loop of henle

- Responsible for concentrating urien in response to vasopressin (ADH)

What is diuresis?

The production of dilute urine

What controls diuresis?

osmoreceptors in the hypothalamus

What occurs during antidiuresis?

dehydration triggers the release of ADH, ADH promotes urine concentration (retains water)

How does ADH allow for water retention?

ADH triggers aquaporin accumulation at membrane surface from storage vesicles, this facilitates water flux and allows for stronger water reabsorption

What are pathogens?

Disease-causing parasites, they can be living or non-living, their key feature is to proliferate/replicate within a host

What are the types of pathogens (living and nonliving)?

Living: Parasitic worms, protozoa, fungi, prokaryote

Nonliving: Virus, prions

What are the two strategies to survive infection?

- Eliminate the parasite (resistance mechanisms)

- Endure the damage and physiological consequences of infection (tolerance mechanisms)

- Resistance and tolerance determine susceptibility

What are the phases of infection?

- Attachment to host

- Breaching barriers and penetration in the body

- Proliferation

What is cellular immunity?

Cells in circulation eat and kill the microbe or infected cell

What is humoral immunity?

Molecules in circulation acting on microbes

What are the three lines of defense?

Epithelial barrier, innate immunity, adaptive immunity

What is the epithelial barrier?

A preexisting barrier in the body that prevents pathogen entry, if this fails pathogens enter the body

What is innate immunity?

A process that takes hours/days including phagocytosis and secreted effectors, the goal is to eliminate pathogens, if failed pathogens persist

What is adaptive immunity?

A process that takes days/weeks including B and T cell antibodies, the goal is to eliminate pathogens, if failed pathogens persist and the infection becomes uncontrolled

When are the pathogen defenses encoded?

- The epithelial barrier is immediate (germline)

- Innate immunity is inducible and fast (germline)

- Adaptive immunity requires somatic DNA recombination, multiple steps to generate, select, and amplify cells and effectors (long)

What are the main weapons of the three immune compartments?

Mucosal immunity, innate immunity, adaptive immunity?

What is mucosal immunity?

Physical: epithelial barrier + gelatinous mucus

Chemical: pH

Enzymatic: lysozymes, digestive enzymes

What "weapons" does innate immunity use?

Cellular: phagocytosis

Humoral: antimicrobial peptides

What "weapons" does adaptive immunity use?

Cellular: T cells and B cells

Humoral: antibodies

What type of animals have an adaptive immune system?

Jawed vertebrates

What is the pathway for innate immunity?

1. The host detects the infection

2. A transcription factor (NF-kB) is activated

3a. Leads to transcription of immune effectors

3b. Leads to the activation of immune cells

4. Kill the invader

What kind of process is the innate immunity pathway?

It is a single negative feedback loop

What are the three types of molecular signatures that lead to recognition?

Damage, a microbe, a non-self molecule

How does recognition work with tissue damage?

- This is damage associated molecular patterns (DAMPs)

- Tissue damage is recognized by pattern recognition receptors (PRRs)

- This is the innate immunity

How does recognition work with a microbe?

- This is pathogen associated molecular patterns (PAMPs)

- Microbial patterns are recognized by pattern recognition receptors (PRRs)

- This is the innate immunity

How does recognition work with non-self molecules?

- This is antigens

- Domains (epitopes) that are not self are recognized by B cell receptors (BCRs) and T cell receptors (TCRs) and antibodies

- This is the adaptive immunity

What occurs during phagocytosis?

1. Pathogen recognition

2. Internalization of the microbe in a vacuole called phagosome

3. The phagosome acidifies, fuses with vacuoles filled with degrading enzymes (lysosome), and generates oxygen species (H2O2, HOCl)

What are antimicrobial peptides?

- They are small peptides (12 to 50 amino acids)

- They are positive charged to bind to negatively charged bacterial membrane amphipathic (allows to insert in membrane)

- Binding leads to pore creation in the bacterial cell membrane, leading to bacterial lysis

What is somatic DNA recombination?

- A process in immune cells by which invaders can be recognized

- Allows to generate a huge diversity of recognition receptors and effector molecules

- Different molecular strategy based on diversity and specificity

What is the pathway for somatic DNA recombination?

1. Generate a repertoire of cells with unique receptors

2. Delete cells with receptors that recognize self

3. Repertoire of cells that recognize non self

4. Activation of a clone of cells that recognize pathogen

5. Proliferation of the cell to secrete antibody with similar specificity

How does T lymphocyte cytotoxicity work?

1. A cell is infected with a virus

2. The infected cell exposes at its surface a self-non-self complex

3. Recognized by the T lymphocyte

4. That kills the infected cell

What is herd immunity?

When a majority of a population are vaccinated, the risk of others who are not vaccinated getting infected decreases

How does cell-cell communication influence physiology?

It regulates cell activity and regulates gene expression and/or protein activities (changes cell activity/function)

How do cells ensure proper physiological function?

- Adjusting their function to changes in their environment

- Coordinate their behavior (sometimes with distant cells)