Thermoregulation, Osmoregulation, and the Human Urinary System

Comprehensive practice questions covering Chapter 13 (Homeostasis, Thermoregulation, Osmoregulation) and Chapter 14 (Human Urinary System) based on lecture notes.

What is the definition of homeostasis?

A vital process by which living organisms maintain a stable internal environment, despite changes in their external environment.

What are the three essential elements that collaborate to maintain homeostasis?

Receptors (sensors), control centre, and effectors.

How do receptors contribute to homeostatic mechanisms?

They are specialized structures that detect changes in the internal or external environment and transmit that information to the control centre.

In homeostasis, what role do the brain, spinal cord, and endocrine glands play?

They act as control centres that receive and process information from receptors to send messages to effectors.

What is a negative feedback system?

A mechanism in which the output or product of a system reduces the activity of the system, commonly used to regulate body temperature and blood glucose levels.

What is a positive feedback system?

A regulatory mechanism in which the output or product enhances the original stimulus, such as during blood clotting or childbirth.

What hormone is released by the pituitary gland during the positive feedback loop of childbirth?

Oxytocin.

What is osmoregulation?

The maintenance of the balance of water and solutes in the body fluids.

How do osmoconformers differ from osmoregulators?

Osmoconformers match their body fluid osmotic concentrations to their environment (e.g., marine invertebrates), while osmoregulators maintain constant internal concentrations despite environmental changes.

Why are freshwater animals considered hypertonic to their environment?

They have higher solute concentrations in their body fluids than the surrounding water, causing water to continuously enter their bodies via osmosis.

What specialized cells do marine animals use to pump salts out of their blood into the environment?

Chloride cells in the gills.

What is anhydrobiosis?

A dormant state entered by certain invertebrates, like tardigrades (water bears), when they lose almost all their body water.

How much water is required to dissolve one gram of ammonia to a nontoxic level?

$500\,mL$.

What is the chemical formula for urea?

$CO(NH_2)_2$.

Which nitrogenous waste requires the least amount of water ($1\,mL$ per gram) for excretion?

Uric acid ($C_5H_4N_4O_3$).

Define ectotherms.

Animals that gain most of their body heat from external sources, such as most invertebrates, fishes, amphibians, and reptiles.

Define endotherms.

Animals that generate the majority of their body heat through internal metabolism, such as birds and mammals.

What is the difference between poikilotherms and homeotherms?

Poikilotherms have body temperatures that vary considerably with the environment, while homeotherms maintain relatively constant internal temperatures.

What are the human responses to overheating (hyperthermia)?

Vasodilation (expansion of blood capillaries), sweating, and decreased secretion of thyroxine to lower metabolic rate.

What are the human responses to cooling (hypothermia)?

Vasoconstriction, shivering, increased metabolic rate, and the contraction of hair follicle muscles (goosebumps) to trap air for insulation.

What organs make up the human urinary system?

Two kidneys, two ureters, one urinary bladder, and one urethra.

Describe the internal structure of the kidney.

The outer portion is the renal cortex, the inner portion is the renal medulla (containing renal pyramids), and the center is the funnel-shaped renal pelvis.

What is the functional unit of the kidney?

The nephron.

What are the two main portions of a nephron?

The renal corpuscle (Glomerulus and Bowman's capsule) and the renal tubule.

How do cortical nephrons and juxtamedullary nephrons differ?

Cortical nephrons (85%) are located primarily in the cortex with short loops of Henle, while juxtamedullary nephrons have long loops of Henle that extend deep into the medulla.

What are the three major steps of urine formation?

Glomerular filtration (ultrafiltration), selective reabsorption, and tubular secretion.

What happens during selective reabsorption in the proximal convoluted tubule?

About 75% of water returns to capillaries by osmosis, and glucose, amino acids, and salts are returned to the blood by active transport.

What is the role of Antidiuretic Hormone (ADH) in the kidneys?

It makes the walls of the collecting ducts more permeable to water, increasing water reabsorption into the blood to produce concentrated urine.

What is aldosterone, and where is it produced?

A hormone produced by the adrenal cortex that regulates sodium and potassium levels by increasing sodium reabsorption and potassium excretion.

What bacteria is most commonly responsible for Urinary Tract Infections (UTIs)?

Escherichia coli (E. coli).

What is Lithotripsy?

A treatment for kidney stones that involves breaking stones into small pieces using shockwaves (ECSWL) or ultrasound (PNL).

Differentiate between haemodialysis and peritoneal dialysis.

Haemodialysis filters blood outside the body via a dialyzer; peritoneal dialysis use the peritoneal membrane in the abdominal cavity to filter waste into a dialysate fluid.

Where was Pakistan's first kidney transplant centre established in 1985?

Sindh Institute of Urology and Transplantation (SIUT) in Karachi.

What is the function of the vasa recta?

Long and straight capillary networks in the medulla that run parallel to the loops of Henle in juxtamedullary nephrons.