Urinary System

Question 1

Homeostasis

Answer 1

is the maintenance of steady internal conditions despite fluctuations in the external environment.
Examples of homeostasis include
-thermoregulation—the maintenance of internal temperature within narrow limits,
-osmoregulation—the control of the gain and loss of water and solutes, and
-excretion—the disposal of nitrogen-containing wastes.

Question 2

Thermoregulation

Answer 2

the process by which animals maintain an internal temperature within a tolerable range and
a form of homeostasis.

Question 3

Ectothermic animals

Answer 3

gain most of their heat from external sources and

include many fish, most amphibians, lizards, and most invertebrates.

Question 4

Endothermic animals

Answer 4

derive body heat mainly from their metabolism and

include birds, mammals, a few reptiles and fish, and many insects.

Question 5

Heat exchange with the environment may occur by

Answer 5

• conduction—the transfer of heat by direct contact (Ex: laying on a hot rock)
• convection—the transfer of heat by movement of air or liquid past a surface,
• radiation—the emission of electromagnetic waves, or
• evaporation—the loss of heat from the surface of a liquid that is losing some of its molecules as a gas.

Question 6

Five (5) general categories of adaptations help animals thermoregulate.

Answer 6

Changes in metabolic rate (Thyroid Hormone)
Insulation – fat and hair
Changes in circulatory system
Evaporative cooling – “sweating”
Behavioral responses

Question 7

Increased metabolic heat production occurs when

Answer 7

a) . hormonal (thyroid hormone) changes boost the metabolic rate in birds and mammals,
b) . organisms can increase or decrease their physical activity level,
c) . birds and mammals shiver (next slide)

Question 8

Thermoregulation Mechanisms

Answer 8

2. Insulation is provided by
   - hair and
   - fat layers.
3. Circulatory adaptations include
   - increased or decreased blood flow to skin
4. Evaporative cooling may involve
   - sweating,
   - panting

Question 9

Osmoregulation

Answer 9

is the homeostatic control of the uptake and loss of water and solutes such as salt and other ions.
Osmoregulators
-must actively regulate water movement

Question 10

Land animals

Answer 10

face the risk of dehydration,
lose water by evaporation and waste disposal, 
gain water by drinking and eating, and
-conserve water 
-behavior adaptations,
-waterproof skin, and
efficient kidneys.-

Question 11

Nitrogenous wastes

Answer 11

Metabolism produces toxic by-products.
Nitrogenous wastes are toxic breakdown products of proteins and nucleic acids.
Animals dispose of nitrogenous wastes in different ways.

Question 12

Ammonia (NH3)

Answer 12

is
poisonous,
too toxic to be stored in the body,
highly mobile and volatile,
results from breakdown of amino acids from proteins

Question 13

Urea

Answer 13

is from the breakdown of proteins

• produced in the vertebrate liver by combining ammonia and carbon dioxide,
• less toxic,
• easier to store, and
• highly soluble in water.

Question 14

urinary system

Answer 14

forms and excretes urine and
regulates water and solutes in body fluids.
Also, don’t forget…the kidneys make EPO… which drives RBC production

Question 15

the kidneys

Answer 15

In humans, the kidneys are the main processing centers of the urinary system.
-kidneys are located on the back wall of the abdominal cavity near the level of the lowest rib

Question 16

Nephrons

Answer 16

• are the functional units of the kidneys,
• extract a fluid filtrate from the blood, and
• refine the filtrate to produce urine.

Question 17

Urine is

Answer 17

• drained from the kidneys by ureters,
• stored in the urinary bladder, and
• expelled through the urethra.

Question 18

Nephron Units

Answer 18

Bowman’s capsule
	Proximal convoluted tubule
	Loop of Henle
	Distal convoluted tubule
	Collecting duct

Question 19

Filtration

Answer 19

Blood pressure forces water and many small molecules through a capillary wall into the start of the capsular space.

Question 20

Reabsorption

Answer 20

refines the filtrate,
reclaims valuable solutes (such as glucose, salt, and amino acids) from the filtrate, and
returns these to the blood.
Most reabsorption occurs in the PCT

Question 21

Reabsorption in the proximal and distal tubules removes

Answer 21

nutrients,
salt, and
water.

Question 22

pH is regulated by

Answer 22

reabsorption of HCO3– and

secretion of H+.

Question 23

secretion

Answer 23

Substances in the blood are transported into the filtrate by the process of secretion. Includes:
H+, urea, penicillin and NH4+

Question 24

excretion

Answer 24

By excretion the final product, urine, is excreted via the ureters, urinary bladder, and urethra.

Question 25

NaCl

Answer 25

High NaCl concentration in the medulla promotes reabsorption of water.

Question 26

Antidiuretic hormone (ADH)

Answer 26

regulates the amount of water excreted by the kidneys by
-signaling nephrons to reabsorb water from the filtrate,
-returning it to the blood, and
-decreasing the amount of water excreted.
regulates the amount of water excreted by the kidneys by
Water loss is sensed by osmoreceptors in the hypothalamus
Cells in the hypothalamus produce ADH which is
-transported to the posterior pituitary where it is secreted
-ADH is carried by the blood to the kidneys where it
-targets cells in the collecting ducts

Question 27

Diuretics

Answer 27

inhibit the release of ADH and

include alcohol and caffeine.