Lecture 22 Osmoregulation and excretion

Question 1

osmoregulation

Answer 1

controls solute concentrations and balances water gain and loss.

Question 2

Excretion

Answer 2

rids the body of nitrogenous metabolites and other waste products.

Question 3

Osmolarity (sides)

Answer 3

Hyperosmotic side:
* Higher solute concentration
* Lower free H2O concentration

Hypoosmotic side:
* Lower solute concentration
* Higher free H2O concentration

Question 4

Osmolarity

Answer 4

determines the movement of water
across a selectively permeable membrane

Question 5

two solutions are Isosmotic

Answer 5

water molecules will cross the membrane at equal rates in both directions

Question 6

Two solutions differ in osmolarity

Answer 6

hypoosmotic (less concentrated)
hyperosmotic (more concentrated)

Question 7

Osmoregulation

Answer 7

control of movement of solutes
between internal fluids and the external environment.

Question 8

Osmoconformers

Answer 8

are isoosmotic with their surroundings and do not regulate their osmolarity.

Question 9

Osmoregulators

Answer 9

expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic
environment.

Question 10

Water animals Marine Animals vs freshwater - Osmoregulators

Answer 10

slide 11

Question 11

Land Animals

Answer 11

● Adaptations to reduce water loss
are key to survival on land.
● Body coverings help prevent
dehydration
● maintain water balance by eating
moist food and producing water
metabolically through cellular
respiration.

Question 12

Summary of osmotic challenges

Answer 12

slide 13

Question 13

Transport epithelia

Answer 13

are epithelial cells specialized for controlled movement of solutes in specific
directions.

They are typically arranged into complex tubular networks.

Animals regulate the solute content of body fluid that bathes their cells.

Question 14

Nitrogenous wastes

Answer 14

Among the most significant wastes are nitrogenous breakdown products of proteins and nucleic acids.

Animals excrete nitrogenous wastes in different forms:
● ammonia
● urea
● uric acid
These differ in toxicity and the energy costs of producing them.

The kind of nitrogenous wastes excreted depends on an animal’s evolutionary history and habitat, especially water availability

Question 15

Excretory systems

Answer 15

● Excretory systems are variations on a tubular theme.
● Excretory systems regulate solute movement between internal fluids and the external environment.
● These systems are central to homeostasis.

Question 16

what does the Mammalian Excretory System consist of?

Answer 16

Kidney and nephron
The vertebrate excretory system also includes ducts and other structures that carry urine from the tubules out of the kidney and out of the body

Question 17

kidney

Answer 17

the excretory organs of vertebrates, function in both excretion and osmoregulation.

The numerous tubles of kidneys are highly organized.

Question 18

Nephron

Answer 18

the functional unit

Question 19

Excretory Processes

Answer 19

Most excretory systems produce urine by
refining a filtrate derived from body
fluids (slide 23)

1.filtration. the excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure accross membrane

2.reabsorbtion. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids

3.secretion. toxins and excess ions are extracted from body fluids and added to the contents of the excretory tubule

4.excretion. the altered filtrate (urine) leaves the system and the body

Question 20

Filtration

Answer 20

Most excretory systems produce urine by
refining a filtrate derived from body
fluids

Question 21

Reabsorption

Answer 21

Reclaiming valuable solutes

Question 22

Secretion

Answer 22

Adding nonessential solutes and
wastes to the filtrate

Question 23

Excretion

Answer 23

Processed filtrate containing nitrogenous
wastes is released from the body

Question 24

REMEMBER selectiely permeable membrane

Answer 24

slide 28 and 29

Question 25

Bowman’s capsule: Filtration

Answer 25

The filtrate produced in Bowman’s
capsule contains salts, glucose,
amino acids, vitamins, nitrogenous
wastes, and other small molecules. (slide 31)

Question 26

Proximal tubule: Reabsorption

Answer 26

Proximal tubule
Reabsorption of ions, water, and nutrients takes place in the

Molecules are transported actively and passively from the filtrate into the
interstitial fluid and then capillaries (glucose reabsorption for example).

As the filtrate passes through the proximal tubule, materials to be excreted become concentrated.

Some toxic materials are actively secreted into the filtrate.
(slide 32)

Question 27

Facilitated diffusion: channel proteins

Answer 27

uses aquaporins

Question 28

Aquaporins

Answer 28

Pores for water.

They are selectively permeable for water
Can be opened and closed, and allow fast passage of many molecules

are the “plumbing system for cells”

look at descending loop (slide 36 and 33)

Question 29

Descending Limb of the Loop of Henle

Answer 29

Reabsorption of water continues through
channels formed by aquaporin proteins.

Movement is driven by the high osmolarity of
the interstitial fluid, which is hyperosmotic to the filtrate.

The filtrate becomes increasingly concentrated.

Question 30

Ascending Limb of the Loop of Henle: diluting by recovering salt

Answer 30

In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid.

The filtrate becomes increasingly dilute. (slide 38)

Question 31

Distal tubule

Answer 31

The distal tubule regulates the K+ and NaCl
concentrations of body fluids.

The controlled movement of ions (H+ and HCO3–) contributes to pH regulation.

Question 32

collecting duct

Answer 32

slide 40

Question 33

Adaptation: long nephrons

Answer 33

Mammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops

Question 34

Water Conservation

Answer 34

● The mammalian kidney’s ability to conserve water is a key terrestrial adaptation.
● Hyperosmotic urine can be produced only because considerable energy is expended to transport solutes against concentration gradients.
● The two primary solutes affecting osmolarity are NaCl and urea.

Question 35

collecting ducts

Answer 35

deals with water conservation
● The collecting duct carries filtrate through the medulla to the renal pelvis.
● One of the most important tasks is reabsorption of solutes and water.
● Urine is hyperosmotic to body fluids.

Question 36

Homeostasis: Variable-Blood osmolarity

Answer 36

A combination of nervous and hormonal controls manages the osmoregulatory functions of the mammalian kidney.

These controls contribute to homeostasis for blood pressure and blood volume.

Osmoreceptor cells in the
hypothalamus monitor blood
osmolarity and regulate
release of ADH from the
posterior pituitary.

When osmolarity rises above
its set point, ADH release into
the bloodstream increases.

When osmolarity drops below
a set point, it causes a
reduction in ADH secretion.

Question 37

Control of collecting duct permeability
Antidiuretic hormone, ADH (vasopressin)

Answer 37

● Released from the posterior pituitary
● Bind and activate membrane receptors on
collecting duct cells.
● Signal cascade ● Insertion of aquaporin proteins into the membrane lining the
collection duct.
● Increase in water recapture
● Reduces urine volume

increases the number of aquaporin
proteins in the membrane of
collecting duct cells

Question 38

Diabetes

Answer 38

Diabetes insipidus (DI) is an uncommon condition that occurs when the kidneys
are unable to conserve water as they perform their function of filtering blood