Chapter 44 - Osmoregulation and Excretion

Water molecules

________ will constantly traverse a selectively permeable barrier that separates the liquids.

Barnacles

________ and mussels in estuaries that are alternately exposed to fresh and saltwater are examples of euryhaline osmoconformers; striped bass and different salmon species are examples of euryhaline osmoregulation (as shown in the image attatched below)

Water balance

________ may be maintained by an animal in two ways.

Osmoregulation

________ is the process by which the absorption and loss of water and solutes are balanced.

blood osmolarity

When ________ exceeds a certain threshold, such as when water intake is insufficient, the posterior pituitary gland secretes antidiuretic hormone (ADH)

Animal

________ cells swell and burst when water intake is high; when water loss is significant, cells shrivel and die.

distal tubule

The ________ and collecting duct regulate the amounts of K+ and NaCl in bodily fluids.

ADH

________ increases the number of epithelial aquaporin channels in the collecting ducts, which improves their permeability to water.

external osmolarity

Most animals, whether osmoconformers or osmoregulatory, can not withstand significant fluctuations in ________ and are referred to be stenohaline (from the Greek stenos, narrow, and halos, salt)

Isoosmotic solutions

________ are those that have the same osmolarity.

Human blood

________ has an osmolarity of around 300 milliosmoles per liter (mOsm /L), whereas saltwater has an osmolarity of about 1, 000 mOsm /L.

steady composition

Many osmoconformers survive in water with a(n) ________ and, as a result, a consistent internal osmolarity.

Angiotensin II

________, which is produced in reaction to renin, constricts arterioles and causes the release of the hormone aldosterone, rising blood pressure, and decreasing renin release.

active transport

The ascending limb is salt permeable but not water permeable; salt exits by diffusion and ________.

Urea

________ leaving the collecting duct adds to the kidney's osmotic gradient.

solute absorption

Just as thermoregulation is based on balancing heat loss and gain, controlling the chemical composition of bodily fluids is based on balancing water and ________ and loss.

Osmoregulation

________ allows animals to exist in conditions that osmoconformers can not, such as freshwater and terrestrial habitats, or to travel.