Homeostasis and osmoregulation

Question 1

What are the two ways of dealing with osmotic changes?

Answer 1

1) Osmoregulation: maintain the body isosmotic state by regulating the ECF to protect the ICF 2) Osmoconformation: tolerate changes in osmotic movement.

Question 2

How are marine fishes compared to their environment?

Answer 2

They’re hyposomotic which means higher internal concentration of water but lower internal concentration of salt. Salt will tend to diffuse into the body whereas water will tend to flow out.

Question 3

How are freshwater fishes compared to their environment?

Answer 3

They are hyperosmotic which means they have lower internal concentratio of water but higher internal concentration of salt. Water will tend to flow in whereas salt will tend to flow out.

Question 4

What is the mechanism that marine fishes developed to cope with their environment?

Answer 4

Marine fishes have to constantly drink seawater and excrete salt through the gills, the produce a smallo amount of concentrated urine.

Question 5

What is the mechanism that freshwater fishes developed to cope with their environment?

Answer 5

They have to conserve salt concentration by uptaking salt from the environment and they produce a lot of diluted urine.

Question 6

How do marine vertebrates cope with excess of salt int their bodies?

Answer 6

They excrete the excess of salt through their kidneys and through salt glands.

Question 7

What are the two main functions of excretory organs?

Answer 7

1) Osmoregulation. 2) Secrete waste product while reabsorbing valuable filtered solutes.

Question 8

Describe the ascending and descending components of the countercurrent system:

Answer 8

Filtrate in the descending limb become progressively more concentrated as it loses water. The ascending filtrate pumps out salt and become hyposmotic.

Question 9

Describe ammonia:

Answer 9

Is toxic, freely soluble in water and easily removed across skin and gills in aquatic animals.

Question 10

Describe urea:

Answer 10

Is soluble ini water, is a product of ammonia detoxification.

Question 11

Describe uric acid:

Answer 11

Nitrogenous end product of protein metabolis and is a semisolid excreta.

Question 12

What are the four components of negative-feedback control?

Answer 12

1) Variable, which is detected by a 2) Sensor. The information is then sent to 3) Integrator which compare the desired value to the actual value and if the value is not correct the 4) effector will generate a stimulus to modify the variable.

Question 13

What is the main role of ADH?

Answer 13

To control the amount of fluid loss in the urine.

Question 14

Describe the synthesis of ADH:

Answer 14

Is produced in the supraoptic nuclei in the hypothalamus as a pre-prohormone and is then store in the posterior pituitary.

Question 15

What is the primary target of ADH?

Answer 15

The kidney

Question 16

How does ADH act?

Answer 16

It binds to vasopressine receptor to induce the migration of aquaporins to the apical membrane and this allowe water to flow back from the filtratea and the urine is thus more concentrated.

Question 17

What happen in case of water deprivation?

Answer 17

Water deprivation results in an increase in osmolarity which stimulate the hypothalamus to produce more ADH.

Question 18

What happens in case of water ingestion?

Answer 18

The osmoreceptor on the hypothalamus perceive a decrease of the osmolarity and reduce ADH production.

Question 19

What are the three blood conduction that stimulates the production of ADH?

Answer 19

1) Blood pressure 2) Blood volume 3) Cardiac output.

Question 20

How does a fall in blood volume stimulates the production of ADH?

Answer 20

It promotes ADH secretion by stopping depolarization of pressure receptor.

Question 21

What are the two main characteristics of positive feedback?

Answer 21

1) Time limitation 2) Intensification of stress.