Question

a.Briefly explain why animals that live in very dry climates have the longest loops of Henle.

b.Animals produce different types of urine depending on their environment and their need to conserve water. True or False?

c.How does the blood-brain barrier protect the brain from potentially dangerous chemicals in the blood?

1.The blood-brain barrier actively transports substances that are dangerous back out of the brain and into the blood.

2.The walls of brain capillaries are far more permeable than the capillaries in the rest of the body.

3.The walls of the brain capillaries are far less permeable than the capillaries in the rest of the body.

4.The blood-brain barrier prevents lipid-soluble substances from crossing the barrier.

d.How hard a muscle contracts is determined by _____.

1.		how fast neurons fire action potentials
2.		how far the muscle is away from the brain
3.		how many neurons connect to it
4.		how many neurons connect to it and how fast neurons fire action potentials
5.		how many neurons connect to it and how far the muscle is away from the brain

e.The sodium-potassium pump pumps:

		1.both sodium and potassium out of the cell.
		2.both sodium and potassium into the cell.
		3.ATP using sodium and potassium.
		4.sodium into and potassium out of the cell.
		5.potassium into and sodium out of the cell. f.What are the two main functions of the choroid layer, located behind the retina in humans? g.You are recording from a neuron with an electrode and determine that the resting membrane potential is around -70 millivolts. What will happen to the membrane potential if you add three times more sodium to the extracellular solution? The membrane potential will stay the same., The membrane potential will become more negative,The membrane potential will become more positive.

Answer 1

Please find the answers below:

Answer a: The loop of Henle represents the site of maximum water and ion re-absorption in the nephron. More is the length of this loop, more efficient is the re-absorption of water and ions. Since animals residing in dry places need to conserve maximum amount of water, they bear the longest loop of Henle.

Answer b: True. Depending upon the ambient temperature, the nature of urine of animal varies. Whereas aquatic animals are ammoniotelic, terrerstrial animals are ureotelic and those living in deserts are uricotelic in nature.

Answer c: Choice 1 (The blood brain barrier represents as the anatomical barrier between the brain and rest of the body thus preventing entry of pathogens and toxins through circulation into the brain)

Answer d: Choice 1 (The stimulus for muscle contraction arrives from the nervous potential difference, and hence, the extent and speed of nerve impulse transmission determines the strength of muscle contraction)