chapter 21

Question 1

what are the four types of animal tissues, what is their structure & what is their function

Answer 1

epithelial, connective, muscle, and nervous

Question 2

what is homeostasis, what is negative feedback, what is positive feedback & what are examples of each

Answer 2

**homeostasis–»an aqueous solution that surrounds body cells and through with materials pass back and forth between the blood and body tissues

**negative feedback–»occurs when a change in some variable causes a reaction which decreases that change [temperature control in the body]

**positive feedback–»occurs when a change in some variable cause a reaction which increases that change [uterine contraction in childbirth]

Question 3

what is osmoregulation

Answer 3

the homeostatic process of maintaining a constant osmotic status [balance between solutes and water] despite fluctuations in the external environment

Question 4

what is excretion

Answer 4

the elimination of metabolic waste products from the body—the process by which substances originally present in cells, tissue fluids, and blood are removed from the body

Question 5

what is the nitrogenous waste produced by humans

Answer 5

urea

Question 6

what are the filtering units of the human kidney

Answer 6

**–»renal arteries—blood enters the kidneys through renal arteries branching from the aorta

**–»renal veins — blood leaves the kidneys by way renal veins emptying into the inferior vena cava

**–»ureters – tubes carrying urine from kidneys to the urinary bladder

**–»urinary bladder — organ for temporary storage of urine

**–»urethra — tube that carries urine and releases it from the body

Question 7

how do hormones regulate the salt and water balance in humans

Answer 7

how do the kidneys ‘know’ when to remove excess water and when to conserve water ? this is controlled indirectly by the hypothalamus in the brain. ““Below normal water content”” (or ““above normal salt content””) is ““sensed”” by specialized nerve cells in the hypothalamus (osmoreceptors) – they ““stimulate”” the release of antidiuretic hormone (ADH) which is ““carried”” by the blood to the kidneys where it increases the permeability of the distal tubule and the collecting duct to water – thus more water is ““reabsorbed”” into the blood, solving the problem of low water content (or high salt content) – this response provides a negative feedback signal to the hypothalamus.