3.7 homeostasis and the kidney

Question 1

what is homeostasis

Answer 1

Homeostasis is the process of maintaining the body in a state of dynamic equilibrium

it describes the mechanism by which constant internal environments is achieved e.g. core body temperature, glucose levels and solute potential.

Question 2

why is homeostasis important?

Answer 2

-so cells of the body can function efficiently

-body cells are provided with constant conditions even during different levels of activity of the organism.

Question 3

what is the role of negative feedback?

Answer 3

There is a set point, also known as a ‘normal level’ for each condition, which is determined by a control centre within the body.
Deviations from the set point are corrected by negative feedback, so that the set point is restored

Question 4

what are examples of negative feedback?

Answer 4

the role of insulin in the control of blood glucose, and the role of antidiuretic hormone (ADH) in controlling blood solute potential

Question 5

what is the role of positive feedback?

Answer 5

positive feedback is used to enhance the size of the stimulus

Question 6

what is an example of positive feedback?

Answer 6

• an example of this is the action of oxytocin on the muscles of the uterus during childbirth

Question 7

what are the 2 main functions of the Urinary System

Answer 7

Osmoregulation
Removal of nitrogenous waste

Question 8

what is osmoregulation

Answer 8

the control of water content and solute composition of body fluids eg blood, tissue fluid and lymph

Question 9

what is excretion?

Answer 9

Excretion is the elimination of waste products of metabolism from an organism.

Question 10

through which blood vessels does oxygenated blood with high levels of urea travel from the heart to the kidneys?

Answer 10

Via Aorta and renal arteries

Question 11

through which blood vessels does deoxygenated blood with low levels of urea return back to the heart?

Answer 11

via renal veins and vena cava

Question 12

how is urine containing a high concentration of urea transported for storage?

Answer 12

Via the ureter and urinary bladder.

Question 13

through which structure is urine passed out the body?

Answer 13

through the urethra

Question 14

what are the 3 main regions of the kidney?

Answer 14

Cortext
Medulla
Renal Pelvis

Question 15

what is the function of the cortex in the kidney?

Answer 15

Cortext is the outer region where the renal arteries divide into tiny artierioles where they serve as a single kidney tubule called a NEPHRON.

1. ultrafiltration takes place in the glomerulus
2. selective reabsorption is carried out by
3. the proximal convoluted tubule
   the excretion of urea in the urine occurs.

Question 16

what is the function of the medulla in the kidneys?

Answer 16

medulla is the central region of the kidney and is the site of osmoregulation

Question 17

what is the role of the renal pelvis in the kidneys?

Answer 17

renal pelvis is the origin of the ureter, it collects the urine formed and passes it to the ureter for transport to the bladder.

Question 18

why cany amino acids be stored?

Answer 18

Amino acids nitrogen group is toxic in excess.
Surplus amino acids are deaminated in the liver forming ammonia which is converted to less toxic urea and transported in blood plasma for excretion.

Question 19

what are the key features that help recognise a cortex

Answer 19

• The capillaries of the glomerulus stain as a darker group of cells / tissues.
• The Bowman’s capsule appears as a clear zone surrounding each glomerulus.

-The cells of the proximal convoluted tubules are cuboidal (square in cross section) with distinct nuclei.

Question 20

what are the key features that help recognise a medulla?

Answer 20

• There are cross-sections of different tubular structures of different diameters and thickness of walls.
• Collecting ducts appear larger than the other structures in traverse section.
• The thin and thick parts of the descending and ascending limbs of the loop of Henle are quite different.
• Blood in the capillaries stains as a solid mass.

Question 21

what are the key features that help recognise a renal pelvis?

Answer 21

• There are large numbers of tubules cut in longitudinal section – along the tubule.
• Depending on the section, you may observe the tubules emptying into a space which is the origin of the ureter.

Question 22

what are the adaptions of cells in proximal tubules to help absorption?

Answer 22

1. Large Surface Area due to its length and large number per kidney
2. Cuboidal Epithelium Cells with microvilli and basal channels
3. Many Mitochondria

Question 23

what is ULTRAFILTRATION

Answer 23

Urea is removed from the blood by the kidney nephrons

Question 24

what are the 5 steps in producing urine in a nephron

Answer 24

1.renal capsule
2. proximal convoluted tubule
3. loop of Henle
4. distal convoluted tubule
5. collecting duct

Question 25

What is the glomerulus and how does it form

Answer 25

Renal artery splits into many arterioles each feeding a nephron. The arteriole splits into numerous capillaries which form a knot called a glomerulus.

Question 26

how does the blood supply enter the glomerulus

Answer 26

through the AFFERENT arteriole and leaves through the EFFERENT arteriole.

Question 27

where does the efferent arteriole carry blood to?

Answer 27

2 other capillary networks 1. the capillaries surrounding the proximal and distal convoluted tubules 2. the capillaries surrounding the loop of Henle known as the vasa recta.

Question 28

why is the afferent arteriole wider than the efferent arteriole

Answer 28

this difference in thickness increases the hydrostatic pressure of the blood plasma.