urinary system part 2

Question 1

what are the functions of the kidneys?

Answer 1

 Regulate Blood composition

• Water Balance
• Ion Balance
• Waste Removal
• Maintain acid/base Balance

 Regulate Blood Pressure

 Stimulate red blood cell production

 Maintain Calcium levels

Question 2

what are the 3 main processes to regulate blood composition?

Answer 2

Glomerular Filtration
◦ Filtering of blood into tubule forming the primitive urine

Tubular Reabsorption
◦ Absorption of substances needed by body from tubule to blood

Tubular Secretion
◦ Secretion of substances to be eliminated from the body into the tubule from the blood

Question 3

maintaining blood pressure

Answer 3

 Kidneys play an important role in maintaining
constant blood pressure.

 ↓ Blood pressure - ↓ Sodium – ↑ Aldosterone
secretion – ↑ Sodium reabsorption - ↑ Water
reabsorption - ↑ Blood volume - ↑ Blood pressure.

Question 4

regulation of blood pressure, stage 1(high volume and pressure) and 2

Answer 4

blood pressure increases

homeostasis disturbed: high blood volume includes elevated blood pressure

Question 5

regulation of blood pressure, stage 3 (stimulation)

Answer 5

receptors and control centres stimulated:

Pituitary: Baroreceptors inhibit posterior pituitary ADH secretion when blood volume increases.

Kidney: Juxtaglomerular apparati inhibit renin release when blood volume increases, which decreases aldosterone secretion

Heart: Atrial cardiac muscle cells secrete ANH (causes atrium walls to stretch) when blood volume increases.

blood vessels: sympathetic division baroreceptors detect increased blood volume, which causes vasodilation of renal arteries

Question 6

regulation of blood pressure, stage 4 (response)

Answer 6

decreased ADH= lower water reabsorption by the distal convoluted tubules and collecting ducts. less water returns to the blood and more water is lost in urine, decreasing the blood volume

decreased aldosterone and increased ANH decreases Na+ reabsorption from the distal convoluted tubule and collecting duct. more Na+ and water are lost in the urine, which decreases blood blood volume.

increased renal blood flow increases the rate of filtrate formation, and more water is lost in the urine

Question 7

regulation of blood pressure, stage 5 (Homeostasis restored)

Answer 7

Reduced blood volume due to loss of water and Na+ in the urine lowers the blood pressure

Question 8

regulation of blood pressure, stage 6 blood pressure is (restored)

Answer 8

blood pressure is restored

Question 9

regulation of blood pressure, stage 1 (Homeostasis disturbed low volume and pressure)

Answer 9

homeostasis disturbed: low blood volume includes lowered blood pressure

Question 10

regulation of blood pressure, stage 2 (stimulus, low volume and pressure)

Answer 10

Pituitary: baroreceptors stimulate posterior pituitary ADH secretion

Kidneys: Juxtaglomerular apparati stimulate renin release when blood volume decreases, which increases aldosterone secretion

Heart: Atrial cardiac muscle cells do not secrete ANH when blood volume decreases.

Blood vessels: sympathetic division baroreceptors detect a decreased blood volume, which causes vasoconstriction of the renal arteries.

Question 11

regulation of blood pressure, stage 3 (response, low volume and pressure)

Answer 11

Decreased renal blood flow decreases filtrate formation, and less water is lost in urine, which increases blood volume.

Increased aldosterone and decreased ANH increased Na+ reabsorption in the distal convoluted tubules and the collecting duct. Less Na+ and water are lost in the urine which increased blood volume.

increased ADH increased the permeability of the distal convoluted tubule and the collecting duct to water. increased ADH also increases the sensation of thirst. less water is lost in the urine

Question 12

maintaining electrolyte balance

Answer 12

 Sodium and chloride tightly controlled.

 Reabsorption dependent on blood volume.

 Large volume can be reabsorbed but even in
dehydrated state some sodium is excreted.

 Kidneys can also excrete large amounts of sodium to compensate for high intake.

Question 13

Diuretics, what are they and their function?

Answer 13

 Increase rate of urine formation.

 Used to treat conditions such as hypertension and cirrhosis of the liver.

 Can lead to problems such as dehydration and electrolyte imbalances.

Question 14

Urine movement (that I need to know)

Answer 14

Ureters: bring urine from renal pelvis to urinary bladder. Lined by transitional epithelium.

Urinary bladder: hollow muscular container. In pelvic cavity posterior to symphysis pubis. Lined with transitional epithelium

Question 15

Urine flow through the Nephron and Ureters

Answer 15

Hydrostatic pressure forces urine through nephron.

Peristalsis moves urine through ureters
from region of renal pelvis to urinary bladder. Occur from once every few seconds to once every 2 to 3 minutes.

• Parasympathetic stimulation: increase frequency.
• Sympathetic stimulation: decrease frequency.

Pressure in bladder compresses ureter and
prevents backflow.

Question 16

Urinary Bladder

Answer 16

 Gravity and peristaltic contractions propel the
urine along the ureter.

 Parasympathetic stimulation contracts the bladder and micturition results if the sphincters (internal
and external urethral sphincters) relax.

 The external sphincter is under voluntary control

Question 17

Reflex and Voluntary control of Micturition

Answer 17

 Bladder filling reflexively
contracts the bladder

 Internal Sphincter
mechanically opens

 Stretch receptors in
bladder send inhibitory
impulses to external
sphincter

 Voluntary signals from
cortex can override the
reflex or allow it to take
place

Question 18

control of the micturition reflex by higher brain centres

Answer 18

A. Ascending pathways carry an increased frequency of action potentials up the spinal cord to the brain when the urinary bladder becomes stretched.

B. Descending pathways carry action potentials to the sacral region of the spinal cord to inhibit the micturation reflex tonically and to stimulate the reflex when stretch of the urinary bladder produces the conscious urge to urinate when one voluntary chooses to urinate

Question 19

Micturation reflex, part 1

Answer 19

1. Urine in the urinary bladder stretches the bladder wall

Question 20

Micturation reflex, part 2

Answer 20

2. action potentials produced by the stretch receptors are carried along pelvic nerves to the sacral region of the spinal cord

Question 21

Micturation reflex, part 3

Answer 21

3. action potentials are carried by the parasympathetic nerves to relax the internal urinary sphincter and to contract the smooth muscles of the urinary bladder. Decreased action potentials carried by the somatic motor nerves cause the external urinary sphincter to relax