PH1124 - kidneys & urinary system

Question 1

why do we need a urinary system?

Answer 1

excretion of metabolic waste products

Question 2

what do they kidneys do? (3)

Answer 2

• excrete waste products into urine
• homeostasis
• secrete hormones

Question 3

what is the definition of excretion?

Answer 3

• removal of a variety of waste products produced by metabolism

Question 4

what happens at the glomerulus?

Answer 4

• ultrafiltration via basement membrane and podocytes

Question 5

what does the glomerulus filtrate contain? (5)

Answer 5

• water
• glucose
• amino acids
• ions
• urea

Question 6

where do substances move from in the proximal convoluted tubule?

Answer 6

• move from proximal tubule to interstitual fluid via the apical to basolateral membrane

Question 7

what happens at the loop of henle?

Answer 7

• descending limb is highly permeable to water but impermeable to solutes (and vice versa for the ascending limb)
• active transport of Na+ out of the lumen followed by Cl-

Question 8

what is water reabsorption regulated by?

Answer 8

• ADH in the collecting duct

Question 9

what does ADH do?

Answer 9

• increases urine osmolality (increases concentration) and decreases water excretion (more water reabsorbed)

Question 10

how does ADH regulate water reabsorption? (3)

Answer 10

• increases water permeability of collecting duct for reabsorption
• (short term) insertion of aquaporin 2 into the apical membrane of the collecting duct by endocytosis
• (long term) ADH increases aquaporin 2 gene expression so more channels are synthesized

Question 11

what is autoregulation?

Answer 11

• small fluctuations in blood pressure are returned to normal as filtration rate in the glomerulus needs to be kept constant

Question 12

how does salt content change blood pressure?

Answer 12

• if blood pressure is low we can retain more sodium which means we retain more water therefore increase blood volume

Question 13

what is renin?

Answer 13

• secreted by the kidney in response to decrease blood flow and promotes vasoconstriction and release of aldosterone from the adrenal cortex

Question 14

how is renin released? (2)

Answer 14

• macular densa cells detect low blood volume/low sodium content
• triggers the granular cells (juxtaglomerular cells) to release renin

Question 15

what is the renin-angiotensin-aldosterone system? (3)

Answer 15

• body’s response to low blood pressure
• renin (primarily release by kidneys) stimulates the formation of angiotensin in blood and tissues
• this in turn stimulates the release of aldosterone from the adrenal cortex causing the body to retain water and increase BP

Question 16

what does aldosterone regulate? (3)

Answer 16

• blood volume
• blood pressure
• levels of Na+, K+, H+

Question 17

what is the fate of angiotensin I? (2)

Answer 17

• travels in circulation system till it reaches the lungs which contain ACE (angiotension converting enzyme)
• CE converts angiotensin I to angiotensin II

Question 18

what is angiotensin II effect on the adrenal cortex? (2)

Answer 18

• aldosterone is produced which increases the sodium and water reabsorption in the kidneys as well as increase secretion of potassium and protons into the urine
• this in turn increases blood volume thus blood pressure returns to normal

Question 19

what is the ureter?

Answer 19

• tubes that carry urine from each kidney to the bladder

Question 20

what is urine backflow prevented by?

Answer 20

• ureterovesical valves

Question 21

how is urine passed from the kidneys to the bladder?

Answer 21

• peristaltic waves

Question 22

what is the bladder mainly composed of?

Answer 22

• smooth muscle

Question 23

what is important to remember about the control of the sphincter muscles in the bladder?

Answer 23

• they are made from striated muscle so can be controlled

Question 24

what are the layers of the bladder wall? (5)

Answer 24

• peritoneum
• fat
• muscle
• lamina propina
• urothelium

Question 25

what is the micturition reflex? (2)

Answer 25

• its activated when the urinary bladder wall is stretched and it results in urination
• this reflex occurs in the spinal cord (specifically in the sacral region) that is modified by the higher centers in the brain the pons and cerebrum

Question 26

what are the phases of the micturition reflex? (2)

Answer 26

• storage phase

- voiding phase

Question 27

what is the storage phase of the micturition reflex? (3)

Answer 27

• as the bladder fills pressure stays low
• when the bladder is full wall tension is detected
• messages sent to brain and locally

Question 28

what is the voiding phase of the micturition reflex? (2)

Answer 28

• voluntary signals relax external sphincter (somatic)

- autonomic contraction of detrusor muscle

Question 29

what makes sure the flow doesn’t stop still bladder is empty?

Answer 29

• urethra plays an excitatory role which maintains flow toll bladder is empty

Question 30

which receptors detect the bladder is full?

Answer 30

• detrusor muscle stretch and viscerosensory nerves sense this

Question 31

what will sympathetic innervation on bladder control do?

Answer 31

• stop urination

Question 32

what will parasympathetic innervation on bladder control do?

Answer 32

• start reflex contractions to start urination

Question 33

how does the sympathetic nervous system stop urination? (2)

Answer 33

• nerve from the micturition center sends signals via the lumbar section in the spinal cord to the hypogastric nerve
• the hypogastric nerve then causes the internal sphincter to contract

Question 34

how does the parasympathetic nervous system allow urination? (2)

Answer 34

• the micturition centre in the brain sends a signal to the pelvic nerve via the sacral region of the spinal cord
• this causes relaxation of the internal sphincters allowing urination

Question 35

how does somatic innervation stop urination?

Answer 35

• voluntary constriction of external sphincter to prevent micturition

Question 36

how is the human able to control urination?

Answer 36

• external sphincter is formed from striated muscle so is under control

Question 37

what type of receptors are present in the sympathetic control of the bladder?

Answer 37

• alpha and beta adrenoceptors that rely on noradrenaline

Question 38

what type of receptors are present in the parasympathetic control of the bladder?

Answer 38

• nicotinic receptors and muscarinic receptors that rely on acetylcholine