Micturition

Question 1

What is the normal pH range of urine?

Answer 1

• between 4.6 - 8.0

- it’s usually acidic

Question 2

What substances are normally found in urine?

Answer 2

• water, electrolytes, hormones, wastes

Question 3

What substances are normally NOT found in urine?

Answer 3

• blood (RBCs), albumin, proteins, glucose, bacteria, etc.

Question 4

How are the ureters inserted into the bladder? What is the significance of this?

Answer 4

• they insert posteriorly and obliquely
• they traverse the bladder wall for a few cm before actually emerging and opening into the bladder cavity
• this prevents backflow into the kidneys when the bladder is full

Question 5

Trigone

Answer 5

• region of smooth muscle in the bladder

- a “triangle” made up of the ureteral openings and the beginning of the urethra

Question 6

As the bladder fills, sympathetic activity ________ and parasympathetic activity _________.

Answer 6

• sympathetic decreases and parasympathetic increases

Question 7

T or F: as a last minute measure, the composition of urine can be altered as it passes through the ureters.

Answer 7

• false!

- once urine hits the renal pelvis, it is no longer able to be changed

Question 8

Polyuria

Answer 8

• defined as > 3 L/day (greater than 2500 mL/day)

- can be due to excessive fluid intake, IV fluids, diabetes, decreased vasopressin, renal impairment

Question 9

Oliguria

Answer 9

• defined as > 400 mL/day

- anuria is > 100 mL/day

Question 10

Pain on urination is known as:

Answer 10

• dysuria

Question 11

Blood in the urination is known as:

Answer 11

• hematuria

Question 12

Sympathetic alpha receptors are ________ and cause ________ of urinary smooth muscle; beta receptors are ________ and cause _______ of urinary smooth muscle.

Answer 12

• alpha receptors are stimulating/excitatory and cause smooth muscle contraction
• beta receptors are inhibitory and cause smooth muscle relaxation

Question 13

Ureters are innervated by which branch(es) of the nervous system?

Answer 13

• both parasympathetic and sympathetic branches

- parasympathetic is more important

Question 14

Mechanism of ureteral peristaltic contractions.

Answer 14

• parasympathetic activity uses ACh on muscarinic receptors of the ureters, causing peristaltic contractions

Question 15

T or F: the actions potentials involved in peristaltic contractions are generated in the renal pelvis.

Answer 15

• true!
• the potentials are auto-generated in the renal pelvis; form there, the ureteral smooth muscle acts as a syncytium (much like the heart) to generate the peristaltic contractions

Question 16

Which centers are involved in the inhibition of the micturition reflex?

Answer 16

• the cortical and suprapontine centers

Question 17

Pelvic Splanchic Nerve

Answer 17

• the parasympathetic branch innervating the lower urinary tract
• originates in S2-S4 region
• innervates the bladder wall

Question 18

Hypogastric Nerves

Answer 18

• the sympathetic branch innervating the lower urinary tract
• originates in T10-L2 region
• innervates the bladder wall and bladder neck

Question 19

Where are the alpha receptors in the bladder located? Where are the beta receptors?

Answer 19

• alpha receptors are in the trigone (the internal urethral sphincter, especially)
• beta receptors are in the bladder wall (the detrusor muscle)

Question 20

Pudendal Nerve

Answer 20

• the somatic branch innervating the lower urinary tract
• originates in S2-S4
• innervates the skeletal muscle of external urethral sphincter

Question 21

At what volume of urine in the bladder will you start to feel pain?

Answer 21

• at about 700 mL, pain will begin

Question 22

How does urine get passed from the renal pelvis, through the ureters, and into the bladder?

Answer 22

• via gravity and peristaltic smooth muscle contractions

- (peristaltic = forward-driving)

Question 23

Membrane Recycling

Answer 23

• how the bladder increases/decreases in size to accommodate varying amounts of urine
• the bladder can exocytose extra portions of membrane to increase in size, and endocytose already existing portions to decrease in size

Question 24

Internal Urethral Sphincter

Answer 24

• smooth muscle

- a part of the bladder (found in the bladder neck)

Question 25

External Urethral Sphincter

Answer 25

- skeletal muscle | - a true sphincter

Question 26

The external urethral sphincter is reinforced/supported by the ________. Together, they make up the _________.

Answer 26

- pelvic diaphragm | - together, they make up the pelvic floor

Question 27

T or F: at rest (when not voiding), the somatic neurons of the external urethral sphincter are always firing.

Answer 27

- true! - in order to prevent micturition at rest, the external urethral sphincter must be contracted, and this requires constant firing of the somatic neurons

Question 28

Voiding requires each muscle involved in micturition to do what?

Answer 28

- the internal and external urethral sphincters must relax | - the bladder/detrusor muscle must contract

Question 29

The internal urethral sphincter passively ________ when the bladder contracts, and vice versa.

Answer 29

- the internal urethral sphincter passively relaxes when the bladder contracts - therefore, the internal sphincter is not parasympathetically innervated itself; its status is based on that of the bladder

Question 30

How much flora does the urinary tract normally have?

Answer 30

- zero! - the urinary tract is normally completely sterile with no normal flora - however, some bacteria is always present at the urethral opening

Question 31

What are the host defenses of the urinary tract?

Answer 31

- urine, itself, it not conducive for most growth - micturition, itself, flushes pathogens from the tract - iron-sequestering proteins in the bladder keep iron supply low for bacteria - THP (prevents bacterial adhesion)