The urinary bladder

Question 1

What is the basic flow of urine from the kidneys to being excreted?

Answer 1

It flows from the kidneys through the ureters into the bladder and is then eliminated via the urethra.

Question 2

What is the detrusor muscle?

Answer 2

Smooth muscle found in the bladder that can contract and relax.

Question 3

What parts of the bladder are important in retaining and holding urine?

Answer 3

The internal and external sphincters.

Question 4

How is urine moved into the bladder?

Answer 4

Peristaltic contractions of the walls of the ureter.

Question 5

How do male and female urinary tracts differ?

Answer 5

Females have an external sphincter and a smaller urethra - the urinary tract is shorter.

Question 6

What does a smaller female urethra impose?

Answer 6

There is a higher chance that they will develop a UTI.

Question 7

What is the capacity of the bladder?

Answer 7

600 and 800ml.

Question 8

What is the detrusor composed of?

Answer 8

Three layers of smooth muscle. The fibres in each layer are arranged differently - spiral, longitudinal and circular.

Question 9

What control is the internal sphincter under?

Answer 9

Involuntary control via smooth muscle.

Question 10

What control is the external sphincter under?

Answer 10

Skeletal muscle.

Question 11

What is tonic contraction?

Answer 11

Contractions that are maintained from several minutes up to hours at a time.

Question 12

What receptors are found on the bladder?

Answer 12

Muscarinic receptors (M3) and beta adrenergic receptors (B3).

Question 13

What receptors does the internal sphincter contain?

Answer 13

M3.

Question 14

What receptors are found on the external sphincter?

Answer 14

B3.

Question 15

Where does direct motor control of the bladder occur?

Answer 15

The pons, which is part of the brainstem.

Question 16

How does the detrusor muscle contract?

Answer 16

The pelvic parasympathetic nerve releases ACh which binds to the M3 receptor.

Question 17

What is the mechanism for “holding in” urine?

Answer 17

The pudendal nerve is a somatic nerve under our control. It releases ACh and acts on the A3 receptor on the internal sphincter, which binds and causes the external sphincter to contract.

Question 18

What is the hypogastric nerve responsible for?

Answer 18

Urine retention.

Question 19

What is the parasympathetic nerve responsible for?

Answer 19

Urination.

Question 20

What is released from the post sympathetic nerve involved in?

Answer 20

Releasing noradrenaline that binds to the B3 receptor on the detrusor muscle to relax it, and binds to the A1 receptor on the internal sphincter to contract it.

Question 21

What is the trigone muscle?

Answer 21

The bladders stretch receptor.

Question 22

What is the neural regulation method of bladder function?

Answer 22

It is an involuntary spinal micturition reflex arc. Stretch receptors in the wall of the urinary bladder, afferent sensory nerve fibres (convey impulses to the spinal cord) and efferent PS nerve fibres (convey impulses to the detrusor and internal sphincter)

Question 23

What is involved in the voluntary control exercised by the CNS and when does it develop?

Answer 23

The cortex, cerebellium and micturition centre are located in the pons that are developed in early childhood - full control is usually present between 3 and 5 years.

Question 24

What part of the spinal cord is involved in micturition.

Answer 24

The sacral portion.

Question 25

What are the two key processes for micturition to occur?

Answer 25

The detrusor muscle must contract and the internal sphincter must relax.

Question 26

What conscious part of the process is necessary for micturition to occur?

Answer 26

The cerebral cortex must allow the external sphincter to relax.

Question 27

What happens when the bladder is in terms of the brain?

Answer 27

Signals are sent to stimulate the hypogastric nerve to retain urine.

Question 28

What happens to prevent urination?

Answer 28

The sympathetic nerve is stimulated which allows us to hold in urine, and the parasympathetic nerve is inhibited so we don’t contract the pertrusor muscle.

Question 29

What happens when the bladder is full?

Answer 29

There is lots of stretching in the muscle and the sensory nerve in the pertrusor muscle will increase its firing to the sacral region.

Question 30

What is the voiding reflex?

Answer 30

The idea that if urination starts, urination will continue and will not stop.

Question 31

What is the basis of the voiding reflex?

Answer 31

The pelvic afferent nerve fibres will keep sending impulses to the sacral region of the spinal cord which works on a neurone that connects to the parasympathetic efferent nerve fibres. The pertrusor muscle will contract and cause a loop.