Micturition and pharmacology of the urinary tract

Question 1

Which 3 muscles control urine outflow?

Answer 1

• Detrusor muscle
• Internal urethral sphincter
• External urethral sphincter

Question 2

Which muscle controlling the outflow of urine is being described here:
- striated muscle controlled by somatic NS

Answer 2

External urethral sphincter

Question 3

Describe the sympathetic effects on the motor supply to the bladder

Answer 3

• Relaxation of detrusor muscle, to accomodate filling

- Contraction of internal sphincter

Question 4

Which muscle can prevent bladder emptying and how?

Answer 4

External sphincter is skeletal muscle under voluntary control

Question 5

Contraction of internal sphincter to accommodate bladder filling acts via?

Answer 5

Via noradrenaline acting on α-1 ADRENO -receptors

Question 6

Relaxation of detrusor muscle to accommodate bladder filling acts via?

Answer 6

Via noradrenaline acting on β-2 ADRENO-receptors

Question 7

Continuous excitation of external urethral sphincter muscle during bladder filling is via?

Answer 7

Via acetylcholine acting on NICOTINIC receptors

Question 8

Contraction of the detrusor muscle during bladder emptying is via?

Answer 8

Acetylcholine acting on MUSCARINIC receptors

Question 9

Which 3 nerves supply somatic and autonomic supply to the bladder?

Answer 9

• hypogastric nerve
• pelvic nerve
• pudendal nerve

Question 10

Which muscles does the hypogastric nerve act on?

Answer 10

Sympathetic motor to internal sphincter (contracts) & detrusor (relaxes)

Question 11

Describe the effects of damage to the pelvic nerve

Answer 11

• lack of parasympathetic neurones to the detrusor, prevents bladder emptying
• bladder will contain urine and will have to be expressed manually

Question 12

Describe the effects of damage to the pudendal nerve

Answer 12

• Detrusor reflex ok, so can void urine

- external sphincter lacks control so may leak urine

Question 13

What are the clinical signs of a spinal lesion in sacral segments of spinal cord?

Answer 13

• Will result in a lack of parasympathetic supply to detrusor muscle and loss of external sphincter
• Sympathetic tone in internal sphincter may be present
• Bladder will be full but easy to express

Question 14

What would you want the main roles of drugs to be to help urinary incontinence?

Answer 14

Increase the activity of sphincter or decrease activity of detrusor

Question 15

What is the role of a-agonists?

Answer 15

Increase action of urethral sphincter

Question 16

What is the role of Muscarinic antagonists?

Answer 16

Decrease activity of detrusor

Question 17

Which drugs is used as it increases urethral outflow resistance and some peripheral vaso-constrictive effects?

Answer 17

Alpha-adrenoreceptor agonist

Question 18

Name some adverse effects of muscarinic antagonsist

Answer 18

Constipation
Tachycardia
Dilated pupils
Urinary retention
Increased intraocular pressure

Question 19

What is the only licensed oestrogen receptor agonist?

Answer 19

Estriol

Question 20

What are oestrogen receptor agonists used to treat?

Answer 20

Urethral sphincter mechanism incompetence that develops in spayed bitches

Question 21

What oestrogenic adverse effects may be seen when using oestrogen receptor agonists?

Answer 21

• Swollen vulva
• Attracted to males
• Swollen mammary glands

Question 22

which 2 drugs increase the activity of the detrusor muscle?

Answer 22

• Muscarinic receptor agonist

- a-adrenergic receptor antagonist

Question 23

When would you want to increase the activity of the detrusor muscle?

Answer 23

When there is urinary retention

Question 24

What are 4 adverse effects of using a muscarinic receptor agonist?

Answer 24

• GI cramping
• Vomiting and diarrhoea
• Salivation
• Bradycardia

Question 25

What is the method of action of a-adrenergic receptor antagonist?

Answer 25

- Management of urinary retention associated with reduced detrusor tone. - Inhibit urinary sphincter

Question 26

Which drugs can be used to relax urethral muscle?

Answer 26

- Ryanodine receptor antagonist | - Sedatives e.g. diazepam

Question 27

What is the method of action of ryanodine receptor antagonists?

Answer 27

Inhibits Ca release from the SR of skeletal muscle cells. It is a post-synaptic muscle relaxant - Used in the management of muscle spasms

Question 28

What is the method of action of sedatives?

Answer 28

- Enhances activity of the major CNS neurotransmitter, GABA | - Used as an anticonvulsant and in the management of muscle spasms

Question 29

Give an example of a urinary acidifier and alkaliniser?

Answer 29

- Methionine | - Potassium citrate

Question 30

Which drug group can be used to treat urinary retention in bitches?

Answer 30

Muscarinic receptor agonist

Question 31

Which drug can be used to treat urinary incontinence caused by urethral sphincter incompetence in bitches?

Answer 31

Oestrogen receptor agonist