Urinary System 5

Question 1

Where does Urine go after leaving the kidneys?

Answer 1

Urine leaves kidneys and flows into ureters leading to the bladder propelled by contractions of ureter wall smooth muscle (gravity also assists)

Urine is stored in the bladder and intermittently ejected during urination, voiding, or micturition

Question 2

What are Bladder structures innervated by?

Answer 2

Bladder structures are innervated by parasympathetic, sympathetic and somatic motor neurons to control filling and micturition.

Question 3

Micturation

Answer 3

Micturation is a medical term for the act of urinating, specifically referring to the process of expelling urine from the bladder through the urethra. It is a normal bodily function that helps eliminate waste and excess fluids from the body. Micturation is controlled by the urinary system, including the bladder, urethra, and various muscles involved in the process. When the bladder fills with urine, nerve signals trigger the need to urinate, and the muscles in the bladder wall contract to expel the urine through the urethra and out of the body.

Question 4

What 3 muscles are used in the filling of the bladder, micturition and voluntary pissing?

Answer 4

Question 5

What Muscles are involved with the FILLING of the Urinary Bladder?
Is it Contracting or Relaxing? Innervation? (3)

Answer 5

Question 6

Urinary Bladder while filling:

Answer 6

• Bladder distends (stretches) with filling.
• Capacity ~700 – 800mL.
• At a certain point in filling mechanoreceptors send “sensation of fullness” signal to brain (~200 – 400 mL).
• Brain has a conscious awareness of “desire to urinate”

Question 7

What Muscles are involved during the MICTURITION of the Urinary Bladder?
Is it Contracting or Relaxing? Innervation? (3)

Answer 7

Question 8

What are the 2 parts of the Micturition Reflex?

Answer 8

• 1st part of micturition reflex – initiation – signal to spinal cord.
• 2nd part of micturition reflex – signal returns from spinal cord – detrusor contracts, both sphincters relax.
• A complete micturition reflex and urinary excretion occurs

Question 9

What Muscles are involved during VOLUNTARY CONTROL of the Urinary Bladder?
Is it Contracting or Relaxing? Innervation? (3)

Answer 9

Question 10

Voluntary Bladder Control:

Answer 10

• Have the ability to initiate and stop micturition reflex (learned behaviour).
• Brain sends signal to maintain stimulation and contraction of external urethral sphincter.
• Can override micturition reflex for a limited time.

Question 11

What can Affect Urinary Flow?

Answer 11

Diuresis
Natriuresis

Question 12

What is Diuresis?

Answer 12

Diuresis – elevated urine flow rate.
* Diuretic – substance that causes diuresis.
* Excretion high volume dilute urine

Often used to treat hypertension (decrease blood volume – decrease blood pressure)

Question 13

What is Natriuresis?

Answer 13

Natriuresis – elevated quantity of sodium in urine flow rate.

• Natriuretic – substance that causes natriuresis.
• Excretion high volume salty urine
• not typically found naturally
• can flush out excess sodium due to humans intaking too much salt

Question 14

How do we maintain Sodium Regulation?

Answer 14

Sodium balance:

• Intake (liquid, food).
• Output (sweat, feces, urine).

Salt intake: “appetite”

• Regulatory – minimal in humans.
• Hedonistic – humans generally consume well in excess of needs.

Question 15

How do we maintain Water Regulation?

Answer 15

Water balance:

Intake (liquid, food, metabolic).

• Metabolic – water generated in metabolic reactions.

Output (insensible, sweat, feces, urine).

• Insensible – skin epithelial and breathing losses

Question 16

How do we Increase Water intake or minimize Water Excretion?

Answer 16

1. Kidneys can minimize losses but need to intake water to replace losses.
2. Stimulate thirst centre in hypothalamus:
   Mechanoreceptors (stretch)
   - detect blood volume changes.
   Baroreceptors
   - detect blood pressure changes.
   Osmoreceptors
   - detect blood osmolarity (most important).
   * Dry mouth
3. Also psychological and conditioned responses for thirst

Question 17

What is hyponatremia?

Answer 17

Unbalanced Intake and Losses

Seen in endurance performance with relatively large losses of solutes (electrolytes, sodium, potassium, etc.) and water.

Issue:

• Consuming large amounts of plain water to replace losses (water being replaced but solutes are not). need to bring in electrolytes
• Fluid compartment shifts lead to cells swelling due to higher osmotic pressure inside the cell
• If enough water moves into cells
  – water intoxication.

Can also see hyponatremia when excessive blood loss, vomiting, or diarrhea coupled with large amounts of only plain water replacement.

Question 18

What can Large Losses of Solutes/ Water Lead to?

Answer 18