Lecture 6-7: Integration Of Salt And Water Balance

Question 0

Describe the negative feedback pathway

Answer 0

Stimulus> sensor or receptor> afferents path > integrating centre > efferent path>effector> response

E.g. Increased Bp> detected by baroreceptors > sends signal to kidney> kidney creats more signal like releases renin > Bp decreases

Question 1

What is the difference between local control and reflex control?

Answer 1

Local- cells in vicinity of change initiate response

Reflex- cells at a distant site control the response

Question 2

What turns off the reflex loop?

Answer 2

Negative feedback

Question 3

What is the difference between positive feed back and negative feedback?

Answer 3

Positive: requires an external stimulus to shut off the cycle

Question 4

Where do baroreceptors pass on their messages to?

Answer 4

The vagus and glossopharyngeal nerves

Question 5

What is the role of the macula densa cells?

Answer 5

They are close to the efferent arterioles and they sense flow of NaCl

It signals juxtoglomerular cells to stop releasing NO which causes vasodilation

Blood will then find it hard to pass through due to no more vasodilation

GFR will decreases blood pressure decreases

Question 6

What doe most of the body systems act on?

Answer 6

Extracellular fluid

Question 7

What determines ecf volume?

Answer 7

NaCl

Question 8

What does Total body water content determine?

Answer 8

Ecf osmolality because we are talking in relation to water

Question 9

Describe the concept of positive and negative Na+ balance

Answer 9

• initial rise in Na increases osmolarity, thirst, release of ADH
  This increases water through consumption, preservation
  Resulting in NO RISE IN SODIUM OSMOLARITY
• osmolarity is back to normal but the WEIGHT HAS INCREASED. The isotonic solution in body so cells do not change shape.
• ECF has increased but ICF will not because osmolarity is the same in relation to the two. Volume has increased though
• kidneys will sense this and will increase sodium excretion
  Water follows and is also excreted

Person will return to original weight

Question 10

When is atrial natriuretic peptide released?

Answer 10

When blood pressure has increased and needs to go down. It signals to the medulla oblongata to decrease Bp

It also acts on the adrenal cortex to inhibit aldosterone

Acts on kidneys to increase GFR but decrease renin

Acts on hypothalamus to inhibits ADH