Short term Blood Pressure control

Question 1

What is the atrial volume reflex?

Answer 1

The effect of increased blood volume stretching the atria and inducing increased fluid loss via the kidneys.

This occurs via a neuronal pathway directly to the kidney and a second pathway to the hypothalamus.

MOA:

1. Atrial stretch
2. Decreased ADH secretion by the hypothalamus and reduced water resorption in the renal tubule.
3. Reflex dilatation of the renal afferant arteriole and increasing the glomerular pressure, to increase filtration of fluid.
4. Increased fluid lost from kidney

Question 2

How do chemoreceptors augment blood pressure?

Answer 2

Blood flow below 80mmhg past the carotid/aortic bodies (and the central receptors in the medulla) is sensed as a low oxygen and low pH environment.

This excites the vasomotor centre and increases arteriolar constriction, leading to increased BP.

Question 3

How do the baroreceptors help to control BP?

Answer 3

Stretch of the carotid sinuses is transmitted via Hering’s nerve to the glossopharyngeal nerve where it meets fibres from the aortic sinus.

These travel up the tractus solitarius and send:

1. Inhibitory signals to the vasomotor centre
2. Excitatory signals to the vagaries parasympathetic centre

Inhibits vasoconstriction and decreases heart rate.

Question 4

How does adipose tissue affect BP?

Answer 4

Adipose tissue secretes adiponectin, a vasodilating hormone, thereby reducing BP.

In obesity, the production of adiponectin decreases.