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Force of contraction increases

Force of contraction increases

Blood vessels

Vessels in skeletal muscle vasodilate, decreasing resistance to blood flow

Blood flow to skeletal muscles increases, resulting from constriction of blood vessels in skin and viscera

Systemic blood pressure

Some increase due to increased cardiac output

Great increase due to vasoconstriction, counteracted in muscle blood vessels during exercise

Airways

Dilated

Some dilation

Reticular formation of brain

Activated

Little effect

Liver

Promotes breakdown of glycogen to glucose, increasing blood sugar level

Little effect on blood sugar

Metabolic rate

Increases

Increases

(1) Decreasing blood pressure and/or sodium ion concentration stimulate secretion of the enzyme renin

(1) Decreasing blood pressure and/or sodium ion concentration stimulate secretion of the enzyme renin

Aldosterone And Blood Pressure

(3) Aldosterone acts on the kidney to conserve sodium ions and (by osmosis) water

(2) Angiotensin II stimulates adrenal cortical cells to secrete aldosterone

Figure 13.29

Aldosterone increases blood volume and pressure by promoting conservation of sodium ions and water (steps 1-4).

(4) Blood pressure and/or sodium ion concentration return toward normal, inhibiting further secretion of renin

(3) Aldosterone acts on the kidney to conserve sodium ions and (by osmosis) water

(2) Angiotensin II stimulates adrenal cortical cells to secrete aldosterone

Figure 13.29

Aldosterone increases blood volume and pressure by promoting conservation of sodium ions and water (steps 1-4).

is indirectly linked to plasma sodium level by the renin-angiotensin system.

Groups of specialized kidney cells (juxtaglomerular cells) are able to respond to changes in blood pressure and the plasma sodium ion concentration. If levels of either of these factors decreases, the cells release an enzyme called renin. Renin decomposes a blood protein called angiotensinogen (an"je-o-ten'sin-o-jen), which re leases a peptide called angiotensin I. Another enzyme (angiotensin-converting enzyme, or ACE) in the lungs converts angiotensin I into another form, angiotensin II, which is carried in the bloodstream (fig. 13.29). When angiotensin II reaches the adrenal cortex, it stimulates the release of aldosterone. ACTH also stimulates secretion of aldosterone and is necessary for aldosterone secretion to respond to other stimuli.

Cortisol
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