Question

of blood Discuss the effects of the following on blood vessel diameter (state specifically the blood vessels involved) and rate flow. Then explain the importance of the reaction observed to the general well-being of the body. local application of cold: local application of heat inflammation (or application of HCI): histamine:

Answer 1

1. During cold, the blood vessels and arteries become narrow which restricts blood flow and reduces oxygen to heart. During cold sometimes when the blood vessels dilate and burst which causes redness.

On exposure to cold there is an increase in the affinity of post junctional alpha adrenoceptors for norepinephrine. This results in powerful constriction of blood vessels and leads to the cessation of blood flow to the distal tissue.

2. Due to local application of heat on blood vessels it produces dilation and there by increases in diameter. It also increases the blood supply which there by increases metabolism.

If heat is applied for very long period, it produces secondary effect which reverses the healing process. Due to this the blood vessels constrict and blood supply to area decreases.

3. Due to inflammation there is increase in blood flow and the particular area becomes hotter and redder. It also leads to dilation of blood vessels.

4. Histamine causes arterial vasodilation , venous constriction and and increased capillary permeability. It there by increases local blood flow. It there by causes dilation of blood vessels.