Lab 12 The Vascular System 199 ARTERIOLES AND CAPILLARIES Blood flow through the
ID: 99612 • Letter: L
Question
Lab 12 The Vascular System 199 ARTERIOLES AND CAPILLARIES Blood flow through the capillaries can be influenced by the diameter of the arterioles. The level of muscle activity in the arterioles alters their diameter. Muscle activity in the arterioles can be influenced by nerve stimulation, mechanical stimulation of the smooth muscle, or a variety of chemicals. Contraction of the muscle causes vasoconstriction of the arterioles producing less blood flow through the capillaries, while relaxation of the muscles causes vasodilation that enhances a greater blood flow through the capillaries. 4. How would stimulation of the sympathetic nervous system containing alpha receptors on the arteriolar muscle change the amount of blood flow through the capillaries? MECHANICAL STIMULATION Rub or scrape a line on the anterior surface of the forearm, where there is little arm hair, with a blunt instrument such as a fingernail, pencil eraser or weighing spoon. The first response is where the skin turns lighter at the point where the scrape was made. This is followed by a flushing red or darker color in the same area. Repeat the process with a greater force if the red response is not generated. 5. What causes the skin to blanch? 6. What causes the skin to flush red or darker?Explanation / Answer
Answer 4: Sympathetic nerves when stimulated release norepinephrine which acts on the alpha receptors causing vasoconstriction especially in the arteriolar muscles of the capillaries supplying blood to the skin, digestive tract and kidneys.
Answer 5:When the skin is pressed, the blood is forced out of the capillaries under the skin.Therfore the skin blanches. This effect may be also observed when the circulation in that area is poor due to inflammation, cold or other problems.
Answer 6: When the pressure is released from the surface of the skin, If the circulation is normal the blood flows back into the capillaries and the skin regains its red color immediately. But if the circulation is sluggish then this flushing of red color will take a while.
Note: This test where the skin blanches when pressure is applied is indicative of overall good health and is often used by Doctors while examining the patient.
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