In this intermediate stage, stress mechanisms cause changes to blood vessels and to blood flow in the head. In Stage 2, each headache type follows a separate path.
Tension Headaches. As energy pours into muscles throughout the body, tensing them for emergency action, the shoulders, neck, scalp and facial muscles also contract. The trapezius muscle, which connects the shoulder, neck and collarbone, may contract into a knot.
In the neck area, muscles, nerves and arteries are all closely packed. Prolonged tension in the muscles of shoulders and neck excites neural pathways that refer pain impulses up to the sweatband area for a second phase of muscular contraction.
These nerve impulses control the synthesis of prostaglandin, a hormonelike substance released by the immune system in response to stress. Prostaglandin immediately induces contraction in the smooth muscles of blood vessels in the headband area, as well as making nerve endings in these blood vessels exquisitely sensitive to pain.
Prostaglandin synthesis is an essential step in muscle contraction headaches. To a lesser extent it also occurs in the vascular headache process. When this step is blocked by intervention, tension headache pain cannot be perceived.
Nowhere is constriction more evident than in the occipital artery, which supplies a network of arterioles that radiate out behind the ears and into the headband area of the scarp. In a desperate attempt to bring in more blood and oxygen, these blood vessels burst into a rigorous dilation.
The overall effect is to dilate blood vessels in a wide band around the head that includes the temples, forehead and hatband area.
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