Some nebulae create their own light, which sometimes has a fluorescent appearance, while others only reflect the light from nearby stars. Nebulae are often seen around dying stars, and it's thought they may be a natural process that occurs when a star is nearing the end of its life. Nebulae resemble thin clouds that have less atoms per cubic inch than a cloud of smoke.
When there is not enough thyroid hormone, neither the heart nor the blood vessels can function normally. In hypothyroidism, the reduced level of thyroid hormone causes the heart muscle to pump less vigorously, and eventually to become weakened. In addition, the heart muscle cannot fully relax after each heart beat.
Causes of heart palpitations. Heart palpitations are frequently caused by stress or anxiety. In addition to making you feel terrible emotionally, stress can have a physical effect on your body. As a result, stress can cause the nerve endings that control your heart to fire more frequently or irregularly. Anxiety and panic attacks can also trigger palpitations by elevating adrenaline levels. Food and drink can cause heart palpitations. Caffeine, nicotine, and alcohol can all affect your heart rate and may also increase the likelihood of irregular heartbeats. Some medications can cause heart palpitations. These include asthma inhalers, over the counter medications such as pseudoephedrine, and thyroid medications.