Acetylcholine is an excitatory neurotransmitter that conducts electrical impulses through a series of actions, making it possible for nerve cells to communicate with muscle cells and generate muscle contractions.

If you want to change your weight, there’s good news: your metabolic rate isn’t fixed for life. Metabolism can and does change over time, and you can take steps to speed it up or slow it down. If you intend to start gaining weight, see your doctor before you begin to hammer out details of a healthy plan to follow.

Losing weight requires you to eat fewer calories than you burn, so it seems logical that eating no calories would lead to the quickest loss. Fasting, however, does not speed up your metabolism -- and may actually backfire by slowing down your metabolic processes to compromise your ability to successfully drop pounds.

ATP is short for adenosine triphosphate, a crucial chemical in human metabolism that has been called "chemical currency" because the cells use it as a direct source of energy.

It's a well-established "rule" that frequent meals boost your metabolism and prompt weight loss, but research doesn't necessarily back this rule up. While this eating pattern helps some people, it isn't absolutely necessary for healthy weight management.

When you’re in your 30s, your basal metabolism begins to drop. From this age on, the average adult will gain a pound a year. Here's what you need to know.

Because a number of factors can affect metabolism, there isn't a particular age when a teen's metabolism slows down -- it varies from one teenager to another.

Many herbs may help slow your heart rate. According to MedlinePlus, your heart rate, or pulse, is the number of times your heart beats in one minute while you are at rest. Numerous factors can affect your resting heart rate, including your fitness level, your age and your health status.

The urinary system consists of the kidneys and bladder, along with the ureters and urethra. It has multiple functions, among them excreting toxins and metabolic by-products, maintaining the body's fluid and acid-base balance, regulating electrolyte levels and secreting several important hormones.

The metabolism gets blamed for weight issues on both ends of the spectrum. If it's too slow, you may battle to lose weight; if it's too fast, you may struggle with gaining. Whether it's slow or fast, tweaking your diet and exercise habits may help you manage your metabolic rate.

Avocados are rich in a number of nutrients, particularly vitamins, fatty acids and compounds called plant sterols. The plant sterols in avocados have an effect on hormones, especially estrogen and progesterone, which are both responsible for regulating ovulation and menstrual cycles.

Your body burns calories every minute of every day, whether you're asleep, watching television, working at the computer or working out.