When the body is injured, signals are sent from the site of damage to the spinal cord. As a central command center, the nervous system regulates the body’s response to the pain through a variety of reflexes.

Whether it wakes you up from a deep sleep or prevents you from falling asleep in the first place, a pounding heartbeat can be distracting and frightening. In some cases, a pounding heart rate at night is relatively harmless and only happens occasionally.

Adrenaline, also called epinephrine, is a hormone secreted by your adrenal glands, which sit on top of each of your kidneys. Once released by these glands, adrenaline produces a variety of effects on your body, including increases in your heart rate.

Every parent worries about unusual health symptoms in a child; a pulse or heart rate that seems too fast or slow naturally produces anxiety. Resting heart rate normally decreases as a child grows to adulthood. The normal heart rate for a 3-year-old child is 70 to 110 beats per minute.

Noradrenaline, or norepinephrine, is a hormone made in the adrenal gland. It is used as a chemical signal between cells of the sympathetic nervous system, a branch of the nervous system in charge of alertness, hyperactivity and quick responses.

Music has been used therapeutically for a number of conditions -- from improving respiration and lowering blood pressure to reducing heart rate and relaxing muscle tension. It has been used to reduce pain, relieve stress and anxiety, influence mood and stimulate movement.

Heart rate is often used as an indicator of health and fitness. Athletes and fitness enthusiasts use heart rate monitors to measure the intensity of their workouts. Resting heart rate is used as a measure of cardiovascular fitness. Typically, the lower your resting heart rate, the more fit you are.

The control of your heart rate is regulated by two mechanisms within your nervous system: the sympathetic system increases the rate and the parasympathetic decreases the rate.

A rapid heart rate, also known as tachycardia or heart palpitation, is the sensation that your heart is beating more forcefully, irregularly or faster than usual. In many cases, when you experience this feeling at night, it is simply because you are more aware of it at rest than when you are busy during the day.

Your heart rate, or pulse, determines the strength of your heart. It is the number of times your heart beats per minute and it measures how hard your heart is working. A fluctuating heart rate is considered abnormal and could indicate an underlying issue.

A typical healthy adult's heart beats an average of 70 times per minute, but this is not a constant rate. Your heart beats faster when you inhale and slower when you exhale.

If you are wondering whether your heart rate went up while you had that crazy dream last night, the simple answer is yes. In fact, whether you have a good dream or a bad dream, your heart and breathing rate always increase during a dream cycle.