The time signature (also known as meter signature, metre signature, bar signature, or measure signature) is a notational convention used in Western musical notation to specify how many beats are in each bar and which note value constitutes one beat. In a musical score, the time signature appears at the beginning of the piece, as a time symbol or stacked numerals, such as or 3
4 (read common time and three four time, respectively), immediately following the key signature or immediately following the clef symbol if the key signature is empty. A mid-score time signature, usually immediately following a barline, indicates a change of meter.
There are various types of time signatures, depending on whether the music follows simple rhythms or involves unusual shifting tempos, including: simple (such as 3
4 or 4
4), compound (e.g., 9
8 or 12
8), complex (e.g., 5
4 or 7
8), mixed (e.g., 5
8 & 3
8 or 6
8 or 3
4), additive (e.g., 3+2+3
8), fractional (e.g., 2½
4), and irrational meters (e.g., 3
10 or 5
Cardiovascular physiology is the study of the circulatory system. More specifically, it addresses the physiology of the heart ("cardio") and blood vessels ("vascular").
These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.
Heart rate refers to the speed of the heartbeat, specifically the number of heartbeats per unit of time. The heart rate is typically expressed as beats per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. Activities that can provoke change include physical exercise, sleep, illness, ingesting, and drugs.
The normal human heart rate ranges from 60–100 bpm. Bradycardia refers to a slow heart rate, defined as below 60 bpm. Tachycardia refers to a fast heart rate, defined as above 100 bpm. When the heart is not beating in a regular pattern, this is referred to as an arrhythmia. These abnormalities of heart rate sometimes, but not always, indicate disease.