Understanding your heart

Click on image to view largerHappy Valentine's Day.

 

System: Cardiovascular

Location: Between your lungs

Physical description: Grapefruit-sized and cone-shaped

Function: To pump oxygen-rich blood throughout your body and oxygen-poor blood to your lungs

Cardiac muscle: Your heart is an incredibly powerful organ. It works constantly without ever pausing to rest. It is made of cardiac muscle, which only exists in the heart. Unlike other types of muscle, cardiac muscle never gets tired.

Four chambers: Your heart is divided into four hollow chambers. The upper two chambers are called atria. They are joined to two lower chambers called ventricles. These are the pumps of your heart. One-way valves between the chambers keep blood flowing through your heart in the right direction. As blood flows through a valve from one chamber into another the valve closes, preventing blood flowing backwards. As the valves snap shut, they make a thumping, 'heart beat' noise.

Heart rate: Without nervous system control, your heart would beat around 100 times per minute. However, when you are relaxed, your parasympathetic nervous system sets a resting heart beat rate of about 70 beats per minute, (resting heart rate is usually between 72-80 beats per minute in women and 64-72 beats per minute in men).

When you exercise or feel anxious your heart beats more quickly, increasing the flow of oxygenated blood to your muscles. This is triggered by your sympathetic nervous system. Your heart rate also increases in response to hormones like adrenalin.

On average, your maximum heart rate is 220 beats per minute minus your age. So a 40 year old would have a maximum heart rate of 180 beats per minute. BBC