2.53 explain how the heart rate changes during exercise and under the influence of adrenaline

2.53 •exercise makes your muscles need more energy, so you respire more

                  •exercise increases the amount of carbon dioxide in the blood

                  •high levels of carbon dioxide are detected by receptors in the aorta and carotid artery

                  •these receptors send signals to the brain

                  •the brain sends signals to the heart, causing it to contract more frequently and with more force

                  •adrenal glands release adrenaline when an organism feels threatened

                  •adrenaline binds to specific receptors in the heart, causing the cardiac muscle to contract more frequently and with more force, increasing the heart rate, so the heart pumps                        more blood

                            •this increases the oxygen supply to the tissues, getting the body ready