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Summary Scientific writing project heart rate and blood pressure BBS1002
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The effect of the pre-exercise heart rate on thepost-exercise blood pressure and heart rate in first
year Biomedical Sciences students
Kalisvaart, L.
ID: i6215145
Tutorial group 31
Faculty of Health, Medicine and Life Sciences (FHML)
Maastricht University
Course BBS1001
10th January, 2020
1
, 1. Introduction
The heart is an important transport pump system in the human body as it pumps blood into
the blood vessels of the circulatory system to provide the tissues and organs with a
consistent flow of nutrients and oxygen (1). The sinoatrial node (SA node), consisting of
cardiac pacemaker cells which have an unstable resting potential that continuously
depolarizes, is located in the wall of the right atrium and is responsible for setting the basic
rhythm. This spontaneously changing membrane potential in the intrinsic conduction system
triggers the heart’s rhythmic contractions (2). A heartrate is a contraction of the heart's
muscle triggered by these rhythmic contractions forcing blood to move through the blood
vessel of the circulatory system (1).
The phases of the heart rate determine the blood pressure in the blood vessels to rise or to
fall (2). In the first phase, the left ventricle contracts and blood expels into the aorta it
introduces a kinetic energy to the blood. As a result, the elastic aorta stretches and aortic
pressure reaches its peak. This pressure peak is called systolic pressure. The diastolic
pressure is caused by closing of the aortic valve and during this second phase the aortic
pressure drops to its lowest level and the heart refills with blood. The force with which the
vessel distends per unit area exerted by the contained blood is called the blood pressure and
is expressed in millimetres per mercury (mm Hg).
At rest, the average heartrate of an adult is 70 beats/minute, the average systolic pressure is
between 90 mmHg and 120 mmHg and the diastolic pressure is between 60 mmHg and 80
mmHg (2). But during exercise both the resting heartrate and blood pressure increase
because muscle metabolic end-products as carbon dioxide and lactic acid are being
produced. The muscle chemoreflex is triggered by these metabolic by-products that stimulate
afferent nerve endings in skeletal muscle cells which leads to an increase in sympathetic
activity and vasoconstriction in non-active tissue (3). The increase in sympathetic activity
leads to the release of the hormone norepinephrine by nerve fibres at their cardiac synapses.
Norepinephrine binds to β1-adrenergic receptors in the heart causing the SA node to fire
more rapidly and the heart will respond by beating faster. The capability to perform exercise
is enabled by an increase in oxygen uptake and a greater cardiac output. Cardiac output is
the amount of blood pumped out by the heart per minute and is determined by the heartrate
and stroke volume; the amount of blood pumped out by the left ventricle in one heartbeat.
Blood pressure is determined by the cardiac output and resistance. Therefore blood pressure
also rises due to an increase in cardiac output and vasoconstriction (4).
An increased heart rate viability during exercise has been associated with a lower mortality
and affected by age and sex (4). Heart rate responses to exercise have been determined as
2
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