A question from last week, Cardiac output ?
A Question from last week, not just no ordinary first aid course. The cardiac output is simply the amount of blood pumped by the heart per minute. Necessarily, the cardiac output is the product of the heart rate, which is the number of beats per minute, and the stroke volume, which is amount pumped per beat.
Starling Forces govern the passive exchange of water between the capillary microcirculation and the interstitial fluid. These forces not only determine the directionality of net water movement between two different compartments but also determines the rate at which water exchange occurs.
Blood Volume (Fluid Exchange Between Capillaries and Tissues)
Capillaries are composed of a single layer of squamous epithelium surrounded by a thin basement membrane. Most capillaries (except those servicing the nervous system) have pores (spaces) between the individual cells that make up the capillary wall.
Control of Heart Rate.
The SA node of the heart is enervated by both sympathetic and parasympathetic nerve fibres. Under conditions of rest the parasympathetic fibres release acetylcholine, which acts to slow the pacemaker potential of the SA node and thus reduce heart rate. Under conditions of physical or emotional activity sympathetic nerve fibres release norepinephrine, which acts to speed up the pacemaker potential of the SA node thus increasing heart rate. Sympathetic nervous system activity also causes the release of adrenaline from the adrenal medulla.
Hormones line adrenaline, enters the blood stream, and is delivered to the heart where it binds with SA node receptors. Binding of epinephrine leads to further increase in heart rate
Cardiac Output (CO) = HR X SV
The cardiac output is usually expressed in litres/minute. For someone weighing about 70 kg (154 lbs), the cardiac output at rest is about 5 litres/minute. In this case, if the heart rate is 70 beats/min, the stroke volume would be a little more than 70 ml/beat.
But of course, this changes dramatically as a person begins to exercise. For a typical, fit young person, the cardiac output might go up to about 20 litres/min at the peak of exercise. However, for a world-class athlete in an endurance sport, the maximum cardiac output might be around 35 litres/min.
Relating to medicine, How will we care for a fit young person post an accident or injury? how would cardiac output change ? Or a fit young person in with meningitis ?