Autonomic Nervous System Control of Heartbeat

Recovery

Recovery after exercise (of breathing and heart rate) is faster in trained athletes.

Cardiac Muscle

Responds to stretching by contracting more strongly. The greater the blood volume entering the ventricle, the greater the force of contraction. This relationship is known as Starling's Law.

Sympathetic Motor Nerve

(Cardiac Nerve) Stimulation via the cardiac nerve increases hear rate through the release of noradrenaline. [noradrenaline = norepinephrine] {Excitatory NT speeds up SA node}

Parasympathetic Motor Nerve

(Vagus Nerve) stimulation via the vagus nerve decreases heart rate through the release of acetylcholine. [Acetylcholine (Inhibitory NT) slows down the SA node]

Processing Medulla Oblongata

Cardiovascular control center: comprises to accelerator center (which acts to speed heart rate and force of contraction) and the inhibitory center (which acts to decrease heart rate and force of contraction). The accelerator center also responds directly to adrenaline in the blood and to changes in blood composition (low blood pH or low oxygen). These responses are mediated through the sympathetic nervous system.

Sensory Nerve

Carotid Reflex: Pressure receptors in the carotid sinus detect stretch caused by increased arterial flow (blood flow leaving the heart). They send impulses to the inhibitory center to mediate decrease in heart rate via the vagus nerve (parasympathetic stimulation). Aortic Reflex: Pressure receptors in the aorta detect stretch caused by increased arterial flow. They send impulses to the inhibitory center to mediate decrease in heart rate via the vagus nerve.

Other Input (Sensory) to Medulla

Cerebral hemispheres may send impulses (e.g. in sexual arousal). Hypothalamus may send impulses (e.g. anger or alarm).

Blood volume

Endurance training increases blood volume (the amount of blood in the body)

Heart Rate

Heart rate (at rest and during exercise) decreases markedly from non-trained people.

Heart Size

Increases. The left ventricle wall becomes thicker and its chamber bigger.

Storke Volume

The volume of blood pumped with each heart beat increases with endurance training.