Control and Modification of Resting Heart Rate

Comprehensive vocabulary flashcards covering the neural and chemical control of heart rate, including the medulla oblongata, autonomic innervation, chemoreceptors, and baroreceptors.

Average resting heart rate

The standard heart rate of a person when at rest, typically measuring approximately $70\,\text{bpm}$.

Medulla oblongata

The region of the brain that controls heart rate via two distinct centres linked to the sinoatrial node.

Sympathetic nervous system

The branch of the autonomic nervous system that acts on the sinoatrial node to increase heart rate.

Parasympathetic nervous system

The branch of the autonomic nervous system that acts on the sinoatrial node to decrease heart rate.

Sinoatrial node (SAN)

The specialized cardiac muscle tissue (pacemaker) whose electrical impulse frequency is regulated by sympathetic and parasympathetic inputs to alter heart rate.

Chemoreceptors

Sensory receptors found in the walls of the carotid arteries and aorta that detect blood pH changes resulting from dissolved $CO_2$ forming acid.

Baroreceptors

Pressure-sensitive receptors located in the walls of the carotid arteries and the aorta that detect changes in blood pressure.

Carotid arteries

Arteries that serve the brain and contain both chemoreceptors and baroreceptors within their walls.

Noradrenaline

The neurotransmitter released by sympathetic nerve endings that stimulates the SAN to increase its frequency of electrical impulses.

Acetylcholine

The neurotransmitter released by parasympathetic nerve endings that stimulates the SAN to decrease its frequency of electrical impulses.

Blood pressure

The physical force exerted by circulating blood pushing against the internal walls of the arteries.

Chemoreceptor reflex to decreased blood pH

A coordination pathway where low pH signals the medulla oblongata to send sympathetic impulses to the SAN, raising heart rate to deliver blood rapidly to the lungs, eliminate $CO_2$, and prevent enzymes from denaturing.

Baroreceptor reflex to increased blood pressure

A regulatory mechanism where high blood pressure stretches receptors in the aorta and carotid walls, triggering parasympathetic impulses to the SAN to reduce heart rate and prevent arterial wall damage.

Cardiovascular response to exercise

An increase in blood flow to supply more oxygen and glucose to respiring tissue in response to elevated $CO_2$ from aerobic respiration and lactic acid from anaerobic respiration.

Resting heart rate regulation

The physiological state where reduced tissue respiration produces less $CO_2$ and increases pH, shifting autonomic balance so that parasympathetic activity exceeds sympathetic activity to lower the heart rate.