November 10

Cardiac Output

The amount of blood pumped by the heart.

Diastolic Filling

The passive filling of the heart with blood during diastole when pressure decreases.

Diastolic Suction

The pulling of blood from the atria into the ventricles, which increases filling during exercise to about three times faster than at rest.

Dynamic Relaxation

The process by which the heart twists and untwists during blood filling and contraction, enabling efficient blood movement.

Torsional Control

The mechanism involving the twisting and untwisting of the heart, essential for maintaining efficient blood circulation during exercise and ensuring diastolic filling.

Reversibility Principle

The concept that exercise adaptations can be reversed if training is halted.

SA Node (Sinoatrial Node)

The primary pacemaker of the heart, initiating electrical impulses.

AV Node (Atrioventricular Node)

A structure in the cardiac system responsible for a conduction delay of electrical impulses to the ventricles.

Parasympathetic Nervous System

The 'rest and digest' system that controls heart rate at rest through the medulla oblongata and vagus nerve, releasing acetylcholine to slow heart rate.

Vagal Tone

The dominant influence of the parasympathetic nervous system at rest, which counters the intrinsic heart rate of 100 beats per minute.

Sympathetic Nervous System

The 'fight or flight' system that counteracts parasympathetic influence during stress or exercise, increasing heart rate and contractility.

Endocrine System (Heart Rate Control)

Influences heart rate through hormones like epinephrine and norepinephrine from the adrenal medulla, increasing heart rate and contractility and prolonging sympathetic responses.

Arteries

Muscular and elastic blood vessels that carry oxygenated blood away from the heart, with the aorta being the largest.

Arterioles

Small arteries that are the site of greatest control over circulation through vasoconstriction and vasodilation.

Capillaries

One-cell thick blood vessels where oxygen, CO_2, and nutrient exchange occurs between blood and tissues.

Vasoconstriction

The narrowing of blood vessels (e.g., in arterioles) to control blood flow.

Vasodilation

The widening of blood vessels (e.g., in arterioles) to control blood flow.

Cardiac output

The amount of blood pumped by the heart, affected by heart rate, stroke volume, and arterial blood oxygen content.

Diastolic Filling

The process where blood passively fills the heart during diastole as pressure decreases. During exercise, filling time decreases, necessitating mechanisms like diastolic suction and torsional control.

Diastolic Suction

The pulling of blood from the atria into the ventricles, increasing filling during exercise to about three times faster than at rest.

Dynamic Relaxation

The process describing how the heart twists and untwists during blood filling and contraction, analogous to the 'ringing of a towel'.

Reversibility Principle

The concept that exercise adaptations can be reversed if training is halted.

SA node (Sinoatrial node)

The intrinsic pacemaker of the heart, setting the heart rate.

AV node (Atrioventricular node)

Plays a critical role in delaying electrical conduction to the ventricles, allowing for proper ventricular filling.

Parasympathetic Nervous System

Part of the extrinsic factors controlling heart rate; functions in 'rest and digest,' slowing heart rate at rest through the medulla oblongata and vagus nerve by releasing acetylcholine.

Acetylcholine

A neurotransmitter released by the parasympathetic nervous system, causing hyperpolarization in cardiac cells and slowing heart rate to about 60-80 beats per minute.

Vagal tone

The dominant influence of the parasympathetic nervous system at rest, countering the intrinsic heart rate of 100 beats per minute.

Sympathetic Nervous System

Part of the extrinsic factors controlling heart rate; functions in 'fight or flight,' counteracting parasympathetic influence during stress or exercise to increase heart rate (up to 250 bpm) and contractility.

Endocrine System (Heart Rate Control)

Exerts influence on heart rate and contractility through hormones like epinephrine and norepinephrine from the adrenal medulla, prolonging sympathetic responses during exercise.

Arteries

Vessels that carry oxygenated blood away from the heart, characterized by muscular and elastic walls allowing vasoconstriction and vasodilation.

Arterioles

Small arteries that control circulation and are the primary site of greatest control over blood flow through vasoconstriction and vasodilation.

Capillaries

Microscopic blood vessels with one-cell thick walls that facilitate the exchange of oxygen, CO2, and nutrients.