Exercise Physiology: Cardiovascular and Respiratory Systems

Circulatory system

Delivers oxygen and nutrients, removes waste, and helps control body temperature.

Cardiac output

Amount of blood the heart pumps per minute; heart rate × stroke volume.

Blood flow redistribution

During exercise, more blood goes to working muscles and less to inactive organs.

Arteries

Blood vessels that carry blood away from the heart.

Veins

Blood vessels that carry blood back toward the heart.

Capillaries

Tiny blood vessels where oxygen, carbon dioxide, and nutrients are exchanged.

Pulmonary circulation

Blood travels from the right heart to the lungs and back to the left heart.

Systemic circulation

Blood travels from the left heart to the body and back to the right heart.

Systole

The contraction phase when the heart ejects blood.

Diastole

The relaxation phase when the heart fills with blood.

Systolic blood pressure

Pressure in the arteries when the heart contracts; the top number.

Diastolic blood pressure

Pressure in the arteries when the heart relaxes; the bottom number.

Mean arterial pressure (MAP)

Average arterial pressure; mainly depends on cardiac output and vascular resistance.

Baroreceptors

Pressure sensors that help regulate blood pressure quickly.

Kidneys and blood pressure

Control blood volume to help regulate blood pressure over the long term.

SA node

The heart's natural pacemaker that starts each electrical impulse.

AV node

Briefly delays the impulse so ventricles can fill before contracting.

Purkinje fibers

Spread the electrical impulse throughout the ventricles.

P wave

ECG signal showing atrial depolarization.

QRS complex

ECG signal showing ventricular depolarization.

T wave

ECG signal showing ventricular repolarization.

Sympathetic nervous system

Speeds heart rate and increases the heart's contraction strength.

Parasympathetic nervous system

Slows heart rate, especially at rest.

Stroke volume

Amount of blood pumped from one ventricle with each beat.

Preload

How much the ventricle fills and stretches before contracting.

Afterload

The resistance the heart must push against to eject blood.

Contractility

The strength of the heart's squeeze.

Frank-Starling mechanism

More heart filling stretches the muscle and produces a stronger contraction.

Venous return

Blood returning to the heart, helped by muscle contractions and breathing.

Vasodilation

Widening of blood vessels to increase blood flow to active muscles.

Blood pressure during aerobic exercise

Systolic pressure rises; diastolic pressure usually changes little.

Cardiovascular drift

During prolonged exercise, stroke volume may fall while heart rate rises.

Beta-blockers

Medicines that lower heart rate and reduce the heart's response to exercise.

Respiratory system

Brings oxygen into blood, removes carbon dioxide, and helps control pH.

Ventilation

Movement of air into and out of the lungs.

Diffusion

Movement of gases from higher to lower partial pressure.

Conducting zone

Airways that move, filter, and humidify air without exchanging gases.

Respiratory zone

The part of the lungs, including alveoli, where gas exchange happens.

Inspiration

Breathing in: the lungs expand, pressure falls, and air enters.

Expiration

Breathing out: lung volume decreases and air moves out.

Airway resistance

Opposition to airflow; increases when airways become narrower.

Asthma

Narrowing of airways that can cause wheezing and difficult breathing.

Dead space

Inhaled air that stays in airways and does not exchange gases.

Alveolar ventilation

The air that reaches the alveoli and can take part in gas exchange.

Tidal volume

Amount of air moved in or out during one normal breath.

Vital capacity

Maximum amount of air exhaled after a full inhalation.

Residual volume

Air still in the lungs after a maximum exhalation.

COPD

Long-term airflow obstruction that makes exhaling difficult.

Fick's law of diffusion

Gas exchange improves with more surface area and worsens with thicker barriers.

Oxygen exchange

Oxygen moves from alveoli into blood, then from blood into active tissues.

Carbon dioxide exchange

Carbon dioxide moves from tissues into blood, then into alveoli to be exhaled.

Ventilation-perfusion matching

Matching air reaching alveoli with blood flow to exchange gases efficiently.

Hemoglobin

Protein in red blood cells that carries most oxygen in the blood.

Oxygen unloading

Hemoglobin releases oxygen where tissues have lower oxygen pressure.

Right shift of hemoglobin curve

Higher temperature and lower pH help hemoglobin release oxygen to muscles.

Myoglobin

Oxygen-binding protein inside muscle that helps oxygen reach mitochondria.

Breathing and blood pH

Breathing out more CO2 helps reduce acidity and increase pH.

Ventilatory response to exercise

Breathing increases to meet exercise demands and regulate carbon dioxide and pH.

Altitude and breathing

Lower oxygen pressure at altitude stimulates faster breathing.

VO2 max

Maximum rate at which the body can take in and use oxygen during exercise.

Fick equation

VO2 = cardiac output × arterial-venous oxygen difference.

Arterial-venous oxygen difference

Difference in oxygen content between blood entering and leaving tissues.

Endurance training and VO2 max

Improves oxygen delivery by the heart and oxygen use by the muscles.

Endurance training and stroke volume

More blood volume, heart filling, and contraction strength increase blood per beat.

Capillary density

More capillaries help trained muscles receive and extract oxygen.

Mitochondria

Cell structures that use oxygen to produce ATP for aerobic exercise.

Mitochondrial adaptations

Endurance training increases mitochondria and the ability to produce aerobic ATP.

Oxygen deficit

Extra non-aerobic energy needed before oxygen uptake catches up at exercise onset.

Fuel use after endurance training

At the same moderate effort, trained muscle uses more fat and spares carbohydrate.

Homeostasis

Maintaining stable internal conditions so exercise can continue.

Antioxidant adaptations

Training increases defenses against exercise-related free radicals.

Lactate at the same workload

Trained muscles often produce less lactate because they rely more on aerobic ATP.

PGC-1α

A regulator that helps trigger growth and renewal of mitochondria.

Detraining

Loss of fitness adaptations when regular training stops.

Sprint interval training (SIT)

Very intense bursts lasting about 10-30 seconds.

High-intensity interval training (HIIT)

Repeated hard intervals, often about 60-240 seconds, with recovery.

ATP-PC system

Provides immediate energy for the first seconds of a maximal sprint.

Fast glycolysis

Produces ATP quickly without requiring oxygen; important during hard efforts.

Anaerobic training adaptations

Improves rapid energy production and the muscle's ability to handle acidity.