PE SAC Chapters 4 & 5: Cardiovascular and Respiratory Systems

Comprehensive vocabulary flashcards covering the structural components, regulatory pathways, acute responses, and functional mechanics of the cardiovascular and respiratory systems.

Cardiovascular System Makeup

The organ system consisting of the heart (pumps blood), blood vessels (arteries, capillaries, and veins that control blood flow), and blood (pumped through the vessels to all body tissues).

Cardiovascular System Functions

The key physiological roles of the cardiovascular system, which include the transport of fuels and gases ($CO_2$ and $O_2$), immune defence, cellular repair and regrowth, and thermoregulation.

Structure of the Heart

A four-chambered muscular pump composed of two upper atria and two lower ventricles, divided sagitally by a septum and transversely into superior aorta and inferior ventricles, with one-way valves preventing backflow.

Pulmonary Circulation

The circulatory pathway carrying deoxygenated blood from the right ventricle through the pulmonary arteries to the alveoli for gas exchange, and returning oxygen-saturated blood via the pulmonary veins to the left atrium.

Systemic Circulation

The circulatory loop that pumps oxygenated blood from the left ventricle through the aorta to the head, upper, and lower body tissues, returning deoxygenated blood via the superior and inferior vena cavae to the right atrium.

Systole

The contraction phase of the cardiac cycle in which both ventricles contract simultaneously, ejecting blood into the pulmonary arteries and aorta, causing pressure in the blood vessels to rise.

Diastole

The relaxation phase of the cardiac cycle where both ventricles relax and fill with blood from the atria in preparation for the next contraction, during which blood vessel pressure is lower.

Red Blood Cells (RBCs)

Formed elements making up approximately $41\%$ of blood, produced in bone marrow, which contain haemoglobin to carry oxygen and provide blood with its red colour.

White Blood Cells (WBCs)

Infection-fighting cells produced in the bone marrow, lymph tissue, and spleen that absorb and digest disease-causing organisms, comprising a portion of the blood's $4\%$ WBC and platelet fraction.

Platelets

Cell fragments produced in the bone marrow that assist in blood clotting to halt blood loss from damaged vessels.

Plasma

The straw-coloured liquid portion representing approximately $55\%$ of blood that transports nutrients and removes waste products, containing fibrinogen to aid in coagulation.

Arterioles

Small-diameter blood vessels that branch off from muscular arteries and lead directly into capillary beds.

Capillaries

Microscopic blood vessels that provide a thin barrier allowing for the diffusion and exchange of gases, water, nutrients, and metabolic waste products between blood and body tissues.

Venules

The smallest venous blood vessels that collect deoxygenated blood from capillaries and transport it into larger veins.

Skeletal Muscle Pump

A mechanism assisting venous return wherein contracting skeletal muscles squeeze deep veins during physical activity, forcing blood past one-way venous valves toward the heart.

Blood Pressure

The hydrostatic force exerted by circulating blood against the walls of blood vessels, recorded as systolic pressure over diastolic pressure with a typical resting value of $120/80\,\text{mmHg}$.

Vascular Shunt

The dynamic redistribution of cardiac output during exercise that diverts blood toward metabolically active skeletal muscles and away from inactive visceral organs.

Precapillary Sphincters

Bands of smooth muscle encircling each capillary where it branches from an arteriole; contracting a sphincter closes blood flow to that capillary branch while relaxing it opens flow.

Vasodilation

The widening of blood vessel lumen that increases blood flow to working muscles during exercise or to the cutaneous circulation to dissipate internal heat.

Vasoconstriction

The narrowing of blood vessel lumen that decreases blood flow to non-essential organs during exercise or restricts peripheral skin blood flow to conserve core heat.

Hypothalamus

The brain's thermoregulatory control centre that integrates temperature input from internal core blood receptors and peripheral skin thermoreceptors.

Radiation (Thermoregulation)

The transfer of thermal energy as heat radiates from the blood vessels through the skin into the surrounding air space.

Conduction (Thermoregulation)

The direct transfer of thermal energy between two physical bodies in contact, such as an athlete using an ice vest during breaks in play.

Convection (Thermoregulation)

Heat exchange mediated by a moving gas or fluid across the skin surface, exemplified by using a fan or pouring cool water over oneself.

Evaporation (Thermoregulation)

The phase change of liquid sweat into water vapour that absorbs heat energy from the skin surface, acting as the primary cooling mechanism during exercise.

Hypothermia

A critical clinical condition characterized by a dangerously low core body temperature falling below $35^\circ\text{C}$.

Hyperthermia

A state of elevated core body temperature exceeding $38.5^\circ\text{C}$, presenting risks of heat exhaustion or heat stroke.

Stroke Volume ($\text{SV}$)

The volume of blood ejected from the ventricles of the heart during a single contraction (systole).

Cardiac Output ($Q$)

The total volume of blood pumped out of the heart per minute, calculated using the formula $Q = \text{SV} \times \text{HR}$.

Stroke Volume Plateau

The leveling off of stroke volume at approximately $50\text{--}60\%$ of maximal heart rate, after which further increases in cardiac output rely solely on heart rate increases.

Arteriovenous Oxygen Difference ($a\text{-}VO_2\text{ difference}$)

The measure of the difference in oxygen concentration between arterial blood and mixed venous blood, which widens during exercise as working muscles extract more oxygen.

Conducting Zone

The upper respiratory air passageways (nose, mouth, pharynx, larynx, trachea, bronchi, and bronchioles) that filter, warm, and humidify air without participating directly in gas exchange.

Respiratory Zone

The anatomical structures where pulmonary gas exchange takes place, consisting of respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Alveoli

Microscopic terminal air sacs (~$300\text{ million}$ per lung with ~$75\,\text{m}^2$ combined surface area) specialized for rapid diffusion of $O_2$ and $CO_2$ with pulmonary capillaries.

Pleura

The protective serous membrane surrounding each lung that secretes pleural fluid to minimize friction during continuous expansion and recoil.

Inspiration

An active respiratory process where the diaphragm contracts and flattens and external intercostals pull ribs up and out, expanding thoracic volume and lowering lung pressure so outside air rushes in.

Expiration

The expulsion of air from the lungs, passive at rest due to lung recoil and muscular relaxation, but active during exercise via internal intercostal and abdominal contraction.

Tidal Volume ($\text{TV}$)

The volume of air inspired or expired during a single normal breathing cycle.

Respiratory Rate ($\text{RR}$)

The frequency of ventilation, quantified as the number of complete breaths taken per minute.

Pulmonary Ventilation ($V_E$)

The total volume of air inhaled and exhaled by the lungs per minute, calculated as the mathematical product of tidal volume and respiratory rate ($V_E = \text{TV} \times \text{RR}$).

External Respiration

The process of pulmonary gas exchange occurring at the alveolar-capillary junction, transferring oxygen into capillary blood and carbon dioxide into alveoli for exhalation.

Internal Respiration

The process of tissue gas exchange occurring at the capillary-muscle interface, transferring oxygen into working cells and carbon dioxide out into capillary blood.

Oxygen Deficit

The temporary state occurring at the start of exercise or upon an intensity increase where muscular oxygen demand exceeds the available oxygen supply.

Steady State

A level of physiological equilibrium during continuous submaximal exercise where oxygen supply fully satisfies the metabolic oxygen demand of the tissues.

Excess Post-Exercise Oxygen Consumption (EPOC)

The measurable volume of oxygen consumed above resting baseline levels during the post-exercise recovery period.

$$VO_2\text{ max}$$

The maximum rate and volume of oxygen that an individual can take in, transport, and utilize within skeletal muscles per minute during exhaustive exercise.