Exam 2- Mason

CARDIOVASCULAR SYSTEM

Structure and Function of the Heart The heart is a four-chambered muscular pump consisting of the right atrium (RA), right ventricle (RV), left atrium (LA), and left ventricle (LV). The LV has the thickest wall due to pumping blood to the entire body.

Valves ensure one-way blood flow:

• Tricuspid valve: RA → RV

• Pulmonary valve: RV → pulmonary arteries → lungs

• Mitral (bicuspid) valve: LA → LV

• Aortic valve: LV → aorta → body

Blood Flow Pathway:

Body → RA → RV → Lungs → LA → LV → Body

The heart is supplied by coronary arteries, which deliver oxygenated blood to the myocardium.

Cardiac Cycle

• Systole: ventricular contraction; produces systolic blood pressure (SBP)

• Diastole: ventricular relaxation; produces diastolic blood pressure (DBP)

Electrical Conduction System

1. SA node initiates impulse (pacemaker)

2. Impulse spreads across atria (atrial contraction)

3. AV node delays signal

4. Bundle of His transmits impulse

5. Purkinje fibers distribute signal → ventricular contraction

Heart Rate Control

• Sympathetic nervous system (SNS): increases heart rate

• Parasympathetic nervous system (PNS, vagus nerve): decreases heart rate • Influenced by hormones (epinephrine), temperature, and fitness level

Response to Acute Exercise

• Heart rate (HR): increases • Stroke volume (SV): increases

• Cardiac output (Q = HR × SV): increases significantly

• Blood flow is redistributed: increased to working muscles, decreased to non-essential organs

Pressure, Flow, and Resistance Flow (Q) = Pressure difference (ΔP) / Resistance (R)

• Increased pressure increases flow

• Increased resistance decreases flow

• Vessel diameter strongly influences resistance

Blood Flow Regulation Controlled primarily by arterioles via:

• Sympathetic vasoconstriction

• Local metabolites (CO2, H+, lactate, adenosine)

• Nitric oxide (vasodilation) • Hormonal control

Functional Sympatholysis

During exercise, local metabolites override sympathetic vasoconstriction, allowing increased blood flow to active muscles.

Venous Return Mechanisms (Upright Exercise)

1. Muscle pump: skeletal muscle contractions push blood toward the heart

2. Respiratory pump: pressure changes during breathing aid venous return

3. Venoconstriction: sympathetic activation constricts veins

Chronic Adaptations to Aerobic Training

• Decreased resting heart rate

• Decreased submaximal heart rate

• Increased stroke volume

• Increased cardiac output

• Increased parasympathetic tone (primary reason for lower resting HR)

Population Differences

• Genetics account for 25–50% of VO2 max variation

• Sex differences account for ~10% variation

• Presence of responders and non-responders

Functions of Blood

• Transport: oxygen, nutrients, hormones, waste

• Regulation: temperature, pH, fluid balance

• Protection: immune function and clotting

RESPIRATORY SYSTEM

Structure and Function The respiratory system delivers oxygen to the alveoli, transfers oxygen to the blood, removes carbon dioxide, and contributes to pH regulation, temperature control, vocalization, and immune defense.

Mechanics of Breathing

• Inspiration: diaphragm contracts, thoracic cavity expands, pressure decreases, air flows into lungs

• Expiration: diaphragm relaxes, thoracic cavity decreases, pressure increases, air flows out

Lung Volumes

• Tidal Volume (VT): normal breath (~500 mL)

• Inspiratory Reserve Volume (IRV): additional inhalation

• Expiratory Reserve Volume (ERV): additional exhalation

• Residual Volume (RV): air remaining after maximal exhalation

Lung Capacities

• Vital Capacity (VC) = VT + IRV + ERV

• Total Lung Capacity (TLC) = VT + IRV + ERV + RV

• Functional Residual Capacity (FRC) = ERV + RV

• Inspiratory Capacity (IC) = VT + IRV

Gas Transport

• Oxygen is transported primarily bound to hemoglobin

• Carbon dioxide is transported mainly as bicarbonate (HCO3-)

pH and Bohr Effect

• Decreased pH (increased acidity) reduces hemoglobin’s affinity for oxygen

• This enhances oxygen unloading to working muscles during exercise

Afferent Feedback

• Chemoreceptors detect changes in CO2, O2, and pH

• Mechanoreceptors detect movement and stretch

• Baroreceptors detect pressure changes

Respiratory Adaptations to Training

• Slight increase in total lung capacity

• Increased VO2 max

• Respiratory system is typically not the limiting factor in performance

RESISTANCE TRAINING ADAPTATIONS Definitions

• Muscular strength: maximal force (1RM)

• Muscular endurance: ability to sustain repeated contractions

Timeline of Adaptations

• Weeks 1–4: neural adaptations dominate (strength gains without hypertrophy)

• Weeks 4–8: hypertrophy begins

• Weeks 8–16: significant increases in muscle cross-sectional area

Neural Adaptations

• Increased motor unit recruitment

• Increased firing rate (rate coding)

• Improved coordination

• Strength gains can occur without hypertrophy

Hypertrophy

• Increase in muscle fiber size

• Increased actin, myosin, and myofibrils

• Type II fibers: 20–45% growth

• Type I fibers: 10–25% growth

• Whole muscle growth: 10–30% in 3–6 months

Mechanisms of Growth

• mTOR signaling pathway increases muscle protein synthesis (MPS) '

• Positive net protein balance leads to muscle growth

• Satellite cells donate nuclei to support growth

Muscle Architecture

• Increased pennation angle (5–20%)

• Slight increase in fiber length

• Increased force production

Connective Tissue and Bone

• Increased tendon stiffness (20–30%)

• Increased collagen synthesis

• Increased bone mineral density

Hormonal Responses

• Testosterone, growth hormone, IGF-1 support hypertrophy

• Acute and chronic hormonal responses contribute to adaptation

Detraining

• Strength loss begins quickly (3–4% per day initially)

• Type I fibers are more affected

Sex Differences

• Men and women gain strength at similar relative rates

AEROBIC AND ANAEROBIC TRAINING Central Adaptations (Cardiovascular)

• Increased stroke volume

• Increased cardiac output

Peripheral Adaptations (Muscle)

• Increased mitochondria

• Increased capillary density

• Increased oxygen extraction

Aerobic Training Adaptations

• Increased VO2 max

• Decreased heart rate

• Improved endurance

Anaerobic Training Adaptations

• Increased muscle size

• Increased glycogen and creatine stores

• Increased buffering capacity

• Increased Type II fibers

Metabolic Adaptations

• Improved energy production efficiency

• Increased lactate tolerance

General Adaptation Framework

• Stress → adaptation → improved performance

Overtraining Signs

• Chronic fatigue

• Decreased performance

• Sleep disturbances

• Mood changes

• Elevated resting heart rate

SAID Principle

• Specific Adaptations to Imposed Demands

Core Principles

• Individuality: responses vary by person

• Specificity: training must match goals

• Progressive overload: increase demand over time

• Reversibility: loss of adaptations when training stops

• Variation (periodization): planned changes in intensity and volume

Training Guidelines

• Large muscle groups before small

• Multi-joint before single-joint exercises

• High intensity before low intensity

Force-Velocity Relationship

• High force = low velocity

• High velocity = low force

Free Weights vs Machines

Free Weights: • Recruit stabilizing muscles • Better for advanced individuals Machines: • Safer and easier to use • Better for beginners • Isolate muscles

HIIT Training

• 2:1 work-to-rest ratio

• Improves aerobic capacity efficiently

Benefits of Exercise

• Improved cardiovascular health

• Improved cognitive function

• Reduced risk of chronic disease

• Maintenance of brain structure and function

Exercise Prescription (6 Factors)

• Mode

• Frequency

• Intensity

• Duration

• Volume

• Progression

ACSM Guidelines

• Moderate: ≥30 min, 5 days/week

• Vigorous: ≥20 min, 3 days/week

Minimum Threshold

• Minimum level required for improvement; varies by individual

Health Screening and Risk Stratification

• Low risk: no major risk factors

• Moderate risk: 2+ risk factors

• High risk: known disease or symptoms

Components of an Exercise Program

• Warm-up

• Endurance training

• Resistance training

• Flexibility

• Cool-down

• Recreational activity

Prolonged Sitting

• Increases insulin resistance

• Negatively affects metabolism

• Not fully offset by exercise

• NEAT (non-exercise activity thermogenesis) helps reduce risk

Body Composition

• Difference between body fat and BMI is important for health assessment