Immune System: Innate and Acquired Immunity

Innate Immune System

• First line of defense against invaders, includes physical and cellular barriers
• Physical barriers are skin (oils), hair, sweat (pH 3-4), mucus membranes, and stomach acid
• Cellular barriers involve phagocytes, which include neutrophils (first responders, abundant) and macrophages, and NK cells (natural killer cells)
• Complementary proteins assist in immune response through opsonization, inflammation, and membrane attack complex

Acquired (Adaptive) Immune System

• Adaptive immunity is acquired and produces a specific response to pathogens
• B cells produce antibodies that prevent viruses/bacteria from binding to cells
• T cells have various functions and some destroy infected cells
• Response to pathogens improves with each exposure, which leads to faster reaction times upon re-infection

Immunity Development

• First infections require time for T and B cells to adapt
• Re-infections or vaccinations lead to faster immune responses due to memory T and B cells

Vaccination

• Vaccination mimics infection and primes the immune system without causing disease
• Memory cells remain ready for future exposure to the pathogen

Exercise and Immune System

• Risk of infection is related to exercise intensity and volume
• Moderate exercise boosts immunity, while overtraining can suppress the immune system
• White blood cell count changes post-exercise and optimal exercise duration for benefit is 1-2 hours
• Overtraining creates an "open window" for infection

Complement Proteins

• Opsonization marks pathogens for phagocytosis by immune cells
• Inflammation is part of the immune response
• Membrane Attack Complex (MAC) helps the immune response

Antibody Types

• Five types of antibodies exist: IgA, IgD, IgE, IgG, and IgM

Immune System and Exercise

• Sedentary activity levels result in average risk of infection
• Moderate exercise volume/intensity results in low risk of infection
• High exercise volume/intensity results in high risk of infection

Exercise Effect Research

• Different muscle actions (eccentric vs. concentric) impact immune cell count
• Total white blood cells and phagocytes increase post-exercise, but normalize after 24 hours
• Balance in exercise intensity is important to maintain immune function

Nervous System Organization

• The structural organization includes the Central Nervous System, containing the brain and spinal cord
• Peripheral Nervous System, containing nerves and ganglia

Functional Organization

• Functional organization involves the Sensory Nervous System
• Somatic Sensory consciously perceives stimuli like sight and sound
• Visceral Sensory unconsciously perceives stimuli like heart function and digestion
• Autonomic Nervous System involves involuntary control (e.g., heart rate)

Neuron Communication

• Communication occurs between presynaptic and postsynaptic neurons through synapses

Resting Membrane Potential

• Most neurons maintain a resting membrane potential of -70 mV
• This potential makes action potential travel

Myelin Sheath

• Exercise helps with multiple sclerosis through neuroplasticity, reduced inflammation, and improved blood flow to the brain
• Normal axons are protected by Schwann cells that form the myelin sheath

Sodium Potassium Pump

• ATP activates the pump to maintain the resting membrane potential of -70 mV

Action Potential

• It starts at -70 mV, needing to reach -55 mV threshold
• Na+ channels open, and Na+ ions enter the cell, causing depolarization
• K+ channels open, and K+ ions leave the cell, causing repolarization
• Following repolarization, it goes down below -70 mV (hyperpolarization)
• It returns back up to resting state at -70 mV

Muscle Spindles

• Muscle spindles detect muscle stretch and conduct action potentials to the spinal cord
• Sensory neurons synapse with alpha motor neurons, and their stimulation causes the muscle to contract

Golgi Tendon

• Golgi tendon organs detect tension applied to a tendon and conduct action potentials to the spinal cord
• Sensory neurons synapse with inhibitory interneurons, which synapse with alpha motor neurons, causing muscle relaxation

Withdrawal Reflex

• Sensory neurons from pain receptors conduct action potentials to the spinal cord
• Excitatory interneurons stimulate alpha motor neurons which innervate flexor muscles, causing the withdrawal reflex

Regular Exercise

• Benefit to Brain: regular exercise increases brain derived neurotrophic factor (BDNF) and overall health of the brain because of BDNF
• Benefit to Body: active skeletal muscle increase in irisin and brain health

Brain Derived Neurotrophic Factor (BDNF)

• BDNF functions in neurogenesis, synaptic plasticity, neuroprotection, and synapse formation
• BDNF is found in the hippocampus and cerebral cortex
• Conditions affected by BDNF include depression, anxiety, schizophrenia, Alzheimer's, Parkinson's, Huntington's, bipolar disorder and chronic stress
• BDNF is improved by regular exercise, healthy diet, stress management, social interaction, mental stimulation, sunlight exposure, and avoiding chronic stress

Muscle Composition

• Muscles are composed of fascicles made of muscle fibers
• Muscle fibers are comprised of myofibrils
• Myofibrils contain sarcomeres, the smallest contracting units
• Satellite cells are located on the border of muscles and are dormant until muscle tear/trauma
• They increase sarcoplasm and contractile potential for muscle repair and growth

Sarcomere Structure

• Z-lines mark the boundaries of sarcomeres
• Proteins include Myosin (pink in cross-section, like golf clubs binding to actin) and Actin (purple/blue in cross-section)
• The power stroke is when myosin binds to actin, causing contraction
• A-band is the area where myosin and actin overlap
• I-band is the region with only actin
• H-zone is the area with only myosin filaments

Muscle Contraction Mechanics

• Sarcoplasmic Reticulum (SR) is specialized for storing calcium
• Transverse Tubules (T-Tubules) transmit action potentials to trigger calcium release
• Neuromuscular junction involves a motor neuron activating the muscle fiber
• The neurotransmitter acetylcholine is released from synaptic vesicles in response to calcium
• Depolarization is caused by the opening of sodium channels

Contraction Process

• Action potential travels down the T-tubules
• Calcium release is stimulated by action potential
• Calcium binds to troponin, freeing actin for myosin binding
• Power stroke is when myosin heads bind to actin, powered by ATP

Muscle Cramps

• Causes include dehydration and electrolyte imbalance, as well as altered neuromuscular control
• Muscle spindles detect stretch and trigger contraction
• Golgi tendon organs inhibit excessive tension

Muscle Fiber Types

• Type 1 (Slow Twitch) offers endurance, high mitochondria, and resists fatigue
• Type 2A (Intermediate) offers moderate power and endurance
• Type 2X (Fast Twitch) means quick, powerful contractions, but low endurance
• Distribution varies among athletes and is influenced by genetics and training

PEDs Used in Sports

• 44% are anabolic agents
• 16% are diuretics and other masking agents
• 15% are stimulants
• 9% are hormone and metabolic modulators
• 6% are glucocorticosteroids
• 4% are beta-2 agonists

Categories of PEDs

• Stimulants, including Adderall and inhalers, are reported in the NCAA
• Beta Blockers are used to reduce performance anxiety
• Diuretics are used for weight management
• Hormone and Metabolic Modulators affect metabolic rate (e.g., T3, T4 from thyroid)

Types of Sports & PEDs

• Beta-blockers and stimulants are used in skill sports requiring coordination
• Androgen doping is used in strength
• Blood doping is used in stamina and endurance
• Growth factors are used in recovery for contact sports

Anabolic Steroids

• Anabolic Steroids are based on cholesterol; testosterone is a core component
• Aim to increase anabolic effects while minimizing androgenic effects
• Derived from three bases: testosterone, dihydrotestosterone, and nandrolone
• Used for medical conditions like cancer and HIV

Medical Uses

• Medical uses include FDA-approved treatments for conditions like cancer and AIDS
• Veterinary uses are in animals but the drugs are misused by athletes

Androgenic & Anabolic Ratings

• Researchers aim to maximize anabolic and minimize androgenic effects
• Female athletes prefer compounds with low androgenic ratings

Genomic and Non-Genomic Effects

• Genomic effects are when steroids alter genetic messages within cells
• Non-genomic effects include immediate effects, such as muscle hypertrophy

Diuretics and Other Drugs

• Diuretics are used to reduce water weight and are dangerous if overdosed
• Insulin can be fatal if overdosed

Side Effects

• Anabolic steroids can cause infertility, mood swings, acne, baldness, gynecomastia, and increased cardiovascular risk
• Growth hormones cause abnormal growth of organs and exacerbate cancer