Exercise Physiology I Final

Anatomy of Skeletal Muscle

muscle belly (epimysium) -> fasiculi (perimysium) -> muscle fiber (endomysium) -> myofibril -> sarcomere

Sarcomere Definition

the basic functional unit of muscle cells

The Anatomy of a Sarcomere: Protein Filaments

Actin (thin filament) and myosin (thick filament)

The Anatomy of a Sarcomere: Thick Filament Globular Heads

Myosin globular heads interact with myosin binding site (actin filament)

The Anatomy of a Sarcomere: Thin Filament Proteins

actin: myosin binding site

tropomyosin: active site at rest

troponin: moves tropomyosin

The Anatomy of a Sarcomere: Titin

stabilizer (nebulin = stabilizing protein)

prevents overstrertching

increase stiffness with muscle activation

Excitation-Contraction Coupling

AP starts in brain -> AP goes to axon terminal -> ACh released and binds to ACh receptors on plasmalemma -> AP travels to T-tubules -> Ca2+ released from SR -> Ca2+ binds to troponin -> troponin-Ca2+ complex moves tropomyosin and exposes myosin binding site -> myosin binds to actin -> muscle contraction

Sliding Filament Theory: Relaxed State

No contraction or interaction

Sliding Filament Theory: Contraction State

defined by the power stroke (filaments slide past each other and sarcomere shortens)

Sliding Filament Theory: After Power Stroke

myosin head detaches and returns to original position, myosin attaches to another active site

Sliding Filament Theory: Continues UNTIL

1) Z- disk reaches myosin filament

2) AP stops and Ca2+ diffuses back into the SR

Energizing the Sliding Filament Theory

1) AP binds to myosin head

2) ATPase on myosin head converts ATP -> ADP+ Pi + energy

3) myosin head releases ADP and returns to ready position

4) new cross bridge forms and myosin binds ATP

Muscle Fibers

Type I (slow twitch)

Type II (fast-twitch)

Muscle Fibers: Type II Variations (slowest to fastest twitch)

Type IIa, Type IIx, Type IIc

Muscle Fibers: Recruitment Pattern

Smallest to largest motor unit

Muscle Contractions: Static (Isometric)

produces force, but does not change in length

myosin cross bridge forms & recycles, does not shorten

Muscle Contractions: Dynamic

Concentric = muscle length and sarcomere shortens, filament slides toward center

Eccentric = muscle length and sarcomere lengthens

Additional Muscle Term: Plasmalemma, what is special about the plasmalemma?

cell membrane of muscle fiber, transports AP

Additional Muscle Term: T-tubule

extension of Plasmalemma that carries AP to muscle fiber

Additional Muscle Term: sarcoplasmic reticulum (SR)

stores Ca2+

Additional Muscle Term: sarcoplasm

cytoplasm of muscle cell , glycogen and myoglobin storage

ATP Models

ATP-PCr, Glycolytic, Oxidative

ATP Models: ATP-PCr

1. classification

2. when during exercise

3. characterization

4. where

5. ATP yield

1. anaerobic

2. first 3-15 s of exercise

3. energy used to reassemble ATP

4. substrate level metabolism

5. 1 mol ATP yield

ATP Models: Glycolytic

1. classification

2. when during exercise

3. characterization

4. where/substrate

5. ATP yield

1. anaerobic

2. 15s - 2 min of exercise

3. glycolysis, 10-12 enzymatic reactions

4. cytosol/glucose or glycogen

5. 2 mol ATP for glucose , 3 mol ATP for glycogen

ATP Models: Oxidative

1. classification

2. when during exercise

3. characterization

4. where/substrate

5. ATP yield

1. aerobic

2. prolonged exercise

3. ATP produced through three steps: glycolysis, Kreb's Cycle, and Electron Transport Chain where oxygen is the final electron acceptor and a proton gradient produces ATP

4. mitochondria/glucose or FFA

5. 32-33 ATP per mol of glucose, 100+ ATP per mol of FFA

ATP Models: Oxidative (Glucose vs. FFA)

Glucose produces 32-33 ATP

FFA produces 100+ ATP

FFA oxidation is slower acting and takes longer than glucose oxidation

Neuron Anatomy

dendrite -> cell body -> axon

Neuron Anatomy: Dendrite

Cell processes receive impulse and carry to cell body

Neuron Anatomy: Cell Body

Contains nucleus, cell processes protrude from cell body

Neuron Anatomy: Axon

Sends impulses from cell body to axon hillock

Neuron Anatomy: Myelin Sheath

speed up propagation of AP through non continuous Schwann cells (fatty sheath around axon) and Nodes of Ranvier (gaps between Schwann cells)

Neuron Activity: Action Potential Direction

Axon -> Synapse -> Dendrite -> Cell Body -> Axon

Neuron Activity: Action Potential Direction (Cells)

Presynaptic Cell -> Synaptic Cleft -> Postsynaptic Cell

Neuron Activity: Signal Change

Electrical -> Chemical -> Electrical

Neuron Activity

RMP -> Depolarization -> Overshoot -> Repolarization -> Hyperpolarization -> RMP

Neuron Activity: Overshoot

Na+ channels close, K+ channels open (-55 mV to +30 mV)

Neuron Activity: Depolarization

Na+ channels open, influx on Na+ into the cell (-70 mV to -55 mV)

Neuron Activity: Repolarization

influx of K+ out of the cell (+30 mV to -70 mV)

Neuron Activity: Hyperpolarization

more K+ exits the cell

Nervous Sytem Breakdown

Central Nervous System (brain and spinal cord) & Peripheral Nervous System (motor and sensory neurons)

Nervous System Breakdown: Peripheral Nervous System

1. Motor (Efferent) -> Somatic (voluntary) and Autonomic (involuntary) -> sympathetic (fight/flight) & parasympathetic (rest/digest)

2. Sensory (Afferent)

Brain Connection to Muscles: Frontal Cortex

Primary Motor Cortex: conscious control of skeletal muscle movement

Brain Connection to Muscles: Basal Ganglia

initiation of sustained and repetitive movement

Brain Connection to Muscles: Cerebellum

rapid and complex movement, corrects and refines movement

Adrenal Medulla: Hormone Release Proportions

Release Catecholamines

80% Epinephrine

20% Norepinephrine

Adrenal Medulla: Fight or Flight

1. increase heart rate, contractile force, and blood pressure

2. increase glycogenolysis of FFA

3. increase blood flow to skeletal muscles

DOMS & when it occurs

Delayed Onset Muscle Soreness

1-2 days after exercise

DOMS: Major cause

eccentric contraction

DOMS: Effects on muscle

increases muscle enzyme concentration in blood 2-10 times, myofilament damage

DOMS: Body Response

Same response pathway as inflammation, includes leukocytes (neutrophils), causes loss of srength

DOMS: Elimination

decrease eccentric work

start with low intensity exercise and gradually increase

start with high intensity, exhaustive training

EAMC & where

exercise associated muscle cramps

where: overworked muscles

EAMC: Causes

1. improper training

2. depletion of muscle energy stores

3. lack of conditioning

4. induced by electrical stimulation

EAMC: Treatment & Reduction

1. stretching

2. change excitatory properties of motor neuron

Acute Muscle Soreness: When

immediately after strenuous or novel exercise

Acute Muscle Soreness: Characterization

accumulation of H+, tissue edema

Acute Muscle Soreness: Resolving

Resolves in minutes to hours

Strength v. Power v. Endurance

Strength = maximal force that a muscle or muscle group can generate

Power = explosive aspect of strength, rate of performing work

Endurance = capacity to perform repeated muscle contractions or sustain a single muscle contraction over time

Resistance Training: Static-Contraction Resistance

isometric: no muscle shortening, produces force

Resistance Training: Dynamic Eccentric Training

Produces greater strength gains compared to CON

Resistance Training: Variable-Resistance Training

lower resistance in weak range of motion, increased resistance in stronger range of motion

Resistance Training: Isokinetic Training

Movement at constant speed

Resistance Training: Plyometric

stretch-shortening cycle exercise, strength and speed

Resistance Training: Electrical Stimulation

Mostly used to restore strength in rehab

Resistance Training: Core Training

Decrease likelihood of injury, increase muscle spindle sensitivity

How to Gain Strength

1. Maximum results when combining ECC and CON exercise

2. Can result from greater motor unit recruitment

Interval Training

repeated bouts of high/moderate intensity with rest or reduced intensity

Interval Training: Duration of Rest

HR recovery

1.

Interval Training: Active Recovery

Active HR < 120 bpm

Interval Training: LSD (Long Slow Distance) Training

train at 60-80% HRmax, main objective is distance not speed

Interval Training: Fartlek Training

pace varies from spring to jog, primarily for distance runners

Interval Training: HIIT

improve aerobic capacity in untrained people, works for busy schedules

Factors That Affect Strength: Increase

1. 3-6 months of resistance training

2. synchronous recruitment = resistance training

Factors That Affect Strength: Decrease

1. Immobilization

2. Major changes after 6 hours

3. 1 week strength loss = 3-4% per day

Factors That Affect Strength: Sex, Race, and Age

Strength training does not differ between sex or race

Aging affects strength gain and training

Factors That Affect Strength: Hypertrophy

Increase in Muscle Size

1. Transient Hypertrophy: after exercise bout due to edema formation from plasma fluid, gone within hours

2. Chronic Hypertrophy: long-term structural change in muscle

Exercise Screening: Low vs. Moderate vs. High-Risk

Low-Risk: no risk factors for CV, pulmonary, or metabolic disease

Moderate-Risk: have 2+ risk factors for CV, pulmonary, or metabolic disease

High-Risk: at least one sign or symptom of disease

Exercise Screening: Who Gets Screened

Screening not mandatory for low-risk and healthy individuals, recommended for moderate-risk and high-risk individuals

ECG: Benefits

detect arrhythmias and myocardial ischemia (ST segment changes) ; positive results require follow-up

Activities for Endurance

Walking, jogging, running, cycling, swimming, rowing