KN 352

Speed-force relationship

- Concentric: Maximal force development decreases at higher speeds - Eccentric: Maximal force development increases at higher speeds

Myosin

- A protein - An enzyme, because it helps react ATP into ADP and phosphate groups (ATPase) - ATP comes along and bonds to myosin head ------> Myosin releases actin

Muscle relaxation

- AP ends, electrical stimulation of SR stops - Ca2+ pumped back into SR - stored until next AP arrives - ATP required - WIthout Ca2+, troponin and tropomyosin return to resting conformation

Thermodynamic Laws

- Conservation of energy - Randomness and entropy in every closed system

Sarcoplasm

- Cytoplasm of muscle cell - Glycogen storage, myoglobin

Resting membrane potential

- Difference in electrical charges b/w outside and inside cell - -70mV - Caused by uneven separation of charged ions - Polarized

Theromdynamic laws

- Energy is neither created or destroyed - All energy systems move toward randomness

Specialty areas

- Environmental physiology: study of effects of environment on the function of the body - Sport physiology: application of concepts to train athletes and enhance sport performance

Harvard Fatigue Laboratory

- Focused on physiology of human movement and effects of environmental stress on exercise - Most contemporary exercise physiologists trace roots back here

Plasmalemma

- Fuses with tendon - Conducts action potential - Maintains pH, transports nutrients via transporters

How does muscle control calcium concentration?

- Motor neuron signals for contraction - Voltage gated sodium channels open up (Sodium flows on) - Positive threshold causes voltage gated calcium channels to open up - Calcium ions flow in and bond to special proteins near pre-synaptic membrane - Causes exocytosis. Vesicles containing neurotransmitters (acetyl choline) get dumped out - Acetylcholine binds to receptors on sarcolemma. Opens sodium channels of muscle cell. Allows sodium to flow into muscle cell. Action potential in muscle cell. Goes down the sarcolemma to the T-tubule. Causes an opening in sarcoplasmic reticulum that releases Calcium into cytoplasm

Satellite cells

- Muscle growth, development - Response to injury, immobilization, training

Chronic adaptation

- Physiological change occurring when body is exposed to repeated bouts over weeks/months - "Constant, habitual, frequent over time"

Peripheral nervous system

- Sensory (afferent): incoming - Motor (Efferent): Outgoing

Type 1 vs 2

- Speed of myosin ATPase varies - Fast= fast contraction cycling - Speed= slower contraction cycling - Staining of muscle biopsy sample - Small piece of muscle removed - Frozen, sliced examined - Gel Electrophoresis - Type 1 vs. Type 2 fibers have different types of myosin - Separates different types of myosin by size

Sarcoplasmic reticulum (SR)

- Storage area with large surface area - Contains calcium

Archibald Hill

- Studied energy metabolism in isolated frog muscle - First physiological studies on runners

Exercise Physiology

- Study of how body structure and function are altered by exposure exercise - Acute vs chronic bouts

Skeletal muscle anatomy

- Surrounded by epimysium - Consists of many bundles (fasciculi)

Actin Myosin process continues until

- Z disk reaches myosin filaments or - AP stops, Ca2+ gets pumped back into SR

Why -70?

- higher Na+ outside cells, medium K+ inside - Inside more negative relative to outside

Threshhold mv

-55 mv IF GP reaches this, AP will occur If not reached, no AP

John Haldane

-Developed methods of measuring oxygen use during exercise - Known for work in human physiology and respiration

Myson and Actin relationship

1) ATP binds to myosin head 2) Myosin releases actin 3) ATP -> ADP + P + energy (Myosin gets cocked into a high energy state) 4) Phosphate is released from myosin - "Releases the spring" - Causes myosin to push on actin - mechanical energy 5) ADP released (back to step 1, but different spot on actin)

Excitation-Contraction Coupling

1) Action potential starts in brain 2) AP arrives at axon terminal, releases ACh 3) ACh crosses synapse, binds to ACh receptors on plasmalemma 4) AP travels down plasmalemma, T-tubules 5) Triggers Ca2+ release from SR 6) Ca2+ enables actin-myosin contraction

ATPase enzyme

ATP -> ADP + P - Releases energy

Troponin

Attaches tropomyosin to actin - Changes shape when there's a high calcium ion concentration - Calcium binds to troponin, moves tropomyosin out the way - Low calcium concentration makes it go back to normal

CNS

Brain, spinal cord

Energy release

Can be calculated from heat produced

Metabolism

Chemical reactions in the body

Tropomyosin

Coils around actin - blocks myosin attachment actin at rest - Keeps myosin from sliding down actin

Early measurements of Harvard Fatigue Laboratory

Collected expired air in a sealed bag, known as the Douglas bag - chemical gas analyzer measured oxygen and carbon dioxide in it

Cross-sectional research

Collects data from diverse population and compares groups in that population

High Ca2+

Contraction

Entropy

Degree of randomness in a system

Strong GP --> AP

Depolarization - AP propgated down axon - Transmitted to next cell

-55 to +30

Depolarizing AP, Na+ influx

-70 to -55

Depolarizing GP, Na+ influx

Ratios

Each person has different ratios Endurance athletes=type 1 Power athletes=type 2 Soleus=type 1 for everyone

Transverse tubules (T-tubules)

Extensions of plasmalemma - Carry action potential deep into muscle fiber.

Tetanus

Frequency of stimulation so high that peak tension of motor unit is reached - Muscle can't be any more tense - Continual stimulation

Substrates

Fuel sources from which we make energy (ATP) - Carbs, fats, proteins

How do depolarization and hyperpolarization contribute to nervous system function?

Graded Potentials - Help cell body decide to pass signal to axon - can excite or inhibit neuron Action Potentials - Pass signal down axon - Excites neuron

Titin

Holds myosin to Z lines

Chronic adaptation to exercise

Improvement of the body's efficiency at rest and during exercise

Cardiac muscle

Involuntary, heart muscles - Metabolically similar to skeletal muscles Uniform contractions

Smooth muscle

Involuntary; hollow organs - Blood vessels for vasomotor control - Intestinal organs for peristalsis Uniform contractions

Inhibitory signal

K+ efflux aka hyperpolarization

K+ channels open

K+ leaves cell (Concentration gradient) - Offset by Na+-K+ pumps

Graded Potentials

Localized changes in membrane potential - Generated by incoming signals from dendrites

Metabolism

Maintains homeostasis and avoids maximum entropy...death

Homeostasis

Maintenance of a constant internal environment

Sarcolemma

Membrane of muscle cell

Muscle fiber/motor unit recruitment

Method for altering force production - Less force production=fewer or smaller motor units - More force production=more or larger motor units - Type 1 motor units smaller than type 2

H-zone

Middle of A-band

M-line

Middle of H-zone

Eccentric contraction

Muscle lengthens while producing force - Cross bridges form, but sarcomere lengthens (Lowering heavy weight)

Isometric contraction

Muscle produces force, but no change in length or joint angle. - Myosin cross bridges form and recycle

Concentric contraction

Muscle shortens while producing force - Sarcomere shortens, filaments slide to center (Normal contraction)

Aging

Muscles lose type 2 motor units

A band

Myosin and Actin - Does not change during contraction - Dark stripes

Na+ channels closed

Na wants to enter but can't - electrical and concentration gradients

Excitary signal

Na+ influx aka depolarization

Depolarization

Occurs when inside of cell becomes less negative (-70-->0) - More Na+ channels open and enter - Required for nerve impulse to arise and travel

Hyperpolarization

Occurs when inside of cell becomes more negative - More K+ channels open, leave cell - Makes more difficult for nerve impulse to arise

I band

Only actin - Gets smaller during contraction - Light stripes

Length-tension relationship

Optimal sarcomere length=optimal overlap - Too short or too stretched=little or no force developed

Bioenergetics

Process of converting substrates into energy - Performed at cellular level

AP

Rapid, substantial depolarization Lasts 1 ms Begins as GP

Type 1 muscle fiber type

Red - 50% of fibers in an average muscle - Peak tension in 110 ms, slow twitch

Low Ca2+

Relaxation

+30 to -70

Repolarizing AP, K+ efflux

Longitudinal research tests

Same subjects and compares results over time - More accurate, but time-consuming and expensive

Summation

Series of multiple stimuli, prior to complete relaxation from first stimulus. - Elicits a greater increase in force/tension than single twitch

Acute exercise

Single bout of exercise - "brief, severe, sharp"

Motor Unit

Single motor nueron + all fibers it innervates - More operating motor units = more contractile force

Neuromuscular junction

Site of communication b/w neuron and muscle

Twitch

Smallest contractile response

Three muscle tissue types

Smooth muscle Cardiac muscle Skeletal muscle

Motor system

Somatic - Voluntary Autonomic - Involuntary - Sympathetic vs Parasympathetic

sarcomere

Space between two z lines - Where actin and myosin interaction occurs - Basic contractile element of skeletal muscle

Sarcoplasmic reticulum

Storage organelle - Calcium ion pumps on membrane - Uses ATP to fuel pumps (ATPase)

Z lines

Striation lines

Muscle fiber

Surrounded by endomysium - Consists of myofibrils divided into sarcomeres

Fasciculi

Surrounded by perimysium - Consists of individual muscle cells (muscle fibers)

Physiology

The study of the function of organisms

Myosin

Thick filaments - Shows up darker under microscope - H and M zone contain only myosin

Actin

Thin filaments - Show up lighter under microscope - I-band contains only actin - Anchored at Z-disk - Equally spaced by titin

Peak power

Type 2x>2a>1 - Effects of different SR, motor units Regardless of fiber type, all muscle fibers reach peak power at 20% peak force

Ergometers

Used to measure physical work in standardized conditions - Treadmills/cycle ergometers most common

Haldane Transformation

Used today in assessing minute ventilation with metabolic carts

Skeletal muscle

Voluntary skeleton muscles - Striated

Type 2 muscle fiber type

White - Peak tension in 50 ms (fast twitch) - Type 2a and 2x

T-tubule

a fold in the membrane of a muscle cell - Can look like a hole

Myofibrils

bundles within a muscle fiber