Human Physiology Chapter 12

What are the effector organs of the somatic vs autonomic nervous system?

Somatic → skeletal muscle; Autonomic → smooth & cardiac muscle

What does muscle contraction generate?

Force

Why are muscle cells considered excitable?

They respond to action potentials

Characteristics of skeletal muscle?

Striated, voluntary, multinucleated, moves bones

Characteristics of cardiac muscle?

Striated, involuntary, uninucleate, found in heart

Characteristics of smooth muscle?

Non-striated, involuntary, found in organs & vessels

What connects muscle to bone?

Tendons

What are fascicles?

Bundles of muscle fibers

What is fascia?

Connective tissue covering muscles

Layers of connective tissue (outer → inner)?

Epimysium → Perimysium → Endomysium

What is the sarcolemma?

Muscle cell membrane

What is sarcoplasm?

Cytoplasm of muscle fiber

What are myofibrils?

Contractile structures inside muscle fibers

Functional unit of muscle?

Sarcomere

What are Z discs?

Boundaries of sarcomere

What does the A band contain?

Thick filaments + overlap

What does the I band contain?

Thin filaments only

What does the H zone contain?

Thick filaments only

What is the function of the M line?

Center of sarcomere

Thick filament protein?

Myosin

Thin filament protein?

Actin

What blocks myosin binding sites?

Tropomyosin

What binds calcium?

Troponin

What is the sliding filament theory?

Filaments slide past each other → sarcomere shortens

Do filaments change length during contraction?

No

What triggers contraction?

Increase in calcium

What does calcium do?

Exposes myosin binding sites

Why is ATP important?

Provides energy for contraction & detachment

What neurotransmitter is released?

Acetylcholine (ACh)

What ion starts the muscle impulse?

Sodium (Na⁺)

What is the power stroke?

Myosin pulls actin inward

What is rigor?

Myosin stuck to actin (no ATP)

What is excitation-contraction coupling?

Action potential → contraction

What is the all-or-none principle?

Full contraction or none

What is recruitment?

Activating more fibers

Concentric contraction?

Muscle shortens

Eccentric contraction?

Muscle lengthens

Isometric contraction?

No length change

Latent period?

Delay before contraction

Contraction period?

Muscle shortens

Relaxation period?

Muscle returns to normal

Refractory period?

Cannot contract again

Twitch?

Single contraction

Wave summation?

Increased force

Tetanus?

Sustained contraction

Treppe?

Increasing strength after rest

3 ATP systems?

Phosphagen, Glycolysis, Aerobic

Uses what molecule?

Creatine phosphate

Duration?

~15 seconds

Net ATP?

2 ATP

Requires oxygen?

No

Byproduct without oxygen?

Lactic acid

ATP produced?

~36 ATP

Requires?

Oxygen

Main energy source?

Yes

Oxygen carrier in blood?

Hemoglobin

Oxygen storage in muscle?

Myoglobin

Oxygen debt?

Extra oxygen after exercise

Slow-twitch fibers?

Endurance, slow contraction

Fast-twitch fibers?

Fast, powerful

Glycolytic fibers?

Fast ATP, few mitochondria