MSUCLE TISSUE

Three types of muscle tissue

Skeletal, Cardiac, Smooth

Function of skeletal muscle

Movement, heat production, posture

Function of cardiac muscle

Pumps blood continuously

Function of smooth muscle

Peristalsis, blood pressure control, pupil size

Skeletal muscle appearance

Striated, multinucleated, voluntary

Cardiac muscle appearance

Striated, one nucleus, involuntary, autorhythmic

Smooth muscle appearance

Non-striated, one nucleus, involuntary

Epimysium

Connective tissue around whole muscle

Perimysium

Connective tissue around fascicles

Endomysium

Connective tissue around muscle fibers

Tendon

Merged connective tissue attaching muscle to bone

Sarcolemma

Muscle fiber plasma membrane

Transverse tubules

Conduct action potentials deep into fiber

Sarcoplasm

Muscle cytoplasm with glycogen & myoglobin

Myofibrils

Contractile organelles causing striations

Sarcoplasmic reticulum

Stores and releases Ca2+

Thick filaments

Myosin

Thin filaments

Actin with troponin and tropomyosin

Sarcomere

Functional contractile unit

Z-disc

Boundary of sarcomere

A-band

Dark band; thick ± thin filaments

I-band

Light band; thin filaments only

H-zone

Thick filaments only

M-line

Center of sarcomere; anchors myosin

Sliding filament theory

Actin slides past myosin causing contraction

Role of calcium

Binds troponin, exposes myosin-binding sites

Neuromuscular junction

Motor neuron meets muscle fiber

Neurotransmitter

ACh (acetylcholine)

Motor end plate

Sarcolemma with ACh receptors

End-plate potential

Na+ in → depolarization

Motor unit

One neuron + all fibers it controls

ATP: immediate source

Creatine phosphate

ATP: short-term source

Anaerobic glycolysis

ATP: long-term source

Aerobic respiration

Slow oxidative fibers

Type I, aerobic, fatigue-resistant

Fast oxidative fibers

Type IIa, intermediate endurance

Fast glycolytic fibers

Type IIb, anaerobic, powerful but fatigue fast

Isometric contraction

Tension without length change

Isotonic contraction

Length change with same tension

Concentric contraction

Muscle shortens

Eccentric contraction

Muscle lengthens under load

Muscle fatigue

Inability to maintain contraction force

Smooth muscle dense bodies

Anchor actin filaments

Cardiac muscle traits

Striated, autorhythmic, many mitochondria

Smooth muscle traits

Small, tapered, non-striated, regenerative