Muscle Tissue and the Neuromuscular Junction Flashcards

skeletal, smooth, cardiac

excitable

conductive

contractile

elasticity

extensibility

Responsive to a stimulus

transfers stimulus along the cell membrane

shorten their length to create tension

return to rest after shortening or lengthening

stretch beyond their resting length

movement

support

posture

temperature regulations

communications

surrounds entire muscle DICT

surrounds fascicles DICT with BV and nerves

surrounds and electrically insulates each muscle fiber ARC with reticular fibers

large sheet external to epimysium

separate muscle from skin ARADCT

attaches a muscle to bone skin or other muscles

this flattened connective tissue

plasma membrane

cytoplasm

smooth ER

muscle fiber running the entire length

contraction = shorten

contain myofilaments

myosin

tail

• Actin
• Tropomyosin
• Troponin

functional unit of muscle

smallest piece functions as a muscle

contains thin filaments not thick

contains thick filament

are dark

center of A band contains thick filaments not thin

protein in center of H zone that attaches thick filaments

• Contracting muscles pull on tendons to produce movement.
• To pull, muscles develop tensions as their sarcomeres shorten.
• For sarcomeres to shorten, thick filaments attach to thin filaments and
pull them toward the centers of the sarcomeres
• The sliding filament theory explains muscle contraction

Calcium ions bind to troponin on actin’s active site

Myosin binds actin to form a cross-bridge (“cocked” formation)

Phosphate is released, the myosin head
moves into low-energy conformation and actin slides towards the M line
(“powerstroke”)

A new molecule of ATP replaces ADP
(cross-bridge detachment)

Cross-bridges break and the cycle repeats

where the axon terminal of an alpha motor neuron and the membrane of a muscle fiber meet

intracellular Na+, exit of intracellular K

action potentials and Ca2+ release

acetylcholinesterase degrades
Ach in synaptic cleft

expanded tip of neuron axon

Membrane sacs in synaptic knob, filled with acetylcholine (ACh)

Narrow space separating synaptic knob and motor end plate

Region of sarcolemma with many folds (increased surface area) under
the synaptic knob

Proteins that bind Ach on the motor end plate

Enzyme in synaptic cleft that breaks down Ach (prevents continuous stimulation of muscle)

a single motor neuron and the muscle fiber it controls

This is due to optimal placement
of actin and myosin for cross-bridge
formation

A wasting of muscle that reduces fiber size

Reduced stimulation results in reduced muscle size, tone, and power

An increase in fast muscle fiber SIZE (not cells!)
Building muscle increases fiber size not number of fibers
Number of myofibrils per fiber increases
More mitochondria and more glycogen stored in the cells
Results from repetitive, exhaustive stimulation of muscle

• More ATP is produced than needed
• ATP transfers the energy to create ADP
ATP + creatine → creatine phosphate + ADP

The reverse reaction generates ATP from
creatine phosphate
Creatine phosphate + ADP → ATP + creatine
• ATP is continuously generated at the same
rate it is used

• Lactic acid build-up after high-intensity exercise
• Glycogen depletion after medium-intensity exercise over long periods of time

Muscle cannot continue contractions even under nervous stimulation

• Smaller than skeletal muscle cells
• Spindle-shaped
• Have centrally-located nucleus
• No T-tubules or visible sarcomeres
• Do not fuse during development
• Connected by junctions
• Have membrane invaginations called caveolae

line walls of hollow organs

responsible for involuntary movements

contraction of organs

1. Ca2+ enters sarcoplasm; interacts with calmodulin
2. Myosin light chain kinase (MLCK)
phosphorylates myosin

3. Myosin-actin cross-bridges form

4. Cross-bridges develop muscle tension
5. Relaxation: removal of Ca2+ and
myosin dephosphorylation