Chapter 6 Review Flashcards
How do cells of the three types of muscle tissues differ from one another anatomically?
Skeletal muscle fibers are long multi-nucleate cells with striations. Cardiac cells are branching, typically uni-nucleate cells with less striations. Smooth muscle cells are spindle shaped, uni-nucleate and non-striated.
Which muscle type has the most elaborate connective tissue wrappings?
Skeletal
What does striated mean relative to muscle cells?
Striped or having bands
How do the movements provided by skeletal muscle differ from those promoted by smooth or cardiac muscle?
Skeletal muscle movements can be very forceful & rapid , whereas smooth muscle movements tend to be slow and rhythmic.
Structures of the skeletal muscle from smallest to largest.
Myofilament, sarcomere, myofibril, muscle fiber (cell), fascicle.
Structures from smallest to largest + functions.
Endomysium - wraps each muscle fiber (or muscle cell)
Perimysium - wraps around a fascicle
Epimysium - wraps entire muscle (many groups of fascicles)
Which type of muscle tissue has involuntary regulation of contraction?
Cardiac and smooth
What is the plasma membrane of a muscle cell called?
Sarcolemma
What are the 4 main functions of muscles?
Produce movement
Maintain posture and body position
Stabilize joints
Generate heat
What is a sarcomere?
Tiny contractile units, which are the structural & functional units of skeletal muscles.
What is a myofibril?
Long, ribbon-like organelles that nearly fill the cytoplasm, composed of bundles of myofilaments.
I band
Light band
A band
Dark band
Z disc
Mid-line interrupter of the I band
H zone
Lighter central area of the A band
M line
Center of the H line
What structure(s) is/are responsible for the banding pattern in skeletal muscle cells?
The alignment of the bands on the myofilaments (actin=light) (myosin=dark)
What is the name of the neurotransmitter that stimulates skeletal muscle fibers?
Acetylcholine (ACh)
What is the gap between the nerve endings and the muscle fiber called?
Synaptic cleft
Neuromuscular junction
A nerve impulse reaches the axon terminal of a motor neuron. CA2+ channels open and calcium enters the axon terminal. Calcium entry causes vesicles to release their contents (ach) via exocytosis. ACH diffused into the synaptic cleft & binds to receptors (voltage-gated channels) in the sarcolemma (muscle cell membrane) opening them. This opening of the voltage-gated channels causes the simultaneous passage of NA+ into the muscle and K+ our of the muscle. This change in electrical conditions (depolarization) leads to a second action potential which is propagated down the T tubules. This causes calcium to be released by the endoplasmic reticulum onto the filaments. Calcium binds to troponin causing tropomyosin to slide out of the binding sites on actin. Charged Myosin heads bind to actin causing a power stroke. (The sliding of actin). A new molecule of ADP re-charges the myosin heads allowing them to unbind and move back into position. Enzymes break down ACH in the synaptic cleft and calcium is reabsorbed into the sarcoplasmic reticulum causing the muscle to relax.
What is the role of calcium ions during skeletal muscle contraction?
Calcium enters the axon terminal causing the release of acetylcholine and it also is released by the sarcoplasmic reticulum causing the release of tropomyosing from the actin binding sites.
Which ions enter the muscle during the generation of an action potential?
Sodium
Which chemical triggers sliding of the muscle filaments?
Calcium
What is the direct source of energy used by muscle fibers for contraction?
Stored ATP