Muscles (Smith) week 1 Flashcards
Skeletal muscle characteristics
Single, very long, cylindrical, multinucleate,
obvious striations, voluntary, not self stimulating, high energy requirement, fast contrating
Cardiac muscle characterisitcs
branching chains of cells,uninucleate, striation, Involuntary, self stimulating, under control of nervous and endocrine system intermediate energy requirement, intermediate speed of contraction
Smooth muscle charateristics
Single cells, fusiform, uninucleate, with no striations, self stimulating, under control of nervous and endocrine systems, lower energy requirement, slow rhythmic contractions
Motor unit
functional unit of the muscle and is composted of the alpha motor neuron and all the muscle cells in innervates
Site of motor unit inntervation
neuromuscular junction (NMJ)
T/F: Each alpha motor neuron’s axon branch and synapse with up to thousands of different muscle fibers?
True
T/F Each individual muscle fiber is connected to only on neuron?
True
What is the sarcoplasmic reticulum (SR)?
intrancellular organelle that stores and releases calcium ions
Terminal cisternae
the enlarged portion of the SR nearest the t-tubules
Calcium is released from the SR via channels called?
ryanodine receptors (RyRs)
Transverse or T- tubules
- smaller tube like structures that run perpendicular to the sarcolemma.
- action potentials travel down the T-tubules during excitation-contraction coupling.
Sarcomere
extends from one Z-disc to the other
functional unit of muscle cell
A-band
myosin containing band, dark in color
I-band
the lighter band, and includes the Z-disc and the actin filaments
shortens during contraction
H-zone
center of the A-band, where acting and myosin DO NOT over lap, M-line is in center of H-zone
shortens during contraction
M-line
in center of H-zone and accessory proteins anchor myosin the M-line
Titins
anchor thick filaments to Z-discs and runs with the thick filaments to the M-line
- holds myosin in place
- helps muscle spring back into shape
T/F: myosin and actin change length during contraction
FALSE
Tropomyosin
blocks binding site on myosin, moves in high concentrations of Calcium
troponin
troponin binds to calcium and shifts and moves the tropomyosin to allow binding of acting to myosin.
-ON ACTIN
Excitation-contraction coupling
the physiological process of converting an electrical stimulus (AP) to a mechanical response (contraction) and the NMJ
Cause of striations in skeletal and cardiac muscles
intercalated disks and fused together via desmosomes
in cardiac there are gap junctions to allow the electric impulse to propagate
Cardiac muscles unique characteristics
- no external innervation needed
- almost exclusive aerobic respiration
- Large mitochondria
- High myoglobin content hence the dark color of the heart
Smooth muscle unique characteristics movement
actin fibers attached to cell wall and dense body in the cytoplasm. When activated the actin fibers slide over myosin bundles and cause the walls to shorten, crinkle the cell
- No troponin
- relaxation of smooth muscle does not always happen when Calcium levels decrease
- Have few mitochondria
