Skeletal Muscles Flashcards
Skeletal Muscles
Intrafusal (5%)
Extrafusal (95%)
detects changes in muscle LENGTH
Intrafusal
innervation: GAMMA motorneurons
for VOLUNTARY MUSCLE CONTRACTION
Extrafusal
innervation: ALPHA motorneurons
2 types of Extrafusal
TYPE I
TYPE II
slow twitch red fiber greater myoglobin and mitochondria oxidative phosphorylation --> sustained contraction for ENDURANCE training
TYPE I
postural muscles of the back
fast twitch white fiber anaerobic glycolysis less myoglobin and mitochondria for WEIGHT/RESISTANCE training, SPRINTING
TYPE II
(+) gap junctions, (+) syncytium for GROSS motor movement
UNITARY SMOOTH MUSCLES
i.e. uterus
(-) gap junctions, for FINE motor movement
MULTI UNIT SMOOTH MUSCLES
i.e. pupil cells
Functional, structural and contractile unit of skeletal and cardiac muscles
area b/w 2 Z lines
sarcomere
Contains MYOSIN that act as CROSS BRIDGES of the sarcomeres
THICK FILAMENTS
1 pair of heavy chains
2 pairs of light chains
Contains ACTIN, TROPOMYOSIN AND TROPONIN
THIN ILAMENTS
“relaxing protein’ that covers actin binding sites at rest
Tropomyosin
3 subunits of Troponin
T - attached troponin complex to tropomyosin
I - inhibits actin-myosin binding
C - calcium binding protein
Part of sarcomere
borders
Z lines (“Zwischenscheibe”)
Part of sarcomere
midline
M line (“Mittelscheibe”)
entire length of the myosin
A band (Anisotropic)
inside A band, PURELY MYOSIN no actin interspersed
H band (Heller)
inside H band; no myosin heads
bare zone
PURELY ACTIN no myosin interspersed
I band
Invagination of the Sarcolemma
Spreads AP to all parts of the muscles
Transverse Tubules
Voltage sensitive receptor that is found in the Transverse Tubules
dihydropyridine receptors (DHPRs)
activates ryanodine receptors
Contains calcium needed for contractions
Sarcoplasmic Reticulum (SR)
amt of calcium released by SR depends on the amount of stored calcium
Calcium release channel in the SR ACTIVATED by DHPR
Ryanodine
Protein that stores Ca2+ in the SR
Calsequestrin
Pumps Ca from ICF to the SR
SERCA
Binds myosin to Z lines, binds Z lines to M line
TITIN
determines the normal stiffness of the ventricular muscles
Stabilizes sarcolemma and prevents contraction induced rupture
DYSTROPHIN
binds actin to beta dystroglycan in the sarcolemma
Binds actin to Z lines
Actinin, CapZ protein
Binds Z lines to sarcolemma
Desmin
Acts as molecular rulers that sets the LENGHT of ACTIN
Nebulin
PARTIAL hydrolysis of ATP
RECOCKING of myosin heads
COMPLETE hydrolysis of ATP
POWER STROKE
Blocks REUPTAKE of choline into presynaptic terminal
Hemicholinium
INHIBITS acetylcholinesterase
Neostigmine
COMPETES with Ach for receptors on Motor End Plate
Curare
BLOCKS RELEASE of Ach from pre-synaptic terminals
Botulinum Toxin
LENGTH is CONSTANT while muscle contracts
force generated is not enough to move or lift an object
NO muscle shortening/lengthening
ISOMETRIC CONTRACTION
i.e. pushing against a wall
LOAD is CONSTANT while muscle contracts
ISOTONIC CONTRACTION
CONCENTRIC - (+) muscle SHORTENING
(i.e. pulling a weight up)
ECCENTRIC - (+) muscle LENGTHENING
(i.e lowering a weight down)
Muscle length
PRELOAD
Load against which muscle contracts
AFTERLOAD
Tension d.t. muscle STRENGHT
Passive tension
Tension d.t. muscle CONTRACTION
Active tension
proportional to the number of cross bridges formed
Occurs 3-6 hrs after death d.t. lack of ATP
Rigor Mortis
Happens when ALL CALCIUM from SR has been RELEASED; no further increased in muscle strength
Tetanus/Tetanic Spasm
Relies PURELY on INTRACELLULAR CALCIUM
Skeletal Muscles
