MUSCLE PHYSIOLOGY Flashcards
- Myosin only
- Light in color
- Thick filament
H zone
- Actin only
- Dark in color
- Thin filaments only on myofibril
I band
- Holds the thick filaments together
- Myosin linked with accessory proteins
M line
Anchors thin filaments and ties all myofibrils together (regular banding)
Z line (disc)
- Actin and myosin overlap
- Has both thick and thin filaments (dark bands) on myofibril
A band
- The invagination of sacrolemma that forms a permeability barrier between cytosol and extracellular space
- Extension of sarcolemma within the sarcoplasm
T tubules
Smallest functional contractile unit of muscle
Sarcomeres
- Striated muscle organelles comprised of sarcomeres that are aligned in series
- Creates contraction
Myofibrils
A protein that converts chemical energy in the form of ATP to mechanical energy, thus generating force and movement.
Myosin molecule
What makes a filament thick?
Myosin
Thin myofilaments
Actin, Troponin, and Tropomyosin
Troponin that binds calcium
Troponin - C
Inhibits the ATPase activity of the actomyosin cross-bridge and effectively blocks the myosin-binding site on actin subunits
Troponin I
Rod shape molecule, two strands of tropomyosin molecules run diametrically opposed along actin filaments
Tropomyosin
Interacts with tropomyosin and anchors troponin to actin
Troponin - T
Stabilize the sarcolemma and, hence, prevent contraction-induced injury (rupture)
DGC - Dystrophin Glycoprotein Complex
Connects actin to the glycoproteins of the extracellular domain of the sarcolemma
Dystrophin
Stabilizes myosin
Titin
- Helps in the alignment of actin
- Encloses actin
Nebulin
Anchors Z disk to sarcolemma
Desmin
- Myofilament with binding sites for myosin head (contains G-Actin)
- Anchored by Z-Discs
- Regulatory proteins of troponin & tropomyosin
- Troponin holds thin filament in place, and tropomyosin blocks active binding sites on actin
Actin (thin filaments)
Activation of the force-generating sites within muscle fibers—the cross-bridges
Muscle contraction
Motor neuron and
the skeletal muscle fibers it innervates
Motor unit
Comprise various tightly controlled, complex circuits throughout the body that allow for both voluntary and involuntary movements through the innervation of effector muscles and glands
Motor neurons
- Where nerves and muscle fibers meet—is an essential synapse for muscle contraction and movement
- Point of contact between a motor neuron and a skeletal muscle cell
Neuromuscular Junction
Conversion of electrical signal to chemical signal cycle
Somatic Nervous System
Temporary depolarization of postsynaptic membrane caused by the flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels
Excitatory Postsynaptic Potentials (EPSP)
- Where nicotinic receptors are found
- The end of a motor neuron that stores acetylcholine
Motor End-Plate
RMP: -90 mV
Duration: 2.5 ms
Muscle action potential
RMP: -70 mV
Duration: 1-2 ms
Nerve action potential
- Occurs when myosin head does not dissociate from actin
- Stiffness of the body that sets in several hours after death
Rigor mortis
Where does the cycle stop when ATP is exhausted?
State C
The consequence of severely lowered calcium levels
Hypocalcemic tetany
Space between a nerve (axon) terminal and motor end-plate (gap between cells) – ACh diffuses across
Synaptic Cleft
Neurotransmitter that binds at a motor end plate to trigger depolarization
Acetylcholine (ACh)
A source of ATP that uses stored ATP in seconds and can generate it for about 15 seconds
Creatinine Phosphate
- A source of ATP that is used for lower demand of ATP delivery with O2 used
- 2 ATP from glycolysis + pyruvate sent to mitochondria makes = 36 ATP
- Hours of sustained activity
Cellular respiration
A sustained muscular contraction resulting from a rapid series of nerve impulses when cholinesterase doesn’t break down ACh caused by bacteria found in dirt and manure
Tetanus
- Temporary lack of O2 in the muscle due to exertion
- Lack of O2 caused by Lactic Acid to build up in muscle tissue leads to muscle soreness
Oxygen debt
Sustained involuntary contraction of a muscle
Muscle cramp
Inability of muscle to maintain its strength of contraction or tension; may be related to insufficient O2, depletion of glycogen, and/or lactic acid buildup
Muscle fatigue
A neuron’s reaction of either firing (with a full-strength response) or not firing.
All-or-none response
The minimal strength required to cause a contraction
Threshold stimulus
Tiny pouches or sacs in the axons that contain chemicals called neurotransmitters.
Synaptic vesicles
Organelle of the muscle fiber that stores calcium
Sarcoplasmic reticulum
Cytoplasm of a muscle cell
Sarcoplasm
Enzyme that degrades Ach immediately after depolarization (neuron stops sending a signal for contraction) for precise contraction control
Cholinesterase (ACh-ase)
Mainly areolar connective tissue around each fiber
Endomysium
- Dense irregular connective tissue surrounding fascicles
- Grain of muscle and allows precise movement
Perimysium
A band or sheet of fibrous connective tissue that covers, supports, and separates muscle
Fascia
Bundle of muscle fibers
Fasicle
Outermost layer of dense irregular connective tissue that separates muscle from organs and allows independent movement
Epimysium
- Specialized muscle tissue found only in the heart
- Striated and involuntary
- Intercalated discs
Cardiac muscle tissue
- Involuntary muscle tissue
- Not striated
- Found in intestines
Smooth muscle tissue
Striated and voluntary
Skeletal muscle tissue
- Theory that actin filaments are pulled closer by myosin, causing Z-Discs to also move closer
- I-Bands shrink and A-Bands stay the same
- At full contraction action and myosin overlap completely
Sliding Filament Theory
Myosin filament with heads that bind to actin by reaching up and ratcheting forward (about 300/filament)
Myosin (thick filaments)
Loss of muscle mass due to lack of use or aging
Atrophy
Increase in size of skeletal muscle through a growth in size of its component cells (increase in myofibrils & connective tissue)
Hypertrophy
Anchoring point that does not move with contraction
Origin
Muscle attachment site that moves toward the origin
Insertion