Skeletal Muscle Cells Flashcards
Sarcolemma
Cell membrane of a muscle fiber cell.
Myofibrils
Long organelles that nearly fill the cytoplasm of a muscle cell.
Sarcomeres
Chains of tiny contractile units that make up Myofibrils.
Myofilaments
Produce the light (I) and dark (A) bending pattern.
Thick/Myosin Filaments
Split ATP to generate muscle contraction.
Myosin Heads
Part of thick filaments, they link the thick and thin filaments together during contraction.
Thin/Actin filaments
Composed of the contractile protein actin and are anchored to the Z line.
Sarcoplasmic reticulum
Stores calcium and releases it when the muscle fibre is stimulated to contract.
Muscle Cell Irritability
The ability to receive and respond to stimulus.
Muscle Cell Contractility
The ability to shorten when adequate stimulus is received.
True or false:
Skeletal muscle cells must be stimulated by nerve impulses to contract
True
Motor unit
One neutron and all the skeletal muscle cells that it stimulates.
Nerve fibre/Axon
Long extension of a Neuron.
Axonal terminals
Firms connections with the Sarcolemma of a different muscle cell. (Neuromuscular Junctions.)
Synaptic cleft
The gap between the nerve endings and muscle cell membranes. Filled with interstitial fluid.
Acetylcholine
The neurotransmitter that stimulates skeletal muscle cells.
Action potential
Acetylcholine is released, the Sarcolemma allows entry of sodium ions. This gives the cell a sudden rush of positive ions causing a change to the electrical conditions - resulting in muscle contraction.
The sliding filament theory
What causes filaments to slide?
Energized by ATP, Cross bridges attach to myosin binding sites on the thin filaments and sliding begins.
True or false:
A skeletal cell is multinucleated
True
What are 2 ways graded muscle contractions are produced?
- By changing the speed of muscle stimulation.
2. By changing the amount of muscle cells being stimulated.
Tetanic contraction
Muscle contractions are completely smooth and sustained.
What are the 3 pathways for ATP regeneration?
- Creatine phosphate
- Aerobic respiration
- Anaerobic glycolysis and lactic acid formation
Creatine phosphate
High energy molecule found in muscle fibres, regenerates ATP.
Aerobic respiration
ATP is regenerated by metabolic pathways that use oxygen. Produces CO2 and H2O.
Anaerobic glycolysis and lactic acid formation
Anaerobic = Without oxygen.
Glycolysis glucose is broken down to pyruvic acid, small amounts of energy are captured in ATP bonds.
When muscle activity is too intense or there is not enough oxygen/glucose, pyruvic acid is converted to lactic acid.
How many days does it take for a horse to recover from muscle fatigue?
3
Muscle fatigue
A muscle us unable to contract even though it is still being stimulated.
What are the types of muscle contractions?
Isotonic
Isometric
Isotonic
The muscle shortens and movement occurs. Ex. Bending the knee and smiling.
Isometric
No movement, muscle does not shorten.
Every skeletal muscle is attached to at least 2 points, what are they?
Origin
Insertion
Origin
Attached to the immovable bone (like the anchor).
Insertion
Attached to the moveable bone, when muscle contracts the insertion moves toward the origin.
Prime mover muscle
The muscle that has the most responsibility when several muscles are contracting.
Antagonist muscle
Muscles that oppose or reverse movement.
Synergist muscle
Help prime movers by producing same movement or reducing unnecessary movement.
Fixator muscles
Hold bone still or stabilize the origin of a prime mover.
