Muscle Anatomy
The Z-discs anchor this specific thin myofilament.
What is Actin?
This travels from the motor neuron down the sarcolemma, signalling a muscle to contract.
What is action potential?
This would happen to the muscle if the motor neuron was working properly.
What is contraction (or it would receive a signal/action potential)?
This type of muscle tissue is found in the intestines and blood vessels.
What is Smooth Muscle?
The characteristic of muscle tissue that allows it to shorten.
What is contractility?
This connective tissue sheath surrounds each individual muscle fiber.
What is the Endomysium?
This specific neurotransmitter is always released by the motor neuron at the NMJ.
What is Acetylcholine (ACh)?
Calcium ions bind to this protein, which then moves tropomyosin off the myosin-binding sites.
What is Troponin?
The muscle rectus femoris is one of the four muscles that make up this large group in the anterior thigh.
What are the Quadriceps?
This is the term for the ability of muscle tissue to return to its original shape after being stretched or contracted.
What is Elasticity?
This connective tissue sheath wraps around a fascicle.
What is the Perimysium?
The space between a motor neuron and skeletal muscle fiber.
What is a synaptic cleft?
When a sarcomere contracts, this dark band, where only myosin is present, shortens.
What is the H-zone?
This muscle, helps you close and squint your eyes.
What is the Orbicularis Oculi?
This is the smallest unit of contraction.
What is a sarcomere?
This structure is the largest of the following: Sarcomere, Myofibril, Muscle fiber, Fascicle.
What is the Fascicle?
These structures penetrate deep into the muscle fiber, carrying the action potential toward the Sarcoplasmic Reticulum.
What are T-tubules (or Transverse tubules)?
This segment of the sarcomere, containing only thin filaments and shortens during contraction.
What is the I-band?
This would happen if you experience lead poisoning.
What is lead toxicity? When the metal can mimic calcium and interfere with calcium ions triggering muscle contractions. This can result in muscle weakness and fatigue.
The two substances that must be present for a cross-bridge to form.
What are ATP and Calcium Ions?
The cell membrane of a muscle fiber is given this specific name.
What is the Sarcolemma?
This organelle releases the calcium ions that trigger muscle contraction.
What is the Sarcoplasmic Reticulum (SR)?
This myofilament(s) does not change in length during contraction.
Therefore...
This band, that represents the entire length of the thick filament and does not change length during contraction.
What are actin and myosin?
What is the A-band?
This is the interruption with SMA (a disease targeting the lower motor neurons). Mention what happens because of this interruption.
What is a loss of action potential arriving at the muscle?
The motor neuron cannot communicate the signal to contract. ACh is not released. Action potential does not reach the muscle fiber's myofibril. The sarcoplasmic reticulum does not release calcium ions. Calcium never binds to troponin. Tropomyosin remains blocking the myosin-binding sites on the actin, so actin can never be pulled by the myosin towards the center of the sarcomere.
This is the very first step in muscle contraction.
What is the delivery of an action potential at the neuromuscular junction?