3-pronged line through middle of A-Band;Site of attachment for Myosin

"Dark zone" -contain thick (myosin) filaments. The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin.(do not change length)

protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber

Protein that makes up most of the thin myofilaments in a sarcomere fiber

Zig-zag line that Actin attaches to & delineate the lateral borders of sarcomeres and are the smallest functional units in striated muscle

"Light Zone"-A light band on each side of the Z line of striated muscle fibers, comprising a region of the sarcomere where thin (actin) filaments are not overlapped by thick (myosin) filaments.

The region of a striated muscle fiber that contains only thick (myosin) filaments. The H zone appears as a lighter band in the middle of the dark A band at the center of a sarcomere

Muscle fiber/cell depolarizes (+30mv inside cell)
Depolarization-Reducing the voltage difference between the inside and outside of a cell’s plasma membrane(the sarcolemma for a muscle fiber), making the inside less negative than the rest

Potassium ions leak out of muscle fiber through ion channels

Sodium channels open allowing Sodium ions to rush into the cell causing Action potential down the sarcolemma(Sodium ions- play essential roles in muscle contraction because of their importance in nerve function. ... Sodium and potassium help your nerve cells send electrical signals, called action potentials, that signal for your muscles to contract.)

Action Potential reaches T-tubules causing proteins to stimulate the ion channels in SR to open and allow Calcium ions to be released

ACh binds to nicotinic (nAChRs) (cholinergic) receptors (protein receptors) on sarcolemma

Neuron releases Acetylcholine into synaptic cleft via exocytosis

ATP is broken down into ADP and Pi by ATPase on the myosin causing the myosin to move into the correct angle to perform the power stroke

Calcium enters the synaptic bulb via voltage gated ion channels
(Calcium ions expose the site on actin, which interacts with myosin. Calcium ions and proteins bond to actin and play crucial role in both contraction and relaxation)

Action Potential moves down axon of neuron and reaches synaptic bulb-(AP-change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal, unique to neurons and muscle fibers)

Myosin is able to form cross-bridges at binding sites on actin

Myosin heads perform power stroke and move actin towards M line (middle) of sarcomere

ATP attaches to myosin heads at ATP binding sites, causing them to release

Myosin detaches from actin and muscle fibers and protein filaments relax

Calcium ions are pumped back into Sarcoplasmic Reticulum via active transport

AChE (Acetylcholinesterase) breaks down ACh into Acetate and Choline in the synapse which are then transported back into the neuron(AChE-enzyme whose primary function is to catalyze and promote the breakdown of a neurotransmitter called acetylcholine)

Sodium-Potassium Pump pumps Sodium ions out of muscle fiber and brings Potassium ions back in ( requires magnesium to function properly)

Striations-muscle tissue that is marked by transverse dark and light bands, is made up of elongated usually multinucleated fibers

Troponin and tropomyosin are two proteins which regulate sarcomere contraction via calcium binding.The key difference between troponin and tropomyosin is that troponin frees the myosin binding sites of actin filaments while tropomyosin blocks the binding sites.

Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K+) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization