Proposed model for the inactivation of some voltage-gated ion channels. According to this model, after channel opening, the pore of the open channel is plugged by a globular cytoplasmic portion of the channel protein. The globular portion (ball of amino acids) is tethered to the rest of the protein by a linker part (chain of amino acids).

Channel inactivation

Neuronal Action Potential - Important Features of the Neuronal Action Potential

Endocrine cells are responsible for producing and releasing hormone molecules into the bloodstream. Endocrine cells are typically grouped together in organs referred to as endocrine glands.

Endocrine gland
Hormone

The Z disk (or Z line) defines the boundaries of a muscle sarcomere. Two adjacent Z disks along the myofibril mark the boundaries of a single sarcomere. The Z disks are the attachment sites for the thin filaments. Therefore, from each Z disk, thin filaments extend to two neighboring sarcomeres. When a muscle fiber contracts, the Z disks of a sarcomere move closer together (i.e., the sarcomere also shortens).

A band
H zone
I band
M line