In: Anatomy and Physiology
The sarcoplasmic reticulum falls under which hierarchical level?
Organ
Cellular
Tissue
Chemical
The correct answer is (B) cellular.
Explanation: The sarcoplasmic reticulum (SR) is a membrane-delimited intracellular organelle that spans the sarcomere and wraps up the contractile myofilaments in striated muscle of almost all species.
The main function of the SR is to store Ca+ ions.
Since it is an intracellular organelle, it comes at the cellular level.
Cellular level: Cell and its organelles.
A cell is the smallest independently functioning unit of a living organism. A human cell typically consists of flexible membranes that enclose cytoplasm, a water-based cellular fluid together with a variety of tiny functioning units called organelles.
Option (A) Organ is incorrect as an organ is an anatomically distinct structure of the body composed of two or more tissue types. Each organ performs one or more specific physiological functions. eg: Liver, Stomach
Option (C) Tissue is incorrect as tissue is a group of many similar cells (though sometimes composed of a few related types) that work together to perform a specific function eg: smooth muscle tissue.
Option (D) Chemical is incorrect as the chemical level of the organization consists of subatomic particles, atoms, and molecules. Molecules are the chemical building blocks of the body such as the water molecules, proteins, and sugars.