involuntary muscle
Học thuậtThân thiện
Definition
Noun: * A muscle that contracts automatically, without conscious thought or intent. It is primarily located within the walls of internal organs (viscera) and structures like blood vessels to control essential bodily functions.
Usage
This term is used in biological, medical, and anatomical contexts to describe muscle tissue that functions automatically. It is often contrasted with "voluntary muscle" (skeletal muscle).
Examples
- The involuntary muscle in the walls of the intestines propels food through the digestive system.
- Smooth muscle is a type of involuntary muscle.
- Unlike the biceps, which you can control, the contraction of an involuntary muscle is not under your direct command.
Advanced Usage
- Physiological Control: The term emphasizes the role of the autonomic nervous system and hormones in controlling these muscles, as opposed to somatic (voluntary) nerve signals.
- Histological Context: In detailed anatomical study, "involuntary muscle" is synonymous with smooth muscle (found in organs and vessels) and cardiac muscle (found in the heart), though some definitions specifically exclude the heart.
Variants and Related Words
- Smooth Muscle (n): The most common type of involuntary muscle, characterized by non-striated, spindle-shaped cells.
- Visceral Muscle (n): Another term for smooth muscle, highlighting its location in the viscera (internal organs).
- Unstriped Muscle (n): A less common synonym for smooth muscle, referring to its lack of the striped (striated) appearance seen under a microscope.
Synonyms
- Unconscious muscle
- Automatic muscle
Antonyms
- Voluntary muscle
- Skeletal muscle
- Striated muscle
Noun
- a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)