cardiac muscle
Definition
Cardiac muscle is a type of muscle tissue that is found only in the heart. It is responsible for the contraction and relaxation of the heart, which allows it to pump blood throughout the body.
Cardiac muscle is striated, which means that it has a striped appearance. This is due to the presence of myofibrils, which are bundles of protein fibres that are arranged in a regular pattern.
Cardiac muscle is involuntary, which means that it cannot be controlled by the conscious mind. It is controlled by the autonomic nervous system, which is a part of the nervous system that regulates involuntary bodily functions.
The cardiac muscle is also known as the heart muscle.
Here are some of the unique properties of cardiac muscle:
- Audtorhythmicity: Cardiac muscle cells have the ability to generate their own electrical impulses, which causes them to contract. This is why the heart can continue to beat even when it is removed from the body.
- Refractory period: After a cardiac muscle cell contracts, it goes through a refractory period, during which it cannot be stimulated to contract again. This prevents the heart from over-contracting and causing damage.
- Syncytium: Cardiac muscle cells are interconnected by gap junctions, which allow electrical impulses to pass from cell to cell. This ensures that the heart contracts as a single unit.
How can the word be used?
Cardiac muscle contracts rhythmically to pump blood throughout the body.
Different forms of the word
Noun: Cardiac muscle.
Adjective: Cardiac.
Verb: To cardiac.
Adverb: Cardiacally.
Plural: Cardiac muscles.
Etymology
The word cardiac muscle comes from the combination of two Greek words: kardia, meaning "heart" and mys, meaning "muscle". This is because cardiac muscle is the type of muscle that makes up the heart.
Question
What does the cardiac muscle do and where can it be found?
AQA Science Exam Question and Answer
Question:
Explain why cardiac muscle is both striated and involuntary.
Answer:
Cardiac muscle is striated because it contains myofibrils, which are bundles of contractile proteins. These proteins are arranged in a repeating pattern that gives the muscle its striated appearance. Cardiac muscle is also involuntary because it is controlled by the autonomic nervous system. This means that we cannot consciously control the contractions of cardiac muscle.
The myofibrils in cardiac muscle contain two types of contractile proteins: actin and myosin. Actin is a thin protein that forms long, thin filaments. Myosin is a thick protein that forms shorter, thicker filaments. When these two proteins interact, they form cross-bridges that cause the muscle to contract.
The autonomic nervous system controls the contractions of cardiac muscle by sending signals to the pacemaker cells in the heart. The pacemaker cells are specialised cells that generate electrical impulses that cause the heart to contract. The frequency of these impulses is determined by the autonomic nervous system.
In summary, cardiac muscle is both striated and involuntary because it contains myofibrils that are made up of actin and myosin proteins, and it is controlled by the autonomic nervous system.