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Questions and Answers
What is the primary role of cardiomyocytes in the heart?
What is the primary role of cardiomyocytes in the heart?
- To generate enough contractile force for the heart to beat effectively (correct)
- To assist in nutrient absorption
- To store energy for contraction
- To provide structural support to the heart
Which feature distinguishes smooth muscle cells from cardiac and skeletal muscle cells?
Which feature distinguishes smooth muscle cells from cardiac and skeletal muscle cells?
- Spindle shape and a single central nucleus (correct)
- Alignment of myofibrils
- High number of T-tubules
- Presence of striations
Where are smooth muscle cells primarily found?
Where are smooth muscle cells primarily found?
- In cardiac tissue only
- Only in skeletal muscle tissues
- In the brain and spinal cord
- In the walls of blood vessels and hollow organs (correct)
What facilitates the depolarization of smooth muscle cells?
What facilitates the depolarization of smooth muscle cells?
What is one of the functions of smooth muscle in the digestive system?
What is one of the functions of smooth muscle in the digestive system?
What is the primary function of muscle cells?
What is the primary function of muscle cells?
Which type of muscle cell is responsible for voluntary movements?
Which type of muscle cell is responsible for voluntary movements?
What is the role of myoglobin in muscle cells?
What is the role of myoglobin in muscle cells?
What are the three types of myofilaments found in muscle cells?
What are the three types of myofilaments found in muscle cells?
The basic unit of striated muscle is known as what?
The basic unit of striated muscle is known as what?
Which protein forms the thick myofilaments?
Which protein forms the thick myofilaments?
What is the cytoplasm of a muscle cell called?
What is the cytoplasm of a muscle cell called?
Which type of muscle cell is involuntary and found in the heart?
Which type of muscle cell is involuntary and found in the heart?
What role do the muscles of the body wall serve?
What role do the muscles of the body wall serve?
What is the primary function of shivering?
What is the primary function of shivering?
What type of muscle cell is predominantly involved in voluntary movements?
What type of muscle cell is predominantly involved in voluntary movements?
What characterizes cardiac muscle cells?
What characterizes cardiac muscle cells?
Which of the following is NOT a characteristic of skeletal muscle cells?
Which of the following is NOT a characteristic of skeletal muscle cells?
What is the main function of smooth muscle tissue?
What is the main function of smooth muscle tissue?
How do skeletal muscle cells differ from cardiac muscle cells regarding their structure?
How do skeletal muscle cells differ from cardiac muscle cells regarding their structure?
What is a unique feature of cardiomyocytes?
What is a unique feature of cardiomyocytes?
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Study Notes
Muscle Cell Structure
- Muscle cells are also known as myocytes, which are the basic unit of all muscular tissues
- The cell membrane of a muscle cell is called the sarcolemma
- The cytoplasm of a muscle cell is called the sarcoplasm
- Sarcoplasm contains myoglobin, an oxygen storage site, and glycogen in the form of granules
- Myofibrils are tubular protein structures that are composed of myofilaments
- There are three types of myofilaments: thick, thin, and elastic
- Thick myofilaments are comprised of myosin
- Thin myofilaments are comprised of actin
- Elastic myofilaments are comprised of titin
- The basic unit of striated (striped) muscle is a sarcomere
- Sarcomeres contain both actin (light bands) and myosin (dark bands) filaments
Muscle Cell Functions
- Skeletal muscles pull on bones, causing movement at the joints
- Examples include: facial expressions, breathing, and support of internal organs
- Muscles of the body wall support internal organs
- Muscle cells are involved in heat generation and maintenance of a stable internal body temperature
- Shivering is a mechanism of the muscular system that generates heat to warm an overly cooled body
- Cardiac muscles aid in heart pumping action, helping blood circulation
Types of Muscle Cells
Skeletal Muscle Cells
- Skeletal muscle cells are long, cylindrical, and striated
- They are multinucleated and contain more than one nucleus
- Skeletal muscle cells have high energy requirements and contain many mitochondria
- Skeletal muscle cells are attached to bones by tendons
- Skeletal muscles can be as long as 30 cm, although they are usually 2 to 3 cm in length
Cardiac Muscle Cells
- Cardiomyocytes are short and narrow, and rectangular in shape
- Each cardiomyocyte contains one nucleus
- Cardiomyocytes are connected by intercalated discs that contain gap junctions for diffusion and cell communication
- These discs appear as dark bands between cells and are a unique feature of cardiomyocytes
Smooth Muscle Cells
- Smooth muscle cells are spindle-shaped and contain a single central nucleus
- They are the smallest type of muscle cell, ranging from 10 to 600 μm in length
- Smooth muscle cells are elastic and important in the expansion of organs such as the kidneys, lungs, and vagina
- Smooth muscle cells are arranged in sheets and contract simultaneously
- Smooth muscle cells contain poorly developed sarcoplasmic reticulums and do not contain T-tubules
- Smooth muscle cells are responsible for involuntary contractions
- They are found in the walls of blood vessels and hollow organs such as the gastrointestinal tract, uterus, and bladder
- They are also present in the eye and are responsible for changing the shape of the lens causing the eye to focus
- Smooth muscle is also responsible for waves of contraction throughout the digestive system (peristalsis)
- Smooth muscle cells contract as a result of depolarization of the sarcolemma which is facilitated by gap junctions
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