Muscle Cell Structure and Functions

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Questions and Answers

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?

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?

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?

Gap junctions Signup and view all the answers

What is one of the functions of smooth muscle in the digestive system?

To create waves of contraction for peristalsis Signup and view all the answers

What is the primary function of muscle cells?

Contraction of tissues Signup and view all the answers

Which type of muscle cell is responsible for voluntary movements?

Skeletal muscle cells Signup and view all the answers

What is the role of myoglobin in muscle cells?

To store oxygen Signup and view all the answers

What are the three types of myofilaments found in muscle cells?

Thick, thin, and elastic Signup and view all the answers

The basic unit of striated muscle is known as what?

Sarcomere Signup and view all the answers

Which protein forms the thick myofilaments?

Myosin Signup and view all the answers

What is the cytoplasm of a muscle cell called?

Sarcoplasm Signup and view all the answers

Which type of muscle cell is involuntary and found in the heart?

Cardiac muscle cells Signup and view all the answers

What role do the muscles of the body wall serve?

They support the internal organs. Signup and view all the answers

What is the primary function of shivering?

To generate heat to warm the body. Signup and view all the answers

What type of muscle cell is predominantly involved in voluntary movements?

Skeletal muscle cells Signup and view all the answers

What characterizes cardiac muscle cells?

They have intercalated discs for communication. Signup and view all the answers

Which of the following is NOT a characteristic of skeletal muscle cells?

They have a single nucleus. Signup and view all the answers

What is the main function of smooth muscle tissue?

Involuntary movements in internal organs Signup and view all the answers

How do skeletal muscle cells differ from cardiac muscle cells regarding their structure?

Skeletal cells are striated and cylindrical. Signup and view all the answers

What is a unique feature of cardiomyocytes?

Presence of intercalated discs Signup and view all the answers

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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Description

Explore the intricate structure and essential functions of muscle cells, known as myocytes. This quiz covers components such as sarcolemma, sarcoplasm, myofibrils, and the role of different myofilaments. Test your knowledge on how skeletal muscles facilitate movement and support various bodily functions.