Skeletal Muscle Tissue and Related Structures

Skeletal Muscle Tissue

Skeletal muscle tissue is a type of muscle tissue that is attached to bones and is responsible for voluntary movements of the body. It is characterized by its striated appearance and multinucleated cells.

• Definition: Skeletal muscle tissue consists of long, cylindrical fibers that contract to produce movement.

• Histological Features: Striations (alternating light and dark bands), multiple peripheral nuclei, and organized sarcomeres.

• Function: Enables voluntary movement, maintains posture, and produces heat.

• Example: Muscles of the limbs, such as the biceps brachii and quadriceps femoris.

Major Muscle Groups

Neck and Facial Muscles

These muscles are involved in movements of the head, neck, and facial expressions.

• Neck Muscles: Include the sternocleidomastoid (rotates and flexes the neck) and trapezius (moves the scapula and supports the arm).

• Facial Muscles: Include the orbicularis oculi (closes the eyelids), zygomaticus major (smiling), and orbicularis oris (puckers the lips).

Arm Muscles (Upper and Lower)

Arm muscles are divided into those of the upper arm (shoulder to elbow) and lower arm (elbow to wrist).

• Upper Arm: Biceps brachii (flexes the elbow), triceps brachii (extends the elbow), deltoid (abducts the arm).

• Lower Arm: Flexor carpi radialis (flexes the wrist), extensor digitorum (extends the fingers).

Abdominal Muscles

These muscles form the anterior and lateral walls of the abdomen and are important for trunk movement and stability.

• Rectus abdominis: Flexes the vertebral column and compresses abdominal contents.

• External and internal obliques: Rotate and laterally flex the trunk.

• Transversus abdominis: Compresses abdominal contents.

Buttocks Muscles

The gluteal muscles are responsible for movement of the hip and thigh.

• Gluteus maximus: Extends and laterally rotates the hip.

• Gluteus medius and minimus: Abduct and medially rotate the thigh.

Calf Muscles

Calf muscles are located at the back of the lower leg and are essential for walking, running, and jumping.

• Gastrocnemius: Plantar flexes the foot and flexes the knee.

• Soleus: Plantar flexes the foot.

Nervous System Structures

Parts of the Neuron

Neurons are the basic functional units of the nervous system, specialized for transmitting electrical signals.

• Cell body (soma): Contains the nucleus and organelles.

• Dendrites: Receive incoming signals from other neurons.

• Axon: Transmits electrical impulses away from the cell body.

• Axon terminals: Release neurotransmitters to communicate with other cells.

Parts of the Central and Peripheral Nervous System

The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).

• Central Nervous System (CNS): Consists of the brain and spinal cord; responsible for processing and integrating information.

• Peripheral Nervous System (PNS): Includes all neural tissue outside the CNS; connects the CNS to limbs and organs.

• Subdivisions of PNS: Somatic nervous system (controls voluntary movements) and autonomic nervous system (controls involuntary functions).

Parts of the Brain

The brain is the control center of the nervous system, responsible for processing sensory information, regulating bodily functions, and enabling cognition.

• Cerebrum: Responsible for higher brain functions such as thought, memory, and voluntary movement.

• Cerebellum: Coordinates movement and balance.

• Brainstem: Controls basic life functions such as breathing, heart rate, and blood pressure.

• Diencephalon: Includes the thalamus and hypothalamus, which regulate sensory and autonomic functions.