Lecture Notes on the Musculoskeletal System

Overview

• The musculoskeletal system is more accurately described as the neuromusculoskeletal system.
  • Movement arises from muscles pulling on bones, initiated by nerve signals.
  • Nerve stimulation leads to muscle contraction, causing bone movement.

Neuron Structure and Function

• Key parts of a neuron:
  • Dendrites: Receive signals.
  • Cell Body (Soma): Integrates signals.
  • Axon: Transmits signals with swollen ends containing neurotransmitters.
• Neurotransmitter: Acetylcholine (ACH) binds to receptors on muscles causing contraction.

Neuromuscular Junction

• Site where nerve meets muscle.
• Nerve stimulates muscle, muscle pulls bone.
• In paralysis, nerve signals are disrupted, leading to muscle atrophy.

Bone Function and Structure

• Bone Composition: Bones are living tissues comprised of cells, not just minerals.
• Bone Cells:
  • Osteoblasts: Build bone by depositing calcium from the blood.
  • Osteoclasts: Break down bone to release calcium into the blood.
• Calcium and Phosphate Homeostasis:
  • Hypercalcemia: Excess calcium; osteoblasts build bone.
  • Hypocalcemia: Low calcium; osteoclasts break down bone.

Bone Protection and Supports

• Bones protect vital organs: cranium (brain), rib cage (heart and lungs), pelvic girdle (bladder).
• Bone Marrow:
  • Red Marrow: Produces red blood cells.
  • Yellow Marrow: Stores fat for energy (ATP production).

Vitamin D and Bone Health

• Vitamin D is essential for calcium absorption.
• Lack of sunlight leads to low vitamin D levels.

Hormones and Bone Mass

• Estrogen and Testosterone:
  • Men: Testosterone maintains muscle and bone mass.
  • Women: Estrogen maintains bone mass; menopause leads to a drop in bone density.

Muscle Types and Actions

• Agonist muscles contract while antagonist muscles relax to facilitate movement.
• Important muscles for practical exams:
  • Deltoid: Shoulder
  • Pectoralis: Chest
  • Orbicularis oris: Around lips
  • Orbicularis oculi: Around eyes
  • Rectus femoris: Thigh
  • Biceps brachii: Upper arm
  • Triceps brachii: Upper arm (back)
  • Trapezius: Upper back
  • Intercostal muscles: Located between ribs, assist in breathing.

Practical Exam Preparation

• Know the location and function of key muscles and bones.
• Understand the roles of neurons, muscles, and bones in generating movement.

This lecture provides a comprehensive overview of the neuromusculoskeletal system, emphasizing the interconnectedness of the nervous, muscular, and skeletal systems in facilitating movement and maintaining homeostasis.