March 3rd Lecture

Upcoming Events

Practice Lab

• Practical Date: Today

• Time: Starting around 3:00 PM

• Location: Room 422

• Duration: 45 minutes to 1 hour depending on the number of stations, with each station having a 90-second evaluation period plus or minus 3 minutes.

Lab Practical

• Date: Wednesday

• Time: Starts at the beginning of your lab session

• Duration: Varies, typically aligned with lab time.

Lecture Exam

• Date: Monday

• Format: Consists of 40 multiple choice questions, two diagrams to interpret or illustrate, and two essays/short answer questions.

• Duration: 1 hour and 30 minutes

• Items to Bring: 886E scantron for the exam, and dissection kits for the upcoming cat dissection in the lab.

Joints Overview

Definition:

• Joints are defined as regions where two or more bones articulate, allowing for varied types of movement and coordinating actions throughout the body.

Types of Joints

1. Fibrous Joints:

   • Characteristics: These joints are immovable and are connected by dense connective tissues. Examples include sutures in the skull.

   • Function: Provide stability and support without allowing movement.

2. Cartilaginous Joints:

   • Characteristics: These joints allow for limited movement and are primarily connected by cartilage.

   • Example: The intervertebral discs of the spine.

   • Function: Provide cushioning and slight flexibility to support spine and organ structures.

3. Synovial Joints:

   • Characteristics: The most common type of joint, allowing for significant movement. Synovial joints have a fluid-filled capsule that aids in motion.

   • Examples: Shoulder and knee joints.

   • Function: Enable a wide range of movements including gliding, rotation, and bending.

Components of Synovial Joints

• Articular Cartilage:

  • Composed of hyaline cartilage, it covers the ends of the bones in the joint.

  • Functions to reduce friction during movement and prevent arthritis by providing a smooth gliding surface.

• Joint Capsule:

  • Fibrous Membrane: Surrounds the joint and is made up of dense fibrous connective tissue for protection and structure.

  • Synovial Membrane: This inner layer produces synovial fluid, which lubricates the joint and is derived from areolar connective tissue.

• Synovial Fluid:

  • Functions:

    • Lubrication: Reduces friction between the articular cartilage during movement.

    • Nourishment: Supplies essential nutrients to the avascular articular cartilage.

    • Cushioning: Absorbs shock and distributes mechanical load during activities.

• Reinforcing Structures:

  • Ligaments: Stabilize joints, composed of dense regular connective tissue that connects bone to bone.

  • Tendons: Attach muscle to bone and assist in stabilizing the joint during movement.

  • Menisci: Fibrocartilage pads that deepen the socket of synovial joints to provide stability and guide joint movement.

  • Bursae: Fluid-filled sacs that cushion and reduce friction between different tissues such as tendons or muscles and bones.

Common Joint Injuries

• Sprains: Result from torn ligaments, leading to instability in the affected joint.

• Strains: Involve stretched ligaments or tendons without actual tearing.

• Torn Achilles Tendon: A common injury particularly among physically active men over the age of 40, requiring surgical intervention.

Arthritis Types

1. Osteoarthritis:

   • Common in seniors; signifies degeneration of articular cartilage leading to pain, stiffness, and bone spurs.

   • Risk factors include age, obesity, and genetic predisposition.

2. Rheumatoid Arthritis:

   • An autoimmune disorder where the body’s immune system mistakenly attacks the synovial lining of joints, causing inflammation, swelling, and pain.

   • It can affect individuals of any age and has fluctuating symptoms.

3. Gouty Arthritis:

   • Occurs due to the deposition of uric acid crystals in the joints, often linked to dietary choices and genetics, leading to sudden, severe pain, redness, and swelling.

Muscular System Introduction

• Focus on Skeletal Muscles, which are primarily responsible for moving bones and facilitating bodily movement. Skeletal muscles are attached to bones via tendons.

Muscle Terminology

• Origin: The attachment point of the muscle that does not move during contraction, typically located proximally.

• Insertion: The muscle attachment point that moves toward the origin during contraction, usually distal.

• Agonists: The primary mover muscle responsible for generating a specific movement.

• Synergists: Muscles that assist agonists in performing a movement, providing additional force or stability.

• Antagonists: Muscles that oppose the action of the agonist, controlling movement.

Muscle Fiber Structure

• Muscle Fiber: Long multinucleated cells which are the basic units of muscle contraction.

• Components:

  • Sarcolemma: The plasma membrane of the muscle fiber that helps maintain the internal environment.

  • T-Tubules: Structures that allow action potentials to propagate deep into the muscle fiber, ensuring uniform contraction.

  • Sarcoplasmic Reticulum: A specialized form of endoplasmic reticulum that stores calcium ions, crucial for muscle contraction.

  • Myofibrils: Long, thread-like components made of actin and myosin filaments, responsible for muscle contraction.

Contraction Mechanism

1. Action Potential:

   • Initiated by a motor neuron, the signal travels along the sarcolemma and into the T-tubules, triggering the contraction process.

2. Calcium Release:

   • Upon stimulation, calcium is released from the sarcoplasmic reticulum, crucial for contraction.

3. Interaction of Actin and Myosin:

   • Myosin heads bind to actin filaments, pulling them inward, and leading to the contraction of the sarcomere.

Muscular Dystrophy

• A genetic disorder that affects the production of dystrophin, a protein essential for muscle fiber stability. Lack of dystrophin leads to unstable actin filaments, causing degeneration and weakness in muscle tissue. Symptoms typically appear in childhood and worsen over time.

Study Tip

• Utilize positive reinforcement in studying: Engaging with affirmations about enjoying the subject can enhance both engagement and performance in course-related tasks. Connecting emotionally with the material may improve retention and comprehension.