A&P EXAM 2

Chapter 8: Joints

General Overview

  • Definition of Joints (Arthro/Arthr): Point where two bones meet.

  • Movement: Joints may allow movement or may be immovable.

  • Function of Joints:

    • Mobility: Varies by joint type, shape, and allows movement in different ways.

    • Stability: Holds skeleton together and protects internal structures, particularly in the axial skeleton where sutures in the skull prevent brain damage.

General Classifications of Joints

Structural Classification

  • Fibrous Joints: No joint cavity; bones connected by collagen fibers.

    • Types:

      • Sutures: Short fibers in skull bones allow minimal movement; can ossify with age.

      • Syndesmosis: Ligament connection; movement depends on length of ligaments.

      • Gomphoses: Connects teeth to the mandible/maxilla via periodontal ligaments.

  • Cartilaginous Joints: No joint cavity; bones joined by cartilage.

    • Types:

      • Synchondroses: Bones united by hyaline cartilage; mostly immovable (e.g. epiphyseal plate).

      • Symphyses: Bones joined by fibrocartilage; allow limited movement (e.g. intervertebral discs).

  • Synovial Joints: Contains a joint cavity, allows free movement.

    • Characteristics:

      1. Articular cartilage: Hyaline cartilage covering ends.

      2. Joint cavity: Small fluid-filled space.

      3. Articular capsule: Fibrous outer layer and synovial membrane inside, producing synovial fluid.

      4. Synovial fluid: Lubricates joints.

      5. Reinforcing ligaments: Connect articulating bones and stabilize the joint.

      6. Innervation and vascularization: Involves sensory nerves and blood supply.

Movement Types by Synovial Joints

  • Nonaxial Movement: No movement around axes; flat surfaces glide over one another.

  • Uniaxial Movement: Movement around one axis; examples include flexion and extension at elbow.

  • Biaxial Movement: Movement around two axes; includes adduction and abduction of fingers.

  • Multiaxial Movement: Movement around multiple axes; joint shape such as ball-and-socket (e.g., shoulder and hip).

Joint Stability Factors

  1. Articular surfaces: How well the bones fit together.

  2. Ligaments: More ligaments enhance strength.

  3. Muscle tone: Tendons connecting muscles to bones help stabilize joints.

Types of Arthritis

  • Osteoarthritis (OA): Common in older adults; cartilage destruction leads to bone rubbing together.

  • Rheumatoid Arthritis (RA): Autoimmune disorder; affects joints on both sides of the body, leading to swelling and pain.

Chapter 11: Nervous System and Nervous Tissue Fundamentals

Functions of the Nervous System

  1. Sensory Input: Monitors changes in internal and external environments via sensory receptors.

  2. Integration: Processing input and deciding on responses, primarily by the CNS.

  3. Motor Output: Efferent responses that activate muscles or glands.

Components of the Nervous System

  • Central Nervous System (CNS): Brain and spinal cord; interprets sensory input and controls motor responses.

  • Peripheral Nervous System (PNS): Nerves extending from CNS to the body; conveys sensory input and motor output.

Types of Neuroglia

  1. Astrocytes: Maintain blood-brain barrier, provide nutrients, and clean up.

  2. Microglial Cells: Monitor neuron health and act in immune response.

  3. Ependymal Cells: Line cavities and circulate cerebrospinal fluid (CSF).

  4. Satellite Cells: Support neurons in PNS.

  5. Oligodendrocytes and Schwann Cells: Myelinate axons in CNS and PNS, respectively.

Neuron Anatomy

  • Cell Body: Contains nucleus and receives signals.

  • Dendrites: Main receptive surfaces for signals.

  • Axon: Conducts impulses away from the body; myelin increases conduction speed.

Membrane Potentials

  • Resting Membrane Potential: Approximately -70mV; caused by ion distribution across the membrane.

  • Graded Potentials: Changes in membrane potential that vary with stimulus strength (depolarizing or hyperpolarizing).

  • Action Potentials: Consistent strength signals sent along axons; generated when threshold is reached, allowing Na+ influx, followed by K+ influx for repolarization.

Transmission of Action Potentials

  • Chemical Synapses: Neurotransmitter release facilitates communication between neurons.

Postsynaptic Potentials

  • EPSP & IPSP: Excitatory and inhibitory postsynaptic potentials that influence the likelihood of generating an action potential (AP).

Neurotransmitters

  • Functions: Facilitate communication between neurons; can be excitatory or inhibitory based on receptor types.