Nervous System Quiz (BMS Learning Outcomes)

Nervous Tissue Characteristics and Cells

• Neurons: The nervous system's fundamental units. Each neuron has a cell body, one axon, and many dendrites. Bundles of axons are called nerves.
• Irritability: Neurons can generate nerve impulses in response to internal or external stimuli.
• Conductivity: Neurons transmit electrical impulses.
• Cell Body: Forms grey matter, located in the brain periphery and spinal cord center. Contains a nucleus and organelles, but lacks mitosis, so cannot be replaced (although regeneration is possible).
• Axon: Carries impulses away from the cell body, can be very long (over 1 meter). Larger axons in the peripheral nervous system are myelinated.
• Schwann Cells: Wrap around axons, creating the myelin sheath, primarily in the peripheral nervous system. Myelin is a fatty substance that electrically insulates the axon.
• Nodes of Ranvier: Gaps in the myelin sheath between Schwann cells. They facilitate fast impulse transmission.
• Dendrites: Extensions of the cell body with a large surface area for receiving signals. Similar structure to axons but shorter. Dense with ion channels for impulse transmission. Link to other dendrites or sensory receptors.
• Synaptic End Bulb: Site of communication between neurons or between a neuron and an effector (muscle or gland). Contains synaptic vesicles storing neurotransmitters (e.g., acetylcholine, noradrenaline).

Supporting Cells (Glial Cells)

• Neuroglia: Non-excitable cells that support and protect neurons in the central nervous system. They continually replicate.
  • Microglia: Primary function is phagocytosis (engulfing debris) in areas of inflammation or cell damage. Commonly found near blood vessels.
  • Astrocytes: Star-shaped cells forming the main supporting tissue of the CNS. Found near blood vessels and in a muccopolysaccharide matrix.
  • Oligodendrocytes: Smaller than astrocytes and create myelin in the central nervous system. Analogous to Schwann cells in the periphery.

Nerve Impulse Mechanisms

• Local Anesthetics: Block nerve impulses by inhibiting sodium channels in nerve cell membranes. Used in dentistry to manage pain during procedures.
• Neuralgia: Excessive nerve impulses can cause neuralgia, like trigeminal neuralgia.
• Herpes Simplex Virus: The virus can lie dormant in the trigeminal ganglion, reactivate, and cause cold sores along the trigeminal nerve.

Divisions of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord.
• Peripheral Nervous System (PNS): All other nerves.
  • Sensory Division: Carries sensory information to the CNS.
  • Motor Division: Carries signals from the CNS to effectors.
    • Somatic: Voluntary movement of skeletal muscles.
    • Autonomic: Involuntary control of smooth muscle, cardiac muscle, and glands.

Key Brain Structures

• Cerebrum: Largest part; responsible for higher mental activities, sensory perception, and voluntary muscle control.
• Hypothalamus: Located in the cerebrum; controls hormones, emotional reactions, hunger/thirst, body temp, and biological clocks.
• Thalamus: Relays sensory information (touch, pain, temperature) from sensory receptors to the brain for initial perception. Involved in arousal and emotions.
• Midbrain: Consists of nuclei that relay information between the cerebrum and spinal cord. Involved in auditory and visual reflexes.
• Pons: Forms a bridge between the cerebrum's hemispheres and processes information from cranial nerves.
• Medulla Oblongata: Continuous with spinal cord; controls vital functions like the cardiovascular and respiratory centers, and reflex centers (e.g., coughing, vomiting).

Spinal Cord

• Structure: Long, cylindrical part of the CNS, extends from the medulla oblongata, suspended in the vertebral canal, surrounded by meninges and cerebrospinal fluid.
• Function: Conveys impulses from the brain to organs and tissues.

Cerebrospinal Fluid (CSF) Functions

• Protection: Cushions the brain and reduces the pressure at the base.
• Buoyancy: Reduces the brain's net weight.
• Waste Removal: Transports waste from the brain to the bloodstream.
• Endocrine Medium: Carries hormones to various brain areas.