Nervous System Overview

Basic Functions of the Nervous System

• Sensation: Involves collecting sensory input from the environment through receptors that monitor internal and external stimuli.
• Integration: Processing and interpreting sensory information to determine appropriate responses.
• Reaction: Motor output activation of muscles and glands via neurotransmitters.

Structural Organization of the Nervous System

• Central Nervous System (CNS): Comprises the brain and spinal cord.
• Peripheral Nervous System (PNS): Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Nervous Tissue Composition

• Grey Matter: Contains neuronal cell bodies, short processes, neuroglia, and blood vessels.
• White Matter: Composed of long processes (axons) of neurons.
• Ganglion: A collection of neuron cell bodies located outside the CNS.
• Nucleus: A collection of neuron cell bodies located inside the CNS.
• Plexus: A network formed by a collection of nerve fibers.

Human Brain Structure

• Located in the cranial cavity and divided into four major regions:
  • Cerebrum: Consists of two cerebral hemispheres.
  • Diencephalon: Includes the thalamus, hypothalamus, subthalamus, and epithalamus.
  • Cerebellum: Responsible for coordination and balance.
  • Brainstem: Comprises the midbrain and pons.

Spinal Cord Details

• Length: Measures approximately 42-45 cm.
• Location: Situated within the vertebral canal.
• Starts at: Medulla oblongata.
• Ends at: Conus medullaris, terminating at the L2 vertebra.
• Spinal Nerves: Gives rise to 31 pairs.

Protection of the CNS

• Bones: Skull and vertebral column provide primary protection.
• Meninges: Three protective layers surrounding the CNS.
• Cerebrospinal Fluid (CSF): Provides cushioning and nourishment.

Meningeal Coverings

• Dura Mater: The outermost layer.
• Arachnoid Mater: The middle layer.
• Pia Mater: The innermost layer closely adhering to the brain and spinal cord.

Peripheral Nerves

• Composed of sensory, motor, or mixed fibers.
• Cranial Nerves: 12 pairs attached to the brain.
• Spinal Nerves: 31 pairs connected to the spinal cord, categorized as:
  • 8 Cervical
  • 12 Thoracic
  • 5 Lumbar
  • 5 Sacral
  • 1 Coccygeal

Spinal Nerves and Nerve Plexuses

• Each spinal nerve has two roots:
  • Dorsal Root: Contains sensory fibers and sensory ganglion (DRG).
  • Ventral Root: Contains motor fibers.
• Plexuses formed primarily from ventral rami, excluding the thoracic region.

Cranial Nerves List

• 1st: Olfactory
• 2nd: Optic
• 3rd: Oculomotor
• 4th: Trochlear
• 5th: Trigeminal
• 6th: Abducent
• 7th: Facial
• 8th: Vestibulocochlear
• 9th: Glossopharyngeal
• 10th: Vagus
• 11th: Accessory
• 12th: Hypoglossal

Dermatomes

• Defined as the skin segment supplied by a segmental spinal nerve.

Autonomic Nervous System (ANS)

• A subdivision of the peripheral nervous system regulating involuntary body activities.
• Innervates cardiac muscle, smooth muscle, and internal organs.

Axonal Structure in ANS

• The first (preganglionic) neuron's axon leaves the CNS to synapse with the second (ganglionic) neuron.
• The second (postganglionic) neuron extends to the target organ.

Divisions of the Autonomic Nervous System

• Sympathetic Division: Involves T1-L2 segments, mobilizing body resources during stress ("fight or flight").
• Parasympathetic Division: Involves cranial outflow and S2-S4 spinal segments, conserving energy and facilitating routine maintenance ("rest and digest").

This quiz delves into the functions and classifications of the Nervous System. It covers crucial elements such as neurons, synapses, myelination, and the formation of the brain and spinal cord. Test your understanding of the structure and function of the nervous system.