Neuroanatomy Lecture Notes

Overview of the Nervous System

• Central Nervous System (CNS)
  • Composed of the brain and spinal cord.
  • Shaded area in diagrams typically represents the spinal cord.
  • The upper structure, often red in diagrams, represents the brain.
• Peripheral Nervous System (PNS)
  • Divided into sensory and motor components.

Functions of the Central Nervous System

1. Receive Sensory Information
   • Gathers information from the environment and body.
   • Uses sensory nerves from the PNS to collect data.
2. Process Information
   • Compares and contrasts current sensory input with past experiences.
3. Generate Motor Responses
   • Decides appropriate responses based on collected and processed information.
   • Outputs responses through motor nerves in the PNS.

Sensory Input and Motor Output

• Sensory information travels to the CNS; responses are issued back to the periphery.
• Sensory system divided into:
  • Special Senses: Elicited from specific organs (e.g., vision, hearing).
  • General Senses: Elicited from various body parts (e.g., touch, temperature).

Types of Sensations

• Special Senses: Highly specific; generated from designated organs.
  • Examples: Vision (eyes), Hearing (ears), Smell (nose), Taste (tongue).
• General Senses: Can be initiated from multiple body parts.
  • Examples: Touch, Pain, Temperature, Proprioception.

Proprioception

• Sense of body position and movement.
• Critical for coordination and movement accuracy.

Conscious vs. Unconscious Sensory Processing

• Sensory information can either:
  • Be processed at the conscious level (e.g., recognition of stimuli).
  • Be processed at an unconscious level (e.g., blood pressure regulation).
• The Cerebral Cortex is responsible for conscious awareness of sensory input.

Motor Responses

• Motor responses can be:
  • Voluntary Motor Responses: Under conscious control (e.g., moving a limb).
  • Involuntary Motor Responses: Automatic functions not under conscious control (e.g., digestion).

Divisions of the Autonomic Nervous System

• Sympathetic Nervous System: Activates in stress situations (fight or flight).
• Parasympathetic Nervous System: Dominates in relaxed states, promoting rest and digestion.

Structure of the Brain

• Forebrain: Includes cerebral hemispheres and deeper structures (telencephalon and diencephalon).
• Midbrain: Also known as mesencephalon.
• Hindbrain: Includes medulla, pons, and cerebellum (also called rhombencephalon).

Gray Matter vs. White Matter

• Gray Matter: Contains neuronal cell bodies; found in the cortex and nuclei.
  • Cortex: Gray matter on the surface of the brain.
  • Nuclei: Aggregates of gray matter within the brain, surrounded by white matter.
• White Matter: Composed of myelinated axons; responsible for transmitting signals between different parts of the CNS.

Types of White Matter Tracts

• Ascending Tracts: Carry sensory information from the body to the brain.
• Descending Tracts: Carry motor commands from the brain to the body.
• Commissural Fibers: Connect the right and left hemispheres.
• Association Fibers: Connect different regions within the same hemisphere.

Reticular Formation

• A network of gray and white matter in the brainstem, critical for various functions including consciousness and sensory processing.

Definitions

• Nerve: A bundle of axons outside the CNS.
• Track: A bundle of axons within the CNS.

Key Points to Remember

• The CNS consists of neurons that conduct signals and glial cells that support them.
• Gray matter consists of neuronal cell bodies; white matter contains axonal connections.
• Understanding the structure and function of both systems is critical for studying neuroanatomy and physiology.