Lecture 3 Slides - Organisation of the Nervous System(1)

Organisation of the Nervous System

• Overview of Biological Psychology and the organisation of the nervous system

Content Covered So Far

• Cells of the Nervous System:

  • Glial Cells: Support neurons and maintain homeostasis.

  • Neurons: Basic functional units.

  • The Neuron:

    • Cell membrane and resting potential.

    • Depolarization and action potential.

    • Propagation of action potentials (transmission of information without attenuation).

  • Synaptic Transmission:

    • Synapses and their pharmacology,

    • Drug actions at the synapse.

  • Current Focus: Nerves and Systems, including function, structure, and organization.

Function of the Nervous System

• Primary Functions:

  • Speed up, integrate, and coordinate physiological and behavioral responses to environmental changes.

• Internal Changes: Shifts related to homeostasis.

• External Changes:

  • Sensory processing, motor coordination, reflexes, cognition, memory, and learning.

  • Complex organisms must effectively respond to rapid changes in both internal and external environments for survival.

Navigating the CNS

• Directional Terms:

  • Superior, Dorsal, Coronal, Anterior, Posterior, Transverse, Rostral, Caudal, Lateral, Inferior, Ventral, Medial, Sagittal, Inferior, Superior, Ventral, Dorsal, Parasagittal.

Terms Defined

• Afferent Neurons:

  • Carry information from periphery to CNS ("Afferent Arrives").

• Efferent Neurons:

  • Carry information from CNS to the periphery ("Efferent Exits").

• Receptor Neurons: Specialized cells sensitive to stimuli.

  • Types include:

    • Photoreceptors: Respond to light.

    • Mechanoreceptors: Respond to mechanical forces.

    • Thermoreceptors: Respond to temperature changes.

    • Chemoreceptors: Respond to chemical stimuli.

• Motor Neurons: Conduct impulses to muscles or glands.

• Interneurons: Communicate between other neurons.

Nervous System Structure

• Central Nervous System (CNS):

  • Comprises the brain and spinal cord (encased in bone).

• Peripheral Nervous System (PNS): Includes two divisions:

  • Somatic Nervous System (SNS):

    • Includes afferent and efferent components; relays information between sensory organs and the CNS.

  • Autonomic Nervous System (ANS): Divides into:

    • Sympathetic System: Involuntary responses ("Fight or Flight").

    • Parasympathetic System: Involuntary responses ("Rest or Digest").

• Neuron Structure:

  • Nerve fiber covered by endoneurium, collections of nerve fibers grouped in fasciculi and covered in perineurium constitutes a nerve.

• Grey Matter:

  • Contains neuronal cell bodies, primarily seen in the cortex and nuclei.

• White Matter:

  • Contains myelinated axons which form pathways.

Afferent and Efferent Neurons

• Bipolar Afferent Cells: Specialized sensory cells involved in olfaction, vision, audition, gustation, and balance.

• Unipolar Afferent Cells: Typical sensory cells with long axons terminating in the spinal cord.

• Multipolar Efferent Cells: Most prevalent in CNS; include motor neurons and interneurons; characterized by long axons synapsing with effectors (muscles/glands).

White Matter

• Myelin: Formed by oligodendrocytes in the CNS and Schwann cells in the PNS; essential for efficient signal transmission.

Organisation of Nervous System

• CNS: Brain and spinal cord regulate voluntary action.

• PNS: Divided into SNS and ANS. The ANS further divides into:

  • Sympathetic Division: Emergency response.

  • Parasympathetic Division: Restorative processes.

Construction of Nerves

• Blood Vessels and Nerve Fibers:

  • A nerve is a bundle of fasciculi covered in epineurium; each fasciculus consists of nerve fibers wrapped in endoneurium and bound by perineurium.

Spinal Cord

• Comprises 31 pairs of spinal nerves (both afferent and efferent) that bifurcate into dorsal and ventral roots as they enter vertebrae. Each nerve pair serves specific body areas.

Dermatomes

• Segments corresponding to spinal nerve innervation; overlap exists across segments, reflecting evolutionary origins.

Detail of Spine

• Grey Matter: Contains neuronal cell bodies.

• White Matter: Contains axons (tracts).

• Dorsal and Ventral Roots: Sensory nerves enter the spinal cord via the dorsal root, while motor nerves exit through the ventral root.

Decussation

• Defined as crossing over of nerve tracts, where most sensory and motor pathways crossover in brainstem areas; includes both ascending and descending tracts that communicate contralaterally.

Autonomic Nervous System

• Manages involuntary functions and consists of the sympathetic (energy-expending) and parasympathetic (energy-conserving) divisions.

Sympathetic vs. Parasympathetic Responses

• Contrast in physiological responses such as pupil dilation and constriction, salivation, heart rate fluctuations, and digestive processes.

Looking Ahead

• Prepare for next session on Brain Anatomy; reviewing lecture slides and introductory literature is encouraged.